Portal Hypertension

Excerpt

Portal hypertension refers to elevated pressure within the portal venous system. Gilbert and Carnot introduced the term "portal hypertension" in 1902 to describe features and complications arising from increased pressure in the liver's venous circulation. The condition involves an increased portal pressure gradient, defined as the difference between portal venous pressure and the pressure within the inferior vena cava or hepatic vein. A normal hepatic venous pressure gradient (HVPG) measures ≤5 mm Hg. A gradient of ≥6 mm Hg suggests portal hypertension, while a range of 5 to 9 mm Hg indicates subclinical disease. Clinically significant portal hypertension (CSPH) begins at a pressure gradient of 10 mm Hg or higher. Decompensating events, eg, ascites, hepatic encephalopathy, and gastrointestinal bleeding, typically occur when HVPG reaches ≥12 mm Hg.

Increased resistance to portal blood flow drives the development of portal hypertension. Most often, this resistance arises within the liver, as seen in cases of cirrhosis, but can also occur outside the liver, even in the absence of cirrhosis. These noncirrhotic causes, grouped as noncirrhotic portal hypertension (NCPH), include prehepatic conditions (eg, portal vein thrombosis) and posthepatic conditions (eg, constrictive pericarditis or Budd-Chiari syndrome). Determining the site of resistance helps identify the underlying cause. Among patients with cirrhosis, complications of portal hypertension remain the leading causes of hospitalization, liver transplantation, and mortality.