Hepatic portal vein

At a glance

English

Hepatic portal vein

Latin (TA2)

Vena portae hepatis

System

Vein

Region

Trunk

Side

Single, on the midline

About the hepatic portal vein

The hepatic portal vein gathers venous blood from almost the whole digestive tract within the abdomen, from the lower oesophagus to the upper anal canal, together with the spleen, pancreas and gallbladder, and delivers it to the liver rather than to the heart. About eight centimetres long, it begins posterior to the pancreatic neck, at the level of the second lumbar vertebra, where the splenic vein joins the superior mesenteric vein; for this reason the start of the vessel is sometimes called the splenomesenteric confluence. The inferior mesenteric vein usually ends in the splenic vein, though it may open at the confluence or into the superior mesenteric vein instead.

From its origin the vein runs upwards and to the right behind the first part of the duodenum and then climbs in the free edge of the lesser omentum (the hepatoduodenal ligament). Here it lies behind the bile duct and the hepatic artery proper, and in front of the epiploic foramen. Along the way it receives the right and left gastric veins, the prepyloric vein, the cystic vein and the paraumbilical veins. At the porta hepatis it splits into right and left branches, which keep dividing inside the liver. The finest portal venules travel with hepatic arterioles and bile ductules in the portal triads and finally empty into the sinusoids.

Because it feeds a second capillary bed, the portal vein is not an ordinary vein. Its system is one of the body's two portal systems, the other being in the pituitary. About three-quarters of the blood reaching the liver comes this way, the rest arriving through the hepatic artery. The arrangement lets liver cells take up absorbed nutrients first and clear swallowed toxins and drugs before they reach the general circulation.

Raised pressure in the portal system, portal hypertension, most often follows cirrhosis. Blood then forces its way through the portosystemic anastomoses, which swell into oesophageal varices, rectal varices or the dilated periumbilical veins called caput medusae, and may bleed. Ascites and splenic enlargement are also typical. On ultrasound a widened vein and slow flow support the diagnosis, and increased pulsatility may point to cirrhosis or high right atrial pressure. Infection of the vein (pylephlebitis), often from diverticulitis, and portal venous gas from bowel ischaemia are rarer findings.

Course and drainage

Begins at

Formed posterior to the pancreatic neck, at about L2, where the splenic and superior mesenteric veins meet.

Drains into

Divides at the porta hepatis into right and left branches, which end in portal venules that empty into the hepatic sinusoids.

Drains

Drains the abdominal digestive tract, spleen, pancreas and gallbladder, bringing nutrient-rich blood to the liver; it supplies most of the liver's blood flow.