Abstract
A female in her 40s was referred to our hospital for further examination of her dilated extrahepatic bile duct detected on plain CT during a health checkup. Transabdominal ultrasonography (US) revealed circumferential wall thickening of the gallbladder without a solid lesion or stones. The extrahepatic bile duct showed fusiform dilatation to a maximum diameter of 12 mm, with the distal bile ducts showing circumferential diffuse thickening accompanied with the inner hypoechoic wall layer. Contrast-enhanced CT, magnetic resonance cholangiopancreatography (MRCP), and endoscopic ultrasonography (EUS), as well as US, demonstrated fusiform dilatation of the extrahepatic bile duct. However, the confluence of the pancreatic duct and bile duct was difficult to demonstrate. Endoscopic retrograde cholangiopancreatography (ERCP) revealed dilatation of the extrahepatic bile duct and simultaneously visualized the main pancreatic duct, which we determined to represent a pancreaticobiliary confluence outside the duodenal wall. Both amylase and lipase levels in the bile juice were markedly elevated. The patient was diagnosed with pancreaticobiliary maljunction (PBM) and congenital biliary dilatation (Todani Classification Ic). Consequently, we performed an extrahepatic bile duct resection and cholecystectomy. Histopathological examination revealed neither malignant findings nor dysplasia in the resected gallbladder and bile duct. The gallbladder mucosa exhibited hyperplasia with inflammation, and the distal bile duct wall showed predominantly hyperplasia. As in this case, PBM with bile duct dilatation may present with gallbladder and bile duct wall thickening due to mucosal hyperplasia. At US examination, it is important not only to detect extrahepatic bile duct dilatation but also to demonstrate the characteristic pathological conditions of this disease.
