Pericardial effusion as a manifestation of feline infectious peritonitis

Abstract Introduction Feline infectious peritonitis (FIP) is a fatal disease caused by feline coronavirus, most commonly associated with effusions in body cavities, while pericardial involvement remains rarely described. Material and Methods A three-year clinical study (2021–2024) included 256 cats with PCR-confirmed effusive FIP, of which 37 presented fluid accumulation exclusively in the pericardial sac. Diagnosis was based on real-time PCR analysis of pericardial fluid, echocardiographic examination and measurement of serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations. Results Mutant feline coronavirus RNA was detected in pericardial fluid samples from all cats, with threshold cycle values ranging from 22 to 26 and highly specific PCR amplification confirmed by consistent melting temperatures (81.0–81.2°C). Ultrasonography revealed pericardial effusion in all 37 cats, with cardiac tamponade observed in 27% of cases and significantly higher NT-proBNP concentrations in affected individuals. Statistical analyses showed no significant associations between breed, age or sex and the occurrence of pericardial effusion, cardiac tamponade or NT-proBNP serum concentrations. Conclusion Pericardial effusion and cardiac tamponade may represent under-recognised manifestations of effusive FIP. Routine echocardiographic evaluation and molecular analysis of pericardial fluid should be considered in cats with suspected FIP and cardiopulmonary signs.