Portal hypertension is a condition in which clots or blockages, caused by conditions such as cirrhosis of the liver or coagulation disorders, increase blood pressure in the hepatic portal vein. This major blood vessel carries blood from the digestive system and spleen to the liver.

The body responds by shunting blood through collateral vessels to carry blood past the blockage. These often lie close to the oesophagus and stomach and, because they are large and fragile, tend to rupture causing extensive internal bleeding. This can also lead to vomiting of blood.

Portal hypertension and the hepatic portal vein

The hepatic portal vein is a major blood vessel that takes blood from the intestines, spleen, pancreas, gallbladder and stomach to the liver. This blood is rich in nutrients, and these are removed for processing by the liver before the blood is returned to the heart.

Portal hypertension develops when the blood pressure in the portal vein rises above normal. This can happen because of obstructions in the portal vein, within the liver, or in the hepatic veins that carry blood from the liver to the heart.

What are the underlying causes of portal hypertension?

The most common cause of portal hypertension is cirrhosis of the liver. The scar tissue that develops in cirrhosis compresses various blood vessels, leading to an increase in resistance that makes it more difficult for blood to flow through the blood vessels.

Other situations in which portal hypertension can develop include:

  • Thrombosis or blood clots in the main hepatic portal vein or in the smaller hepatic veins. These can be the result of disorders that increase blood clotting. Another common cause of thrombosis in blood vessels of the liver is inflammatory bowel disease.
  • Tumours, benign and malignant, that press on the hepatic portal vein, can lead to portal hypertension.
  • Chronic schistosomiasis, also called bilharzia, is due to a serious infestation with some species of liver fluke. Schistosomiasis is endemic in sub-Saharan Africa, parts of South America and Southeast Asia, as well as in some of the Caribbean islands and in parts of the Middle East, such as Egypt. The adult parasite develops in the liver and then lays eggs that pass through blood vessels into the digestive system to exit the body and establish new infections. Some eggs become trapped in the tissues and the body mounts a vigorous immune response to them, which causes severe tissue damage. This can block blood vessels in the liver, causing portal hypertension.
  • Viral hepatitis can cause liver damage and increase resistance to blood flow.
  • Budd-Chiari syndrome, a rare disorder in which blood cannot easily flow out of the liver because of obstruction, causing both portal hypertension and the build-up of fluid in the abdomen (ascites).
  • Increased blood flow to the liver. This is common in people whose spleen is enlarged due to disease.

Complications of portal hypertension

In someone who develops portal hypertension, the body finds other ways to return blood to the heart without going through the liver. As the liver is effectively bypassed, toxins that would normally be removed by the liver remain in the blood, causing widespread damage to organs and tissues. Lung, liver and heart problems can develop and the brain is also affected, leading to memory problems and confusion.

The bypassing blood vessels are themselves a major problem. Protruding blood vessels form in the walls of the upper stomach and oesophagus and become swollen as the blood forces its way back to the heart via alternative routes. These blood vessels, called varices, have particularly thin walls and rupture easily. This can cause small bleeds or major episodes of internal bleeding or vomiting of blood. White blood cell counts fall and patients experience low platelet levels, which makes bleeding more likely.

The impact of internal bleeding in portal hypertension

If small haemorrhages of the varices occur, this can lead to anaemia, which becomes worse over time if the portal hypertension is not treated. Major rupture of the varices can cause loss of blood through vomiting or through the large bowel and anus. The blood, which has passed through the digestive system, has a characteristic black, tarry appearance.

Bright red, fresh blood can be lost through haemorrhoids near the anus if the large veins in the rectum and anus start to carry extra diverted blood. However, having haemorrhoids in itself does not mean that you are likely to have portal hypertension.

The general disturbance in blood flow also leads to the build-up of large volumes of ascites (fluid in the abdomen). The abdomen can become very distended as a result. Peritonitis, inflammation of the abdominal wall, and kidney failure can also sometimes develop.