A case of biliary atresia with pancreaticobiliary maljunction.

Background: The pathogenesis of biliary atresia (BA) is still unknown. There are several reports on the etiology of BA, including pancreaticobiliary maljunction (PBM). We experienced a case of Kasai type IIIa BA with PBM, in which we found elevation of pancreatic enzymes in the gallbladder. We evaluated whether PBM is related to the pathogenesis of BA based on our findings.

Case Presentation: The patient was born at 40 weeks of gestation. His body weight at birth was 2850 g. At the age of 4 days, he had an acholic stool and was referred to our hospital. Abdominal ultrasonography showed that triangular cord sign was negative. The gallbladder was isolated with a diameter of 19 mm, and it contracted in response to oral feeding. His ultrasonographic findings were atypical for BA, but his jaundice did not improve. Therefore, we performed an operation at the age of 56 days. Intraoperative cholangiography showed a common bile duct and pancreatic duct and a common channel patent, while the common hepatic duct or intrahepatic duct was not visualized. Bile in the gallbladder contained colorless fluid, which showed elevated lipase level (34,100 IU/L). We performed Kasai portoenterostomy under the diagnosis of Kasai type IIIa BA with PBM. The patient's postoperative course was uneventful, and he was discharged on day 30 after the operation. Histopathological evaluation showed that the lumens of the common bile duct and cystic duct were patent. However, the common hepatic duct was closed, and only bile ductules with diameters of less than 50 μm were isolated. Infiltration of lymphocytes was detected in the porta hepatis. No apparent inflammation was observed around the cystic duct, which was constantly exposed to pancreatic juice because of reflux through PBM.

Conclusions: Reflux of pancreatic juice through PBM might not be an etiological factor for BA, but might be associated with patency of the common and cystic bile ducts in Kasai type IIIa BA.