Last reviewed 08/2021

The portal vein is formed by the union of the splenic and the superior mesenteric veins at the level of L2 behind the head of the pancreas. There is a mild gradient across the liver to the hepatic vein in which blood is returned to the heart via the inferior vena cava.

In portal hypertension, blood is diverted into collaterals between the portal and the systemic venous systems, principally at:

  • the gastro-oesophageal junction
  • rectum
  • left renal vein
  • left testicular vein
  • the diaphragm
  • retroperitoneum
  • the anterior abdominal wall via the umbilical vein