A case of choledochocele mimicking choledocholithiasis on MR cholangiography: A new differential diagnosis of pseudo-filling defect.

We present the case of a 79-year-old female with acute cholangitis and cholecystitis who presented with right upper quadrant pain. Thin-collimation MR cholangiogram showed a filling defect measuring 1 cm, which was less prominent on single-slab images. Endoscopy showed dynamic ballooning and collapsing of the ampulla of Vater, and a cholangiogram showed characteristic bulging at the distal common bile duct, which led to the diagnosis of choledochocele. It is important to differentiate choledochocele as a cause of filling defect of the lower common bile duct on the MR cholangiogram.