Case Report: Cholangioscopic and histopathological findings before and after treatment in immune-related cholangitis.

Immune-related cholangitis is a rare immune-related adverse event, and its diagnostic criteria and treatment strategies have not yet been established. Here, we report a case of immune-related cholangitis in which treatment response could be objectively visualized through reassessment of cholangioscopic and histopathological findings before and after treatment. A 79-year-old man with recurrent cutaneous squamous cell carcinoma of the scalp developed high fever and general fatigue after six courses of nivolumab, and laboratory tests revealed marked elevation of hepatobiliary enzymes. Contrast-enhanced computed tomography and endoscopic ultrasonography showed bile duct wall thickening, endoscopic retrograde cholangiopancreatography demonstrated shaggy irregularity in the distal bile duct, and peroral cholangioscopy revealed diffuse surface irregularity and granular changes of the biliary mucosa. Furthermore, cholangioscopy-guided bile duct biopsy demonstrated marked lymphocytic infiltration, particularly infiltration of CD8-positive T cells, leading to a diagnosis of immune-related cholangitis. Prednisolone and ursodeoxycholic acid were initiated, with nivolumab discontinued, after which the clinical symptoms and hepatobiliary enzyme levels gradually improved. Furthermore, on Day 28 after treatment initiation, reassessment by cholangioscopy and bile duct biopsy confirmed improvement in the cholangioscopic findings and reduction of lymphocytic infiltration, particularly CD8-positive T-cell infiltration, on bile duct biopsy. These objective findings supported tapering of steroid therapy. To our knowledge, very few cases have described reassessment of cholangioscopic and histopathological findings before and after treatment in immune-related cholangitis. We suggest that such evaluation may contribute to confirming treatment response and guiding therapeutic strategy in immune-related cholangitis.