Portal Hypertension

Excerpt

Portal hypertension is increased pressure within the portal venous system. It is determined by the increased portal pressure gradient (the difference in pressures between the portal venous pressure and the pressure within the inferior vena cava or the hepatic vein. This pressure gradient is normally less than or equal to 5 mmHg. A pressure gradient of 6 mmHg or more between the portal and hepatic veins (or inferior vena cava) suggests the presence of portal hypertension in most cases. When the pressure gradient is greater than 10 mmHg, portal hypertension becomes clinically significant. A pressure gradient between 5 to 9 mmHg usually reflects subclinical disease. This gradient is measured by the determination of the hepatic venous pressure gradient (HVPG). Portal hypertension develops when resistance to portal blood flow increases. This resistance often occurs within the liver, as in cirrhosis. It can also be outside of the liver, such as prehepatic in portal vein thrombosis or posthepatic in the case of constrictive pericarditis or Budd-Chiari syndrome. Identification of the level of resistance to portal blood flow allows the determination of the cause of portal hypertension. This condition is the most frequent cause of hospitalization, variceal bleed, liver transplantation, and death in patients with cirrhosis. Gilbert and Carnot coined the term "portal hypertension" in 1902.