What causes portal hypertension?
Portal vein thrombosis is only one cause of portal hypertension, and usually happens in children whose liver is otherwise normal. Often the high blood pressure is due to a blockage, typically a large clot, in the large vein to the liver, and as a result,
blood no longer flows normally (this blockage is known as extra-hepatic portal vein thrombosis, EHPVT).
In an attempt to get around the blockage, the body grows new blood vessels (called varices) that connect blood flow from the intestine directly to the general circulation, bypassing the liver. The new blood vessels are commonly found near the stomach, esophagus and spleen. When this liver bypass occurs, waste products that are normally removed by the liver pass into general circulation.
Two factors can increase blood pressure in the portal blood vessels: increased volume of blood flowing through the vessels and increased resistance to the blood flow through the liver. In Western countries, the most common cause of portal hypertension is increased resistance to blood flow caused by cirrhosis (most often due to excessive alcohol intake).
No one knows what causes the blood to form clot. Some theories suggest that an infection or inflammation of the umbilical vein may trigger the clot formation, but studies are still inconclusive. |
