The liver filters venous blood from abdominal organs.
Portal hypertension is increased blood pressure in the veins of abdominal organs.
The primary vein that carries blood from the abdominal organs to the liver is called the portal vein. When this vein clots or when the liver develops scar tissue from disease and compresses the vein, the blood pressure in the vein goes up and portal hypertension develops. Blood backing up in the veins of abdominal organs causes typical signs of portal hypertension such as ascites to develop. Ascites is free fluid in the abdomen caused by blood being under high pressure and some of its liquid portion squeezing through the vessels and settling in the abdomen. Hypersplenism is an enlarged spleen caused by blood congestion and increased destruction of blood cells due to spleen hyperactivity.