S3474 Unmasking Mirizzi Syndrome: A Case Study of Malignancy Mimicry and Infectious Complications Post-ERCP and Subtotal Fenestrating Cholecystectomy

Introduction: Mirizzi syndrome is a rare complication of cholelithiasis, characterized by impaction of a gallstone in the cystic duct or Hartmann’s pouch, causing external compression of the common hepatic duct (CHD) or common bile duct (CBD). Its clinical and radiologic overlap with biliary malignancies, especially in the setting of elevated tumor markers like CA 19-9, makes diagnosis challenging. Definitive treatment is often surgical, with potential for rare complications such as biloma—an encapsulated bile collection outside the biliary system, often iatrogenic following interventions like cholecystectomy or endoscopic retrograde cholangiopancreatography (ERCP). Case Description/Methods: A 53-year-old woman with non-insulin dependent type II diabetes mellitus presented with 4 days of nausea, vomiting, fever, and epigastric pain, alongside 2 months of unintentional weight loss. Labs showed elevated liver enzymes (AST 1792, ALT 1098, ALP 767), a GGT of 922, and CA 19-9 of 114 U/mL. Initial computed tomography A/P raised concern for a biliary system tumor. Magnetic resonance cholangiopancreatography (MRCP) revealed intra and extrahepatic biliary dilation and a distended cystic duct with a 9 mm stone compressing the CBD, suggestive of Mirizzi Syndrome. ERCP with CBD stenting and subsequent robotic-assisted cholecystectomy were performed. Intraoperative findings necessitated subtotal fenestrating cholecystectomy with indocyanine green (ICG) cholangiography due to inflammation and anatomic distortion. Seven weeks post-stent removal, the patient was readmitted with sepsis, right upper quadrant pain, and liver function tests (LFTs) derangements. Computed tomography A/P and right upper quadrant US revealed a biloma in the gallbladder fossa. Percutaneous drainage yielded 200 mL of bile, positive for Klebsiella pneumoniae. Due to rising LFTs and CBD dilation on the computed tomography A/P, repeat ERCP confirmed and removed a retained stone. The biloma resolved, and the patient was discharged on oral antibiotics with planned surgical follow-up. Discussion: Mirizzi syndrome poses diagnostic difficulty due to its mimicry of malignancy on imaging and CA 19-9 elevation, which may also occur in benign biliary obstruction. MRCP and ERCP are essential in diagnosis, with ERCP being the gold standard. Surgical management depends on disease severity; in this case, distorted anatomy required a tailored approach. Bilomas are rare post-intervention complications that can become infected, compounding morbidity. Prompt recognition and multidisciplinary management with percutaneous drainage, antibiotics, and repeat ERCP (if persistent) are key to favorable outcomes.