Anomalous pancreaticobiliary junction (pancreaticobiliary maljunction)

In pancreaticobiliary maljunction the two ducts unite outside the duodenal wall to form a long common channel not controlled by the sphincter of Oddi, allowing reflux of pancreatic enzymes into the biliary tree; it often coexists with a choledochal cyst, and Cancer Research UK lists both as congenital risk factors for gallbladder cancer, quoting about seven times the risk for the maljunction from a meta-analysis of case-control studies (Deng 2011). It is usually diagnosed on MRCP by measuring the common channel and the narrow distal segment. In a 2025 Japanese MRCP series the maljunction was found in 0.44 percent of 2,046 benign cholecystectomies but in 16 percent of gallbladder cancers and 1.3 percent of bile duct cancers; a milder variant, high confluence of the pancreaticobiliary ducts, was present in about 1 percent of the population and 4.2 percent of gallbladder cancers. Combining prevalence with national cancer data, the authors estimated a 2.4 percent ten-year incidence of gallbladder cancer with the maljunction, 38 times the general population (Shirai 2025). That figure is the argument for removing the gallbladder, and a dilated bile duct where present, once the anomaly is found; Cancer Research UK lists the maljunction and choledochal cysts among the congenital risk factors and notes most people with these conditions develop symptoms in childhood, some only as adults.