Portal hypertension is elevated pressure within the portal vein (the vein that carries blood from the digestive organs to the liver). This can be caused by fundamental liver disease, obstruction, or structural changes. The increase in pressure is caused by a blockage in the blood flow through the liver.
Increased pressure in the portal vein causes large veins (varices) to develop across the esophagus and stomach to get around the blockage. The varices become fragile and can bleed easily.
The most common cause of portal hypertension is cirrhosis, or scarring of the liver. Cirrhosis is a result of a liver injury after healing. This injury can be caused by hepatitis, alcohol abuse, or other causes of liver damage. Other causes of portal hypertension are thrombosis, or a blood clot that develops in the portal vein.