Compendium | October 2009 by davidpsu

VOLUME 31 NUMBER 10 OCTOBER 2009

Compendium CompendiumVet.com | Peer Reviewed | Listed in MEDLINE

9 CE Contact Hours

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Canine Glaucoma

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Urate Urolithiasis

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Vol 31(10) October 2009

CONTI N U I NG EDUCATION FOR VETERI NARIANS ®

COMPENDIUM CONTINUING EDUCATION FOR VETERINARIANS®

Hot Topics in Pet Food Regulation

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October 2009 Vol 31(10) CompendiumVet.com | Peer Reviewed | Listed in MEDLINE

EXECUTIVE EDITOR Tracey L. Giannouris, MA 800-426-9119, ext 52447 | tgiannouris@vetlearn.com

PUBLISHED BY

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October 2009 Vol 31(10) CompendiumVet.com | Peer Reviewed | Listed in MEDLINE

EDITORIAL BOARD Anesthesia Nora S. Matthews, DVM, DACVA Texas A&M University

Internal Medicine Dana G. Allen, DVM, MSc, DACVIM Ontario Veterinary College

Cardiology Bruce Keene, DVM, MSc, DACVIM North Carolina State University

Internal Medicine and Emergency/ Critical Care Alison R. Gaynor, DVM, DACVIM (Internal Medicine), DACVECC North Grafton, Massachusetts

Clinical Chemistry, Hematology, and Urinalysis Betsy Welles, DVM, PhD, DACVP Auburn University

EDITOR IN CHIEF Douglass K. Macintire, DVM, MS, DACVIM, DACVECC

Department of Clinical Sciences College of Veterinary Medicine Auburn University, AL 36849

Dentistry Gary B. Beard, DVM, DAVDC Auburn University R. Michael Peak, DVM, DAVDC The Pet Dentist—Tampa Bay Veterinary Dentistry Largo, Florida Emergency/Critical Care and Respiratory Medicine Lesley King, MVB, MRCVS, DACVECC, DACVIM University of Pennsylvania Endocrinology and Metabolic Disorders Marie E. Kerl, DVM, DACVIM, DACVECC University of Missouri-Columbia

EXECUTIVE ADVISORY BOARD MEMBERS Behavior Sharon L. Crowell-Davis, DVM, PhD, DACVB The University of Georgia Dermatology Craig E. Grifﬁn, DVM, DACVD Animal Dermatology Clinic San Diego, California Wayne S. Rosenkrantz, DVM, DACVD Animal Dermatology Clinic Tustin, California Nutrition Kathryn E. Michel, DVM, MS, DACVN University of Pennsylvania Surgery Elizabeth M. Hardie, DVM, PhD, DACVS North Carolina State University

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CompendiumVet.com

Epidemiology Philip H. Kass, DVM, MPVM, MS, PhD, DACVPM University of California, Davis Exotics Avian Thomas N. Tully, Jr, DVM, MS, DABVP (Avian), ECAMS Louisiana State University Reptiles Douglas R. Mader, MS, DVM, DABVP (DC) Marathon Veterinary Hospital Marathon, Florida Small Mammals Karen Rosenthal, DVM, MS, DABVP (Avian) University of Pennsylvania Feline Medicine Michael R. Lappin, DVM, PhD, DACVIM (Internal Medicine) Colorado State University Margie Scherk, DVM, DABVP (Feline Medicine) Cats Only Veterinary Clinic Vancouver, British Columbia Gastroenterology Debra L. Zoran, DVM, MS, PhD, DACVIM (Internal Medicine) Texas A&M University Infectious Disease Derek P. Burney, DVM, PhD, DACVIM Gulf Coast Veterinary Specialists Houston, Texas

Nephrology Catherine E. Langston, DVM, DACVIM Animal Medical Center New York, New York Neurology Curtis W. Dewey, DVM, MS, DACVIM (Neurology), DACVS Cornell University Hospital for Animals Oncology Ann E. Hohenhaus, DVM, DACVIM (Oncology and Internal Medicine) Animal Medical Center New York, New York Gregory K. Ogilvie, DVM, DACVIM (Internal Medicine, Oncology), DECVIM-CA (Oncology) CVS Angel Care Cancer Center and Special Care Foundation for Companion Animals Carlsbad, California Ophthalmology David A. Wilkie, DVM, MS, DACVO The Ohio State University Parasitology Byron L. Blagburn, MS, PhD Auburn University David S. Lindsay, PhD Virginia Polytechnic Institute and State University Pharmacology Katrina L. Mealey, DVM, PhD, DACVIM, DACVCP Washington State University Rehabilitation and Physical Therapy Darryl Millis, MS, DVM, DACVS University of Tennessee Surgery Philipp Mayhew, BVM&S, MRCVS, DACVS Columbia River Veterinary Specialists Vancouver, Washington C. Thomas Nelson, DVM Animal Medical Center Anniston, Alabama Toxicology Tina Wismer, DVM, DABVT, DABT ASPCA National Animal Poison Control Center Urbana, Illinois

AMERICAN BOARD OF VETERINARY PRACTITIONERS (ABVP) REVIEW BOARD Kurt Blaicher, DVM, DABVP (Canine/Feline) Plainﬁeld Animal Hospital Plainﬁeld, New Jersey Canine and Feline Medicine Eric Chafetz, DVM, DABVP (Canine/Feline) Vienna Animal Hospital Vienna, Virginia Canine and Feline Medicine Henry E. Childers, DVM, DABVP (Canine/Feline) Cranston Animal Hospital Cranston, Rhode Island Canine and Feline Medicine John G. DeVries, DVM, DABVP (Canine/Feline) Oradell Animal Hospital Paramus, New Jersey Canine and Feline Medicine David E. Harling, DVM, DABVP (Canine/Feline), DACVO Reidsville Veterinary Hospital Reidsville, North Carolina Canine and Feline Medicine, Ophthalmology Jeffrey Katuna, DVM, DABVP Wellesley-Natick Veterinary Hospital Natick, Massachusetts Canine and Feline Medicine Robert J. Neunzig, DVM, DABVP (Canine/Feline) The Pet Hospital Bessemer City, North Carolina Canine and Feline Medicine

Compendium is a refereed journal. Articles published herein have been reviewed by at least two academic experts on the respective topic and by an ABVP practitioner. Any statements, claims, or product endorsements made in Compendium are solely the opinions of our authors and advertisers and do not necessarily reﬂect the views of the Publisher or Editorial Board.

EEach CE article is accredited for 3 contact hours by A Auburn University College of Veterinary Medicine.

October 2009 Vol 31(10)

Features CompendiumVet.com | Peer Reviewed | Listed in MEDLINE

462 Focus on Nutrition US Pet Food Regulation: Hot Topics ❯❯ David A. Dzanis Regulations governing pet food processing, ingredient, and labeling standards are changing, and veterinary organizations are making their opinions heard.

468

Urate Urolithiasis

FREE

❯❯ John McCue, Cathy Langston, Douglas Palma, and Kelly Gisselman This article is the ﬁrst in a series addressing the management of different types of urinary stones.

Cystic urate uroliths. PAGE 470

476 Surgical Views

450

Canine Glaucoma: Pathophysiology and Diagnosis

FREE

❯❯ Shelby L. Reinstein, Amy J. Rankin, and Rachel Allbaugh

454

Canine Glaucoma: Medical and Surgical Treatment Options

FREE

❯❯ Shelby L. Reinstein, Amy J. Rankin, and Rachel Allbaugh Many conditions can cause glaucoma in dogs. Early, accurate diagnosis can help preserve vision at least temporarily in some cases. These two articles provide a brief overview of diagnosis and management of canine glaucoma.

Endoscopic Removal of Urinary Calculi ❯❯ Clarence A. Rawlings The author describes the advantages, limitations, and techniques of endoscopy for urolith removal.

On the Cover Siobhan Norris (right) holds Beasley still as Dr. Reinstein measures the pressure in Beasley’s eye.

Setup for a laparoscopicassisted cystotomy. PAGE 480

Illustration © The University of Georgia

Departments 444 CompendiumVet.com 446 Editorial: Overcoming the RD Complex ❯❯ C. Thomas Nelson

487 Client Handout: Feeding Your Pet: How Much Is Too Much?

485 Index to Advertisers 485 Product Forum 486 Market Showcase

Cover photo by Holly Palin

486 Classiﬁed Advertising Compendium: Continuing Education for Veterinarians®

443

WEB EXCLUSIVES

October

2009 Vol 31(10)

CE ARTICLES WEBEXCLUSIVE

VIDEOS

❯❯ Laparoscopic Organ Biopsy Videos The April 2009 Surgical Views article, “Techniques for Laparoscopic and Laparoscopic-Assisted Biopsy of Abdominal Organs,” by Dr. Philipp Mayhew, describes laparoscopic techniques that can be used to harvest biopsy samples from the liver, kidneys, pancreas, and gastrointestinal tract. Six videos, contributed by Drs. Mayhew and Stephen J. Mehler, demonstrate the use of some of the techniques and instruments discussed in this article.

❯❯ Arterial and Venous Blood Gases: Indications, Interpretations, and Clinical Applications ❯❯ Ricardo Irizarry and Adam Reiss Blood gas analysis is frequently requested as part of the point-of-care testing for emergency or critical care patients presenting with metabolic or respiratory abnormalities. With the advent of portable units, information regarding a patient’s acid– base, ventilation, and oxygenation status can be rapidly obtained. This article provides essential information on arterial and venous blood gas analysis with the goal of helping clinicians integrate such data in their case management.

❯❯ Feline Infectious Peritonitis ❯❯ Teresa L. Goodson, Susan C. Randell, and Lisa E. Moore Feline infectious peritonitis (FIP) frequently results in death in cats. It is caused by a mutated, highly contagious coronavirus, and it is more common in indoor cats in multicat households. A complex interaction between the coronavirus and the feline immune system causes disseminated vasculitis, which is the hallmark of FIP. WEB-EXCLUSIVE ARTICLES

❯❯ Beyond Blood Gases: Making Use of Additional Oxygenation Parameters and Plasma Electrolytes in the Emergency Room ❯❯ Ricardo Irizarry and Adam Reiss When provided with an emergency blood gas or

electrolyte readout, clinicians must identify the critical parameters that require immediate intervention. This article provides concepts in oxygenation and electrolyte evaluation to help ﬁne-tune the initial treatment and monitoring orders for emergency patients.

❯❯ Case Report: Surgical Stabilization of a Craniocervical Junction Abnormality With Atlanto-Occipital Overlapping in a Dog ❯❯ Curtis W. Dewey, Soﬁa Cerda-Gonzalez, Peter V. Scrivani, Andrea L. Looney, and Gena M. Silver A 3-year-old male neutered Pomeranian presented with severe, poorly localizable pain that was unresponsive to a combination of oral medications (gabapentin, tramadol, prednisone, and methocarbamol) and a fentanyl patch. NEWS BITES

❯❯ Three Dog Coat Genes Could Lead to Understanding of Human Diseases Caused by Multiple Genes A National Institutes of Health study has shown that variations in only three genes account for the seven major types of coat seen in purebred dogs. The ﬁndings point the way toward understanding complex human diseases caused by multiple genes.

❯❯ Cancer Researchers Test if Spice Can Kill Feline Cancer Cells A simple compound derived from a kitchen spice may have the ability to stop cancer cells from growing in cats. Curcumin, a compound in turmeric, appears to stop the growth of cancer in laboratory cell tests. E-NEWSLETTER ❯❯ COMPENDIUM EXTRA, a monthly e-newsletter, provides Web-exclusive articles and news as well as a preview of this month’s journal. Sign up at CompendiumVet.com.

444

Compendium

Canadian News

Coming Events November 2009 2009 Veterinary Continuing Education Series: Feline Medicine—November 3, David Lam Campus, Douglas College, Coquitlam, British Columbia. This free program will focus on some of the basics of feline medicine. It will be hosted by Dr. Margie Scherk, DVM, DABVP (Feline), and will offer 1.5 CE credits. For more information, e-mail lisa.timmons@purina. nestle.com or visit www.bcvma.org. Calgary Academy of Veterinary Medicine: Radiology—November 4, Clara Christie Theatre, Health Sciences, University of Calgary, Alberta. This seminar will offer 1.5 hours of scientific CE and will be presented by Dr. Tim Spotswood. For additional information, call 403-863-7160, e-mail info@cavm.ab.ca, or visit cavm.ab.ca/ce_calendar.html. Focus and Flourish: Cruciates—November 7, location to be announced. This 2-day workshop will focus on cruciate surgery and is ideal for practitioners with all levels of experience with cruciate repairs. The workshop will be taught in an intimate, interactive, hands-on environment. For more information, call 519-219-0573, e-mail focusandflourish@rogers.com, or visit www.focusandflourish.com. Toronto Academy of Veterinary Medicine: Practice Management—November 10, Dave and Buster’s, Toronto, Ontario. This seminar will focus on different aspects of practice management and will be hosted by Shawn McVey, MA, MSW. The course will offer 5.5 CE credits. For more information, call 800-670-1702 or visit tavm.org. Lifelearn Inc. Continuing Education: Small Animal Laser Surgery—November 13–14, Ontario Veterinary College University of Guelph, Ontario. This seminar will offer 14 hours of CE credit. It is designed to provide practitioners with an introduction to the uses of CO2 lasers in veterinary surgery. For further information, call 800-375-7994 or visit www.lifelearn.com. December 2009 Lifelearn Inc. Continuing Education: Flexible Endoscopy—December 4–6, Ontario Veterinary College University of Guelph, Ontario. This seminar will offer 42 hours of CE credit. It is designed to provide practitioners with upper and lower GI endoscopic experience. An advanced module planned for 2010 will also offer 42 CE credit hours. For further information, call 800-375-7994 or visit www.lifelearn.com. Calgary Academy of Veterinary Medicine: Hematology—December 6, Clara Christie Theatre, Health Sciences, University of Calgary, Alberta. This seminar will offer 6 hours of scientific CE and will be presented by Dr. Marjorie Brooks. For additional information, call 403-863-7160, e-mail info@cavm.ab.ca, or visit cavm.ab.ca/ ce_calendar.html.

OVC Grad Frank W. Schoﬁeld Named Person of Historic Signiﬁcance

910 Ontario Veterinary College (OVC) grad and former faculty member, Dr. Frank W. Schofield, has been designated a person of national historic significance by Parks Canada on a recommendation from the Historic Sites and Monuments Board of Canada. During his career, Dr. Schofield published 143 papers and reports. His most famous discovery was the identification of mouldy sweet clover as the cause of a bleeding disease of sheep and cattle, which pointed the way to the discovery of the vitamin K inhibitors that are now used throughout the world to control unwanted coagulation. “Dr. Frank W. Schofield is remem-

bered by the veterinary profession as possibly the greatest scientist to have ever worked at the Ontario Veterinary College,” says Dr. J. Harold Reed, DVM, who initiated the nomination procedure 3 years ago, following a discussion with Dean Elizabeth Stone at the Schofield Lecture, named in Dr. Schofield’s honor. Dr. Schofield also spent many years in Korea, teaching bacteriology at a college in Seoul and later teaching at Seoul National University. He died in Seoul in 1970 and is the only westerner buried in the Patriot section of the Seoul National Cemetery. He was given this honor for his support of the 1919 Samil Independence Movement.

University of Calgary Opens New Clinical Skills Building

he University of Calgary has ofﬁcially opened a new state-of-the-art veterinary building—the Clinical Skills Building—on its Spy Hill Campus. The Province of Alberta provided $80 million to the faculty of veterinary medicine for the veterinary school’s much-needed infrastructure. Most of this amount—$65 million—went to the Clinical Skills Building. The remaining funds were allocated to classroom, research, and administrative space at the Foothills Campus. “The new facility features leadingedge imaging, surgical, and diagnostic areas for large and small animals,” says Doug Horner, minister of advanced education and technology. “Not only will it offer an advanced learning environment, it will help our students expand their understanding of the interactions

between animal and human health and build our province’s capacity to protect our food supply and exports.” The veterinary school accepted its ﬁrst class of undergraduate students in 2008. Graduate students started in 2006. The university held an openhouse event for the public at the Clinical Skills Building on August 29.

SPREAD YOUR GOOD NEWS Canadian News c/o Veterinary Learning Systems 780 Township Line Road Yardley, PA 19067, USA E-MAIL editor@CompendiumVet.com FAX 800-556-3288 WEB CompendiumVet.com

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445

Editorial ❯❯ C. Thomas Nelson, DVM Animal Medical Center Anniston, Alabama

Overcoming the RD Complex*

ll of us, at one time or another, have had a client, friend, or family member ask, “Why didn’t you become a REAL DOCTOR [RD]?” In fact, most of us (especially those of my generation) have asked ourselves the same question or have even considered going back to medical school at some point in our lives. These feelings may have been initiated by substandard wages or by the frustration we experience when we cannot fully apply our skills to a particular case because the owners cannot afford it.

If you want to practice medicine like the RDs do, upgrade your staff. But why does John Q. Public repeatedly ask this seemingly ridiculous question? After all, our education is equivalent to an RD’s, and we use much of the same equipment. Maybe it is because we don’t always act like “real doctors.” When was the last time you saw a medical doctor administer a routine vaccination, collect blood samples for laboratory testing, place an intravenous catheter, take a radiograph, or change sheets on a hospital bed? I do remember an old M*A*S*H episode in which Dr. Charles Emerson Winchester III was forced to change and wash linens during a Salmonella outbreak, but that was ﬁction, not real life. The biggest difference between veterinarians and MDs is not in their training, but in their support staff. “Real” physicians see patients, make diagnoses, prescribe treatments, and perform surgery. All other tasks are left to the registered nurses, licensed vocational nurses, medical technicians, phlebotomists, radiology technicians, physical therapists, *Adapted and updated with permission from Texas Veterinary Medical Journal, October 1992.

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orderlies, etc. Veterinarians tend to do everything themselves. For some, it is a necessity; for others, it is a lack of confidence in their staff. I have visited practices where the veterinarian bathed and dipped dogs. In others, the vet personally medicated each and every animal in the hospital. If this is the way you want to practice medicine, more power to you. But if you want to practice like the RDs do, upgrade your staff. In the early 1970s, the AVMA recognized the need for qualified paraprofessionals and formed a committee to establish guidelines and accredit schools of veterinary technology. Thus the veterinary technician was born. A veterinary technician is a combination of registered nurse, medical laboratory technician, radiography technician, and anesthesia assistant all rolled into one. These individuals are not just taught how to do technical procedures, they are also taught why. Thirty-eight states now recognize the training these individuals have obtained, have incorporated them into their veterinary practice acts, and acknowledge them with the designation of licensed, certified, or registered veterinary technician (LVT, CVT, and RVT, respectively). This recognition allows technicians who have graduated from AVMAaccredited schools and passed their board exams to legally perform certain procedures previously restricted to licensed veterinarians and, in some states, to supervise veterinary assistants.a I must warn you: these individuals command a higher salary than on-the-job-trained animal health assistants. But they are worth it. First, your clients appreciate the fact you have upgraded your practice by adding a veterinary technician to your staff. They are used to seeing paraprofessionals when they go to their own doctors. When they a A list of state laws regarding the duties of veterinary assistants is available at avma.org/advocacy/state/ issues/scope_vet_assistant_duties.pdf.

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Cat owners listen to their cats. Listen to your cat owners. Cats and their owners agree: a topical dewormer beats a pill any day. In fact, nearly 90% of cat owners prefer topical drops to pills or tablets.* So listen to your cat owners. Choose the only feline dewormer that treats and controls roundworms, hookworms and tapeworms with the ease and convenience of a topical application: ProfenderÂŽ Topical Solution. *From a survey of 736 cat owners. Data on file.

Federal (U.S.A.) law restricts this drug to use by or on the order of a licensed veterinarian. Children should not contact application site for twenty-four (24) hours. See Page 448 for Product Information Summary

P08711n

Editorial see a technician in your clinic, it enforces their belief that you really do care to provide the best treatment for their pets. Second, most pet owners are used to the veterinarian administering injections and collecting samples. However, they are also used to receiving shots from a registered nurse themselves, and it will seem only natural for a technician to administer an injection. Third, and most important, hiring a veterinary technician frees you to do the tasks you were trained to do: see clients, make diagnoses, prescribe treatments, and perform surgery. The end result is a marked increase in productivity and net profits. When our practices grow larger and get busier, our first instinct is to hire a new veterinarian. In most practices, the added burden can be handled more efficiently and economically by a veterinary technician. In fact, many newly graduated veterinarians are hired to do work that falls well within the scope of a technician’s training. These individuals quickly become disenchanted and look for employment elsewhere. Technicians are more likely to stick around. Statistics show the average duration of employment at a single practice to be only 2 years for a veterinarian, whereas a veterinary technician’s average time of employment is more than 5 years. RVTs are an integral part of the veterinary health care team. From the first day they enter an AVMA-accredited technician program, they are taught the value of the team concept. Today’s veterinary practices are becoming larger and more complex, and well-trained paraprofessionals are a necessity. Like a football team, the practices with the most skilled players are going to be the most successful. If you are not sure what a veterinary technician is trained to do, visit the AVMA Web site and look at the Accreditation Policies and Procedures of the AVMA Committee on Veterinary Technician Education and Activities. The list of essential and recommended skills for veterinary technology students is available at avma. org/education/cvea/cvteaappendix_ i.asp.

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CE Article 1 Courtesy of Elizabeth Guiliano, DVM, MS, DACVO, University of Missouri

3 CE CREDITS

Canine Glaucoma: Pathophysiology and Diagnosis* ❯❯ Shelby L. Reinstein, DVM, MS The University of Pennsylvania

❯❯ Amy J. Rankin, DVM, MS, DACVO ❯❯ Rachel Allbaugh, DVM, MS, DACVO Kansas State University

At a Glance Canine Glaucoma Page 450

Diagnosis Page 451

Top Five Breeds of Dogs With a High Prevalence of Primary Glaucoma

Abstract: Canine glaucoma encompasses a diverse group of diseases associated with an increase in intraocular pressure that results in retinal ganglion cell death and eventual blindness. Dogs may have congenital, primary, or secondary glaucoma. The diagnosis is made by recognizing clinical signs, interpreting ophthalmic examination ﬁndings, and determining intraocular pressure. Identifying the underlying cause of the glaucoma is essential to providing appropriate treatment recommendations.

queous humor is produced by the ciliary body and flows through the pupil into the anterior chamber of the eye. In dogs, most aqueous humor exits the eye through the iridocorneal angle; approximately 10% to 15% exits the eye through uveoscleral outflow.1 Normal intraocular pressure (IOP; range: 10 to 25 mm Hg2–4) is maintained by an equilibrium between aqueous humor production and drainage. Canine glaucoma is usually due to a disturbance in the conventional outflow pathway that results in an increased IOP.

Page 451

Comparison of Available Tonometry Methods Page 452

*A companion article, “Canine Glaucoma: Medical and Surgical Treatment Options,” begins on page 454.

450

Canine Glaucoma Traditionally, glaucoma has been defined as an elevated IOP beyond that which permits normal visual function.2 Recent research has indicated that canine glaucoma is a common end point of several ophthalmic diseases. Canine glaucoma can be classified as congenital, primary, or secondary. Congenital glaucoma is rare in dogs. It is caused by abnormalities in the aqueous humor outflow pathways. Puppies generally present young (3 to 6 months of age)

with an acute onset of buphthalmia and corneal edema. The disease may be unilateral or bilateral and may be associated with other ocular anomalies.2 Primary glaucoma is considered a heritable condition in some breeds2 (BOX 1). The disease is progressive and may result from changes in the iridocorneal angle or from abnormal metabolism of the trabecular cells within the outflow pathway.2 Primary glaucoma is further classified as open-, narrow-, or closed-angle, based on the appearance of the drainage angle.2,5 It is always a bilateral condition. Secondary glaucoma results when another condition disrupts aqueous humor outflow. Several disease conditions can lead to secondary glaucoma, including cataract, lens luxation, hyphema, intraocular neoplasia, retinal detachment, and uveitis.2 In some of these conditions, the release of vasoactive factors may lead to the formation of a preiridal fibrovascular membrane and subsequent secondary glaucoma.2 Although secondary glaucoma is not considered heritable, some of the inciting causes do have a genetic basis (e.g., cataract, lens luxation). Dogs of breeds that are predisposed

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Canine Glaucoma: Pathophysiology and Diagnosis CE to these conditions that have developed a high IOP in one eye should have the contralateral eye routinely monitored for the development of disease.6,7 Additionally, if cataract surgery is performed, postoperative glaucoma is a potential complication that can be vision threatening.8,9 If secondary glaucoma can be diagnosed early and managed appropriately, vision may be preserved.

Diagnosis The history, clinical presentation, and ophthalmic examination ﬁndings assist in diagnosing glaucoma. It is crucial for the veterinarian to determine the stage of the glaucoma (acute or chronic) to provide appropriate treatment.

Clinical Signs Glaucoma can be a painful condition. Signs of ocular pain include blepharospasm, epiphora, and an elevated third eyelid. Episcleral congestion or corneal edema may also be present, and owners may describe the eye as reddish or blue.2,10 Dogs may also present without vision, lacking menace responses, pupillary light reflexes (PLRs), and dazzle reflexes.11 Unfortunately, most subtle or transient increases in IOP lack overt clinical signs in the acute phases, and most dogs present with chronic glaucoma. IOP, corneal edema, and visual status may be similar in acute and chronic glaucoma. Globe size and fundic examination help determine the duration of the disease. Signs of acute glaucoma may include a normal-sized globe with corneal edema, mydriasis, and a relatively normal retina. Dogs with chronic glaucoma generally present with buphthalmia, blindness, corneal edema, and fi xed, dilated pupils in one or both eyes. Fundic examination may reveal retinal degeneration and optic disc cupping.2,12

Ophthalmic Examination The first objective of the ophthalmic examination is to determine the visual status and potential of each eye. Menace responses and direct and consensual PLRs should be assessed. If these responses are absent, dazzle reflexes should be assessed by shining a bright light into each eye in turn and monitoring for a blink response. A recent study11 demonstrated that dogs with acute glaucoma and absent menace responses, PLRs, and dazzle reflexes

BOX 1

Top Five Breeds of Dogs With a High Prevalence of Primary Glaucomaa American cocker spaniel (5.52%) Basset hound (5.44%) Chow chow (4.70%) Shar-pei (4.40%) Boston terrier (2.88%) a Gelatt KN, MacKay EO. Prevalence of the breed-related glaucomas in pure-bred dogs in North America. Vet Ophthalmol 2004;7(2):97-111.

may regain some visual function in days to weeks if aggressive medical or surgical management is pursued early in the course of the IOP elevation. Determination of IOP in both eyes involves proper restraint (avoiding neck pressure) and correct use of equipment to obtain accurate measurements.4 A recent study13 demonstrated that body position can affect IOP readings in dogs without glaucoma; therefore, it is important to keep the dog’s body position consistent during IOP measurement. There are three methods of measuring IOP: indentation, applanation, and rebound tonometry. Indentation tonometers, such as the Schiotz, indent the corneal surface and provide a measurement that can be converted for use in dogs by using the accompanying human conversion table.14 Applanation tonometers, such as the TonoPen VET (Reichert), measure IOP by ﬂattening the corneal surface and are commonly used in general practice. Rebound tonometers (e.g., TonoVet, Icare) measure IOP by projecting a small probe at the corneal surface and analyzing the characteristics of its rebound. Rebound tonometers have been shown to be as accurate and easy to use as applanation tonometers.3,15 Because IOP measurements obtained using different instruments vary,15 it is recommended that the same instrument be consistently used when monitoring a patient. TABLE 1 compares the three most commonly used tonometers. Canine glaucoma does not usually present symmetrically, and because primary glaucoma is always a bilateral disease, it is critical to thoroughly evaluate and routinely monitor the contralateral eye. Depending on the breed of dog,

QuickNotes If secondary glaucoma can be diagnosed early and managed appropriately, vision may be preserved.

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FREE CE Canine Glaucoma: Pathophysiology and Diagnosis

TABLE 1

Comparison of Available Tonometry Methods3,10,15,a

Criteria

Indentation Tonometry

Applanation Tonometry

Rebound Tonometry

Instrument

Schiotz tonometer

Tono-Pen VET

TonoVet

Average costb

~$300

$2500+

Corneal contact areac

3 mm

1 mm

Clinical considerations

Requires appropriate patient positioning and restraint

Minimal patient positioning and restraint

Readings must be converted to mm Hg using a chart

Digital display of pressures and accuracy

Requires topical anesthetic

Does not require topical anesthetic

a Leiva M, Naranjo C, Pena MT. Comparison of the rebound tonometer (ICare) to the applanation tonometer (Tonopen XL) in normotensive dogs. Vet Ophthalmol 2006;9(1):17-21. b Prices vary by supplier. c The amount of corneal exposure required may exceed this area.

QuickNotes It is important to keep the dog’s body position consistent during IOP measurement.

primary glaucoma usually manifests in middle or old age2; therefore, routine monitoring of at-risk puppies is not useful. When a dog presents with unilateral glaucoma, gonioscopy (iridocorneal angle examination) can be performed by a veterinary ophthalmologist to determine if the drainage angle is abnormal. This information helps differentiate primary and secondary glaucoma. Prophylactic medical therapy in the contralateral eye of an affected dog can signiﬁcantly prolong visual status.16 In a multicenter clinical trial,16 topical 0.5% betaxolol twice daily or topical 0.25% demecarium bromide once daily and a topical corticosteroid once daily signiﬁcantly delayed or prevented the onset of glaucoma in the second eye. Untreated control dogs developed glaucoma in the second eye earlier (median:

8 months) than eyes treated with prophylactic medication (median: approximately 31 months). Sharing this timeline with owners of dogs with primary closed-angle glaucoma helps keep the progressive nature of the disease in perspective and provides motivation to maintain compliance with the recommended prophylactic medications.

Conclusion Canine glaucoma may be congenital, primary, or secondary in origin. It is crucial to determine the underlying cause of the glaucoma, the chronicity of the condition, and the visual potential of the affected eye because these factors decide the appropriate treatment recommendations and affect prognosis. REFERENCES ON PAGE 466

3 CE CREDITS

CE TEST 1 This article qualiﬁes for 3 contact hours of continuing education credit from the Auburn University College of Veterinary Medicine. Subscribers may take individual CE tests online and get real-time scores at CompendiumVet.com. Those who wish to apply this credit to fulﬁll state relicensure requirements should consult their respective state authorities regarding the applicability of this program.

1. Canine glaucoma usually results from a. an increase in the amount of aqueous humor produced by the ciliary body. b. a disturbance in the aqueous humor outﬂow pathway. c. external pressure on the globe (tumor, cyst, abscess). d. a and b

452

2. Normal canine IOP is _______ mm Hg. a. 5 to 10 c. 15 to 30 b. 10 to 25 d. 20 to 30 3. Which statement is true with regard to congenital canine glaucoma? a. It is a common condition in certain breeds of dogs.

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Canine Glaucoma CE

b. It is usually a result of an early traumatic injury to the globe. c. It becomes clinically evident in the ﬁrst 2 to 3 years of life. d. It may be unilateral or bilateral and may be associated with other ocular anomalies. 4. Which statement is true with regard to primary canine glaucoma? a. It is a heritable condition in many breeds. b. It is the result of a malformation of the drainage angle. c. It is always a bilateral disease process. d. all of the above 5. Secondary canine glaucoma can be caused by a. lens luxation, uveitis, or intraocular neoplasia. b. conjunctivitis and blepharitis. c. cataracts and cataract surgery. d. a and c 6. A 6-year-old spayed bassett hound presents with buphthalmia, corneal edema, and a dilated pupil with no PLR. A cupped optic disc and retinal degeneration are visible on fundic examination. This dog has _______ glaucoma. a. acute c. congenital b. chronic d. none of the above 7. If a dog with elevated IOP lacks a menace response and direct and consensual PLRs, a. the prognosis for vision is grave. b. the dog must have chronic glaucoma. c. dazzle reﬂexes should be assessed. d. magnetic resonance imaging should be performed to attempt to identify intracranial disease.

The simple truth:

8. Accurate determination of IOP requires a. proper restraint and avoidance of excessive neck pressure. b. sedation or light anesthesia. c. a dark environment. d. that no topical medications be applied to the eye.

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9. Which statement regarding tonometers is true? a. The reading obtained with the Schiotz tonometer must be converted to mm Hg using the supplied conversion chart. b. Applanation tonometry and rebound tonometry require a topical anesthetic. c. The newest tonometer, the TonoVet, is the only style of tonometer that provides a digital display of the IOP. d. Rebound tonometry has been shown to be more accurate than applanation tonometry.

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10. In a case of apparently unilateral glaucoma, evaluation of the contralateral eye is crucial because a. primary glaucoma is always a bilateral disease, even though it may present asymmetrically. b. gonioscopy may help to identify an eye that is at risk for developing glaucoma. c. prophylactic medical therapy can signiﬁcantly prolong visual status in an eye at risk for developing glaucoma. d. all of the above

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CE Article 2 Author Shelby L. Reinstein, DVM, MS, with Beasley at The University of Pennsylvania. Photograph by Holly Palin

Canine Glaucoma: Medical and Surgical Treatment Options* ❯❯ Shelby L. Reinstein, DVM, MS The University of Pennsylvania

❯❯ Amy J. Rankin, DVM, MS, DACVO ❯❯ Rachel Allbaugh, DVM, MS, DACVO

Abstract: Canine glaucoma can be treated medically or surgically, depending on the underlying cause, disease stage, desired outcome, available equipment, and owner’s ﬁnancial limitations. Common medications for glaucoma include hyperosmotics, β-blockers, carbonic anhydrase inhibitors, cholinergics, and prostaglandin analogues. Surgical options include aqueous humor shunts, cyclodestructive procedures, enucleation, intrascleral prostheses, and chemical ablation. Each patient requires a customized treatment plan that generally includes a combination of medications and, potentially, surgical intervention.

Kansas State University

T At a Glance Antiglaucoma Medications Page 454

Surgery for Glaucoma Page 456

*A companion article, “Canine Glaucoma: Pathophysiology and Diagnosis,” begins on page 450.

454

via β-adrenergic blockade in the ciliary body.2 A large clinical trial in dogs demonstrated that predisposed eyes treated topically with 0.5% betaxolol twice daily as a prophylactic glaucoma therapy developed glaucoma much later than nontreated eyes.3 Timolol maleate is a nonselective β antagonist. Topical administration of timolol causes mild miosis in dogs and may increase aqueous humor outﬂow in addition to inhibiting Antiglaucoma Medications production.3,4 Medications for glaucoma either decrease Both β1-selective and nonselective β aqueous humor production or increase aque- antagonists may have undesirable carous humor outﬂow. There is no single opti- diac effects, including bradycardia, synmal therapeutic protocol for all dogs with cope, or reduced myocardial contractility. glaucoma, and many patients require mul- Additionally, blockade of β2 receptors by tiple medications. Studies of antiglaucoma nonselective β blockers could produce medications show that dogs with glaucoma adverse respiratory effects, especially in demonstrate a greater decline in IOP than patients with asthma, so timolol should not do dogs with a normal IOP.1 TABLE 1 gives be used in dogs with cardiac or pulmonary an overview of antiglaucoma medications. disease.3

he goals of glaucoma therapy are to preserve or regain vision by maintaining normal intraocular pressure (IOP) and to alleviate pain. The therapeutic plan depends on the patient’s visual status, the chronicity of the condition, and the underlying cause (primary or secondary). Congenital glaucoma is rare and cannot be treated well.

Medications to Decrease Aqueous Humor Production β Blockers Betaxolol is a selective β1 antagonist that decreases the production of aqueous humor

Carbonic Anhydrase Inhibitors Systemic and topical carbonic anhydrase inhibitors (CAIs) are available. Inhibition of carbonic anhydrase decreases aqueous humor production by reducing the syn-

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Canine Glaucoma: Treatment Options CE TABLE 1

Antiglaucoma Medications1,8,a,b

Drug

Recommended Dose or Timing

Available Preparations

Contraindications

β Blockers Betaxolol

0.25% and 0.5% solutions

Timolol maleate

0.25% and 0.5% solutions

q12h

Keratoconjunctivitis sicca, cardiac or respiratory disease

2.5–5 mg/kg q8–12h PO

Hypokalemia, metabolic acidosis

Carbonic anhydrase inhibitors Methazolamide

25- and 50-mg tablets

Brinzolamide

1% solution

Dorzolamide

2% solution

Dorzolamide–timolol maleate

2% dorzolamide and 0.5% timolol maleate

q12h

Pilocarpine

1% solution

q8–12h

Demecarium bromidec

0.125% and 0.25% solutions

q12–24h

None, but may cause irritation shortly after instillation q8h None, but may cause irritation shortly after instillation Keratoconjunctivitis sicca, cardiac or respiratory disease

Cholinergics Anterior lens luxation, uveitis Prostaglandin analogues Latanoprost

0.005% solution

Travoprost

0.004% solution

Bimatoprost

0.03% solution

q12–24h

Severe uveitis, anterior lens luxation

Cardiac or renal disease, dehydration

Hyperosmotic agents Mannitol

20% solution

1–1.5 g/kg IV slowly over 20 min

Glycerin

50% and 75% solutions

1–2 g/kg PO

a b c

Cardiac or renal disease, diabetes mellitus, dehydration

Willis AM, Diehl KA, Robbin TE. Advances in topical glaucoma therapy. Vet Ophthalmol 2002;5(1):9-17. Medications are topical ophthalmic preparations unless otherwise noted. Must be compounded.

thesis of bicarbonate in the ciliary body.1,2 The oral CAIs acetazolamide and methazolamide can have systemic adverse effects. Acetazolamide is no longer recommended due to the high incidence of such effects. Adverse effects associated with the use of methazolamide include gastrointestinal upset, metabolic acidosis, and hypokalemia.5 Topical CAIs reach adequate ciliary body concentrations and have a lower risk of systemic adverse effects. Brinzolamide signiﬁcantly reduces IOP in dogs with glaucoma.1 Dorzolamide has been shown to reduce IOP as effectively as methazolamide with many

fewer systemic effects. No additional decline in IOP is obtained from the combination of an oral CAI with a topical CAI; therefore, we recommend the use of a topical CAI for long-term management.6,7 The most common adverse effect of topical dorzolamide is transient blepharospasm after instillation.7,8 A solution of 2% dorzolamide and 0.5% timolol maleate is available. This combination therapy is as efﬁcacious in reducing IOP as concurrent use of each drug,9 but the commercially available combination improves client compliance because it requires only twice-daily administration.8,9

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FREE CE Canine Glaucoma: Treatment Options

Other Medications α2 Agonists and epinephrine have historically been used to treat glaucoma, but with recent advances in glaucoma therapy, other drugs with increased efﬁcacy and fewer potential adverse effects (β blockers, CAIs) may be more appropriate.8,10,11

Medications to Increase Aqueous Humor Outflow Cholinergic Agents

QuickNotes Many patients with glaucoma require multiple medications.

456

an effect on the conventional outﬂow pathway as well.1,13 These drugs may also cause a reduction in aqueous humor production.14 Prostaglandin analogues should be avoided in cases of glaucoma secondary to anterior lens luxation or uveitis. Latanoprost is a selective prostaglandin F2α receptor agonist that results in a dramatic decrease in IOP within 20 minutes.15 Travoprost and bimatoprost are newer prostaglandin analogues shown to be efﬁcacious in dogs.1

Parasympathomimetics are used in the treat- Hyperosmotic Agents ment of canine glaucoma except when intraocular Hyperosmotic agents reduce the production inflammation is present. Parasympathomimetics of aqueous humor by reducing plasma flow are used in long-term management of canine through the ciliary body, thereby dehydrating glaucoma and are often combined with CAIs the vitreous.5 The main indication for the use and/or β blockers to improve IOP control.1 They of hyperosmotic agents in canine glaucoma is induce contraction of the ciliary body muscu- emergency management of increased IOP. For lature and severe miosis, which subsequently maximum efficacy, water should be withheld opens the drainage angle, facilitating aqueous for 4 hours after administration. humor outflow. Parasympathomimetics are conMannitol is an osmotic diuretic that has traindicated in dogs with anterior lens luxation been shown to significantly reduce IOP within and anterior uveitis. 15 minutes of administration and can remain Pilocarpine is a direct-acting parasympa- effective for 6 to 10 hours.16 Mannitol can be thomimetic that simulates the action of acetyl- used safely in most dogs but should not be choline on the iris and ciliary body.2 Because used in dogs with cardiac or renal disease or of the nonphysiologic pH of the solution, topi- in dehydrated patients. cal administration causes irritation in most Oral glycerin causes a significant decrease dogs; therefore, this drug is not generally rec- in IOP within 30 minutes of administration ommended as a first-line therapy.1,5 and has a duration of effect of 10 hours.16 Demecarium bromide is an indirect-acting Glycerin should not be used in dogs with diaparasympathomimetic that increases the dura- betes mellitus. The most common side effect tion of the acetylcholine normally produced in of oral administration is gastrointestinal upset. the ciliary body. The main advantage of demeIn an emergency situation, we recommend carium bromide is its long duration of action. starting with a topical prostaglandin analogue. Demecarium bromide 0.25% has been shown to The IOP should be rechecked after 20 to significantly delay the onset of primary glaucoma 30 minutes. If it is still elevated, an osmotic in predisposed eyes when used in combination diuretic may be indicated. After application with a topical steroid.3 Demecarium bromide of a topical prostaglandin analogue, a topical 0.125% and 0.25% are available from compound- CAI can be administered to gain further coning pharmacies. Topical demecarium bromide trol of the IOP. If not contraindicated, a topical can reach systemic concentrations high enough β blocker can also be administered. to result in toxicosis. Although this adverse effect is uncommon, the drug should be used with Surgery for Glaucoma caution in small dogs.12 Signs of toxicosis include When medical therapy can no longer control diarrhea, salivation, and vomiting.2 the IOP, surgery may be indicated. The time for which medical therapy is effective depends Prostaglandin Analogues on the individual patient. If the IOP becomes Prostaglandin analogues are the newest topical uncontrollable or the dog is uncomfortable, glaucoma drugs used in dogs. They are thought to early referral to a veterinary ophthalmologist lower IOP primarily by increasing uveoscleral out- for surgical management is ideal. Some surgical flow of aqueous humor via their action on iris and procedures that can alleviate pain associated ciliary body musculature; however, research shows with end-stage glaucoma in nonvisual eyes

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Canine Glaucoma: Treatment Options CE can be performed by a general practitioner. As with medical therapy, surgical procedures to address glaucoma either reduce aqueous humor production or improve aqueous humor outﬂow. The procedure chosen depends on the dog’s visual status and the desired cosmetic outcome. Medical therapy is usually still necessary after procedures that preserve vision.

Surgery to Decrease Aqueous Humor Production

ECPC had controlled IOPs at 1 year and 77% retained vision at 1 year.a

Surgery to Increase Aqueous Humor Outflow Currently, gonioimplants and the Cullen frontal sinus shunt are the most commonly used shunts in veterinary ophthalmology. Gonioimplants consist of an implant and tubing that allows aqueous humor to drain from the anterior chamber into the subconjunctival space. Gonioimplants can be combined with surgical techniques to decrease aqueous humor production but usually do not suffice for sole long-term management. The Cullen frontal sinus shunt is a valved tube that is anchored into the frontal sinus and directed into the anterior chamber of the eye.21,22 Complications of shunting procedures include occlusion of the tube with fibrin, fibrosis around the implant, extrusion of the implant, and postoperative hypotony.1,22,23

Cyclodestruction, or destruction of the ciliary body, decreases the production of aqueous humor and can be performed using cryotherapy, transscleral lasers, or endoscopic cyclophotocoagulation. Cyclocryotherapy uses either liquid nitrogen or nitrous oxide applied to the sclera by a probe to cause cryonecrosis of the ciliary body. Cryotherapy can cause severe uveitis, cataracts, and retinal detachment and is therefore not generally recommended in visual eyes.1 Transscleral cyclophotocoagulation (TSCP) Salvage Procedures uses a diode or Nd:YAG laser to irradiate the Chronic end-stage glaucoma may be painful, ciliary body. Studies have shown this proce- and buphthalmic globes are predisposed to dure to be effective in controlling IOP.17,18 The exposure keratitis. Surgical options for chronimost common complications of TSCP are cally glaucomatous globes include enucleation, recurrence of glaucoma requiring a second evisceration with intrascleral prosthesis, and procedure, secondary cataract formation, and chemical ablation. ulcerative keratitis.19 This procedure may be combined with implantation of an anterior Enucleation chamber shunt (gonioimplant) for better con- Enucleation is relatively inexpensive and has trol of postoperative IOP spikes. Two studies few complications. An orbital prosthesis may be have shown the combination procedure to be placed to improve the cosmetic appearance. The successful, with up to 58% of dogs retaining main disadvantage of enucleation is the postoperative appearance of the patient. The beneﬁts vision after 1 year.18,20 One of the main disadvantages of the non- include the potential for histopathologic examiinvasive cyclodestructive techniques is the nation of the globe and immediate pain control.1 inability to see the extent of destruction of the ciliary body. Endoscopic cyclophotocoagu- Intrascleral Prosthesis lation (ECPC; endolaser) uses a diode endo- Evisceration and intraocular placement of a scopic laser to deliver energy to the ciliary silicone ball has a 95% success rate and, often, body. Most patients require phacoemulsiﬁca- very good cosmetic results. Postoperative comtion and intraocular lens implantation before plications are minimal but may include corneal the procedure to prevent cataract formation. ulcers and persistent corneal edema.1,23 Other reported complications include uncontrolled IOP, corneal ulceration, retinal detach- Chemical Ablation ment, and hyphema secondary to postoperative Pharmacologic destruction of the ciliary body hypotony. This procedure offers a high success is accomplished by injecting gentamicin and rate of IOP control and vision preservation and dexamethasone into the vitreous cavity. Commay allow a decrease in antiglaucoma medica- plications include inadequate control of IOP, tions. In a study of 106 dogs with primary and aPersonal communication, D. Bras, DVM, MS, DACVO, secondary glaucoma, 93% of dogs treated with MedVet, Worthington, OH, February 5, 2008.

QuickNotes As with medical therapy, surgical procedures to address glaucoma either reduce aqueous humor production or improve aqueous humor outﬂow.

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hyphema, uveitis, retinal detachment, cataract development, and phthisis bulbi.23

Conclusion Canine glaucoma is difficult to manage, but there are many therapeutic options. Owner expectations, visual status, and cause of the disease help dictate the appropriate treatment course. References 1. Gelatt KN, Brooks DE, Kallberg ME. The canine glaucomas. In: Gelatt KN, ed. Veterinary Ophthalmology. 4th ed. Ames, Iowa: Blackwell Publishing; 2007:753-811. 2. Bartlett J, Jaanus S. Clinical Ocular Pharmacology. 2nd ed. Stoneham, MA: Butterworth Publishers; 1989:929. 3. Miller PE, Schmidt GM, Vainisi SJ, et al. The efficacy of topical prophylactic antiglaucoma therapy in primary closed angle glaucoma in dogs: a multicenter clinical trial. JAAHA 2000;36(5):431-438. 4. Wilkie DA, Latimer CA. Effects of topical administration of timolol maleate on intraocular pressure and pupil size in dogs. Am J Vet Res 1991;52(3):432-435. 5. Derick RJ, Craig EL, Weber PA. Glaucoma therapy. In: Mauger TF, Craig EL, eds. Havener’s Ocular Pharmacology. 6th ed. St. Louis: Mosby; 1994:172-200. 6. Cawrse MA, Ward DA, Hendrix DV. Effects of topical application of a 2% solution of dorzolamide on intraocular pressure and aqueous humor flow rate in clinically normal dogs. Am J Vet Res 2001;62(6):859-863. 7. Gelatt KN, MacKay EO. Changes in intraocular pressure associated with topical dorzolamide and oral methazolamide in glaucomatous dogs. Vet Ophthalmol 2001;4(1):61-67. 8. Willis AM. Ocular hypotensive drugs. Vet Clin North Am Small Anim Pract 2004;34(3):755-776. 9. Plummer CE, MacKay EO, Gelatt KN. Comparison of the effects of topical administration of a fixed combination of dorzolamide-timolol to monotherapy with timolol or dorzolamide on IOP, pupil size, and heart rate in glaucomatous dogs. Vet Ophthalmol 2006;9(4):245-249. 10. Robin AL. Short-term effects of unilateral 1% apraclonidine therapy. Arch Ophthalmol 1988;106(7):912-915. 11. Toris CB, Tafoya ME, Camras CB, Yablonski ME. Effects of apraclonidine on aqueous humor dynamics in human eyes. Ophthalmology 1995;102(3):456-461. 12. Ward DA, Abney K, Oliver JW. The effects of topical ocular application of 0.25% demecarium bromide on serum acetylcholinesterase levels in normal dogs. Vet Ophthalmol 2003;6(1):23-25. 13. Richter M, Krauss AH-P, Woodward D, Lutjen-Drecoll E. Morphological changes in the anterior eye segment after long-term treatment with different receptor selective prostaglandin agonists and a prostamide. Invest Ophthalmol Vis Sci 2003;44(10):4419-4426. 14. Ward DA. Effects of latanoprost on aqueous humor flow rate in normal dogs. Proc 36th Annu Meet Am Coll Vet Ophthalmologists 2005:15. 15. Studer ME, Martin CL, Stiles J. Effects of 0.005% latanoprost solution on intraocular pressure in healthy dogs and cats. Am J Vet Res 2000;61(10):1220-1224. 16. Lorimer DW, Hakanson NE, Pion PD, Merideth RE. The effect of intravenous mannitol or oral glycerol on intraocular pressure in dogs. Cornell Vet 1989;79(3):249-258. 17. Nasisse MP, Davidson MG, English RV, et al. Treatment of glaucoma by use of transscleral neodymium:yttrium aluminum garnet laser cyclocoagulation in dogs. JAVMA 1990;197(3):350-354. 18. Sapienza JS, van der Woerdt A. Combined transscleral diode laser cyclophotocoagulation and Ahmed gonioimplantation in dogs with primary glaucoma: 51 cases (1996-2004). Vet Ophthalmol 2005;8(2):121-127. 19. Hardman C, Stanley RG. Diode laser transscleral cyclophotocoagulation for the treatment of primary glaucoma in 18 dogs: a retrospective study. Vet Ophthalmol 2001;4(3):209-215. 20. Bentley E, Miller PE, Murphy CJ, Schoster JV. Combined cycloablation and gonioimplantation for treatment of glaucoma in dogs: 18 cases (1992-1998). JAVMA 1999;215(10):1469-1472. 21. Cullen CL, Allen AL, Grahn BH. Anterior chamber to frontal sinus shunt for the diversion of aqueous humor: a pilot study in four normal dogs. Vet Ophthalmol 1998;1(1):31-39. 22. Cullen CL. Cullen frontal sinus valved glaucoma shunt: preliminary findings in dogs with primary glaucoma. Vet Ophthalmol 2004;7(5):311-318. 23. Cook CS. Surgery for glaucoma. Vet Clin North Am Small Anim Pract 1997; 27(5):1109-1129.

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FREE CE Canine Glaucoma: Treatment Options

3 CE CREDITS

CE TEST 2 This article qualiﬁes for 3 contact hours of continuing education credit from the Auburn University College of Veterinary

Medicine. Subscribers may take individual CE tests online and get real-time scores at CompendiumVet.com. Those who wish to apply this credit to fulﬁll state relicensure requirements should consult their respective state authorities regarding the applicability of this program. 1. The goal of therapy for canine glaucoma is to a. preserve or regain vision in the eye. b. maintain normal IOP. c. alleviate pain. d. all of the above 2. The treatment of glaucoma should aim to ______ the production and/or ________ the outﬂow of aqueous humor. a. increase; increase b. decrease; increase c. decrease; decrease d. increase; decrease 3. Which statement regarding topical β blockers is true? a. Betaxolol is a nonselective β antagonist. b. Timolol maleate is a selective β1 antagonist. c. β Blockers decrease the production of aqueous humor via β-adrenergic blockade in the cornea. d. β Blockers are contraindicated in patients with cardiac or respiratory disease. 4. Which statement regarding CAIs is true? a. Brinzolamide and dorzolamide are topical medications that reduce systemic side effects while achieving adequate ocular concentrations. b. CAIs increase the production of aqueous humor by reducing synthesis of bicarbonate in the ciliary body. c. Common side effects of oral CAIs include gastrointestinal upset, metabolic alkalosis, and hyperkalemia. d. Of the oral CAIs, acetazolamide is preferred to methazolamide because it is associated with fewer adverse effects.

5. Which statement regarding parasympathomimetics is true? a. Parasympathomimetics are contraindicated for use in patients with uveitis or anterior lens luxation. b. Parasympathomimetics lower IOP by inducing mydriasis, therefore opening the iridocorneal angle. c. Pilocarpine is generally well tolerated by most dogs. d. The main advantage of demecarium bromide is its short duration of action.

8. Surgical treatment of canine glaucoma a. should not be performed in visual eyes. b. can alleviate pain associated with end-stage glaucoma in blind eyes. c. can decrease the production or increase the outﬂow of aqueous humor, depending on the technique chosen. d. b and c

6. Which statement regarding prostaglandin analogues is true? a. They are thought to increase uveoscleral outﬂow of aqueous humor. b. They may decrease IOP by reducing the production of aqueous humor. c. They are contraindicated for use in patients with uveitis or anterior lens luxation. d. all of the above

9. Which statement regarding cyclodestructive techniques is true? a. Destruction of the ciliary body can be accomplished using cryotherapy, transscleral lasers, or endoscopic cyclophotocoagulation. b. Cyclocryotherapy has few complications and is thus considered a safe procedure for all patients with glaucoma. c. Transscleral cyclophotocoagulation may induce cataract formation. d. a and c

7. Which statement regarding hyperosmotic agents is true? a. Hyperosmotic agents reduce the formation of aqueous humor by increasing plasma ﬂow through the ciliary body. b. Hyperosmotic agents are indicated for long-term control of glaucoma. c. Mannitol decreases IOP within 15 minutes of administration, but its effect only persists for approximately 1 hour. d. Oral glycerin is contraindicated in diabetic patients.

10. Which statement regarding salvage surgical procedures for glaucoma is true? a. Enucleation is relatively inexpensive and has few complications. b. Evisceration and placement of an intrascleral prosthesis improves the cosmetic appearance. c. Complications of chemical ablation of the ciliary body include inadequate control of IOP, hyphema, uveitis, retinal detachment, cataract formation, and phthisis bulbi. d. all of the above

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US Pet Food Regulation:

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❯❯ David A. Dzanis, DVM, PhD, DACVNa Dzanis Consulting & Collaborations Santa Clarita, California

Abstract: The US Food and Drug Administration (FDA) Amendments Act of 2007 mandates promulgation of new federal regulations regarding processing, ingredient, and labeling standards for pet foods. Veterinary organizations have submitted comments to assist FDA in this matter. The Association of American Feed Control Ofﬁcials (AAFCO) is also considering changes that will affect state regulation of pet foods, including revision of the AAFCO Dog and Cat Food Nutrient Proﬁles and feeding trial protocols, an American College of Veterinary Nutrition proposal to mandate calorie content statements on all dog and cat food labels, and new Good Manufacturing Practices regulations for all animal feeds.

At a Glance US Food and Drug Administration Page 462

Association of American Feed Control Ofﬁcials Page 463

Dr. Dzanis is a consultant for the pet food and related industries on matters pertaining to nutrition, labeling, and regulation. He formerly served as the veterinary nutritionist for the US Food and Drug Administration and represented the agency on the Association of American Feed Control Ofﬁcials Pet Food Committee.

462

everal changes to the means by which do not specify rules for declaration of nutrient pet foods are regulated are forthcom- content, substantiation of nutritional adequacy, ing. Some of these changes are in reac- or other important aspects of pet food labeltion to the widely reported recall of dog and ing.1 These issues are instead addressed in the cat foods in 2007, while others were under regulations of states that have adopted the way well before the recall. In both cases, vet- Association of American Feed Control Officials erinary organizations are involved in the pro- (AAFCO) Model Bill and Regulations.2 cess. Because pet owners often consult with veterinarians on matters relating to pet food, FDA Amendments Act of 2007 it behooves practitioners to be familiar with Subsequent to a hearing regarding the 2007 recall, the US Congress passed the FDA these developments. Amendments Act of 2007 (FDAAA).3 Most of US Food and Drug Administration the FDAAA does not pertain to pet foods, but The Center for Veterinary Medicine within the what it does include with respect to pet foods US Food and Drug Administration (FDA) has is far-reaching. The responsibility is placed authority over all animal feeds in interstate on FDA to improve its abilities to detect and commerce. While this authority includes pet respond to future incidents involving pet foods (complete and balanced foods, treats, food–borne illness, including better communisupplements, and edible chews), there are no cation with both the public and industry on federal regulations stipulating requirements for the status of recalls. Establishment of a reportpet foods specifically (with minor exceptions, able food registry, wherein pet food compasuch as specifying the conditions of use for nies must promptly report incidents that may iron oxide as a coloring agent in dog and cat lead to unsafe products, is also a component of foods). For example, while FDA regulations set the FDAAA. This mandatory reporting system forth the basic labeling requirements for all ani- went into effect in September 2009.4 While the words themselves are few (BOX 1), mal feeds (e.g., statement of identity, net weight declaration, ingredient declaration, manufac- the FDAAA requirement for FDA to establish turer’s or distributor’s name and address), they specific pet food regulations, especially with

Compendium: Continuing Education for Veterinarians® | October 2009 | CompendiumVet.com

CONTRIBUTED BY THE AMERICAN COLLEGE OF VETERINARY NUTRITION About ACVN regard to nutrition and labeling, may have the biggest impact on commercial pet foods. FDA has invited public comments on this matter, and the American College of Veterinary Nutrition (ACVN), American Academy of Veterinary Nutrition (AAVN), and AVMA have all submitted recommendations. Among the many issues raised by these organizations are the need for calorie content statements, replacement of the crude ﬁber label guarantee with a more nutritionally relevant measure, and wording on therapeutic diet labels to advise veterinarians and the public that efﬁcacy claims for such products may not have been subject to regulatory scrutiny. The complete comments of these groups, as well as those of other organizations and individuals, may be viewed by visiting regulations.gov (search on “FDA-2007-N-0442” in the “Keyword” box). While the FDAAA mandates that these regulations be promulgated by September 2009, the proposed rules had not been made available for public review and comment at the time this article went to press.

Other Actions For years before the 2007 recall, FDA had been developing its Animal Feed Safety System (AFSS), a “comprehensive” and “risk-based” program designed to “identify and address gaps” in the management of risk to human and animal health from exposure to animal feeds (including pet foods).5 Components of the system include the ingredient approval process, contaminant limits, process control (i.e., Good Manufacturing Practices; GMPs), and regulatory oversight. FDA has been intimately involved in the AAFCO process for many years. In August 2007, FDA and AAFCO signed a Memorandum of Understanding with respect to the latter’s Feed Ingredient Deﬁnition procedure.2 While not the same as a formal Food Additive Petition under FDA regulations, this memorandum increases FDA oversight of the AAFCO procedures for new, amended, or deleted ingredients. FDA has also commissioned a report from the National Research Council (NRC) to help in its safety assessment of novel ingredients.6

BOX 1 EXCERPT FROM THE FDAAA AFFECTING PET FOODS3

SEC. 1002. ENSURING THE SAFETY OF PET FOOD. (a) Processing and Ingredient Standards. Not later than 2 years after the date of the enactment of this Act, the Secretary of Health and Human Services (referred to in this title as the “Secretary”), in consultation with the Association of American Feed Control Ofﬁcials and other relevant stakeholder groups, including veterinary medical associations, animal health organizations, and pet food manufacturers, shall by regulation establish (1) ingredient standards and deﬁnitions with respect to pet food; (2) processing standards for pet food; and (3) updated standards for the labeling of pet food that include nutritional and ingredient information.

Association of American Feed Control Ofﬁcials Nutritional Adequacy

Founded in 1988, the primary objective of the American College of Veterinary Nutrition (ACVN) is to advance the specialty area of veterinary nutrition and increase the competence of those who practice in this ﬁeld by establishing requirements for certiﬁcation in veterinary nutrition, encouraging continuing professional education, promoting research, and enhancing the dissemination of new knowledge of veterinary nutrition through didactic teaching and postgraduate programs. For more information, contact: American College of Veterinary Nutrition, c/o Dawn Cauthen, Administrative Assistant, School of Veterinary Medicine: Dept. of Molecular Biosciences One Shields Avenue Davis, California 95616-8741 Telephone: 530-752-1059 Fax: 530-752-4698 Email: dawncauthen@yahoo.com Web: acvn.org

The AAFCO Model Regulations for Pet Food and Specialty Pet Food establish minimum nutritional requirements for dog and cat foods labeled as “complete and balanced” or identiﬁed by similar terminology.2 Before the 1990s, one method of nutritional adequacy substantiation was based on the product meeting NRC recommendations for minimum nutrient content. However, because of problems with using the NRC recommendations (which were largely based on feeding of puriﬁed laboratory diets) as they related to the practicalities

TO LEARN MORE

Dr. Dzanis’ previous article on pet food regulation, “Regulation of Pet Foods in the United States” (July 2009), is available on CompendiumVet.com.

CompendiumVet.com | October 2009 | Compendium: Continuing Education for Veterinarians®

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of commercial pet food production, an expert At the same time, the panel instituted changes panel comprising members from academia to improve the scientific rigor of the AAFCO and the industry was convened by AAFCO to feeding trial protocols (an alternative means of address these issues.7 The result of the pan- substantiating nutritional adequacy). el’s deliberation was the AAFCO Dog and Cat Neither the profiles nor the protocols have Food Nutrient Profiles, which are still in use. been revised since 1995. In 2006, NRC pubBOX 2 ACVN PROPOSAL TO AAFCO REGARDING CALORIE CONTENT STATEMENTS ON DOG AND CAT FOOD LABELSa

QuickNotes A mandatory reporting system for incidents that may lead to unsafe pet food products went into effect in September 2009.

Regulation PF9. Statements of Calorie Content (a) Except as required in PF(10), tThe label of a dog or cat food mayshall bear a statement of calorie content when the labeland meets all of the following: (1) The statement shall be separate and distinct from the “Guaranteed Analysis” and appear under the heading “Calorie Content”; (2) The statement shall be measured in terms of metabolizable energy (ME) on an “as fed” basis and must be expressed both as “kilocalories per kilogram” (“kcal/kg”) of product, and may also be expressedas kilocalories per familiar household measure (e.g., cans, cups, poundsbiscuits); and (3) The calorie content is determined by one of the following methods: A. By calculation using the following “Modified Atwater” formula: ME (kcal/kg) = 10[(3.5 × CP) + (8.5 × CF) + (3.5 × NFE)] Where: ME = Metabolizable Energy CP = % crude protein “as fed” CF = % crude fat “as fed” NFE = % nitrogen-free extract (carbohydrate) “as fed” And the percentages of CP and CF are arithmetic averages from proximate analyses of at least four production batches of the product, and the NFE is calculated as the difference between 100 and the sum of CP, CF, and the percentages of crude fiber, moisture, and ash (determined in the same manner as CP and CF); or B. In accordance with a testing procedure established by AAFCO. (4) An affidavit shall be provided upon the request of ____, substantiating that the calorie content was determined by: A. Regulation PF9(a)(3)A in which case the summary data used in the calculation shall accompany the affidavit; or B. Regulation PF9(a)(3)B in which case the summary data used in the determination of calorie content shall accompany the affidavit. (5) The calorie content statement shall appear as one of the following: A. The claim on the label or other labeling shall be followed parenthetically by the word “calculated” when the calorie content is determined in accordance with Regulation PF9(a)(3)A; or B. The claim on the label or other labeling shall be followed parenthetically by the word “fed” when the calorie content is determined in accordance with Regulation PF9(a)(3)B, and tThe value of calorie content stated on the label which is determined in accordance with Regulation PF9(a)(3)B shall not exceed or understate the value determined in accordance with PF9(a)(3)A by more than 15%. (b) Comparative claims shall not be false, misleading, or given undue emphasis and shall be based on the same methodology for the products compared. aAs originally proposed in 2005 (some revisions have been made as deliberations continue). Proposed additions and deletions

are in underline and strikethrough, respectively.

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Compendium: Continuing Education for Veterinarians® | October 2009 | CompendiumVet.com

lished a new document on the nutrient requirements of dogs and cats, including updated scientific information as well as practical considerations pertaining to pet food production.8 Currently, AAFCO has convened a new panel of experts to review the NRC publication and update the profiles as appropriate, as well as to review and revise the feeding protocols to further their scientific soundness. Some portions of the panel’s report are expected to be released for public comment in 2010.

Calorie Content Presently, except for dog and cat food products labeled lite, low calorie, less calories, or like terms, calorie content declarations on pet food labels are voluntary. As a result, many dog and cat food labels do not contain this information, and these values are often difficult to obtain from other sources. Calorie content statements are mandatory for “lite” and similarly labeled pet foods. However, some product labels avoid these specific terms and instead use wording such as weight management formula, for less active dogs, or other, similar phrases. These alternative phrases still imply control of energy intake, but because they do not expressly refer to calories, the labels do not have to declare caloric content. In 2005, ACVN submitted a proposal to AAFCO that, among other things, would mandate calorie content statements on all dog and cat food labels, including snacks and treats (BOX 2). In light of the reported high incidence of overweight and obese pets in the United States, this is a prudent action. Knowledge of calorie content in all types of foods could help veterinarians and owners prevent excess pet weight gain, not just treat the aftermath. Beyond the issue of obesity, knowledge of calorie content for a given product is helpful when determining appropriate feeding amounts for dogs and cats at any life stage, be they growing kittens, working dogs, or lactating dams; hence, limitation of the required label statement to just the “lite” and “less calories” categories of food is insufficient. The ACVN proposal has been endorsed by AAVN, AVMA, and the American Animal Hospital Association. A statistically sound survey of practicing veterinarians found that an overwhelming proportion (97%) would like to see calorie content statements on pet food

labels.9 Despite these facts, the ACVN proposal has been vigorously opposed by segments of the pet food industry. As a result, after 4 years of debate within AAFCO, deliberations on this matter are ongoing.

Good Manufacturing Practices Historically, safety of pet foods has been monitored by regulators through inspection (including sampling for analysis) of the ﬁnished product. Under this practice, a laboratory ﬁnding of product contamination with a pathogenic organism or chemical toxin could be used as evidence of adulteration so that regulatory action could be taken. However, in

CompendiumVet.com | October 2009 | Compendium: Continuing Education for Veterinarians®

465

QuickNotes AAFCO has recently enacted new model regulations for GMPs that affect all animal feeds, including pet foods.

the past, regulatory officials have spent little violation of the GMPs could be de facto evidence effort on monitoring the processes that may that a product manufactured under these condilead to contamination. GMPs are in place for tions was adulterated, irrespective or in lieu of a canned products to help prevent safety issues negative laboratory finding of contamination. specifically related to the complicated sterilization process, as well as for medicated feeds Conclusion (feeds containing an approved drug, such as As evidenced by recent changes, steps to further an antibiotic or coccidiostat), but not for ani- ensure the safety of pet foods have become a high-priority matter for regulators. Other conmal feeds or pet foods in general. After a number of years of deliberation, cerns to be addressed in the near future may AAFCO has recently enacted new model reg- include establishment of FDA mandatory recall ulations for GMPs that affect all animal feeds, authority and increased oversight of imported including pet foods. These new rules establish products. By virtue of their expertise in the field additional requirements regarding handling of of animal health, veterinarians are in a unique materials, training of personnel, sanitation, pro- position to contribute their viewpoints as these cessing, transportation, and record keeping. A deliberations continue.

References 1. Code of Federal Regulations, Title 21, Part 501. Washington, DC: Government Printing Office; 2009. 2. AAFCO Official Publication. Oxford, IN: Association of American Feed Control Officials; 2008. 3. Food and Drug Administration Amendments Act of 2007. Accessed August 2009 at http://frwebgate.access.gpo.gov/cgi-bin/ getdoc.cgi?dbname=110_cong_public_laws&docid=f:publ085. 110.pdf. 4. US Food and Drug Administration. Reportable food registry. Accessed September 2009 at fda.gov/Food/FoodSafety/FoodSafety Programs/RFR/default.htm. 5. US Food and Drug Administration. Animal Feed Safety System.

Accessed February 2009 at http://www.fda.gov/cvm/AFSS.htm. 6. National Research Council. Safety of Dietary Supplements for Horses, Dogs and Cats. Washington, DC: National Academies Press; 2009. 7. Dzanis DA. AAFCO dog and cat food nutrient proﬁles. In: Bonagura JD, ed. Kirk’s Current Veterinary Therapy XIII. Philadelphia: WB Saunders; 2000:1228-1230. 8. National Research Council. Nutrient Requirements of Dogs and Cats. Washington, DC: National Academies Press; 2006. 9. Haberl A, Kilgos K, Bufﬁngton CAT. Comparison of owners’ and veterinarians’ perceptions, knowledge, and use of nutritional information on pet food labels. Proc 7th Annu Workshop Pet Food Labeling Regul 2001.

FREE CE Canine Glaucoma: Pathophysiology and Diagnosis

CONTINUED FROM PAGE 452

References 1. Abrams KL. Medical and surgical management of the glaucoma patient. Clin Tech Small Anim Pract 2001;16(1):71-76. 2. Gelatt KN, Brooks DE, Kallberg ME. The canine glaucomas. In: Gelatt KN, ed. Veterinary Ophthalmology. 4th ed. Ames, Iowa: Blackwell Publishing; 2007:753-811. 3. Knollinger AM, La Croix NC, Barrett PM, Miller PE. Evaluation of a rebound tonometer for measuring intraocular pressure in dogs and horses. JAVMA 2005;227(2):244-248. 4. Pauli AM, Bentley E, Diehl KA, Miller PE. Effects of the application of neck pressure by a collar or harness on intraocular pressure in dogs. JAAHA 2006;42(3):207-211. 5. Reilly CM, Morris R, Dubielzig RR. Canine goniodysgenesis-related glaucoma: a morphologic review of 100 cases looking at inﬂammation and pigment dispersion. Vet Ophthalmol 2005;8(4):253-258. 6. Gelatt KN, MacKay EO. Secondary glaucomas in the dog in North America. Vet Ophthalmol 2004;7(4):245-259. 7. Johnsen DA, Maggs DJ, Kass PH. Evaluation of risk factors for development of secondary glaucoma in dogs: 156 cases (19992004). JAVMA 2006;229(8):1270-1274. 8. Lannek EB, Miller PE. Development of glaucoma after phacoemulsiﬁcation for removal of cataracts in dogs: 22 cases (19871997). JAVMA 2001;218(1):70-76.

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9. Biros DJ, Gelatt KN, Brooks DE, et al. Development of glaucoma after cataract surgery in dogs: 220 cases (1987-1998). JAVMA 2000;216(11):1780-1786. 10. Gelatt KN. The canine glaucomas. In: Essentials of Veterinary Ophthalmology. Ames, Iowa: Blackwell Publishing; 2005:165-196. 11. Grozdanic SD, Matic M, Betts DM, et al. Recovery of canine retina and optic nerve function after acute elevation of intraocular pressure: implications for canine glaucoma treatment. Vet Ophthalmol 2007;10(suppl 1):101-107. 12. Martin CL. Evaluation of patients with decreased vision or blindness. Clin Tech Small Anim Pract 2001;16(1):62-70. 13. Broadwater JJ, Schorling JJ, Herring IP, Elvinger F. Effect of body position on intraocular pressure in dogs without glaucoma. Am J Vet Res 2008;69(4):527-530. 14. Miller PE, Pickett JP. Comparison of the human and canine Schiotz tonometry conversion tables in clinically normal dogs. JAVMA 1992;201(7):1021-1025. 15. Gorig C, Coenen RT, Stades FC, et al. Comparison of the use of new handheld tonometers and established applanation tonometers in dogs. Am J Vet Res 2006;67(1):134-144. 16. Miller PE, Schmidt GM, Vainisi SJ, et al. The efﬁcacy of topical prophylactic antiglaucoma therapy in primary closed angle glaucoma in dogs: a multicenter clinical trial. JAAHA 2000;36(5):431-438.

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3 CE CREDITS

CE Article 3

Urate Urolithiasis ❯❯ John McCue, DVM ❯❯ Cathy Langston, DVM, DACVIM (Small Animal Internal Medicine) ❯❯ Douglas Palma, DVM ❯❯ Kelly Gisselman, DVM Animal Medical Center New York

Abstract: Urate uroliths belong to the purine family of uroliths and are the third most common urolith type in dogs and cats. In dalmatians, an autosomal recessive trait is responsible for hyperuricosuria and a predisposition to urate urolithiasis. In other dog breeds and in cats, urate uroliths are predominantly associated with liver disease, speciﬁcally portosystemic vascular anomalies. Idiopathic urate uroliths may occur in animals without liver disease. Ammonium urate uroliths are most common. Urate uroliths are amenable to medical dissolution. This article reviews the pathogenesis and management of urate urolithiasis.

At a Glance Pathogenesis Page 468

Diagnosis Page 470

Treatment Page 470

Evaluating Response to Medical Therapy Page 473

Prevention Page 473

Cats Page 474

TO LEARN MORE This article is part of a series on the pathogenesis and treatment of urolithiasis. The first article, “Diagnosis of Urolithiasis” (August 2008), is available on CompendiumVet.com.

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Urate and xanthine uroliths belong to the family of naturally occurring purine uroliths. Ammonium urate, a salt of uric acid, is the most common substance in urate uroliths.1 Urate uroliths are the third most common type of urolith in dogs but account for only 5% to 8% of uroliths submitted for analysis.2,3 A genetic predisposition has been documented in dalmatians and is suspected in English bulldogs.1,3 Other breeds re ported to be overrepresented include the Yorkshire terrier, miniature schnauzer, shih tzu, and Russian black terrier.3,4 Urate uroliths are also associated with portovascular anomalies, although they can occur with any severe hepatic dysfunction.5 Similar to dogs, the prevalence of urate-containing uroliths in cats is low; however, these uroliths constitute the third most common feline urolith type submitted for analysis.6,7 Siamese cats may be predisposed.6,7 The pathogenesis in cats (with the exception of portosystemic vascular anomalies) remains unclear.8

Pathogenesis Ingested protein and endogenous protein turnover are sources of purines, which are metabolized to hypoxanthine. Through the action of xanthine oxidase, hypoxanthine is converted to xanthine and uric acid (FIGURE 1). In most mammals, uric acid is converted to allantoin by the action of hepatic uricase, and only scant amounts of uric acid are excreted in urine.1 Allantoin is very soluble compared with uric acid.1 Uric acid excreted in the urine may complex with various cations (e.g., ammonium, sodium) to form urate salts. Ammonium is exceptional in its ability to precipitate uric acid in the form of ammonium urate9 (FIGURE 2). As urine becomes supersaturated with urate salts, urate uroliths may form. Whether uric acid complexes with other substances to form a less soluble salt depends on several factors. Hyperuricosuria is one factor implicated in the development of urate urolithiasis. Other factors include increased renal excretion or microbial urease production of ammo-

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Urate Urolithiasis CE nium ions, aciduria, and the presence of promoters (e.g., cellular debris, crystals) or lack of inhibitors (e.g., urinary glycoproteins) of urolith formation.1

FIGURE 1

Dalmatians It is hypothesized that despite adequate concentrations of hepatic uricase, dalmatians have a defect in transmembrane transport of uric acid in hepatocytes and renal tubular cells.10 Early studies have shown that the hepatic membrane transport defect plays a significant role in hyperuricosuria in this breed.10 As a result, these dogs have a higher serum concentration of uric acid, and filtered uric acid is poorly reabsorbed in the renal tubules.10 Although dalmatians exhibit relative hyperuricosuria, not all form uroliths.1 Urate urolith– forming dalmatians have been shown to excrete higher levels of uric acid in their urine; however, the pathogenesis in urolith-forming dogs is multifactorial.1,6,9–11 Approximately 92% to 97% of the urate uroliths from dalmatians that are submitted for analysis are from male dogs11,12 (FIGURE 2). The estimated prevalence of urate urolithiasis in male dalmatians ranges from 27% to 34%.13 Differences in anatomy, genetic factors, and urine composition are thought to account for the disparity in incidence between male and female dalmatians. In general, the urethra of female dogs is shorter and wider than that of males, which may allow small stones to be voided before detectable clinical signs develop. In one large, retrospective analysis of breed-related data for stone formation,14 male dalmatians were shown, in general, to have a significantly increased risk of urolith formation compared with females. Differences in the relative levels of inhibitors or promoters of calculogenesis may also exist between the sexes.15 An autosomal recessive mode of inheritance controlled by a single autosomal gene pair (CFA03) was recently demonstrated for hyperuricosuria in dalmatians.16 However, it is not yet clear that this genetic marker will help breeders in identifying urolith-forming dogs.16

Other Breeds In non-dalmatian breeds, most uric acid is metabolized in the liver to allantoin. The small amount of uric acid that is ﬁltered at the glomeruli is largely reabsorbed by the proximal

QuickNotes Dalmatians and English bulldogs have a genetic predisposition to urate urolithiasis.

Purine metabolic pathway.

tubules, and trace amounts are excreted in the urine. Relatively little is known about naturally occurring urate urolithiasis in non-dalmatian breeds of dogs.17 Among these, English bulldogs have the highest incidence.3,18 Mildly elevated serum uric acid levels have been documented in English bulldogs with urate urolithiasis and normal hepatic function.1

Hepatic Dysfunction Hepatic insufficiency and portovascular anomalies can predispose dogs and cats to urate urolithiasis by reducing hepatic conversion of uric acid to allantoin and of ammonia to urea. Urate urolithiasis is a common finding in patients with portovascular anomalies, but it is infrequently associated with hepatic insufficiency due to other causes.5

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FIGURE 2

with urate urolithiasis. The chemical composition of a removed urolith can be confirmed by submission to a reference laboratory for quantitative analysis. Quantitative analysis can provide definitive information about mineral composition and guide therapy. Reference laboratories should be contacted for specific sample handling and submission instructions. In addition to urinalysis, urine should be submitted for culture to rule out concurrent infection as a complicating factor in management.

Imaging

QuickNotes Male dalmatians are overrepresented for clinical disease.

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Approximately 97% of urate uroliths are found Cystic urate uroliths removed from a in the bladder or urethra, with only 3% found 7-year-old castrated dalmatian. Inset: in the kidneys or ureters.3 The stones are radioPhotomicrograph (400× magnification) of lucent, usually small (range: <1 mm to 1.5 cm), ammonium urate crystals in urine sediand round or ovoid. These characteristics lead ment. Note the characteristic brown-gold of to a 20% false-negative detection rate with ammonium urate crystals in sediment. These crystals are commonly described as having a survey radiography.19 Larger stones and those “thorn-apple” appearance (black arrow). mixed with other components (particularly secondary infection–induced struvite) may be more visible. Double-contrast cystography Diagnosis is the best method for determining the size, Clinical Signs shape, and number of stones. This technique Clinical signs are usually referable to the level has a detection rate of 78% for stones >1.0 of the urinary tract affected and are indistin- mm and allows urethral calculi to be visualguishable from those of other lower urinary ized.20 Ultrasonography may be used to visutract disease. Signs consistent with hepatic alize urate uroliths in the bladder or kidney. encephalopathy or liver failure may be noted Ureteroliths often require excretory urography if urate stones are a consequence of hepatic for detection.1,19 dysfunction.1,5 The average age at which urate urolithiasis is detected in dalmatians is 4.5 Treatment Diet years (range: <1 to 16 years).14 Urate uroliths are often amenable to dissolution Laboratory Evaluation through a combination of dietary modification, The results of a complete blood count and urine alkalization, and control of secondserum biochemical profile are usually nor- ary infections (FIGURE 3). Protein (particularly mal. Azotemia, metabolic acidosis, and purine) restriction is the foundation of medical hyperkalemia are common in cases of management. Currently, two veterinary diets obstructive uropathy. Changes compatible are marketed for this purpose in dogs. These with concurrent liver dysfunction may be diets are formulated to maintain alkaline urine. present. Alkaline phosphatase and alanine Protein restriction indirectly alters renal medulaminotransferase activities may be normal lary tonicity by lowering blood urea nitrogen or increased and albumin and glucose lev- (BUN) content, which limits concentrating abilels may be decreased. Increased fasting and ity. Feeding a canned diet or adding water to postprandial bile acid levels and/or increased dry formulations further increases urine volume. plasma ammonia concentrations are concur- Diets severely restricted in protein content are rent findings in animals with portovascular contraindicated in growing or lactating animals. anomalies.5 Urinalysis may reveal urate crys- Recipes for homemade diets and modifications talluria. This finding should be considered of commercially available formulas have been abnormal in cats and non-dalmatian dogs1,17; published, but their effectiveness has not been however, urate crystalluria is not synonymous established.1,21

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Urate Urolithiasis CE FIGURE 3

Treatment algorithm for canine urate urolithiasis. CompendiumVet.com | October 2009 | Compendium: Continuing Education for VeterinariansÂŽ

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QuickNotes Urate uroliths are amenable to medical dissolution.

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Urine Alkalinization Adverse effects noted in people include skin Urine pH is an important modifier of urate sol- rash, gastrointestinal disturbances, thromboubility. The optimum target range for urine pH cytopenia, vasculitis, and hepatitis with other is 7.0 to 7.5.1,8–10,19 Urine pH values >7.5 may pre- immune-mediated reactions. Many of these dispose dogs to the formation of calcium phos- reactions were noted in people with existing phate uroliths.1,19 Additional agents are used renal dysfunction.26 There is only one report when optimal urine pH is not achieved with of potential immune-mediated hemolytic anediet alone (FIGURE 3). Potassium citrate (initial mia and trigeminal neuropathy in a dog.26 dose: 40 to 90 mg/kg PO q12h) is the preferred Allopurinol should be used only in conjuncagent. Deposition of calcium phosphate over tion with a protein-restricted diet. Excessive existing uroliths may complicate dissolution. purine precursors in the diet may predispose Xanthine oxidase inhibitors are used to patients to xanthinuria and the formation of decrease uric acid production. Allopurinol, a xanthine uroliths.27 If xanthine urolithiasis synthetic isomer of hypoxanthine, is a potent occurs, allopurinol should be discontinued for inhibitor of xanthine oxidase22 that inhibits the 1 to 2 months while dietary therapy and urine conversion of hypoxanthine to xanthine and alkalinization is continued to allow the uroof xanthine to uric acid. Its biotransformation liths to dissolve. Xanthine exhibits solubility takes place primarily in the liver.22 Allopurinol characteristics similar to those of urate in alkais poorly bound to plasma proteins and is line urine. Following resolution of xanthine excreted primarily by the kidneys; therefore, urolithiasis, allopurinol can be reintroduced it should be used cautiously in animals with with a 25% reduction in dose. hepatic or renal dysfunction. Its half-life in In patients with cystic uroliths that are dogs is approximately 2.5 hours. The bioavail- smaller in diameter than the distended urethra, ability of allopurinol is not affected by food. voiding urohydropulsion or catheter-assisted The initial dose of allopurinol is 15 mg/kg retrieval may be used to retrieve remaining PO bid for 4 weeks, at which time, the size, uroliths and monitor therapy1 (FIGURE 3). shape, and number of calculi should be reevaluated. The level of uric acid excretion in the Infection Control urine may be used to guide dose adjustments Any existing urinary tract infection should be after the first month. Measurement of urinary eliminated. Infections are generally considered uric acid excretion over 24 hours (target level: to be secondary to urolith-induced trauma or to <300 mg urate/24 hr) gives the most accurate catheterization or other invasive procedures.28 value; however, it is difficult to obtain a complete 24-hour urine collection.23 Single urinary Nonmedical Management uric acid:creatinine ratios can be used to doc- If medical dissolution is not pursued, surgical and nonsurgical options are available. Surgery ument a decrease in uric acid excretion.24 On average, urate cystoliths dissolve over is the most definitive method of treatment.1 3.5 months (range: 1 to 18 months) when a Surgical attenuation is recommended for defincombination of diet, pH modification, and itive treatment of identified cystic calculi.5 In xanthine oxidase inhibition is used.1 In male patients with portosystemic shunts, correction dogs, dissolving cystoliths may move into the of the shunt may result in spontaneous dissourethra and cause clinical signs of obstruction. lution of urate uroliths if hepatic perfusion is Retrograde urohydropropulsion can be used reestablished. If shunt correction is contraindito relieve obstructions.21 cated, dietary management is recommended.5 Allopurinol should not be used in patients Voiding urohydropulsion has been described with portosystemic shunts.5 Decreased hepatic as a means of obtaining stones for analysis and metabolism may result in a prolonged half-life for removing cystic uroliths, when appropriand adverse effects, including augmented xan- ate.19 Retrograde urohydropulsion can be used thine oxidase inhibition that causes xanthine to temporarily relieve any urethral obstruction urolithiasis. Allopurinol is also an inhibitor while a patient is stabilized for surgery.19,a of the hepatic microsomal P450 system and a Voiding and retrograde urohydropulsion, along should be used judiciously with other drugs with other methods of removing uroliths, will be that depend on biotransformation in the liver.25 described in a future article in this series.

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Urate Urolithiasis CE Lithotripsy is a recent addition to the list of management options for urinary calculi in dogs and cats. Shock wave lithotripsy and laser lithotripsy techniques have been described.29–31 Although extracorporeal shock wave lithotripsy (ESWL) is useful in managing nephroliths and ureteroliths, its use for urate uroliths is poorly described, perhaps partly because these uroliths occur infrequently in the upper urinary tract.29 Successful resolution was achieved in two of ﬁve dogs with purine uroliths of the upper urinary tract using ESWL.30 ESWL is not currently recommended for treatment of cystic uroliths in dogs and cats. Laser lithotripsy has been evaluated for the treatment of ureteral, cystic, and urethral uroliths. Laser lithotripsy has become more widely available and may be more practical than ESWL for veterinary patients. When a holmium:YAG laser is used to fragment uroliths, stone composition does not have a signiﬁcant effect on fragmentation time.29 Laser fragmentation of urate uroliths can result in uric acid conversion to cyanide.31 The risk of clinical toxicity is considered to be very low, and laser lithotripsy has been used for urate uroliths without complications.30 As more experience is gained with laser lithotripsy and this procedure becomes more widely available at referral institutions, it may replace other therapies for cystic urate urolithiasis.

Evaluating Response to Medical Therapy Periodic evaluation is necessary to assess owner compliance and the rate of urolith dissolution. After the initial enumeration and measurement of uroliths, patients should be reevaluated monthly until uroliths are no longer present. Double-contrast cystography or ultrasonography is usually necessary. Urine pH, speciﬁc gravity, and sediment analysis should be evaluated along with BUN to determine the success of medical therapy. If uroliths fail to decrease in size, or if they increase in size during the initial 8 weeks of therapy, the diagnosis should be reevaluated or an alternative management option pursued.1

Prevention The foundation of preventive therapy is increased water consumption and dietary modiﬁcation (TABLE 1). The aforementioned prescription diets are appropriate for long-term

TABLE 1

Summary of Urate Prevention Strategies

Intervention

Comments

Goals

Diet

Foundation of all prevention strategies; may be useful as sole therapy

Restricted purine content Alkalinized urine Increased water consumption

Allopurinol

Use as needed for refractory cases

Alkalinized urine

Monitoring

Recheck urinalysis and BUN every 4–8 weeks

Urine pH 7.0–7.5 Urine speciﬁc gravity <1.020 No urate crystals BUN <10 mg/dL

If no recurrence for 2–4 months, recheck every 6 months If uroliths recur, refer to Figure 3

BOX 1

Purine Content of Common Foodsa High content: foods to avoid Organ meats Fish (salmon, tuna, Shellﬁsh mackerel, sardines) Moderate content: moderate use Other ﬁsh Legumes Spinach Peas Muscle meats Mushrooms Negligible Breads Cheese Fruits Milk

Fats Eggs Carbohydrates Nuts

aNot an all-inclusive list.

feeding. Feeding of an exclusively canned diet is recommended. Use of ultralow-protein diets has been associated with dilated cardiomyopathy in English bulldogs and a few dalmatians.32,33 Taurine and/or carnitine deﬁciency may underlie the development of dilated cardiomyopathy in predisposed dogs.32 Oral taurine supplementation has not been deﬁnitively shown to affect outcome.33 It has been suggested that English bulldogs be fed a low-protein renal diet instead of an ultralow-

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protein diet, with allopurinol administered as needed.34 Allopurinol may be continued as maintenance therapy in cases of recurrent urate urolithiasis. Because of the risk of xanthine uroliths with long-term administration, regular monitoring is important.1 Despite general hyperuricosuria in dalmatians, prescription diets may not be indicated in all patients and should be used on an individual basis.1,8,11,19 Because of the low risk of clinical urate urolithiasis, the rationale for prophylaxis in female dalmatians has been questioned.11 The general recommendation is to limit protein sources that are high in purines in this breed19 (BOX 1). It is suggested that protein consumption be limited to <20% protein on a dry matter basis.1 Given the relatively late onset of clinical signs and multiple factors involved, breeding selection against this trait is difﬁcult.

ciated with diets high in purine precursors.8 Surgery remains the treatment of choice in cats, as medical dissolution protocols have not been developed for this species. Additional studies of the efﬁcacy and safety of allopurinol in cats are needed. Successful dissolution has been noted only anecdotally. Any concurrent infections should be treated based on culture and sensitivity testing. Prevention is similar to that in dogs and is centered on feeding a low-protein diet, limited in purine precursors, that promotes formation of moderately dilute urine of neutral pH.14 There is no feline equivalent of the canine prescription diets; however, prescription feline diets for the management of renal disease have been used with success. Many of these diets are formulated with potassium citrate. Prevention of recurrence was noted to be >90% with one such diet.34 The addition of supplemental potassium citrate can be used to achieve an appropriate urine pH.

Cats

QuickNotes Urate uroliths are radiolucent on survey radiographs.

Urate uroliths are the third most common urolith type in cats, accounting for approximately 6% to 9% of feline uroliths submitted for analysis.6,7 Unlike struvite and calcium oxalate uroliths, the incidence of urate uroliths seems to have remained stable over the past 2 decades. In cats, urate uroliths are found almost exclusively in the bladder, and males and females are equally affected.7 With the exception of portovascular anomalies, the pathogenesis of urate uroliths in cats is unknown. Screening for occult hepatopathy is recommended in all cats with urate-containing uroliths.8,34 Suggested risk factors in cats include the formation of highly acidic, highly concentrated urine asso-

Conclusion Urate and xanthine uroliths are generally uncommon, except in dalmatians. Ultrasonography and double-contrast cystography are the best imaging techniques for diagnosing these radiopaque calculi. The presence of urate uroliths or crystalluria in a breed that is not predisposed should prompt evaluation for a portosystemic shunt. Urate uroliths are generally small and may be removed by dissolution, nonsurgical, or surgical techniques. Purine- and protein-restricted diets that alkalinize the urine are recommended for dissolution, as well as for prevention in male dalmatians. Allopurinol is used in some cases to aid dissolution and prevention.

References 1. Bartges JW, Osborne CA, Lulich JP, et al. Canine urate urolithiasis: etiopathogenesis, diagnosis, and management. Vet Clin North Am Small Anim Pract 1999;29(1):161-191. 2. Osborne CA, Lulich JP, Polzin DJ, et al. Analysis of 77,000 canine uroliths. Perspectives from the Minnesota Urolith Center. Vet Clin North Am Small Anim Pract 1999;29:17-38. 3. Houston DM, Moore AE, Favrin MG, et al. Canine urolithiasis: a look at over 16,000 urolith submissions to the Canadian Veterinary Urolith Centre from February 1998 to April 2003. Can Vet J 2004;45(3):225-230. 4. Bende B, Nemeth T. High prevalence of urate urolithiasis in the Russian black terrier. Vet Rec 2004;155(8):239-240. 5. Bartges JW, Cornelius LM, Osborne CA. Ammonium urate uroliths in dogs with portosystemic shunts. In: Bonagura JD, ed. Kirk’s Current Veterinary Therapy XIII. Philadelphia: WB Saunders; 2000:872. 6. Houston DM, Moore AEP, Favrin MG, et al. Feline urethral plugs and bladder uroliths: a review of 5484 submissions (1998–2003).

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Can Vet J 2003;44:974-977. 7. Cannon AB, Westropp JL, Ruby AL, et al. Evaluation of trends in urolith composition in cats: 5,230 cases (1985-2004). JAVMA 2007;231:570-576. 8. Osborne CA. Diseases of the lower urinary tract. In: Finco DR, Osborne CA, eds. Canine and Feline Urology and Nephrology. Baltimore: Lippincott Williams and Wilkins; 1995:822-833. 9. Sorenson JL, Ling GV. Diagnosis, prevention, and treatment of urate urolithiasis in dalmatians. JAVMA 1993;203(6):863-869. 10. Sorenson JL, Ling GV. Metabolic and genetic aspects of urate urolithiasis in dalmatians. JAVMA 1993;203(6):857-862. 11. Albasan H, Lulich JP, Osborne CA, et al. Evaluation of the association between sex and risk of forming urate uroliths in dalmatians. JAVMA 2005;227(4):565-569. 12. Ling GV, Franti CE, Ruby AL, et al. Urolithiasis in dogs I: mineral prevalence and interrelations of mineral composition, age, and sex. Am J Vet Res 1998;59:624-629.

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Urate Urolithiasis CE 13. Bannasch DL, Ling GV, Bea J, et al. Inheritance of urinary calculi in the dalmatian. J Vet Intern Med 2004;18:483-487. 14. Ling GV, Franti CE, Ruby Al, et al. Urolithiasis in dogs II: breed prevalence and interrelations of breed, sex, age, and mineral composition. Am J Vet Res 1998;59(5):630-642. 15. Carvalho M, Lulich JP, Osborne CA, Nakagawa Y. Role of urinary inhibitors of crystallization in uric acid nephrolithiasis: dalmatian dog model. Urology 2003;62(3):566-570. 16. Safra N, Schaible RH, Bannasch DL. Linkage analysis with an interbreed backcross maps dalmatian hyperuricosuria to CFA03. Mamm Genome 2006;17(4):340-345. 17. Kruger JM, Osborne CA. Etiopathogenesis of uric acid and ammonium urate uroliths in non-dalmatian dogs. Vet Clin North Am Small Anim Pract 1986;16:87-126. 18. Bartges JW, Osborne CA, Lulich JP, et al. Prevalence of cysteine and urate uroliths in bulldogs and urate uroliths in dalmatians. JAVMA 1994;204(12):1914-1918. 19. Adams LG, Syme HM. Canine lower urinary tract diseases. In: Ettinger SJ, Feldman E, eds. Textbook of Veterinary Internal Medicine. Philadelphia: WB Saunders; 2006:1850-1874. 20. Weichselbaum RC, Feeney DA, Jessen CR, et al. Urocytolith detection: comparison of survey, contrast radiographic and ultrasonographic techniques in an in vitro bladder phantom. Vet Radiol Ultrasound 1999;40(4):386-400. 21. Osborne CA, Bartges JW, Lulich JP, et al. Canine urolithiasis. In: Hand MS, Thatcher CD, Remillard RL, et al, eds. Small Animal Clinical Nutrition. 4th ed. Topeka: Mark Morris Institute; 2000:605-688. 22. Hande K, Reed E, Chabner B. Allopurinol kinetics. Clin Pharmacol Ther 1978;23(3):598-605. 23. Bartges JW, Osborne CA, Felice CJ, et al. Reliability of single

urine and serum samples for estimation of 24-hour urinary uric acid excretion in six healthy beagles. Am J Vet Res 1994;55:472-476. 24. Moentk JA, Dibartola SP, Bufﬁngton CA. Effect of allopurinol on urine urate-to-creatinine rations in normal dalmatians. JAAHA 1994;30:483-486. 25. Vessell ES, Passananti GT, Greene FE. Impairment of drug metabolism in man by allopurinol and nortriptyline. New Engl J Med 1970;313:1484-1499. 26. Pedroia V. Allopurinol-induced immune disorders. Canine Pract 1980;8:19-22. 27. Bartges JW. Canine xanthine uroliths: risk factor management. In: Kirk RW, Bonagura JD, eds. Kirk’s Current Veterinary Therapy IX. Philadelphia: WB Saunders; 1992:900-905. 28. Lees GE. Bacterial urinary tract infections. Vet Clin North Am Small Anim Pract 1996;26:297-304. 29. Davidson EB, Ritchey JW, Higbee RD, et al. Laser lithotripsy for treatment of canine uroliths. Vet Surg 2004;33:56-61. 30. Adams LG. Lithotripsy using shockwaves and lasers. Proc 24th Annu ACVIM Forum 2006:439-441. 31. Teichman JM, Vassar GJ, Glickman RD, et al. Holmium:YAG lithotripsy: photothermal mechanism converts uric acid calculi to cyanide. J Urol 1998;160:320-324. 32. Freeman LM, Mitchel KE, Brown DJ, et al. Idiopathic dilated cardiomyopathy in dalmatians: nine cases (1990-1995). JAVMA 1996;209(9):1592-1596. 33. Freeman LM, Rush JE, Brown DJ, et al. Relationship between circulating and dietary taurine concentrations in dogs with dilated cardiomyopathy. Vet Ther 2001;2(4):370-378. 34. Bartges J, Kirk C. Nutrition and urolithiasis. Proc 25th Annu ACVIM Forum 2007:13-15.

3 CE CREDITS

CE TEST 3 This article qualiﬁes for 3 contact hours of continuing education credit from the Auburn University College of Veterinary

4. The target urine pH for prevention of urate crystallization is a. <6.5. c. 7.0–7.5. b. 6.6–7.0. d. >7.5. 5. A predisposition for formation of urate uroliths is suspected in _______ cats. a. Siamese b. Persian c. Himalayan d. Abyssinian 6. What percentage of urate uroliths are found in the upper urinary tract? a. 3% c. 8% b. 5% d. 20% 7. Which parameter is not useful when evaluating response to medical therapy for urate urolithiasis? a. serum BUN b. urine sediment c. survey radiographs d. urine pH

8. The detection rate of urate urocystoliths using double-contrast cystography is _______ for stones >1.0 mm. a. 65% c. 85% b. 78% d. 100% 9. _______ is a recognized side effect of allopurinol therapy in dogs. a. Pyoderma b. Liver failure c. Xanthine urolithiasis d. Thrombocytopenia 10. Use of ultralow-protein diets formulated for prevention of urate urolithiasis is implicated in the development of _______ in predisposed English bulldogs. a. dilated cardiomyopathy b. liver failure c. renal disease d. xanthine urolithiasis

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In collaboration with the American College of Veterinary Surgeons

Endoscopic Removal of Urinary Calculi ❯❯ Clarence A. Rawlings, DVM, PhD, DACVSa The University of Georgia

At a Glance Patient and Technique Selection Page 476

Preoperative Patient Management Page 477

Transurethral Cystoscopy Page 478

Laparoscopic-Assisted Cystoscopy Page 479

Intraoperative Nephroscopy and Cystoscopy Page 482

Other Minimally Invasive Techniques Page 484

Postoperative Patient Management Page 484

aDr. Rawlings discloses that he

has received ﬁnancial support from Biovision, Covidien, Ellman International, Endoscopic Support Services, and Karl Storz Veterinary Endoscopy.

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espite advances in the prevention 7-kg female dog can usually accommodate and management of urinary cal- a 2.7-mm cystoscope with a 14.5-Fr sheath. culi, calculus removal remains a These dimensions should allow a calcucommon need in small animal practice. In lus 6 to 7 mm in diameter to be removed fact, changes in calculus management have through the urethra. In male dogs, tranincreased the percentage of calculi that are surethral removal is limited to much smaller difﬁcult to manage medically.1 Endoscopic calculi because the stones must traverse the techniques that reduce the need for calcu- os penis region of the urethra. Calculi in lus removal by traditional laparotomy and male cats can be removed by laparoscopiccystotomy have been developed. In my assisted cystoscopy, but the urethra is too experience, most cystic and urethral cal- small for current transurethral cystoscopy culi can be removed by transurethral or techniques. The ability to endoscopically laparoscopic-assisted cystoscopy. These remove cystic and urethral calculi has techniques decrease trauma to and urine largely replaced the need for hydropulsion contamination of the abdomen. Endoscopy in female dogs. also improves the ability to examine the Transurethral cystoscopic calculus removal urinary system for disease and the pres- in female dogs has been enhanced in some ence of more calculi. specialty hospitals by cystoscopic lithotripsy.3–11 As with basket removal of calculi Patient and Technique Selection from the lower urinary tract, lithotripsy can Nearly all calculi in female dogs and cats be more widely used in female dogs than can be removed by either transurethral male dogs. Cystic lithotripsy is indicated cystoscopy or laparoscopic-assisted cystos- for calculi that are too large to be removed copy, in my experience. Most male dogs cystoscopically with baskets. The current can be treated with laparoscopic-assisted contraindications to lithotripsy are large cystoscopy.2 Transurethral cystoscopy is calculi and high numbers of calculi in relapreferred for female cats and dogs because tion to the operator’s expertise. Trauma and it is less invasive than laparoscopic-assisted time required to fragment and remove large techniques; however, calculi must be small or multiple calculi can be excessive during enough to be pulled through the urethra if inappropriate lithotripsy. transurethral cystoscopy is to be successful. Laparoscopic-assisted cystoscopy through Size criteria are continually being modi- one or two small abdominal incisions has ﬁed, but I have found that in female cats proven to be an effective and relatively simple and dogs, calculi can be removed that are way to remove calculi from female and male twice the diameter of the largest cystoscope dogs and cats.2–12 The primary contraindicaappropriate for the patient. For example, a tion is the presence of stones several centi-

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meters in diameter that require removal through y a long abdominal incision. Although cystoscopy can still be used to examine the urinary sys-tem after removal of larger calculi, the longer incision might as well be for a traditional lapa-y rotomy and cystotomy. The presence of a very large number of smaller calculi can discourage some endoscopists, but the use of lavage and suction permits removal of larger numbers off stones during laparoscopic-assisted cystoscopy. In the hospitals in which I practice, tradi-tional laparotomy and cystotomy are usuallyy reserved for patients with very large calculi or those requiring other complex abdominal pro-cedures, such as nephrectomy. However, some additional procedures are better performed during laparoscopy than by laparotomy. An example would be a liver biopsy, for which lap-aroscopy is minimally invasive and can be used to obtain multiple tissue samples from selected sites as well as a bile sample for culture. Some subspecialists successfully remove calculi from the ureters and bladder using advanced endourologic techniques.2–11 These techniques are widely performed in people; in the veterinary setting, they have been most commonly applied in larger female dogs. Lithotripsy and endoscopic removal of calculi from the kidneys and ureters are typically referral procedures, in contrast to the endoscopic techniques for transurethral and laparoscopic-assisted cystoscopic procedures, which have been performed by general practitioners trained in endoscopy.

Surgical Views is a collaborative series between the American College of Veterinary Surgeons (ACVS) and Compendium. Upcoming topics in this series include vacuumassisted wound closure, conventional foreign object removal, and suspensory ligament rupture. All Surgical Views articles are peer-reviewed by ACVS diplomates. To locate a diplomate, ACVS has an online directory that includes practice setting, species emphasis, and research interests (acvs.org/VeterinaryProfessionals/FindaSurgeon).

ing techniques are commonly used, but urinary contrast procedures seem to be less frequently employed. Ultrasonography by an experienced ultrasonographer is particularly useful for monitoring dogs with recurrent calculi, especially when the calculi are small. If present, prerenal and postrenal azotemia or uremia should be addressed before calculus removal in all but the most urgent cases of obstruction. Conﬁrmed renal dysfunction may require modiﬁcation of the plan for calculus removal. In patients with a preexisting urinary FIGURE 1

Courtesy of Chris Herron

Preoperative Patient Management Patient evaluation is directed toward determining renal function, the presence of urinary tract infection, systemic organ function, and the number, size, and distribution of calculi. Tests include a complete blood count, serum chemistry proﬁle, urinalysis, and urine culture. Abdominal radiography is indicated to determine the size, number, and distribution of radiopaque calculi. Radiopaque calculi are composed of struvite, silica, and calcium oxalate; more radiolucent calculi contain urate, uric acid, and cystine. Abdominal ultrasonography is preferred to radiography for detecting radiolucent calculi and helps obtain more information about renal structure and function. Both imag-

Calculus removal from the urethra, bladder, proximal ureter, and renal pelvis frequently involves a 2.7- or 1.9-mm cystoscope with a basket retrieval instrument. The basket retrieval instrument is passed through the cystoscope’s operating channel, and the basket is kept inside the channel until a stone is visualized through the scope. To capture the stone, the basket is advanced through the end of the channel. Once around the calculus, the basket is tightened.

CompendiumVet.com | October 2009 | Compendium: Continuing Education for Veterinarians®

477

FIGURE 2

Radiograph showing a urethral calculus (circle). Urine culture results at the time of radiography had no bacterial growth. Using radiography and ultrasonography, the dimensions of the calculi were measured to determine whether transurethral cystoscopy could be used to remove them. The dog weighed 10 kg, and the largest calculus appeared to be 5 mm in diameter.

TO LEARN MORE

tract infection, culture and antibiotic administration should be attempted before emergency relief of urinary obstruction. In patients with recurrent urinary tract infections, collection of a bladder mucosal sample for culture should be considered during calculus removal. Regardless of the protocol used to control urine contamination of the abdomen, the risk of contamination dictates the use of antibiotics during cystoscopy and laparoscopicassisted cystoscopy.

For descriptions of other laparoscopic techniques, see “Laparoscopic-Assisted and Laparoscopic Prophylactic Gastropexy: Indications and Techniques” (February 2009) and “Techniques for Laparoscopic and Laparoscopic-Assisted Biopsy of Abdominal Organs” (April 2009), available on CompendiumVet.com.

478

Endoscopic view of the larger calculus at the outflow tract, just before being snared with the basket retrieval device.

Transurethral Cystoscopy Calculus removal using a stone basket is less invasive than and preferred to cystotomy during laparotomy or laparoscopic-assisted cystoscopy if the calculi are small enough for removal via the urethra. The clinician must be a competent and experienced cystoscopist to attempt calculus removal using a basket retrieval instrument. In general, basket removal can be attempted for calculi <3 mm in diameter in female cats and male dogs. In female dogs, calculi removed

The removed calculi were 6 mm in diameter. Despite attempts to medically prevent recurrence, clinical signs developed, and more calculi were diagnosed using ultrasonography and removed by cystoscopy.

Courtesy of Clarence A. Rawlings, DVM, PhD, DACVS

Transurethral cystoscopy in a 6-year-old spayed schnauzer. The patient had a 3-week history of repeated straining to void and inappropriate voiding inside the house. The dog had previously had a cystotomy to remove calcium oxalate calculi.

using this method should be no more than twice the diameter of the largest cystoscope that can be placed in the urethra. Commonly used cystoscope sizes are 1.9 mm for female cats and dogs weighing <5 kg, 2.7 mm for female dogs between 5 and 15 kg, and 3.5 or 4.0 mm for larger female dogs (FIGURE 1). The two smaller cystoscope sizes can be used to retrieve calculi in nearly all female dogs. A 1.9-mm cystoscope and a basket retrieval instrument have been used to remove calculi during cystoscopic examination of the urethra and bladder of male cats after perineal urethrostomy. It is not uncommon during transurethral cystoscopic calculus removal to find lesions that may be related to recurrent urinary tract infections. These include strictures, transitional cell carcinoma, inflammatory polyps, and persisting cystotomy closure sutures. Basket retrieval devices with three or four wires are preferred (FIGURE 1). They should easily fit through the operating channel of the cystoscope. After diagnostic cystoscopy is used to examine the lower urinary tract and flush the bladder, the basket is passed through the

Compendium: Continuing Education for Veterinarians® | October 2009 | CompendiumVet.com

Laparoscopic-Assisted Cystoscopy Cystoscopy via minilaparotomy was initially reported as laparoscopic-assisted cystoscopy.2 Laparoscopic assistance requires a laparoscope and two trocars, in contrast to the more recently reported technique of percutaneous cystolithotomy, also called keyhole transvesicular cystourethroscopy.12 Both laparoscopic-assisted and

FIGURE 3

Courtesy of Chris Herron

operating channel (FIGURE 2). Individual techniques vary, but I prefer to have the bladder only mildly distended and to keep the lavage flow rate low. This practice concentrates the calculi and reduces the swirling effect that can be produced by higher flow rates. Having the patient in dorsal recumbency and tilted with the head up can also move the calculi toward the outflow tract. External abdominal manipulation of the bladder can be helpful. The basket is opened in the area of the calculi and gradually closed during cystoscopic examination. Some clinicians prefer to tighten the wires very securely around the stones. I often use less force to cradle the calculi during extraction. The basket distention helps to gradually dilate the urethra during extraction and reduces the likelihood of calculus fragmentation due to basket compression. This procedure is repeated until all the calculi are removed. Vigorous flushing may be used to remove the smallest calculi. Leaving the cystoscope sheath in the urethra with the cranial end in the outflow tract while squeezing on the bladder can provide a conduit for small calculi to be flushed from the bladder. Laser lithotripsy uses a holmium:YAG laser as well as a cystoscope. Some urologists routinely perform laser lithotripsy of calculi in the bladder, ureters, and kidneys. Patient selection is critical because the time for fracture and extraction can be excessive for large or multiple calculi. Candidates for laser lithotripsy are patients that do not meet the criteria for other forms of endoscopic calculi removal. In general, laser lithotripsy appears to require a longer time for removal of calculi while resulting in a similar percentage of retained calculi as traditional cystotomy.10,11 Clinical studies of minilaparotomy cystotomy have fewer patients, but this technique appears to ensure a very favorable percentage of calculi removal.2,12

The basic scopes used to diagnose and remove calculi are the 2.7-mm rigid cystoscope (top) and the 2.5/2.8-mm flexible fiberoptic urethroscope (bottom). Cats and dogs weighing <5 kg frequently require a 1.9-mm cystoscope. The flexible scope is usually reserved for use in male dogs.

transvesicular cystoscopy require the use of a rigid cystoscope to examine the bladder and urethra and to remove calculi. A 2.7-mm cystoscope is generally used, except in cats and small dogs, for which a 1.9-mm cystoscope is preferred. After calculi are removed from the bladder and outflow tract, the urethra is examined with a rigid cystoscope (female dogs) or a 2.5/2.8-mm flexible fiberoptic urethroscope (male dogs; FIGURE 3). Urethral calculi in male dogs are removed by either retrograde flushing or a basket retrieval device passed beside the urethroscope during laparoscopic-assisted cystoscopy. Urethrostomy is rarely required to remove calculi obstructing the urethra just caudal to the os penis. Laparoscopic-assisted cystoscopy has been combined with other laparoscopic procedures such as liver biopsy or laparoscopic-assisted gastrointestinal foreign body removal. In laparoscopic-assisted cystoscopy, the laparoscope trocar is placed on the midline just caudal to the umbilicus to enable identification of the apex of the moderately distended urinary bladder. A second trocar, through which a 5-mm Babcock forceps can be passed to grasp the apex of the bladder, is then placed (FIGURE 4). The second trocar site is on the midline for female dogs, cats, and some male dogs, depending on the position of the prepuce in relationship to the

QuickNotes Endoscopy improves the ability to examine the urinary system for disease and the presence of more calculi.

CompendiumVet.com | October 2009 | Compendium: Continuing Education for Veterinarians®

479

FIGURE 4 Laparoscopic-assisted cystotomy technique.

QuickNotes Setup for laparoscopic-assisted cystotomy. The monitor is to the rear of the patient. A right-handed surgeon stands to the patient’s left (top of illustration). The urinary bladder is mildly distended.

The bladder is secured to the patient, and a minicystotomy is made. A rigid cystoscope and retrieval devices are passed through the minicystotomy.

Calculi can be quickly grasped by placing a retrieval forceps alongside the cystoscope. Basket retrieval devices can also be used.

The cranial margin of the bladder is grasped and lifted to an extended trocar incision site. Insufflation pressure is decreased when the bladder is lifted.

Calculi can be removed with a variety of instruments, depending on the size and number of stones.

apex of the bladder. In most male dogs, the sec- just sufficient to secure it to the abdominal wall. ond trocar site is placed laterally (e.g., on the A variety of techniques can be used to keep the left side for a right-handed surgeon). The apex bladder firmly secured to the abdominal wall of the bladder is grasped with the forceps and and prevent urine contamination of the perilifted to the trocar site, which is extended as toneal cavity. In the most common technique, a minilaparotomy (FIGURE 4). If any bladder four quadrate attachments with interrupted lumen is cranial to the trocar site, inspection cruciate sutures are placed, and their long tags and removal of calculi from the cranial pouch are secured to drapes. Some surgeons prefer to of the bladder becomes difficult. The bladder is place a temporary continuous suture between not exteriorized, with the minilaparotomy being the bladder and skin.

480

Compendium: Continuing Education for Veterinarians® | October 2009 | CompendiumVet.com

FIGURE 5 Equipment for intraoperative nephroscopy to remove renal calculi.

Intraoperative nephroscopy using a basket retrieval device can be an effective alternative, especially for calculi lodged in the proximal area of the ureter.

Once the bladder is securely sealed to the abdominal wall, a small cystotomy is performed and a rigid cystoscope (1.9 mm for cats and small dogs and 2.7 mm for larger dogs; FIGURE 4) is placed into the bladder. The bladder is lavaged in a fashion similar to that for transurethral cystoscopy. Some clinicians prefer to have a urethral catheter as an additional infusion source. The bladder and entire urethra of female dogs and the prostatic urethra of males are examined with the rigid cystoscope. Calculi can be removed with a variety of instruments, depending on the size and number of stones. Alligator forceps, 5-mm Babcock forceps, and arthroscopic grasping forceps are passed parallel to the cystoscope to grasp and retrieve calculi (FIGURE 4). Another removal technique is to use a wire basket retrieval instrument passed through the operating channel of the cystoscope. The entire assembly of cystoscope and forceps or basket retrieval device is removed with each stone and replaced into the bladder to retrieve the next. Once the larger calculi are removed, some

Intraoperative nephroscopy to remove renal calculi is similar to arthroscopy. A grasping device, such as an alligator forceps, is passed beside the cystoscope. Practice with inanimate models can markedly improve calculus retrieval skills.

smaller ones can be flushed from the bladder using urethral catheter flushing and surgical suction. The cystoscope is then advanced through the urethra in female dogs and cats. A 2.5- to 2.8mm flexible urethroscope can be passed from the bladder to the os penis in most male dogs and through the os penis in male dogs larger than 12 to 15 kg. Only the cranial portion of the urethra is examined in male cats. It is common to watch a urethral catheter pass around irregularly shaped calculi without feeling resistance to the catheter’s passage. In my experience, urethral strictures just proximal to the os penis from prior calculi obstruction and trauma are common in dogs. Knowledge of such strictures can justify a scrotal urethrostomy. After calculus removal and flushing, the cystotomy is closed in a single layer, using an appositional suture pattern, avoiding the mucosa. Greater omentum is sutured to the bladder closure. Keyhole transvesicular cystourethroscopy is performed in a similar fashion except that laparoscopy is not used and the apex of the

QuickNotes Practice with inanimate models can markedly improve calculus retrieval skills.

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481

FIGURE 6

Radiograph showing the renal calculi (arrows). These calculi were diagnosed 6 months before cystotomy to remove them.

QuickNotes Urinary calculi often recur.

One of the calculi is examined during nephroscopy.

bladder is grasped with surgical instruments passed through a small laparotomy.12 Again, it is critical that the cranial portion of the bladder be selected to avoid having bladder cranial to the cystotomy site. The remainder of the procedure is similar. Both laparoscopic-assisted and transvesicular cystoscopy techniques have been reported as being effective in the hands of the technique developers.2,12 Both allow the same excellent examination of the lower urinary tract, limit bladder trauma, limit urine contamination of the abdomen, and should increase the likelihood of complete removal of calculi.

Intraoperative Nephroscopy and Cystoscopy Rigid endoscopy during an open laparotomy causes minimal insult to the urinary system from the renal pelvis to the urethra,13 improves lighting, and increases magniﬁcation much more effectively than magnifying loupes and diode head lights. The optical space within the lumen of the renal pelvis and ureters is obtained as for cystoscopy, using saline infusion. The most frequent intraoperative use of endoscopy is to examine the renal pelvis and recesses when removing renoliths.13 The approach is similar to arthroscopy, with a scope being placed through a puncture in the greater curvature (lateral margin) of the kidney. Penetration of the pelvis is easy when the pelvis

482

The removed calculi. Recovery was uncomplicated.

Courtesy of Dr. Rawlings

Removal of renal calculi from a 12-year-old castrated Maltese.

is dilated. Calculi have been removed by using an alligator forceps placed beside a 30° scope or through a separate puncture to achieve triangulation or by using a basket retrieval device placed through the operating channel of the cystoscope (FIGURES 5 AND 6). Unlike nephrotomy, this minimally invasive retrieval of renal calculi using a scope placed through the renal pelvis does not require transient occlusion of renal vessels. The scope can also be passed through the proximal part of the ureter. When removing calculi endoscopically, the renal recesses must be thoroughly examined to ensure complete stone removal. The kidney perforations are closed by ﬁrmly apposing their sides or by placing small sutures in the capsule across the perforation. The scope can be used to differentiate between intraluminal calculi and mural calciﬁcation. I have also used an arthroscope to examine dilated ureters when removing ureteral calculi or performing a neocystostomy or ureterotomy. Cystoscopes and ureteroscopes have also been used to examine the lumen of the bladder and urethra during traditional laparotomy. Calculus removal via laparotomy in these cases usually involves major procedures such as nephrectomy or removal of stones from the kidney or ureter, which are not amenable to less invasive techniques. The cystoscope can be passed through a minicystotomy before a

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cystotomy is performed, for example, to determine the precise area before resection of an inﬂammatory polyp.14

Other Minimally Invasive Techniques Calculus removal treatments for dogs and cats are gradually being adapted from those used for people. Laser and electrohydraulic lithotripsy are already being used for cystic calculi in dogs and cats.3–11 Laser lithotripsy and ureteral stenting during ureteroscopy are routinely used for ureteral calculi in people; however, size is a limiting factor in small animals, especially cats and small dogs. In people, renal calculi are removed by percutaneous nephrolithotomy, ureterolithotomy, and cystolithotomy, typically involving lithotripsy, basketing, and flushing. Finally, extracorporeal shock wave lithotripsy is an alternative to reduce calculus size so that urine flow can flush the fragments.13,15

Postoperative Patient Management Case management must be directed to the patient’s needs. At least one lateral radiograph should be taken after calculus removal while the patient is anesthetized to ensure that residual radiopaque

calculi are not present. Appropriate fluid management helps maintain renal function and flush residual blood and calculi fragments. Although laparoscopic procedures are less invasive than traditional surgery, pain medication is routinely used. Typical protocols include administering opioids during the initial recovery period and either NSAIDs or opioids for the first few days after calculus removal. Bupivacaine can be infused into the urethra for additional transient analgesia. Dietary management to reduce calculus formation is usually delayed until the patient is fully recovered and the final calculi analysis obtained. Nutritional therapy soon after surgery should focus on supporting early healing. Urinary calculi often recur. Patients with a history of calculus removal must be closely monitored by the owner and veterinarian. Those with a history of urinary tract infection must have regular urinalysis and, if indicated, urine cultures. When feasible, dietary management should be considered. Dogs and cats in which calculi recur despite good medical management are candidates for ultrasonography studies every 4 to 6 months. Radiography can also be considered for radiopaque calculi.

References 1. Ling GV, Thurmond MC, Choi YK, et al. Changes in proportion of canine urinary calculi composed of calcium oxalate or struvite in specimens analyzed from 1981 through 2001. J Vet Intern Med 2003;17:817-823. 2. Rawlings CA, Barsanti JA, Mahaffey MB, Canalis C. Use of laparoscopic-assisted cystoscopy for removal of calculi in dogs. JAVMA 2003;222:759-761. 3. Senior DF. Electrohydraulic shock-wave lithotripsy for experimental canine struvite bladder stone disease. Vet Surg 1988;22:213-219. 4. Adams LG, Senior DF. Electrohydraulic and extracorporeal shock-wave lithotripsy. Vet Clin North America Small Anim Pract 1999;29:293-302. 5. Lane IF. Lithotripsy: an update on urologic applications in small animals. Vet Clin North Am Small Anim Pract 2004;34(4):1011-1025. 6. Davidson EB, Ritchey JW, Higbee RD, et al. Laser lithotripsy for treatment of canine uroliths. Vet Surg 2004;33:56-61. 7. Grant DC, Were SR, Gevedon ML. Holmium:YAG laser lithotripsy for urolithiasis in dogs. J Vet Intern Med 2008;22(3):534-539. 8. Adams L, Berent A, Moore A, Bagley D. Laser lithotripsy for the removal of uroliths in 73 dogs. JAVMA 2008;232(7):1026-1034.

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9. Defarges A, Dunn M. Use of electrohydraulic lithotripsy in 28 dogs with bladder and urethral calculi. J Vet Intern Med 2008;22(6):1267-1273. 10. Bevan JM, Lulich JP, Albasan H, Osborne CA. Comparison of laser lithotripsy and cystotomy for the management of dogs with urolithiasis. JAVMA 2009;234:1286-1294. 11. Lulich JP, Osborne CA, Albasan H, et al. Efficacy and safety of laser lithotripsy in fragmentation of urocystoliths and urethroliths for removal in dogs. JAVMA 2009;234:1279-1285. 12. Runge JJ, Mayhew P, Berent A, et al. Keyhole transvesicular cystourethroscopy for the retrieval of cystic and urethral calculi in dogs and cats. 43rd Annu Meet Am Coll Vet Surg 2008. 13. McCarthy TC. Otheroscopies. In: McCarthy TC, ed. Veterinary Endoscopy for the Small Animal Practitioner. St Louis: Elsevier Saunders; 2005:423-445. 14. Rawlings CA. Resection of inflammatory polyps in dogs using laparoscopic-assisted cystoscopy. JAAHA 2007;43:1-5. 15. Block G, Adams LG, Widmer WR, et al. Use of extracorporeal shock wave lithotripsy for treatment of nephrolithiasis and ureterolithiasis in five dogs. JAVMA 1996;208(4):531.

Compendium: Continuing Education for Veterinarians® | October 2009

1. Title of Publication: Compendium: Continuing Education For Veterinarians, 2. Publication Number: 1940-8307, 3. Date of Filing: October 1, 2009, 4. Frequency of Issue: Monthly, 5. Number of Issues Published Annually: 12, 6. Annual Subscription Price: $79, 7. Complete Mailing Address of Known Ofﬁce of Publication: Veterinary Learning Systems, 780 Township Line Road, Yardley, Bucks County, PA 19067, Contact Person: Christine Polcino, Telephone: 267-685-2419, 8. Complete Mailing Address of Headquarters or General Business Ofﬁce of the Publisher: Veterinary Learning Systems, 780 Township Line Road, Yardley, PA 19067, 9. Full Names and Complete Mailing Addresses of Publisher, Editor, and Managing Editor—Publisher: Derrick Kraemer, Veterinary Learning Systems, 780 Township Line Road, Yardley, PA 19067; Editor: Tracey Giannouris, 780 Township Line Road, Yardley, PA 19067; Managing Editor: Kirk McKay, 780 Township Line Road, Yardley, PA 19067, 10. Owner: Veterinary Learning Systems/MediMedia USA, 780 Township Line Road, Yardley, PA 19067, 11. Known Bondholders, Mortgagees, and Other Security Holders Owning or Holding 1 Percent or More of Total Amount of Bonds, Mortgages or Other Securities: None, 12. Tax Status – Has Not Changed During Preceding 12 Months, 13. Publication Title – Compendium: Continuing Education For Veterinarians, 14. Issue Date for Circulation Data Below: July 2009, 15. Extent and Nature of Circulation—15a.Total Number of Copies (Net Press Run) - Average Number Copies Each Issue During Preceding 12 Months: 53,957, Actual Number Copies of Single Issue Published Nearest to Filing Date: 50,631, 15b(1) Mailed Outside-County Paid Subscriptions Stated on PS Form 3541 - Average Number Copies Each Issue During Preceding 12 Months: 5,631, Actual Number Copies of Single Issue Published Nearest to Filing Date: 4,785, 15b(3). Paid Distribution Outside the Mail Including Sales Through Dealers and Carriers, Street Vendors, Counter Sales, and other Paid Distribution Outside USPS - Average No. Copies Each Issue During Preceding 12 Months: 0, Actual No. Copies of Single Issue Published Nearest to Filing Date: 0, 15c. Total Paid Distribution - Average No. Copies Each Issue During Preceding 12 Months: 5,631, Actual No. Copies of Single Issue Published Nearest to Filing Date: 4,785, 15d(1). Free or Nominal Rate Outside-County Copies Included on PS Form 3541 - Average No. Copies Each Issue During Preceding 12 Months: 45,646, Actual No. Copies of Single Issue Published Nearest to Filing Date: 43,935, 15d(4). Free or Nominal Rate Distribution Outside the Mail - Average No. Copies Each Issue During Preceding 12 Months: 0, Actual No. Copies of Single Issue Published Nearest To Filing Date: 0, 15e. Total Free or Nominal Rate Distribution - Average No. Copies Each Issue During Preceding 12 Months: 45,646, Actual No. Copies of Single Issue Published Nearest to Filing Date: 43,935, 15f. Total Distribution - Average No. Copies Each Issue During Preceding 12 Months: 51,277, Actual No. Copies of Single Issue Published Nearest to Filing Date: 48,720, 15g. Copies not Distributed - Average No. Copies Each Issue During Preceding 12 Months: 2,680, Actual No. Copies of Single Issue Published Nearest to Filing Date: 1,911, 15h. Total - Average No. Copies Each Issue During Preceding 12 Months: 53,957, Actual No. Copies of Single Issue Published Nearest to Filing Date: 50,631, 15i. Percent Paid - Average No. Copies Each Issue During Preceding 12 Months: 11%, Actual No. Copies of Single Issue Published Nearest to Filing Date: 10%, 16. This Statement of Ownership will be printed in the October 2009 issue of this publication. 17. I certify that the statements made by me above are correct and complete: Derrick Kraemer, Publisher.

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VCA Antech

Hospital Purchase Program

Inside front cover (US only)

Veterinary Learning Systems

Veterinary Technician

483

Vetstreet

Pet Portals

458, 459

Western Veterinary Conference

2010 Conference

Back cover

WhereTechsConnect.com

Job Marketplace

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CompendiumVet.com | October 2009 | Compendium: Continuing Education for Veterinarians®

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CLASSIFIED C MARKET L A SSSSI F I ED SHOWCASE ADVERTISING ADV E R T ISI NG

CLASSIFIEDS CONTINUING VETERINARIANS MEDICALWANTED EDUCATION

Mid-South Regional Conference November 13, 14, 15, 2009 Harrah’s Casino and Convention Center (formerly the Grand Casino and Convention Center) Tunica, Mississippi.

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For advertising information call Susan Deakins 1-800-237-9851, ext. 258 or Email: comp@rja-ads.com Publisher’s Disclaimer: Advertising appearing in this issue does not necessarily reflect the opinions of nor constitute or imply endorsement or recommendation by the Publisher. The Publisher is not responsible for any statements or data made by the Advertiser.

CLASSIFIEDS VETERINARIANS WANTED

VETERINARIANS WANTED

NORTH CAROLINA – Well-established, 24-hour, AAHA-accredited small animal hospital in central North Carolina needs an emergency/critical care veterinarian and an associate veterinarian. Located only hours from the mountains and coastlines, our busy, progressive, and expanding five-doctor practice is fully equipped and staffed by 25 highly motivated veterinarians, technicians, and lay staff. Established more than 27 years, our hospital has an excellent client base and strong emphasis on quality care. Work in a great practice environment with an excellent opportunity for career development. Competitive salary and benefits include 401(k), profit sharing, CE, and insurance. Experience preferred. Send resume to Dr. Karl B. Milliren, 303 National Highway, Thomasville, NC 27360; email tvh303@cs.com; fax 336-475-0140.

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TEXAS Associate Veterinarian Full-time position for enthusiastic individual with excellent work ethic. Busy small animal clinic located in thriving West Texas has full diagnostic and surgical capabilities, including ultrasound, endoscopy, and neurosurgery. All interested applicants welcome. Call 432-332-5782

Compendium: Continuing Education for Veterinarians® | October 2009 | CompendiumVet.com

RELIEF VETERINARY SERVICES Log in at VetRelief.com Relief veterinarians: search for work dates, view job details, then bid. Hospitals: post your job openings; no charge until you hire. Contact: www.vetrelief.com info@vetrelief.com • 949-234-1960

CLIENT HANDOUT

What You Should Know About

Feeding Your Pet: How Much Is Too Much? As every loving pet owner knows, it’s hard to resist a furry face begging for a special treat. We look into those big brown eyes, hear that hopeful purr, and feel that the best way to reward all that devotion is by giving our favorite dog or cat something tasty to eat. In reality, though, this is often the worst way to repay our pet’s affection. When treats make up too much of a pet’s diet (≥10%), the nutritional balance of an otherwise healthy diet can be upset. Too many treats can also lead to obesity, which increases the risk for other serious health problems, including osteoarthritis, diabetes (in cats), heart and respiratory diseases, and many types of cancers. Overweight pets are also at increased risk for complications during anesthesia if they need to undergo surgery or other procedures. And if a pet already has a health condition, obesity makes the problem that much harder to manage. Despite these concerns, however, pet obesity has become something of an epidemic in the United States. Studies indicate that nearly 50% of adult dogs and cats in the United States are overweight or obese, and this percentage increases among older pets.a Finally, apart from contributing to potentially dangerous health conditions, obesity can affect your pet’s overall comfort and quality of life. Being overweight can lower your pet’s energy level and hamper his or her ability to enjoy an active lifestyle with you and your family. a

Association for Pet Obesity Prevention. 2008 National Pet Obesity Awareness Day Study. Accessed September 2009 at petobesity prevention.com.

What Causes Obesity? Simply put, obesity results when an animal eats more calories than it burns off during normal activities or exercise. Factors that can contribute to obesity include: Overfeeding or overeating Inactivity or low activity levels Breed Age Sex Reproductive status (intact versus spayed/neutered) Preexisting diseases (e.g., hypothyroidism, diabetes mellitus, Cushing’s disease) Weight problems also frequently result from inactivity. This is why it is vitally important to follow your veterinarian’s advice on what particular diet to choose and how much and how often to feed your pet. Pay close attention to the labels of the pet foods that you buy. For example, an adult pet shouldn’t be fed a diet formulated for puppy or kitten

Managing the Battle of the Bulge Feed a well-balanced, veterinarian-approved diet. If necessary, feed a calorie-restricted diet. When you treat your pet, give healthy treats. Make sure your pet gets plenty of regular age- and health-appropriate exercise. Don’t allow your pet to have unrestricted access to food—its own or another pet’s! Make sure all family members are on the same page when it comes to feeding—and treating—your pet.

Produced in association with Vetstreet. A customizable, downloadable version of this client handout is also available at CompendiumVet.com.

10/09

CLIENT HANDOUT

Feeding Your Pet growth periods. If your pet has a weight problem, there are many good-quality adult maintenance and weight control diets to choose from, and your veterinarian can advise you on which best meets your pet’s needs. Weight problems also frequently result from inactivity, so it is essential to give your pet plenty of opportunities for regular exercise that is appropriate for his or her age and health status. A vigorous daily walk— provided your veterinarian approves—is an excellent place to start for many canine companions. And while most cats typically won’t tolerate leash walking, regular play periods with fun toys, such as a laser pointer or tossed ball, can provide satisfactory activity levels and help maintain their health. It is also important to realize that certain breeds, especially smaller ones, are more prone to being overweight or obese, as are many senior pets. In extreme old age, however, the situation is often reversed, and weight loss can be the problem.

How Do I Know If My Pet Is Obese? No matter whether your pet is a dog or a cat, and regardless of what size or breed it is, you should be able to feel its ribs. Many owners mistakenly think that the ability to feel ribs means their pet is too thin. In reality, being able to feel some ribs is a sign that your pet is at a healthy weight. Additionally, when you look down at your pet’s back, you should be able to see a distinct “waist” where the body narrows, just behind the rib cage and in front of the hindquarters. When viewed from the

A Caution for Cats Never begin a weight loss program for your cat without ﬁrst consulting your veterinarian. Cats are prone to a disease called feline hepatic lipidosis (fatty liver), in which the liver accumulates a large amount of fat and cannot function properly. It is a serious disease that can be fatal. Greatly restricting a cat’s diet or changing the diet to one that an obese cat will not eat can lead to the development of this disease.

Did you know that a single dog biscuit can contribute as much as an extra 100 calories per day to a dog’s diet? side, your pet’s abdomen should appear to be slightly tucked up behind the rib cage. If your pet has fat deposits over its back and at the base of its tail, or if it lacks a waist or an abdominal tuck, chances are that it has a weight problem. Veterinarians typically use a measurement called a body condition scale, or body condition score, to assess whether a pet is underweight, overweight, or just right (healthy). Your veterinarian can use this scale to show you the proper way to assess your pet’s weight.

Overcoming Obesity Despite the fact that obesity is generally due to a very simple problem—too much food!— it can be frustratingly difficult to solve. You need to enlist your veterinarian’s help. First, your veterinarian will give your pet a thorough physical examination and ask you for a complete nutritional history. The more specific your answers are, the better your veterinarian will understand how to approach your pet’s weight problem. To track how much your pet eats, it may be helpful for your family to keep a “food diary.” Everyone in the family should write down how much he or she feeds the pet, every time the pet is fed. Treats count! You may be surprised to learn that the daily “treat or two” you think your pet is getting is really four, five, or six. Also be sure to keep track of any tidbits you give during training sessions or when encouraging a pet to take medication, such as hiding a pill in a piece of cheese. Weight loss is difficult, and it can take a long time, but following your veterinarian’s recommendations regarding special diets, portion control, treat modification, and any prescribed exercise programs will help make your pet’s weight loss program a healthy success. Be sure to keep any recommended follow-up appointments so that your veterinarian can track your pet’s progress and adjust any recommendations.

Produced in association with Vetstreet. A customizable, downloadable version of this client handout is also available at CompendiumVet.com.

10/09

We believe you re too good to be micromanaged. We believe in providing more resources, not taking them away. We believe a econd opinion, or third, or fourth, can make yours even stronger. We believe in getting out of the way and letting doctors be octors. We believe you own your career. We believe you went to vet school for a very furry reason. We believe people need eterinarians as much as Pets do. We believe you’re better at your job when you’ve had some time away from it. We believe in iving you the tools you need to do your job. We believe no matter how good you are, you can always get better. We believe t xcellent doctors make excellent colleagues. We believe mentors can learn as much as mentees. We believe in saving the lives f Pets and improving the lives of vets. We believe that you should be focused on your patient, not your paperwork. We belie hat flexible hours make for refreshed doctors. We believe cats aren’t the only animals that purr. 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If your passion is

VETERINARY MEDICINE, count on our 82 years Head for WVC to build the skills that build practices

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82nd Annual Western Veterinary Conference Questions: call 702-739-6698 toll-free 866-800-7326

Mandalay Bay Resort and Casino | Las Vegas | February 14-18, 2010

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