Chylous abdominal effusion in a cat with feline infectious peritonitis.

A 10-year-old cat was diagnosed with chyloperitoneum based on the effusion characteristics. Feline coronavirus serology was positive. The owner declined further evaluation and elected euthanasia. Necropsy revealed vasculitis with multifocal areas of necrosis and lymphocytic-plasmacytic inflammation in multiple solid organs, most likely due to feline infectious peritonitis (FIP). Immunohistochemistry was negative for FIP antigen. Notwithstanding, the final diagnosis of FIP was based on the characteristic histopathological lesions. Underlying causes of chyloperitoneum in cats and humans are discussed, and possible pathogenesis of the chyloperitoneum in association with a vasculitis such as FIP is discussed.