This Publication Is Searchable The Merck Manual of Diagnosis and Therapy Section 4. Hepatic And Biliary Disorders Chapter 38. Signs Of Liver Disease Portal Hypertension Increased pressure in the portal venous system. The portal vein is formed by the superior mesenteric and splenic veins. It drains blood from the abdominal GI tract, spleen, and pancreas into the liver.
Blood flows out of the sinusoids via the hepatic veins, which drain into the inferior vena cava.
Higher values are defined as portal hypertension. Etiology and Pathophysiology Portal hypertension results from increased portal flow or, in most cases, increased resistance to flow. Increased flow is a rare cause, although it often contributes to portal hypertension in cirrhosis and occasionally is important in massive splenomegaly resulting from hematologic disorders. Table 38-1 shows the classification and most common causes of portal hypertension. In industrialized nations, cirrhosis is by far the most common cause of portal hypertension, although schistosomiasis predominates in some tropical and subtropical climates.