Type Vb double common bile duct complicated by gallbladder cancer

Double common bile duct (DCBD) is an extremely rare biliary anomaly with subtype-dependent oncological risk. We report a case of DCBD (Choi classification type Vb) complicated by gallbladder cancer. A 75-year-old woman was incidentally found to have a gallbladder fundus tumor on screening ultrasonography. Preoperative imaging suggested gallbladder cancer within clinical T3 or less. Biliary evaluation by magnetic resonance cholangiopancreatography (MRCP), drip infusion cholangiography-computed tomography (DIC-CT), and endoscopic retrograde cholangiopancreatography (ERCP) confirmed Choi type Vb DCBD without pancreaticobiliary maljunction (PBM). The patient underwent open extended cholecystectomy with a stepwise intraoperative strategy guided by frozen section analysis. Frozen section confirmed adenocarcinoma; as the cystic duct margin was tumor-free, lymph node dissection was limited to the cystic duct nodes without hepatoduodenal ligament dissection. Final pathology: adenocarcinoma (well to moderately differentiated), pT1b, pN0 (0/3), pStage IB (Union for International Cancer Control [UICC] 9th edition), pR0. The patient was discharged on postoperative day 11 and remained recurrence-free at 6 months. To our knowledge, this is the fourth reported type Vb DCBD case in the English-language literature and the first associated with gallbladder cancer. Preoperative evaluation of biliary anatomy, including PBM status, and a stepwise intraoperative approach are essential for safe and oncologically appropriate management.