Hepatic encephalopathy associated with extensive hepatic diaphragmatic herniation in an adult horse

BACKGROUND: Diaphragmatic hernia in horses is a rare condition, most commonly presenting with signs of colic and, less frequently, respiratory compromise. Hepatic herniation through a diaphragmatic defect with secondary hepatic failure and encephalopathy has rarely been documented in horses. CASE PRESENTATION: A 5-year-old Mangalarga Marchador stallion was evaluated for progressive neurological deterioration, including obtundation, head pressing, ataxia, and circling. Serum biochemistry revealed severe hepatobiliary dysfunction, characterised by increased gamma-glutamyl transferase and alkaline phosphatase activities, hyperbilirubinaemia and hypertriglyceridaemia. The horse died within 12 h of admission. Post-mortem examination revealed a chronic pleuroperitoneal diaphragmatic defect with herniation of the left lateral, left medial, and quadrate hepatic lobes into the thoracic cavity. The herniated portion showed severe atrophy, haemorrhagic necrosis, cholestasis, and ductular proliferation, while the non-herniated hepatic mass exhibited bridging fibrosis and nodular regenerative remodelling. Histopathological examination of the brain confirmed the presence of Alzheimer type II astrocytes in the cerebral cortical grey matter, consistent with hepatic encephalopathy. CONCLUSIONS: This case documents an unusual manifestation of equine diaphragmatic hernia in which extensive chronic hepatic incarceration resulted in severe hepatobiliary dysfunction and hepatic encephalopathy. The findings suggest that diaphragmatic hernia with hepatic involvement should be considered in the differential diagnosis of horses presenting with severe hepatopathy and neurological signs compatible with hepatic encephalopathy, particularly when classical signs of colic are absent.