TYPE IVa CHOLEDOCHAL CYST

4-year-old girl with a history of choledochal cyst. Pre-surgical evaluation.

The VI MRCP image on the left show the common bile duct overlapping the duodenum. There is suggestion of a cystic structure in the common bile duct region, but it is not clearly visualized due to overlapping structures. The image on the right is the same image with the stomach and gallbladder cut away in order to eliminate overlapping structures when the volume is viewed in other projections.

 

Rotating the VI MRCP data volume with the overlapping structures cut away allows clear visualization of the anatomy of the choledochal cyst. Portions of the intrahepatic ducts are now also seen to also be dilated (i.e. a type IVa choledochal cyst). This specific diagnosis can not be made confidently using only the Standard MRCP images.

 

These Standard MRCP images also show the choledochal cyst, but do not provide any additional anatomic information. The choledochal cyst is obscured by overlying duodenum on the left image and could easily be confused with duodenum on the right image.

 

The Standard MRCP image on the left shows high signal in the duodenum with a round high signal structure more superiorly towards the porta hepatis. Only on the Axial T2 MRI movie on the right can it be determined that this round structure is a portion of the common bile duct (i.e. a choledochal cyst).