Incidentally detected localized Todani Type IVa choledochal cyst in an asymptomatic adult female: A rare case report.

Background: Todani Type IVa choledochal cysts are rare congenital malformations involving both intrahepatic and extrahepatic bile ducts. Adult-onset, asymptomatic, and localized presentations are exceptionally uncommon and pose a surgical challenge, particularly when considering the extent of resection and reconstruction required.

Case Presentation: We report the case of a 24-year-old asymptomatic female who was incidentally diagnosed with a localized Todani Type IVa cyst involving the left hepatic lobe and the common bile duct. Imaging revealed segmental intrahepatic cystic dilatation confined to the left lobe, with the right hepatic system remaining unaffected. The patient underwent a successful left hepatectomy and complete excision of the extrahepatic bile duct, followed by a Roux-en-Y hepaticojejunostomy directly anastomosed to the right hepatic duct. She was discharged on postoperative day 3 in excellent condition.

Clinical Discussion: Unlike most reported cases involving diffuse or bilobar intrahepatic extension or complicated pediatric presentations, our patient had a rare, unilobar adult Type IVa cyst with no inflammatory or malignant features. The decision to perform partial hepatectomy was guided by precise preoperative imaging, allowing complete resection without the need for liver transplantation. This case highlights the role of anatomical localization and individualized surgical planning in managing select cases of Type IVa choledochal cysts.

Conclusion: This case illustrates a rare adult presentation of localized Todani Type IVa choledochal cyst, successfully treated with left hepatectomy and Roux-en-Y hepaticojejunostomy. It supports the use of tailored surgical strategies based on precise anatomical assessment, especially in asymptomatic patients with unilobar involvement.