Post written by Lawrence Ku, MD, from the Division of Gastroenterology, Harbor-UCLA Medical Center, Torrance, California, USA.

This case highlights the diagnostic dilemma of differentiating between 2 types of choledochal cysts, type II versus type VI. Although rare, these choledochal cysts have significant malignant potential, ranging from 5 to 7.5%. Malignant transformation of type VI choledochal cysts has been described in 2/15 adult cases based on the review of literature. Both type II and type VI choledochal cysts require surgical resection.

The decision of a multidisciplinary meeting in our case was to proceed with EUS/ERCP prior to surgical resection as a definitive diagnosis could not be established on pre-operative imaging. ERCP with direct cholangioscopy was instrumental in the diagnosis of type VI choledochal cyst with no gross evidence of malignancy. Pre-operative diagnosis allowed for appropriate surgical planning; our patient underwent outpatient laparoscopic cholecystectomy with en bloc cyst resection rather than the more extensive Roux-en-Y hepaticojejunostomy. Pathology confirmed no dysplasia.

Our case presents a rarely occurring type VI choledochal cyst and demonstrates both the advantages of ERCP with direct cholangioscopy and the technical limitations of various imaging modalities. Neither MRCP nor EUS could definitively identify the origin of the choledochal cyst as bile duct (type II) or cystic duct (type VI); ERCP with cholangioscopy provided the answer.

Cholangioscopy is a valuable tool for evaluation of complex biliary anatomy allowing for direct visualization of the lesion and for simultaneous tissue acquisition if needed.

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