The liver is like a sewage treatment plant in the body, where the blood from the intestines flows some of the wastes and poisons 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 increases the pressure in the portal vein due to occlusion of blood vessels in the liver, some of the blood bypasses the liver and goes directly to the lungs. Those harmful substances may damage the endothelium of the pulmonary arteries, causing pulmonary hypertension, also known as portal hypertension. There is no direct relationship between the severity of liver disease and the condition of pulmonary hypertension, and it is not a given that you will develop pulmonary hypertension if you have liver disease. Therefore, it may have something to do with you, which means that you are more likely to get pulmonary hypertension than others.