Type Vb Double Common Bile Duct: A Rare Case Associated With Cholangiocarcinoma.

Double common bile duct (DCBD), also called extrahepatic biliary duct duplication, is a rare anatomical variation of the biliary anatomy that involves either the presence of a septum within the common bile duct (CBD) or an accessory CBD. The first case of DCBD was reported by Vesarius in 1543. A classification system for DCBD that included five types was proposed in 2007. Type V DCBD involves a duplicated extrahepatic bile duct with common drainage of both ducts into the duodenum and can be further divided into type Va, where there are no communicating channels, and type Vb, where there are one or more communicating channels. By 2021, only eight cases of type V DCBD had been reported, of which only two were type Vb DCBDs. As far as we know, this is the third reported case of type Vb DCBD. In addition to choledocholithiasis, cholangitis, and pancreatitis, DCBD has been associated with an increased risk of malignancies such as cholangiocarcinoma and upper gastrointestinal tract cancers. Here, we present a case of a 28-year-old female with intrahepatic cholangiocarcinoma undergoing chemotherapy who was referred to our hospital for evaluation of worsening jaundice and suspicion of infected percutaneous transhepatic cholangiography (PTC) drain. After extensive investigation, she was found to have a type Vb DCBD, which meant that her PTC drain was only providing partial therapy for her biliary obstruction. Following the placement of metal stents in both CBDs, her jaundice resolved, allowing her to continue her chemotherapy regimen. In conclusion, this case highlights one of the rarest bile duct anatomical variations, a type Vb DCBD, as well as the importance of evaluating young cholangiocarcinoma patients with magnetic resonance cholangiopancreatography (MRCP) for the presence of a DCBD, especially when they present with worsening jaundice despite receiving appropriate therapy. These patients require stenting of both CBDs to properly address their biliary obstruction.