The portal vein is rarely variable. It often receives the left gastric vein, and may also receive an accessory splenic, inferior phrenic branch, pancreaticoduodenal, a pulmonary vein or right gastroepiploic vein. The hepatoduodenal ligament constitutes the anterior margin of the foramen of Winslow and enclosed the common bile duct, hepatic artery, and portal vein.
Branches forming the portal vein are also variable.
The splenic vein may anastomose with the renal or with the superior mesenteric vein. The superior mesenteric vein has been reported opening into the renal vein. It has also been reported to be doubled. An account of two instances of uncommon formation in the viscera of the human body. Anson, B.J., Ed.