Imaging Findings of Mirizzi Syndrome Associated With Acalculous Cholecystitis: A Case Report.

Right upper quadrant pain is one of the most frequent reasons for consultations in the emergency room. Gallbladder pathology is among the most common etiologies and can include cholecystitis, cholelithiasis, choledocholithiasis, and cholangitis, among others. Mirizzi syndrome is a complication that manifests as hepatobiliary dysfunction due to a gallstone causing extrinsic compression of the common bile duct. However, acute cholecystitis can externally obstruct the common bile duct and mimic Mirizzi syndrome in the absence of a causative gallstone. The relevance of this syndrome lies in its timely imaging diagnosis, allowing physicians to rule out other biliary pathologies and to identify its different presentations before surgical intervention. A 72-year-old male presented with abdominal pain in the right upper quadrant for the past four days. The pain persisted, prompting his admission to the emergency department. On examination, he reported abdominal pain with a positive Murphy sign. Initial abdominal ultrasound revealed dilation of the common hepatic duct, hydrocholecyst, and thickening of the gallbladder wall. Abdominal computed tomography (CT) suggested extrinsic compression of the extrahepatic bile duct by the gallbladder. Laboratory tests revealed significant leukocytosis with neutrophilia, and inflammatory markers, including C-reactive protein and erythrocyte sedimentation rate, were elevated. Liver function tests, however, remained within normal limits, with only a slight elevation in gamma-glutamyl transferase (GGT). Magnetic resonance imaging with gadolinium ruled out neoplasia of the pancreas. A magnetic resonance cholangiopancreatography (MRCP) confirmed dilation of the extrahepatic bile duct caused by extrinsic compression from the gallbladder infundibulum at the hepatic hilum and proximal common bile duct, along with slight dilation of the intrahepatic bile duct. Hydrocholecyst and gallbladder wall thickening with signal changes due to edema were also observed. These findings confirmed an extremely rare alithiasic presentation of type I Mirizzi syndrome. The patient was offered a cholecystectomy; however, he declined surgical treatment. Conservative management was pursued, and a follow-up ultrasound performed two days later showed a significant reduction in gallbladder volume, correlating with clinical improvement.