If you review the portal circulation you may recall that normal blood flow to and from the liver depends on proper functioning of the portal vein, the hepatic artery and the hepatic veins. Disease process that damage or alter the blood flow through the liver or its major vessels are responsible for development of portal hypertension. Normal portal pressure is 5 to 10 mm/Hg and portal hypertension exists when this pressure rises. Let us define portal hypertension.
When the pressure in the uortai system increases or rise above 10 mm/Hg due to obstruction of any major portion of portal and hepatic venous bed and collaterals form as a result of poor blood flow through major venous channels. The spleen and other organs that empty into portal system also begin to undergo the effects of congestion.
The portal hypertension may be of two types.
i) Intrahepatic portal hypertension
ii) Extrahepatic portal hypertension