Choledochal or pancreatic cyst? Role of endoscopic ultrasound as an adjunct for diagnosis: a case series.

BACKGROUND: Choledochal cysts (CC) are a cystic dilation of the intra- or extrahepatic biliary tree. They are rare, and are associated with a risk of malignant transformation. Due to the close proximity to the pancreas, Type II CC, in which a diverticular outpouching is connected to the extrahepatic bile duct via a narrow stalk, can be difficult to differentiate from pancreatic cysts. The aim of this study was to determine the role of endoscopic ultrasound (EUS) in the diagnosis of Type II CC.

METHODS: A retrospective review of all patients seen in the Multidisciplinary Pancreatic Cyst Clinic at Johns Hopkins Hospital from November 2010 to March 2014 was performed to identify patients classified as having Type II CC on computed tomography (CT) or magnetic resonance imaging (MRI) who also underwent EUS. Patient demographics, clinical presentation, imaging, and follow-up were recorded.

RESULTS: Four female patients with median age of 52 years, three of whom were identified as having Type II CC and one as equivocal for CC on MRI, and two as having Type II CC, one equivocal for CC and one as branch-duct intraductal papillary mucinous neoplasm on CT. On EUS, no communication was seen in any cases between the CC and common bile duct. EUS-guided fluid aspiration from each cyst demonstrated clear fluid with undetectable bilirubin and either elevated CEA or amylase confirming the diagnosis of pancreatic cyst.

CONCLUSIONS: EUS is a useful tool for the differentiation of equivocal cases of CC. It can show a very small separation as little as 1 mm between two structures, and cyst fluid analysis can be performed and used to further differentiate between biliary cysts and other cystic structures.