Pancreas Divisum, Biliary Cysts, and Other Congenital Anomalies

Ectopic Major Papilla

The major papilla, which is typically located in the mid-duodenum or distal second duodenum, is occasionally located in the third duodenum. Ectopic distal location of the ampulla is associated with anomalous pancreaticobiliary junction (APBJ), congenital biliary dilatation, and biliary cysts. The distal displacement of the papilla may correspond to the length of an abnormally long common channel and may reflect failure of the ducts to migrate normally into the duodenum during embryologic development. Rarely the major papilla may be located in the duodenal bulb. Double papilla of Vater has been described. When the papilla is in an anomalous location, the oblique intramural course of the bile duct is often absent, leaving less room for endoscopic biliary sphincterotomy.

Anomalous Pancreaticobiliary Junction

The bile duct and pancreatic duct typically form a common channel of 1 to 6 mm in the papilla of Vater. Less commonly a long common channel is present ( Fig. 35.1 ), which may be termed the anomalous pancreaticobiliary junction (APBJ). Synonyms include anomalous union of pancreaticobiliary duct, anomalous arrangement of the pancreaticobiliary duct, or anomalous pancreaticobiliary union. APBJ may be subdivided into pancreaticobiliary malunion (PBM), in which the junction of the bile duct and pancreatic duct lies outside of the duodenal wall, with free communication between the ducts when the ampullary sphincter is contracting, and high confluence of pancreaticobiliary ducts (HCPBD), in which contractions of the duodenal wall or sphincter interrupt communication between the ducts. APBJ can also be subclassified according to the presence or absence of pancreas divisum, a dilated common channel, and an acute angle between the bile duct and pancreatic duct. These findings may influence treatment strategy in symptomatic patients, particularly those with biliary cysts. APBJ promotes reflux of pancreatic juice into the biliary system, and a bile amylase concentration of >8000 IU/L may be considered diagnostic of an anomalous ductal junction.

APBJ appears to be a risk factor for the development of malignancy in a biliary cyst, as discussed in the next section. Patients with APBJ and no biliary cyst have an increased risk of biliary cancer and develop gallbladder cancer at an earlier age ( Fig. 35.2 ). The risk of gallbladder cancer in patients with HCPBD may be somewhat lower than the risk seen with PBM. Either way, the finding of an isolated APBJ should prompt consideration of prophylactic cholecystectomy and perhaps longitudinal surveillance of the bile duct. Unexplained thickening of the gallbladder wall identified on transabdominal ultrasonography has been associated with underlying APBJ.