Accessory gallbladder lithiasis presenting as acute cholangitis.

Accessory gallbladder is an uncommon congenital anomaly that may present significant diagnostic and surgical challenges, particularly when associated with biliary complications. We report a case presenting features of common bile duct obstruction and cholangitis. Multimodality imaging, including computed tomography and magnetic resonance cholangiopancreatography, enabled preoperative identification of an accessory gallbladder. Magnetic resonance cholangiopancreatography was especially useful in differentiating this anomaly from other cystic biliary lesions and in accurately delineating the biliary anatomy. These findings guided management, allowing detection of common bile duct stone migration and appropriate treatment. This case highlights the key role of imaging in the accurate diagnosis of rare biliary anomalies and in reducing the risk of surgical complications.