Severe chronic neutrophilic cholangiohepatitis with massive choledocholithiasis and hepatolithiasis in a pony

Summary A 20‐year‐old Camargue pony mare was referred for acute‐onset neurological signs and intermittent colic. Clinical examination revealed obtundation, cranial nerve deficits, head pressing, ventral strabismus and ataxia. Laboratory analyses showed marked hyperammonaemia, hyperbilirubinemia, severe increases in liver enzymes, hypoalbuminaemia and elevated bile acids. Liver biopsy demonstrated severe chronic neutrophilic cholangiohepatitis with bridging fibrosis, ductular proliferation and hepatic lipidosis. Despite intensive supportive therapy, the pony developed acute colic accompanied by fever and gastric reflux and was euthanised because of a poor prognosis. Gross necropsy revealed a markedly dilated common bile duct containing a single large choledocholith (140 g; 11 × 5 cm), multiple hepatoliths (up to 2 cm) and a fibrotic liver. Histopathological examination of the brain identified Alzheimer type II astrocytes, consistent with hepatic encephalopathy. This case underscores the importance of considering biliary lithiasis in mature equids presenting with hepatic and neurological signs, and highlights the critical role of early diagnosis before the development of irreversible hepatic fibrosis.