Diagnosis and Management of Colic in the field setting

MVMA 2023 Diagnosis and management of colic in the field setting Alison LaCarrubba, DVM, ABVP (Equine Practice), Associate Teaching Professor

A majority of our after-hours emergency calls involve colic. We know that colic, by definition is abdominal pain associated with the gastro-intestinal system. There are other types of pain associated with the abdomen that can be confused with colic. It is important to do a complete and thorough examination on every colic suspect to determine the cause of pain in order to embark on the correct treatment plan. The vast majority of colic can be managed in the field. Statistically, approximately 80% of horses with colic will resolve with medical therapy. The most common causes of medical colic include spasmodic colic, gas colic and impaction colic. We need to ask ourselves if this colic is medical or surgical? Does the patient have a surgical option? Is this a large colon problem or small intestinal problem? Do we think the colic is caused by colitis? The answers to these questions will inform our treatment plan. What are the common clinical signs of colic? Owners will frequently report, inappetence, standing alone, pawing at the ground, flank watching, phlegmon response, kicking at abdomen, getting up and down, sweating, anxiety, distressed appearance, down horse. When examining the horse it is important to rule out other major issues that can result in these similar clinical signs. Horses with fever will often be in-appetent and depressed. It is important to not skip any steps during the examination and to obtain a temperature on all horses when it is safe to do so. Other conditions that may result in distress include esophageal obstruction (choke), urinary obstruction/urethral stone, pneumonia and even dystocia. A down horse can sometimes be difficult to assess and common causes of the down horse include colic, neurological disease, laminitis, and catastrophic musculoskeletal issues, such as a limb fracture.

In order to make an accurate diagnosis a thorough exam will be conducted. This will start with a distance examination which includes behavior – what is the horse doing? What is the body condition? Is the animal emaciated and perhaps this is not something that just started or does the horse appear to be in good flesh and look healthy otherwise? Does the horse have a normal respiratory rate and effort? These are all things that are important and can be assessed before laying hands on the animal. After a distance examination is conducted a thorough physical examination will be next. The importance of a complete and thorough physical examination cannot be overstated! The horse should have a halter and lead rope on and be properly restrained, ideally by a veterinary assistant. Mucus membranes will be assessed for color, moisture and capillary refill time. Information gained from evaluation of mucus membranes is incredibly valuable to understanding the systemic health of the animal. By evaluating the mucus membranes we can begin to rule in or out, shock, endotoxemia, dehydration and determine how severe the immediate situation is. Vital parameters will be important in understanding the severity of the colic as well. Along with this we will evaluate for heart disease, such as an arrhythmia or murmur as well as a thorough auscultation of the lung fields. The abdomen will then be auscultated to evaluate borborygmi - absence or reduction of normal gastrointestinal sounds, increased GI sounds or even sounds that are fluidic and consistent with colitis, which can certainly be a cause of severe colic. During the examination the hair coat will be evaluated, body will be palpated to ascertain accurate BCS and the demeanor of the animal will be assessed.

Once the physical examination is complete, we will continue to hone in the exact cause of the colic and for this we will need to employ further, more invasive diagnostics. Nasogastric intubation is often the best place to start. In some cases this can be done without sedation, but if the horse is anxious or difficult, an alpha-two agonist can be helpful to provide sedation and analgesia. Dosage will vary depending on the patient and severity of the colic. Alpha-two agonists have a significant impact on the cardiovascular system and in a severely compromised patient, this should be avoided, as a significant change in heart rate and blood pressure could compromised the patient. Along these lines, once it has been determined the horse is in fact experiencing a painful colic episode, it is important to administer a non-steroidal anti-inflammatory such as flunixin meglumine to provide comfort. This is best given intravenous and will take approximately 20 minutes to take effect. During this time, if the horse is sedated with an alpha-two agonist, such as xylazine, the sedative effects can help to control the pain until the anti-inflammatory kicks in. Flunixin meglumine is the better choice for visceral pain over phenylbutazone. Buscopan (Hyoscine butylbromide) is an anticholinergic medication used to treat crampy abdominal pain, and esophageal spasms during a choke episode and can be a valuable tool during a spasmodic colic episode. Butorphanol is an opioid partial agonist and will provide short acting but substantial pain relief when administered. For those colics whose pain is difficult to manage butorphanol can be an important tool.

The pain the animal is experiencing may involve gastric dilitiation and passing the nasogastric tube early in the process will alleviate pain associated with gastric distention. The goals of passing the tube include gastric decompression, reflux evaluation – present or not and how severe, as well as providing treatment using the administration of cathartics as needed. The tube can be passed, then left in place until further diagnostics are complete, then medications administered as warranted via the tube. If there is no abnormal reflux and medical colic is suspected, the tube can be used to pass water and electrolytes, magnesium sulfate, or less commonly currently, mineral oil. Evidence points to the positive effects or oral electrolyte/water administration in relief of medical colic. An average 1000 –1200lb horses stomach can hold approximately 6-10 liters. Anything more than 2 liters of net reflux would be considered abnormal and no additional fluid should be added. Treating impaction colic with fluid administration directly into the gastrointestinal tract is recommended. When evaluating reflux it is also important to examine the color, texture and odor.

Examination per rectum can provide important and relevant information. It is important to be safe in order to be effective in this situation. Ideally the horse will be placed in stocks for trans rectal palpation. If this is not possible sedation with an alpha-two agonist and a twitch, situationally dependent, maybe necessary. Safety first for the veterinarian and the horse! Trans rectal examination can provide information on the exact cause of the colic and this can be valuable for further treatment or referral options. Further diagnostics will be dependent on owner finances, and what is available to the practitioner in a field setting. Abdominal ultrasound is a valuable tool to better discern the exact cause of the colic. This is a more thorough way to examine and evaluate the abdomen than rectal palpation alone. Other important diagnostics that will give us information on the health of the gastrointestinal tract include obtaining abdominal fluid, serum amyloid A (abdominal and systemic) and lactate (abdominal and systemic). When abdominal fluid is obtained, evaluate color, clarity and protein level and this can all be done stall side. Total protein should be less than 2 mg/dL, lactate <2mmol/l and SAA

0-20 mg/L. Evaluating total nucleated cell count can be more difficult in the field, when time is of the essence and often is not completed. Normal tncc should be <10,000 cells/l. A significant increase in tncc is indicative of peritonitis which might be caused by a variety of reasons, one of which might be a surgical lesion. Comparing the above parameters – systemic versus abdominal fluid can be helpful as well.

Treatment of colic will depend on the specific findings of the complete work up described, as well as owner finance and specific referral options. For the average field medical colic, the 80% that respond to medical management, the treatment does not go beyond what has been discussed in the field setting- pain management, rehydration, etc. Other field colics may not be surgical but will require repeat administration of water and/or electrolytes over many hours to days to relieve a persistent impaction. A catheter can be placed in the field and IV fluid administration can be conducted in a field setting. Usually this is done with a single large fluid bolus but depending on the situation fluids can be administered over many hours. This can be time consuming or impossible given the busy schedule of most equine veterinarians. Leaving a catheter in place or leaving a horse on IV fluid therapy with only an owner is not recommended. Sometimes it is immediately obvious the horse will need surgery and if that is an option then the horse will have the pain managed, nasogastric tube passe and be sent to a referral center immediately. Other times the horse has a surgical lesion that is not immediately obvious and it will require repeated examinations in the field before the horse is sent. If the horse is refractory to treatment and must be examined multiple times it would be prudent to obtain blood for a serum biochemical profile as well as a complete blood count. If ultrasound was not originally performed it would be important to do so on the follow up visit. If this is not possible a repeat examination per rectum is recommended. Repeat serum lactate and SAA as well as abdominal lactate and SAA.

How do you know when a horse should be referred for surgery or for more extensive medical treatment? The most common reason for referral is that the horse is refractory to pain management. A horses heart rate consistently over 60 bpm that does not respond to the administration of systemic NSAID therapy can be an indication to refer a horse. Other indications include, positive net reflux, abnormal rectal palpation findings (such as significant impaction, distended SI, severely distended large colon, small colon impaction, displacement, etc.), abnormal abdominal fluid, diarrhea, systemic compromise (muddy or brick red mm, toxic line). Although most of our field colics will respond to on farm therapy it is critical to understand when referral is warranted in order to get the horses the help they need in the quickest time frame.

Equine Internal Medicine. Reed SM, Bayly WM, Sellon DC. Elsevier 2018. Clinical Veterinary Advisor. Wilson DA. Elsevier 2012.

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Food Animal

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Food Animal

Celeste Morris, DVM, MBA, MPVM

Assistant Professor, Food Animal Ambulatory Service University of Missouri College of Veterinary Medicine Columbia, Mo.

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