Mirizzi Syndrome With a Hepatic Duct Confluence Fistula and Stone Migration Into the Left Hepatic Duct: A Case Report

Mirizzi syndrome (MS) is an uncommon complication of cholelithiasis, in which an impacted gallstone causes extrahepatic biliary obstruction via extrinsic duct compression. Advanced disease may progress to cholecystobiliary fistula formation. We report the case of a 75-year-old man with cardiometabolic comorbidities who presented with cholestatic liver biochemistry and imaging findings consistent with chronic calculous cholecystitis. Computed tomography and magnetic resonance cholangiopancreatography revealed a distended gallbladder packed with stones, hilar biliary narrowing, and a variant biliary configuration in which the right posterior sectoral duct drained into the left hepatic duct and the right anterior sectoral duct drained into the common hepatic duct. Endoscopic retrograde cholangiopancreatography (ERCP) enabled the clearance of distal common bile duct stones and placement of biliary stents for decompression, but did not definitively delineate the fistula. During laparoscopic surgery, the gallbladder was densely inflamed and intrahepatic, with a sizeable cholecystobiliary fistula at the hepatic duct confluence and intraductal stones within the confluence and the left hepatic duct. We did not identify previous reports describing this pattern of stone migration in the setting of pre-existing variant biliary anatomy. A laparoscopic fundus-first, fenestrated subtotal cholecystectomy was performed along with stone extraction and controlled external drainage. Postoperatively, hepatic and subphrenic abscesses with retained stones were managed with antibiotics, image-guided drainage, repeat ERCP for stent removal, and delayed laparoscopic washout with stone retrieval. This case highlights the limitations of preoperative imaging in complex fistulating MS and supports multimodal investigation, intraoperative contingency strategies, and planned staged management in high-risk patients.