Portal Hypertension

The liver serves many purposes within the body from making carbohydrates, proteins and fats to synthesizing bile to help digest found. Because of this, the liver requires a significant blood supply. As opposed to other organs in the body, the majority of this blood supply (75%) comes from the venous system through the portal system. Blood vessels from the stomach, small intestine, pancreas, and spleen converge and form the portal vein delivering nutrients and chemical building blocks to the liver. Once in the liver, the portal vein and hepatic artery (which accounts for 25% of the liver's blood supply) come together to form sinusoids, spaces where the blood is filtered. From there, blood makes its way to the Vena cava, the largest vein in the body to return to the heart.

Portal hypertension describes elevated pressure within the portal system, including the portal vein and the tributary veins that drain into it. The pressure within the portal system is not normally measured and is not an issue except if an illness or disease occurs that makes it difficult for blood to flow through the liver tissue. This damming effect increases pressure within the portal venous system and causes potential problems with liver function. It is the onset of symptoms associated with liver disease that might cause the health care professional to look for the presence of portal hypertension.

Portal hypertension occurs when there is an obstruction of blood flow through the liver and pressure rises within the portal vein. This obstruction can be intrahepatic (intra=within +hepatic=liver), pre-hepatic (pre=before) or post- hepatic (post=after).

Intrahepatic causes of portal hypertension include cirrhosis and hepatic fibrosis or scarring. A wide variety of illnesses are implicated as the cause of portal hypertension. Examples include the following:

• Alcohol abuse,
• Hepatitis B and C infections,
• Fatty liver (NASH, non-alcoholic steatohepatitis),
• Wilson's disease, an abnormality of copper metabolism,
• Hemochromatosis (iron overload), excess iron buildup
• Cystic fibrosis
• Primary sclerosing cholangitis, a hardening of the bile ducts
• Biliary atresia, poorly formed bile ducts
• Parasite infections such as schistosomiasis

• Portal vein thrombosis or blood clots within the portal vein
• Congenital portal vein atresia or failure of the portal vein to develop

Post-hepatic causes are due to obstruction of blood flow from the liver to the heart and can include:

• Hepatic vein thrombosis
• Inferior Vena cava thrombosis
• Restrictive pericarditis, where the lining of the heart stiffens and does not allow the heart to relax and expand when blood returns to it. Causes may include tuberculosis, fungal infections, tumors, connective tissue disorders (for example, scleroderma), and complications from radiation therapy.

Source: MedicineNet.com
http://www.medicinenet.com/portal_hypertension/article.htm