Portal hypertension overview
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Portal hypertension is hypertension in the portal stem which causes an obstruction in the portal vein and its branches. It is often defined as a portal pressure gradient (the difference in pressure between the portal vein and the hepatic veins) of 12 mm Hg or greater. Many conditions can result in portal hypertension. In North America and Europe, it is usually the result of an intrahepatic block due to cirrhosis of the liver. However, in less industrialized parts of the world, climate permitting, the major cause is schistosomiasis.
Pathophysiology
Portal venous pressure is determined by portal blood flow and portal vascular resistance. Increased portal vascular resistance is often the main factor responsible for it. The consequences of portal hypertension are due to blood being forced down alternate channels by the increased resistance to flow through the portal system. Due to formation of alternate channels initially some of the portal blood and later most of it is shunted directly to the systemic circularion bypassing the liver.