Successful treatment of feline infectious peritonitis with pericardiectomy and GS-441524

A five-year-old male castrated domestic shorthair cat was referred for respiratory distress and pleural effusion. Echocardiography identified a moderate to severe volume of echogenic pericardial effusion (PCE), pericardial thickening, and a mild volume of anechoic pleural effusion. Computed tomography with intravenous contrast confirmed a large volume of PCE with concurrent pericardial thickening; a pericardiectomy was subsequently performed. Cytological analysis of the PCE was consistent with predominantly neutrophilic inflammation. Histopathology of the pericardium showed severe, pyogranulomatous, plasmacytic, and fibrinous pericarditis and vasculitis. Feline coronavirus reverse-transcriptase polymerase chain reaction performed on the PCE was positive, and the cat was treated with GS-441524 and a tapering dose of prednisolone. A recheck echocardiogram two months later showed no effusions. Treatment with GS-441524 was discontinued after a 12-week course, and the cat is alive 14 months after diagnosis, with no recurrence of effusions. This is a unique case of feline infectious peritonitis presenting with PCE that responded positively to both surgical and medical interventions.