Primary differentials for chyloabdomen in the cat include: Idiopathic chyloabdomen, cardiac disease (cardiomyopathy, pericardial effusion), lymphoma, and lymphatic trauma/rupture.

Cardiac disease and thoracic disease were eliminated as differentials by performing a normal echocardiogram. No passive congestion was noted in the hepatic veins, and therefore thoracic disease was essentially ruled out. Therefore, an obstructive lymphatic pathology would make most sense here. Given the clinical signs of the patient, and the lack of response to therapy, lymphoma or similar lymphatic obstructive neoplasia was likely but could not be proven. When confronted with these cases it’s important to rule out all other causes of chyloabdomen. Cardiac disease and passive congestive thoracic disease is easily ruled out with an echocardiogram and examination of the hepatic vasculature. The other objective is to screen the abdomen for evidence of lymphoproliferative disease such as enlarged lymph nodes that have distorted contour. None of this was overtly visible in this patient. At times, neoplasia can invade lymphatics before forming a mass visible on ultrasound. This is suspected to be one of those cases but could not be proven given that postmortem examination was not permitted.  Idiopathic causes of chyloabdomen with also possible in this patient. However given the progressive clinical decline, occult neoplasia would make most sense.