The liver is like a sewage treatment plant in the body. Blood from the intestines flows some waste and toxins through the portal vein into the liver and out of the body. Normally, blood flows through the liver and then into the lungs. When liver disease occludes blood vessels in the liver resulting in increased portal pressure, some of the blood bypasses the liver and goes directly to the lungs, and those harmful substances may damage the pulmonary artery endothelium, causing pulmonary hypertension, also known as portal pulmonary hypertension. There is no direct relationship between the severity of liver disease and the condition of pulmonary hypertension, and it is not certain that you will develop pulmonary hypertension if you have liver disease; the incidence of pulmonary hypertension in patients with liver disease is 2 to 5 percent. Therefore, it may be related to you yourself, that is, you are more likely to have pulmonary hypertension than others.