Veterinary Medicine - September 2008 - (Page 494)

A challenging case PEER-REVIEWED 1A & 1B. Lateral and ventrodorsal thoracic radiographs obtained on initial presentation after drainage of the cystic lesion. A soft tissue opacity is apparent in the cat’s cranial mediastinum. spectral Doppler examinations of the mitral and tricuspid valves nor the right and left ventricular out ow tracts. The right heart size appeared normal, and septal wall attening was not seen. Also, no pulmonary arterial dilatation or linear lesions within the pulmonary vasculature suggesting patent heartworm disease were identi ed. We did not perform heartworm antigen and antibody testing because the heartworm disease incidence in our area was thought to be low and imaging revealed no evidence of heartworm disease. Cytologic examination of the cyst uid revealed red blood cells and red blood cell phagocytosis, consistent with hemorrhage. Grossly, the pleural uid had a milky appearance, and, cytologically, it appeared to be a lymphocytic effusion, which was consistent with chyle. No neoplastic cells were observed. Differential diagnoses and initial treatment Our primary differential diagnoses for chylothorax in this cat were idiopathic chylothorax and chylothorax secondary to compression of the cranial vena cava by the cyst. Although not a traditional treatment for idiopathic chylothorax, we initiated prednisone (0.75 mg/kg orally once a day for seven days) to reduce in ammation that could have been associated with the cyst’s compression of the cranial vena cava. We discussed surgical treatment options with the owner, which included removing the cystic structure and possibly ligating the thoracic duct and performing a partial pericardiectomy. On physical examination a week later, the cat weighed 14.3 lb (6.5 kg), and its respiratory rate and effort and thoracic auscultation ndings were unremarkable. The owner reported that the cat had remained asymptomatic and had received its last dose of prednisone that day. Thoracic ultrasonography revealed that the cyst measured 4 cm in diameter. A scant amount of pleural effusion was noted, which was too small to safely remove with thoracentesis. Thoracic radiographic ndings were unchanged, and the results of a complete blood count, serum chemistry pro le, urinalysis, and total T4 concentration were unremarkable. and was eupneic; thoracic auscultation results were unremarkable. Thoracic radiographs were not obtained because the cat was eupneic and surgery would be performed regardless of the ndings. First surgery About 30 minutes before anesthesia was induced, morphine was given subcutaneously. Anesthesia was induced with ketamine and diazepam given intravenously. The patient was then intubated, and anesthesia was maintained with sevo urane. A median sternotomy was performed, and since pleural effusion was not detected, we decided not to ligate the thoracic duct or to perform a partial pericardiectomy. Because the chylous effusion had not reaccumulated after we reduced the cyst’s size, we thought that the underlying cause of the chylothorax was likely compression of the cranial vena cava by the cyst. However, cats with idiopathic chylothorax can reaccumulate uid at any time or at any rate. No evidence of brosing pleuritis was present, and no brotic material was seen on the surface of the lungs, pericardium, or pleural cavity. The cranial mediastinal cyst was about 5 cm in diameter, was uniformly SECOND PRESENTATION Two weeks after the cat’s initial presentation, the owner elected to pursue surgery. A presurgical physical examination revealed that the cat weighed 14.3 lb (6.5 kg) 494 September 2008 VETERINARY MEDICINE

Table of Contents Feed for the Digital Edition of Veterinary Medicine - September 2008

Veterinary Medicine - September 2008 Contents Leading Off Practical Matters Idea Exchange A Challengin Case: Thymic Cyst and Recurrent Chylothorax in a Cat 10 Life-Threatening Behavior Myths CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - September 2008

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