Eosinophilic cholangitis without peripheral eosinophilia presenting as a localized bile duct stricture mimicking perihilar cholangiocarcinoma.

Eosinophilic cholangitis is a rare condition characterized by the infiltration of the bile duct wall by inflammatory cells, predominantly eosinophils, leading to bile duct wall thickening, narrowing, and dilatation. Differentiation between primary sclerosing cholangitis and cholangiocarcinoma remains challenging owing to overlapping clinical and radiological features, and no standardized diagnostic criteria currently exist. We report a case of eosinophilic cholangitis presenting as a localized biliary stricture in a 65 year-old man. The patient underwent computed tomography for the evaluation of worsening diabetes, which incidentally revealed a stricture at the hepatic hilum. Magnetic resonance cholangiopancreatography and endoscopic retrograde cholangiopancreatography (ERCP) demonstrated a hilar biliary stricture with left intrahepatic bile duct dilatation. Bile cytology was interpreted as atypical, brush cytology was negative for malignancy, and bile duct biopsy showed no evidence of malignancy. Transoral cholangioscopy also revealed no malignant features; however, follow-up ERCP showed progression of the right-sided biliary stricture. As hilar cholangiocarcinoma could not be ruled out, the patient opted for surgical intervention. A left hepatectomy with caudate lobectomy was performed. Histopathological examination revealed no malignancy but showed submucosal fibrosis and inflammatory cell infiltration. Notably, marked eosinophilic infiltration was observed at the site of the right biliary stricture. The final diagnosis of the patient was eosinophilic cholangitis.