Abnormal increase of resistance to blood flow within the hepatic PORTAL SYSTEM, frequently seen in LIVER CIRRHOSIS and conditions with obstruction of the PORTAL VEIN.
A condition in which the hepatic venous outflow is obstructed anywhere from the small HEPATIC VEINS to the junction of the INFERIOR VENA CAVA and the RIGHT ATRIUM. Usually the blockage is extrahepatic and caused by blood clots (THROMBUS) or fibrous webs. Parenchymal FIBROSIS is uncommon.