Portal hypertension is high blood pressure in the veins that filter blood from the intestines through the liver (portal system of the liver). It may cause complications such as fluid buildup in the abdominal cavity (ascites) or enlarged veins (varices) in the esophagus or stomach.

Cirrhosis, a process that destroys the liver, is the most common cause of portal hypertension in the United States. Normally, blood from the spleen and intestines is filtered through the liver by way of the portal vein. However, when the buildup of scar tissue caused by cirrhosis reduces the flow of blood through the liver, pressure may build up in the portal vein, causing portal hypertension.

Portal hypertension is different from the high blood pressure (systemic hypertension) many people develop as they get older.