hepatic and biliary disorders
Portal Hypertension
Introduction
Portal hypertension is elevated pressure in the portal vein. It is caused most often by cirrhosis (in North America), schistosomiasis (in endemic areas), or hepatic vascular abnormalities. Consequences include esophageal varices and portosystemic encephalopathy. Diagnosis is based on clinical criteria, often in conjunction with imaging tests and endoscopy. Treatment involves prevention of gastrointestinal (GI) bleeding with endoscopy, drugs, or both and sometimes with portacaval shunting or liver transplantation. (See also Liver Structure and Function and The portal vein, formed by the superior mesenteric and splenic veins, drains blood from the abdominal GI tract, spleen, and pancreas into the liver. Within reticuloendothelium-lined blood channels (sinusoids), blood from the terminal portal venules merges with hepatic arterial blood. Blood flows out of the sinusoids via the hepatic veins into the inferior vena cava. Normal portal pressure is 5 to 10 mm Hg (7 to 14 cm H2O), which exceeds inferior vena caval pressure by 4 to 5 mm Hg (portal venous gradient). Higher values are defined as portal hypertension. 