Staged management of a giant adult Todani type IVa choledochal cyst mimicking gallbladder hydrops.

Choledochal cysts are uncommon congenital bile duct dilatations, and adult presentation is often complicated by obstruction, cholangitis, pancreatitis, stones, or malignant transformation. We report a 53-year-old woman with obstructive jaundice and severe hepatobiliary injury. Ultrasonography and contrast-enhanced computed tomography showed a giant extrahepatic bile duct cyst measuring ~15-16 cm, marked intrahepatic duct dilatation, gallbladder distension, and enhancing biliary walls without a visible obstructing stone, consistent with a Todani type IVa choledochal cyst complicated by cholangitis. Ultrasound-guided percutaneous biliary drainage was performed, with marked biochemical improvement. Definitive open surgery included cholecystectomy, complete extrahepatic cyst excision, and Roux-en-Y hepaticojejunostomy. This case highlights a surgical pitfall in which a giant bile duct cyst mimics gallbladder hydrops and supports staged decompression before definitive biliary reconstruction when cholangitis is present.