A 60-year-old female, with a history of laparoscopic cholecystectomy in 1996, which was converted to an open approach due to bleeding from an unidentified vessel, was referred to our practice for surgical management of a common bile duct stone that was not amenable to endoscopic retrograde cholangiopancreatography (ERCP). An abdominal computed tomography (CT) scan was obtained at our facilities to better delineate the patient’s biliary anatomy. The CT scan revealed multiple incidental findings of intestinal malrotation, a left-sided inferior vena cava (IVC), azygous continuation of the IVC, and a double portal system, characterized by the presence of two distinct portal veins entering the liver. In this scan, the superior mesenteric vein was seen giving a branch anterior to the pancreas before joining the splenic vein behind the pancreas (Figure 1).

This anterior branch continues towards the porta hepatis as a portal vein, and the posterior branch joined by the splenic vein continues laterally to the right and enters the liver at its edge close to segment VI as the second portal vein (Figure 2). The two portal veins were noted to communicate inside the liver parenchyma near segment VIII (Figure 3).

Due to the patient’s previous surgical history, and her preference for an open common bile duct (CBD) exploration was performed, the patient’s anomalous anatomy was identified intraoperatively (Figure 4) behind dense adhesions from her previous operation. Other than meticulous dissection and care during the procedure these findings did not alter the surgical plan or the operation's course. Postoperatively the patient did very well and she was discharged home on postoperative day 3.