A Biliary Behemoth: A Report of a Rare Case of a Giant Choledochal Cyst.

Choledochal cysts are very uncommon congenital anomalies of the biliary tract, most commonly diagnosed in childhood. Adult presentation is uncommon and often atypical. Giant choledochal cysts, defined as cysts measuring more than 10 cm, are exceptionally rare and present significant diagnostic and surgical challenges. A 19-year-old female presented with a two-month history of dull-aching abdominal pain, progressive right upper quadrant abdominal swelling, and features of obstructive jaundice. Physical examination revealed deep jaundice and a large, non-tender abdominal mass. Imaging studies, including ultrasonography, contrast-enhanced computed tomography, and magnetic resonance cholangiopancreatography, demonstrated a large cystic lesion communicating with the gallbladder and common bile duct, consistent with a Todani type IA choledochal cyst. Exploratory laparotomy revealed a massive extra-hepatic biliary cyst measuring approximately 20 × 25 × 28 cm and containing over 1.6 L of bile. Complete excision of the cyst along with cholecystectomy was performed, followed by Roux-en-Y hepaticojejunostomy for biliary reconstruction. Giant choledochal cysts in adults are rare and may mimic other intra-abdominal cystic lesions due to their size and mass effect on adjacent organs. Accurate preoperative diagnosis is crucial for appropriate surgical planning. Complete excision of the cyst with biliary reconstruction is mandatory to prevent complications such as cholangitis, biliary cirrhosis, pancreatitis, and malignant transformation. Giant choledochal cysts are an extremely rare presentation of congenital biliary disease in adults. Despite diagnostic difficulties, timely recognition and complete surgical excision with biliary reconstruction offer excellent outcomes and remain the cornerstone of management.