Incomplete Annular Pancreas with Ectopic Opening of the Pancreatic and Bile Ducts into the Pyloric Ring: First Report of a Rare Anomaly

Abstract

The patient was a 56-year-old woman who had experienced epigastralgia and dorsal pain several times over the last 20 years. She was admitted for a diagnosis of acute cholecystitis, and severe intra- and extrahepatic bile duct dilatation with inner air density was noted. No papilla of Vater was present in the descending duodenum, and 2 small holes were present in the pyloric ring. Bile excretion from one of the small holes was observed under forward-viewing endoscope. It was considered that the pancreatic and bile ducts separately opened into the pyloric ring. Based on these findings, malformation of the pancreaticobiliary duct was diagnosed. She did not wish treatment, but the obstruction associated with duodenal stenosis was noted after 2 years. Pancreatoduodenectomy was performed as curative treatment for duodenal stenosis and retrograde biliary infection through the bile duct opening in the pyloric ring. The ventral pancreas encompassed almost the entire circumference of the pyloric ring, suggesting a subtype of annular pancreas. Generally, lesions are present in the descending part of the duodenum in an annular pancreas, and the pancreatic and bile ducts join in the papillary region. However, in this patient, (1) the pancreas encompassed the pyloric ring, (2) the pancreatic and bile ducts opened separately, and (3) the openings of the pancreatic and bile ducts were present in the pyloric ring. The pancreas and biliary tract develop through a complex process, which may cause various types of malformation of the pancreaticobiliary system, but no similar case report was found on a literature search. This case was very rare and could not be classified in any type of congenital anomaly of the pancreas. We would classify it as a subtype of annular pancreas with separate ectopic opening of the pancreatic and bile ducts into the pyloric ring.

Keywords: Annular pancreas; Malformation; Pancreatoduodenectomy.

Fig. 1

a Contrast computed tomography shows mild pancreatic duct dilation and air density in the pancreatic (arrow) and common bile ducts (arrowhead). b The common bile duct shows dilatation. Air density can be seen in the intrahepatic and extrahepatic bile ducts. Orifices of the pancreatic and bile ducts appear to be close to the duodenal bulb (arrow).

Fig. 2

Upper gastrointestinal endoscopy shows no duodenal papillae in the second segment of the duodenum, but two small juxtaposed orifices (arrow) are present on the pyloric ring (arrowhead).

Fig. 3

a When contrast agent was administered into each orifice, the bile duct and the pancreatic duct were outlined separately. b The duct of Santorini (arrow) showed no dilatation and appeared to be relatively thin as compared to the duct of Wirsung (arrowhead), but both fused at the head of the pancreas, and neither was annular.

Fig. 4

The ventral pancreas can be seen to surround the pyloric ring (arrowhead) subcircularly and there is no pancreatic tissue at the second segment of the duodenum (arrow). The dorsal pancreas is located in a higher than normal position.

Fig. 5

a The ventral pancreas surrounded the pyloric ring subcircularly and no pancreatic tissue was seen at the second segment of the duodenum. b Macroscopic findings of the resected specimen also show the orifices of the pancreatic and bile ducts to be located on the pyloric ring.

Fig. 6

Histopathological findings demonstrate fibrillization and fatty replacement, mainly in the ventral pancreas. The bile duct also shows ulceration and fibrillization near the orifice (H&E, ×20).