Common bile duct duplication: the more the murkier

Abstract

Congenital duplication of the common bile duct is an extremely rare anomaly of the biliary tract, which putatively represents failure of regression of the embryological double biliary system. Depending on the morphology of the duplicated bile duct, the anomaly can be classified into five distinct subtypes as per the modified classification (proposed by Choi et al). Among the five subtypes of bile duct duplication, type V duplication is considered to be the least common with only two previous cases of type Va variant reported in medical literature prior to the current report.

Figure 1

Thick slab (2D) MRCP image showing duplicated extrahepatic bile ducts running parallel (arrowheads) and reuniting into a common channel (dotted arrow) at the level of the head of the pancreas consistent with type Va double common bile duct. In addition, a filling-defect suggestive of an obstructive calculus is seen in the common channel just above the ampulla (arrow). The cystic duct is inserting into the right-sided bile duct

Figure 2

Modified double common bile duct classification proposed by Choi et al. Type I, septum dividing the bile duct lumen; type II, the distal bile duct bifurcates and each channel drains independently; type III, double bile ducts without (a) or with intrahepatic communicating channels (b); type IV, double bile duct with extrahepatic communicating channel(s); and type V, single biliary drainage of double bile ducts without (a) or with communicating channels (b)