Cholangiocarcinoma of the common bile duct, as seen during an ERCP procedure

Following administration of contrast material into the biliary system and duodenum during an endoscopic retrograde cholangiopancreatography (ERCP) examination (black), circumferential narrowing of the distal common bile duct is produced by a cholangiocarcinoma (arrow). The tumor is causing proximal bile duct dilatation and is also extending into the adjacent duodenum (arrowhead), producing a C-shaped eccentric impression.