Cholecysto-biliary fistula mimicking type 1 Mirizzi syndrome: A case report.

backgroundMirizzi syndrome is a rare complication of chronic gallstone disease in which an impacted stone causes compression or erosion of the common hepatic duct. Accurate preoperative diagnosis is crucial but often challenging. We report a case that was preoperatively diagnosed as type 1 Mirizzi syndrome but was found intraoperatively to be type 4, involving a cholecysto-biliary fistula and complete erosion of the common hepatic duct. CASE SUMMARY: A 74-year-old woman presented with right upper quadrant discomfort. Initial workup including ultrasound and magnetic resonance cholangiopancreatography suggested Mirizzi syndrome type 1 due to extrinsic compression of the common hepatic duct. Endoscopic retrograde cholangiopancreatography confirmed a large stone without evidence of fistula. The patient underwent robotic-assisted cholecystectomy, during which a 4 cm stone was found eroding into the common hepatic duct, consistent with type 4 Mirizzi syndrome. Intraoperative cholangioscopy confirmed the fistula and allowed primary repair. The patient recovered uneventfully and was discharged on postoperative day one.

conclusionPreoperative imaging may fail to identify fistula formation in Mirizzi syndrome. Intraoperative assessment remains critical for accurate diagnosis and safe surgical management.