Presumed idiopathic suppurative and fibrinous pericarditis and pericardial effusion in a cat.

Case summary: An 8-year-old male castrated Persian cat was presented to a university teaching hospital for pericardial effusion, fever and hyporexia. Pericardial effusion cytology evaluated previously by the referring veterinarian revealed possible intracellular filamentous bacteria. The cat underwent a CT scan, which revealed severe pericarditis and fibrinous material within the pericardial sac that was adhering to the epicardium, as well as diffuse consolidation of the right middle lung lobe. Subsequently, a median sternotomy, subtotal pericardiectomy and right middle lung lobectomy were performed. Histopathology of pericardial tissue identified a marked chronic, neutrophil-predominant fibrinous pericarditis but no bacteria were visualized. No evidence of infection or neoplasia was identified. The cat's pyrexia and hyporexia persisted postoperatively and were refractory to several weeks of antibiotic therapy and several days of antiviral administration but rapidly responded to anti-inflammatory steroid administration. The cat was discharged after 12 days in hospital and did not have a recurrence of clinical signs at follow-up 6 months later. Relevance and novel information: This is the first report of successful management of presumed idiopathic and fibrinous pericarditis and pleural effusion in a cat.