Preduodenal portal vein

Passage of the portal vein anterior to the duodenum is a rare vascular anomaly that is a result of a variation in the normal developmental pattern of the right and left vitelline veins and their three anastomotic channels. In operations on the duodenum or biliary tract in patients with this condition, there is marked danger of inadvertent tearing, division, ligation, or excessive handling causing thrombosis. One case is added to the twenty-five previously reported in the literature.