The Road Not Taken: Endoscopic Management of an Unexpected Enteric Biliary Fistula.

Ascending cholangitis represents an endoscopic emergency demanding prompt recognition and intervention, typically via endoscopic retrograde cholangiopancreatography (ERCP). While routine ERCP access is achieved through the major papilla in the duodenum, this case highlights a unique anatomical variation: a choledochoduodenal fistulous tract in an 81-year-old male presenting with ascending cholangitis. Notably, the ERCP was successfully performed by utilizing this fistulous tract as the primary access point for intervention. This case underscores the importance of recognizing such rare anatomical anomalies in biliary diseases and their implications for endoscopic management.