Mesenteric lymphatic malformation with chylothorax in a cat.

Case summary: An 8-year-old female spayed Russian Blue cat presented for acute progressive dyspnoea. The patient had pleural effusion and was diagnosed with chylothorax. A multiphase contrast-enhanced CT scan of thoracic and abdominal cavities was performed to facilitate diagnosis and surgical planning. Incidentally, a large lobulated, elongated, cystic and encapsulated peritoneal mass was found. Contrast pooled within the peritoneal mass during lymphography, suggesting lymphatic origin. The patient was eventually euthanased as a result of recurrence of chylothorax. Necropsy revealed multiple irregular, thin-walled pockets of chylous fluid pooling within the mesentery. Histopathology of the affected mesentery was compatible with a diagnosis of lymphatic malformation.

Relevance and novel information: To the authors' knowledge, this is the first case describing a feline presentation of mesenteric lymphatic malformation. This is also the first case reporting the presentation of chylothorax for a veterinary patient with mesenteric lymphatic malformation.