Mirizzi Syndrome Mimicking Cholangiocarcinoma Complicated by Infected Biloma Formation Following Complex Biliary Intervention: A Case Report

Mirizzi syndrome is a rare but clinically significant complication of chronic cholelithiasis. It is characterized by extrinsic compression of the common hepatic duct (CHD) by an impacted gallstone in the gallbladder neck or cystic duct. Although rare, this condition can closely mimic cholangiocarcinoma, particularly in the presence of elevated tumor markers or atypical imaging findings. Timely recognition is essential, as misdiagnosis may lead to inappropriate surgical or oncologic interventions. We present a diagnostically challenging case of Type I Mirizzi syndrome complicated by infected biloma formation occurring shortly after elective biliary stent removal in the setting of prior subtotal cholecystectomy and a retained common bile duct (CBD) stone. A 53-year-old female presented with nausea, vomiting, weight loss, and elevated transaminases. Imaging revealed biliary ductal dilatation and abnormal gallbladder morphology, raising suspicion for a biliary tract malignancy. CA 19-9 was mildly elevated initially but decreased following biliary decompression, further supporting a benign obstructive process rather than malignancy. Magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography (MRCP) protocol demonstrated distal CBD compression by an enlarged cystic duct containing a filling defect, consistent with Type I Mirizzi syndrome. The diagnosis was confirmed via endoscopic retrograde cholangiopancreatography (ERCP), which also served as the initial therapeutic intervention with biliary sphincterotomy, stone extraction, and stent placement. The patient subsequently underwent robotic-assisted cholecystectomy with a subtotal fenestrating technique due to difficult anatomy, with an initially uncomplicated postoperative course. Seven weeks after cholecystectomy, the patient underwent elective biliary stent removal and re-presented within 48 hours with abdominal pain and signs of biliary sepsis. Imaging confirmed a complex fluid collection in the gallbladder fossa consistent with a biloma, along with recurrent CBD dilation and a retained CBD stone contributing to recurrent biliary obstruction. The patient underwent percutaneous drainage followed by repeat ERCP with stone extraction. Cultures of biloma fluid and blood grew Klebsiella pneumoniae and Escherichia coli, respectively, consistent with biliary sepsis. With antibiotic therapy and successful drainage, the patient improved clinically and was discharged with outpatient follow-up. This case highlights the diagnostic complexity of Mirizzi syndrome, particularly its ability to masquerade as malignancy due to overlapping radiologic and biochemical features. It also underscores the importance of recognizing infected biloma formation and recurrent biliary obstruction as potential complications following complex biliary interventions, particularly in patients undergoing subtotal cholecystectomy and biliary stent management. Management is inherently multidisciplinary, involving interventional radiology, gastroenterology, and surgery. Early recognition and timely intervention are essential to prevent infectious sequelae and optimize outcomes.