Thoracoscopic thoracic duct ligation and thoracoscopic pericardectomy for treatment of chylothorax i

Veterinary Surgery 39:21–27, 2010

Thoracoscopic Thoracic Duct Ligation and Thoracoscopic Pericardectomy for Treatment of Chylothorax in Dogs DAVID A. ALLMAN,

DVM,

MARYANN G. RADLINSKY, DVM, MS, Diplomate ACVS, ALAN G. RALPH, CLARENCE A. RAWLINGS, DVM, PhD, Diplomate ACVS

DVM,

and

Objective—To report the use of thoracoscopic thoracic duct ligation (TDL) and pericardectomy for treatment of chylothorax.

Study Design—Case series.

Animals—Dogs with chylothorax (n ¼ 12).

Methods—Dogs with secondary or idiopathic chylothorax had thoracoscopy performed in sternal recumbency through 3 portals in the caudal right hemithorax for TDL and were then repositioned in dorsal recumbency for pericardectomy. Portals were placed in the 5th and 7th intercostal spaces of the right hemithorax with 1 transdiaphragmatic portal in the right paraxiphoid position. Followup was performed by recheck examination or telephone interview to determine outcome.

Results—Seven dogs (58%) had idiopathic chylothorax; 6 dogs (85.7%) had complete resolution of their effusion, whereas only 2 of the 5 nonidiopathic dogs (40%) had complete resolution.

Conclusions—Thoracoscopy is minimally invasive, provides excellent observation, and allows for ligation of the thoracic duct in the caudal thorax. Patients with idiopathic chylothorax may have a better prognosis after TDL and pericardectomy than dogs with nonidiopathic chylothorax.

Clinical Relevance—Thoracoscopy for ligation of the thoracic duct and pericardectomy is an acceptable surgical technique for treatment of chylothorax. r Copyright 2010 by The American College of Veterinary Surgeons

angectasia, venous thrombi, and congenital abnormalities of the thoracic duct.2 Treatment of chylothorax should 1st be directed at correcting the primary disease if an underlying cause of the effusion is diagnosed. The term idiopathic chylothorax is applied to cases in which no primary cause of the effusion can be identified.

Both conservative and surgical management protocols have been proposed for the treatment of idiopathic chylothorax. Conservative management of idiopathic chylothorax may consist of a low fat diet, supplementation with the nutraceutical rutin, and thoracocentesis as needed. Resolution of chylothorax with these treatments is difficult to differentiate from spontaneous resolution; however, resolution is thought to be more likely in traumatic or iatrogenic cases.3 Published resolution rates with conservative management of chylothorax are 28% (2 of 7

INTRODUCTION

C

HYLE IS an opaque fluid absorbed by the intestinal lacteals during digestion.1 Chyle consists of lymphocytes, proteins, and triglycerides within chylomicrons.1 Chylothorax is the accumulation of chyle within the pleural space.1 The accumulation of a chylous effusion is thought to occur secondary to decreased drainage of the thoracic duct into the venous system and/or an increased lymph burden within the thoracic lymphatic system.2 Patients with chylothorax should be evaluated for a primary or underlying cause of their effusion. Causes include primary cardiac disease (e.g. cardiomyopathy, heartworm disease, and tricuspid dysplasia), pericardial effusion, mediastinal or thoracic neoplasia, traumatic thoracic duct rupture, iatrogenic thoracic duct damage, lymph-

From the Department of Small Animal Medicine and Surgery, College of Veterinary Medicine, University of Georgia, Athens, GA. Corresponding author: David A. Allman, DVM, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824. E-mail: allmand@cvm.msu.edu.

Submitted October 2008; Accepted March 2009 r Copyright 2010 by The American College of Veterinary Surgeons 0161-3499/09 doi:10.1111/j.1532-950X.2009.00623.x

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THORACOSCOPIC THORACIC DUCT LIGATION AND PERICARDECTOMY

dogs)4; 26% (5 of 19 dogs and cats)5; and 75% (3 of 4 cats).6 Published resolution rates in people range from 25% to 80%7–9; however, an overall resolution rate of 50% is likely more clinically relevant in humans.8 The resolution of chylous effusions in dogs and cats treated with conservative management can take from 2 to 8 weeks4,6,10 or may be as rapid as 1–2 weeks with traumatic ruptures.11 Surgical intervention for chylothorax is usually considered if a patient fails to respond to conservative management. Reported surgical techniques in dogs and cats include thoracic duct ligation (TDL),11,12 TDL with pericardectomy,2 cisterna chyli ablation (CCA) with TDL,13 thoracic duct embolization,14 pleurodesis,15 pleurovenous shunting, pleuroperitoneal shunting,16 and thoracic omentalization.17 TDL with pericardectomy has the highest reported success rate with 100% in 10 dogs, and 80% in 10 cats in 1 study.2 CCA with TDL has a reported success rate of 88% in 8 dogs.13 Video-assisted thoracic surgery (VATS) was 1st reported for the treatment of chylothorax in people in 1992.18 As with most minimally invasive procedures, VATS was associated with decreased patient morbidity and a shorter hospital stay.8,19 A technique for successful video assisted TDL in animals has been described,20 but we are unaware of any case series describing a minimally invasive surgical technique for treatment of chylothorax in companion animals. Thus, our purpose was to report treatment of chylothorax in 12 dogs that had thoracoscopic TDL and pericardectomy and to discuss its potential influence on the clinical approach to chylothorax.

MATERIALS AND METHODS Twelve dogs (December 2000–September 2007) were admitted for surgical correction of chylothorax. Each dog had undergone some degree of conservative management including any of the following: low fat diet, rutin, and repeated drainage of chyle via thoracocentesis. Despite therapy, each dog continued to accumulate chyle in the pleural space.

Dogs had physical examination, complete blood count, serum biochemical profile evaluation, heartworm testing, thoracic radiographs, electrocardiogram, echocardiography, and thoracic ultrasound. Chylothorax was confirmed by fluid analysis, comparing serum triglyceride and cholesterol levels with that of the pleural fluid, pleural fluid cytology, and bacterial culture. Idiopathic chylothorax was diagnosed by exclusion based on history, physical examination, and diagnostic testing.

Anesthetic protocols varied for each dog; however, percent saturation of hemoglobin, end-expiratory carbon dioxide, direct or indirect arterial blood pressure, and continuous electrocardiogram were monitored in all dogs. Orotracheal intubation was performed and all dogs were maintained with

bilateral lung ventilation. Surgical procedures were performed or supervised by the same surgeon (M.G.R.). Surgical times for each dog were recorded from 1st incision and ended with final skin closure.

Follow up was performed by recheck examination at the teaching hospital or telephone contact with the owner or referring veterinarian. Veterinary clinical evaluation for followup was not required for study inclusion but information was obtained when possible. Successful outcome was defined as resolution of all clinical signs and lack of pleural effusion on thoracic radiographs at least 8 weeks postoperatively. Minimum follow-up time for dogs with a successful outcome was 6 months. Death was recorded as related or not related to respiratory disease. Respiratory disease was considered related to chylothorax or persistent pleural effusion unless otherwise diagnosed by a veterinarian.

Thoracoscopic TDL The entire thorax from manubrium to the level of the 2nd lumbar vertebra was clipped and an initial aseptic skin preparation performed. The dog was positioned in sternal recumbency tilted slightly toward the left, and the right hemithorax was aseptically prepared and draped. A video monitor was placed on the dog’s left side and the surgeons were positioned on the dog’s right. Three thoracoscopic portals were established for introduction of surgical instruments. A 1–2 cm skin incision for thoracoscope portal placement was made at midthorax in the 10th intercostal. Tissues were bluntly dissected with a Kelly forceps and after pneumothorax, a 5 mm blunt obturator/flexible portal assembly (Endopath TT012; Ethicon Endo-Surgery Inc., Cincinnati, OH) was inserted into the chest. A 5 mm outer diameter, 301 rigid telescope (Karl Storz Veterinary Endoscopy-America Inc., Goleta, CA) was introduced through the portal. After examination of the right hemithorax, the thoracoscope was used to facilitate the placement of 2 additional portals. A 5 mm trocar/portal assembly (Endopath 355; Ethicon Endo-Surgery Inc.) was inserted in the dorsal third of the 9th or 10th intercostal space for passage of surgical instruments. A 15 mm blunt obturator/flexible portal assembly (Flexipath FP015; Ethicon Endo-Surgery Inc.) was inserted in the dorsal 3rd of the 11th or 12th intercostal space for instrument passage and hemostatic clip application (10 mm Microline clip applier, Microline Pentaxt, Beverly, MA).

After establishing the 3 thoracoscopic portals, a straight grasping forceps was placed through the caudal portal and was used to retract the mediastinal pleura laterally toward the thoracoscope. Microscissors passed through the cranial portal were used to incise the mediastinal pleura longitudinally ventrolateral to the aorta. The mediastinal pleura ventral to the sympathetic chain was likewise incised. Straight grasping forceps were used to retract and stabilize the mediastinum during these incisions. Significant ventral retraction of the aorta using closed, curved forceps was required to aid dissection ventrolateral to the aorta and thus ventral to the thoracic duct bilaterally. Curved dissecting forceps were used to dissect across the mediastinum just dorsal to the aorta, and then dissection

23

ALLMAN ET AL was again aimed ventrolateral before the left mediastinal pleura was perforated. Dissection is attempted ventrolateral to the aorta rather than just lateral or dorsal to the aorta to include any aberrant branches of the thoracic duct in the isolated tissues. Dissection was then performed dorsal to the thoracic duct in a plane of dissection ventral to the sympathetic trunk. Once the thoracic duct and its branches were isolated, the forceps in the clip portal were replaced with the 10 mm hemostatic clip applier. Curved dissecting forceps in the instrument portal were used to retract the aorta ventrally for observation of the structures before clip application. Clips were applied with inward pressure across visible branches of the thoracic duct. If branches could not be individually identified, clips were placed on the dissected tissue in an en bloc fashion.

Verification of complete TDL after clip application was attempted in 3 dogs (dogs 5, 7, and 8) by lymphangiography of a mesenteric lymphatic vessel or coloration of a lymph node with methylene blue. A right paracostal laparotomy was performed for isolation of a mesenteric lymph node. Lymphatic vessel catheterization was performed using a 24 G over the needle catheter in the region of the colonic lymph nodes. The catheter was sutured to the adjacent seromuscular layer of the colon; the extension set was sutured to the body wall and skin adjacent to the incision. The abdomen was temporarily closed with 2-0 nylon in a simple continuous pattern. The skin was closed with 3-0 nylon in a continuous locking pattern and the dog was transported to an imaging suite for lymphangiography.

Aqueous contrast material (Renographin-76; Solvay Animal Health Inc., Medota Heights, MN) was diluted in an equal volume of sterile saline (0.9% NaCl) solution. The diluted contrast material (0.4–2.5 mL/kg) was injected into the lymphatic catheter extension set and a lymphangiogram performed. Coloration of both mesenteric and popliteal lymph nodes was attempted. The mesenteric lymph node was accessed via a right paracostal approach. The popliteal lymph nodes were palpated and injected percutaneously A 1% aqueous solution of methylene blue was injected directly into the lymph nodes at a dose o0.5 mg/kg not to exceed 10 mg. The right paracostal incisions were closed.

The thoracotomy sites were closed in 3 layers: the intercostal muscles with 2-0 polydioxanone in a simple interrupted or cruciate pattern, the subcutis with 3-0 polydioxanone in a cruciate pattern, and the skin with 3-0 nylon in a simple interrupted pattern.

Thoracoscopic Pericardectomy After TDL, the dog was positioned in dorsal recumbency, and the thorax was aseptically prepared and draped for pericardectomy. Three to 4 portals were created with the same technique described for TDL. Portal locations included 1 right paraxiphoid transdiaphragmatic portal and 2 portals in the middle 3rd of the right hemithorax between the 5th and 7th intercostal spaces; if needed portals, were placed in the contralateral hemithorax between the 5th and 7th intercostal spaces.

The 301 rigid telescope was inserted through the transdiaphrag-

matic portal to guide placement of other portals. The pericardium was grasped through the right hemithorax and pulled laterally using 1 straight grasping forceps. The pericardium was carefully evaluated and the phrenic nerves identified. The pericardium was incised with microscissors or a vessel sealing device (LigaSuret, Covidien, Boulder, CO) at the most tented location. A 4-cm-diameter pericardial window was created ventral to the phrenic nerves. In addition to the pericardial window 2–3 vertical fenestrations were made in the pericardium starting at the phrenic nerve and extending to the apex of the heart. The excised pericardium was removed through the instrument portal and submitted for histopathology.

The thoracotomy sites were closed as described for TDL. An appropriately sized thoracostomy tube was placed, and the chest was evacuated of any residual fluid and air at the time of closure.

RESULTS Twelve dogs (5 males, 7 females) were included (Table 1).

Breeds were Borzoi (n ¼ 3), Labrador Retriever (2), mixed breed (2), and 1 each of German Shepherd, Greyhound, Siberian Husky, Bull Mastiff, and Golden Retriever. Dogs were aged 6 months–10.5 years (mean, 5.7 years). Clinical signs were tachypnea (n ¼ 10), cough (4), difficulty breathing (4), lethargy (3), anorexia (2), inappetence (2), and weight loss (1).

Duration of clinical signs ranged from 2 days to 1 year. The most acute case (dog 1) was admitted with a lung lobe torsion and had a right 5th intercostal space thoracotomy. Chylous effusion was suspected intraoperatively and later confirmed by fluid analysis. Dog 1 had successful thoracoscopic TDL and pericardectomy 7 days after lung lobectomy.

Nonidiopathic Chylothorax Six dogs were diagnosed with nonidiopathic chylothorax. Dog 6 was originally diagnosed as idiopathic, and her effusion resolved after TDL and pericardectomy; however, 7 weeks later effusion reoccurred, mesothelioma was diagnosed, and the dog was euthanatized. Dog 7 was diagnosed with constrictive pericarditis by echocardiography and increased right atrial pressures (RAP) at 28/ 4 mmHg. The echocardiographic diagnosis was based on transmitral and pulmonary vein flow velocities and correlating those velocities to phases of respiration. The effusion resolved postoperatively, and postoperative echocardiographic findings and RAP (4/ 3 mmHg) normalized. Dog 8 was diagnosed with pyothorax at 14 weeks of age and had thoracoscopic mediastinectomy and pericardectomy; 2.5 months later, chylothorax was diagnosed and treated by thoracoscopic TDL. Her effusion was no longer chylous after TDL, but she was

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THORACOSCOPIC THORACIC DUCT LIGATION AND PERICARDECTOMY Table 1. Summary Data for 12 Dogs with Chylothorax Treated by Thoracoscopic Thoracic Duct Ligation and Pericardectomy Surgical Time (minutes)

Discharge (days)

Idiopathic chylothorax Right middle lung lobe torsion

90

15

3 weeks

Idiopathic chylothorax

110

4

Chronic fibrosing pericarditis

3 weeks

Idiopathic chylothorax Renal azotemia Idiopathic chylothorax

172

4

Mesothelial hyperplasia

210

4

Idiopathic chylothorax

135

6

Fibrinopurulent pericarditis Mesothelial hyperplasia, mild lymphoplasmacytic inflammation

Dog

Signalment

Duration

Diagnosis

1

5.5 years FS Greyhound 38 kg

2 days

2

9.5 years MC Labrador Retriever 37.3 kg

3

10.5 years FS mixed breed 20.6 kg 8 years FS Siberian Husky 20 kg 3 years M Borzoi 32.1 kg

4 5

1–2 months 1 year

6

8 years FS German Shepherd dog 33 kg

2 weeks

Pericardial effusion, cardiac tamponade chylothorax

210

24

7

10 months FS Bull Mastiff 43.6 kg

2 weeks

235

1

8

6 months F mixed breed 14.2 kg

1 week

Constrictive pericarditis chylothorax 2 month postthoracic surgery and chylothorax

176

3

9

3.5 years male Borzoi 49.4 kg

1 year

240

N/A

10

7 years MC Labrador Retriever 36.3 kg 3 years F Borzoi

2 months

Idiopathic chylothorax, pyothorax Streptococcus spp.

Right ventricular enlargement, chylothorax Idiopathic chylothorax

210

10

155

4

275

7

11

12

9 years MC Golden Retriever

2 weeks

2 months

Fungal disease, chylothorax

Pericardial Histopathology

Outcome

Mesothelial hyperplasia

2 years. Clinically normal Died of unrelated neoplasia 1 year. Clinically normal Euthanatized— chronic renal disease 3 years. Clinically normal 3 years. Clinically normal 2.5 years. Clinically normal Lung lobectomy 1 year after TDL for lung lobe torsion. No chylous effusion noted 7 weeks. Euthanatized Signs recurred, mesothelioma on necropsy

Mediastinal mesothelial hyperplasia with neutrophilic and histiocytic inflammation and pericardial lymphoplasmacytic and neutrophilic inflammation Fibrin deposition and hemorrhage Mediastinum lymphoplasmacytic inflammation with purulent exudate pericardium (previous surgery) lymphoplasmacytic inflammation Normal pericardium

Reactive mesothelium with lymphoplasmacytic inflammation Severe papillary Mesothelial hyperplasia with neutrophilic and lymphoplasmacytic inflammation Multifocal, moderate pyogranulomatous pleuritis, with intralesional dematiaceous fungal hyphae Mild lymphoplasmacytic mediastinitis Diffuse, moderate pericardial fibrosis

2 years. Clinically normal 11 days. Euthanatized Persistent modified transudate

1 day. Euthanatized Systemic inflammatory response syndrome 5 weeks. Euthanatized Persistent modified transudate 6 months. Clinically normal

10 months. Clinically normal

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ALLMAN ET AL

euthanatized 11 days postoperatively because of a persistent modified transudate.

Dog 10 was diagnosed preoperatively with cranial and caudal vena cava dilation and right ventricular enlargement. This evidence of heart failure was considered mild and priority was placed on TDL and pericardectomy because of a high volume chylous effusion. Eight days postoperatively, the dog developed gastric dilatation volvulus (GDV) overnight and this was surgically corrected.

He recovered well; however, his effusion never resolved postoperatively, and he was euthanatized 5 weeks after TDL because of a persistent modified transudate.

Chylothorax in dog 12 was originally diagnosed as idiopathic; however, a biopsy of his pleura taken intraoperatively revealed intralesional dematiaceous fungal hyphae, which was confirmed with polymerase chain reaction testing of the pleural biopsy. Dog 12 was treated with itraconazole for 1 month after TDL and pericardectomy, and the effusion resolved.

Idiopathic chylothorax Dog 9 with a 1-year history of chylothorax had been treated conservatively. There were no intraoperative complications, but the dog developed hyperthermia (105.21F [40.71C]), tachycardia (200 beats/min), tachypnea (80 breaths/min), and a leukopenia of 2.4 103/mL (reference interval, 5.5–13.9 4 103/mL) 24 hours postoperatively. These signs were consistent with a severe onset systemic inflammatory response syndrome,21 and the dog was euthanatized 24 hours postoperatively. No cause of the patient’s deterioration could be identified at necropsy; however, samples of the dog’s pleural effusion grew Streptococcus species months before surgery. Effusion cytology on admission was not consistent with infection but microbial cultures grew Streptococcus spp.

Referring veterinarian records indicate a diagnosis of chylothorax based on pleural fluid analysis without evidence of bacterial organisms before this dogs 1st positive bacterial culture. Therefore, dog 9’s diagnosis remained idiopathic chylothorax.

Surgical Time Surgical time included TDL, pericardectomy, and lymphangiography and coloration of the thoracic duct when attempted. Mean time was 184 minutes (range, 90– 275 minutes). Each procedure was successfully completed; however, complete ligation could not be verified in any dog except dog 5. Complete ligation was verified by a right paracostal approach for lymphatic catheterization and lymphangiography of a mesenteric lymphatic vessel.

Lymphatic catheterization and thoracic duct coloration via mesenteric lymph node injection in dog 7 failed. Per-

cutaneous injection of methylene blue in the popliteal lymph nodes of dog 8 failed to color the thoracic duct.

Histopathology Histopathology of the excised portion of pericardium yielded fibrosing pericarditis, varying types of inflammation, and reactive mesothelial hyperplasia (Table 1). In dog 12, a diagnosis of fungal disease was made on tissue biopsies, emphasizing the need for histopathology in all cases.

Outcome Duration of follow-up for survivors ranged from 6 months to 3 years (median, 1.65 years; mean, 1.7 years).

The 8 long-term surviving dogs were reported to have successful outcomes by recheck examination or telephone interview with the referring veterinarian or owner. Six of the 7 dogs (85.7%) diagnosed with idiopathic chylothorax had complete resolution of their effusion after thoracoscopic TDL and pericardectomy. Two of 5 dogs (40%) with chylothorax secondary to another disease process had complete resolution of their effusion after thoracoscopic TDL and pericardectomy. Eleven dogs (92%) survived to discharge, and 8 of the surviving dogs (73%) had successful outcomes.

DISCUSSION Conservative management of chylothorax is warranted as an initial approach because of cases that will resolve medically or spontaneously; however, when unsuccessful, conservative therapy is not benign. Excessive or chronic loss of chyle can result in hypoprotienemia, lymphopenia, and the need for repeated thoracocentesis.8 With repeated thoracocentesis of a chronic chylous effusion electrolyte imbalances can occur,22 the effusion can become inflammatory, pyothorax can result, fibrosing pleuritis may develop,11 and the cost of therapy increases.

Lymphocyte depletion in humans can be sufficient to place a patient at risk for septicemia within 8 days of chyle drainage.8 Dog 9 had medical management with thoracocentesis for 1 year and was not on antimicrobial therapy on admission, and microbial culture results were not available until after surgery. This dog had a persistent bacterial growth in the effusion and it is possible that this may have been related to his negative outcome.

Development of a minimally invasive technique for TDL in people resulted in a standard of care promoting earlier surgical intervention for chylothorax.8,23,24 Because consequences can arise from conservative treatment and most cases of chylothorax that resolve show im-

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THORACOSCOPIC THORACIC DUCT LIGATION AND PERICARDECTOMY

provement within the first 4 weeks,4,6,10,11 we suggest that a more standard approach to chylothorax be defined. We feel that surgery should be considered in patients with high output effusions that require thoracocentesis more than weekly, or effusions that persist 44 weeks without obvious clinical improvement.

TDL with pericardectomy via thoracotomy and TDL with CCA via thoracotomy are 2 of the most successful reported surgical techniques for idiopathic chylothorax in veterinary medicine.2–13 We had a similar success rate of 85% for idiopathic cases; however, with only 7 dogs having idiopathic chylothorax, it is difficult to interpret the results. In dogs 6 and 12 preoperative diagnostics did not identify an underlying cause for chylothorax; however, mesothelioma and fungal infection were later diagnosed. Because the results of surgical intervention in secondary chylothorax are not well known, we chose to include these cases in our series.

We have gained increased comfort with the technique and hope that success rates will continue to improve. As with all minimally invasive surgical techniques, the ultimate goals are to minimize morbidity, improve detailed observation, reduce overall length of hospitalization, and maintain success rates associated with traditional open procedures. No complications were noted as a direct result of thoracoscopic TDL and pericardectomy. The GDV that occurred in dog 8 is thought to have been coincidental and related to the increased risk of large breed dogs for GDV.25 Modifications of the technique after its original publication include the transition from one lung ventilation to bilateral lung ventilation and the movement of access portals more caudally to the 9th, 10th, and 11th intercostal spaces for TDL. We also attempted to include a method of verifying complete ligation of the thoracic duct and its branches some dogs. Lymphangiography by lymphatic vessel injection was attempted in dogs 5 and 7 and by nodal coloration in dogs 7 and 8. Methods of contrast application included colonic lymphatic vessel injection, mesenteric nodal injection, and popliteal nodal injection.26,27 Only lymphatic vessel injection in dog 5 was successful. Based on lymphangiography’s variable success, added surgical time, and intraoperative anesthetic considerations; its use by the authors to verify complete ligation of the thoracic duct remained limited.

Despite the limited use of lymphangiography in this report, we still encourage its use for verification of complete TDL. Initially, postoperative thoracic tubes were left in situ until almost all pleural effusion (in excess of 1 mL/kg/ day) had resolved. This practice has been changed to earlier tube removal once marked decreases in fluid production are noted, decreasing hospitalization time. None of these dogs had long-term persistent chylous effusion

after surgery; however, presence of a persistent modified transudate after TDL in dogs 8 and 10 resulted in euthanasia. The cause of this effusion is unknown. We speculate that the source of this modified transudate may be present before TDL (i.e. severe pleuritis) and separate from the chylous portion of the effusion. Alternatively, the persistent effusion could be the result of torn or aberrant TD branches that are producing a low volume ongoing chylous effusion.

In conclusion, thoracoscopic TDL and pericardectomy is safe, feasible, and effective for treatment of chylothorax in dogs. We hope that this technique will promote earlier surgical intervention in chylothorax.

Substantial challenges remain with the diagnosis of secondary versus idiopathic chylothorax, reliable lymphangiography, and occurrence of persistent modified transudates after TDL and pericardectomy. Larger studies will be needed to further evaluate these challenges and the efficacy or thoracoscopic TDL and pericardectomy as a treatment modality for chylothorax in dogs.

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