Severe pericardial effusion in a cat with peritoneopericardial diaphragmatic hernia and incarcerated hepatic sarcoma

CASE SUMMARY: A 4-year-old female neutered domestic longhair cat was presented at a referral hospital for dyspnoea with a history of suspected pleural effusion. Thoracic ultrasonography demonstrated a large-volume pericardial effusion causing cardiac tamponade and a cystic mass within the pericardium. CT revealed a peritoneopericardial diaphragmatic hernia (PPDH) caused by a defect of the ventral diaphragm. Herniated contents consisted of the right lateral and caudate liver lobes, and an associated cystic hepatic mass. Ventral midline coeliotomy was performed for herniorrhaphy and partial pericardiectomy, together with lobectomy of the incarcerated liver mass. Histopathology and immunohistochemistry diagnosed a poorly differentiated hepatic sarcoma with inflammation and remodelling in the adjacent incarcerated liver parenchyma. The patient developed metastatic sarcoma 2 months after surgery and was euthanased as a result. RELEVANCE AND NOVEL INFORMATION: Pericardial effusion causing cardiac tamponade is a previously unreported sequelae to PPDH in cats. Reports on the presence of malignancy in incarcerated liver are scarce and the location is not typical for a sarcoma in this species.