Cardiac etiology is the leading cause of feline chylothorax: 35 cases (2006-2022)

To identify the most frequent underlying causes of chylothorax in cats and to assess whether clinical and laboratory findings at presentation could predict etiology and outcome.

Cats diagnosed with chylothorax were retrospectively enrolled in 2 veterinary centers between 2006 and 2022. Data collected for each case included signalment, history, physical examination findings, pleural effusion analysis, hematologic and imaging results, etiology, treatment (medical and/or surgical), and survival time. Descriptive statistics and multinomial logistic regression were used to identify markers of etiology. Associations with survival were assessed with the Cox proportional hazards models.

35 cats met the inclusion criteria. Cardiac disease was the most common etiology (57%), followed by idiopathic (31%), neoplasia (9%), and peritoneopericardial diaphragmatic hernia (3%). Cats with neoplastic chylothorax were significantly older than those in other etiologic groups. Cats with cardiac chylothorax had a higher left atrial-to-aortic ratio (median, 2.4) than cats in other etiologic groups (< 1.4). Median survival times for cardiac, idiopathic, neoplastic, and peritoneopericardial diaphragmatic hernia etiology were 172, 416, 38, and 27 days, respectively. Regardless of the chylothorax etiology, survival was negatively correlated to older cats and low rectal temperature on initial arrival to the hospital.

Cardiac disease was the predominant cause of chylothorax. All cats with a left atrial-to-aortic ratio > 1.4 had a cardiac etiology. All cats aged over 14 years had a neoplastic etiology. Felines with a cardiac etiology had a poorer prognosis than idiopathic cases. Neoplastic cats had the shortest survival time.

An echocardiogram should be considered for all cats diagnosed with chylothorax.