Clinically significant portal hypertension is evident when the___ exceeds ___ mm Hg.
A. Wedged hepatic venous pressure, 10Portal hypertension occurs when the pressure in the portal system is increased due to factors that may be divided into three categories. Presinusoidal causes of portal hypertension include sinistral/extrahepatic (splenic vein thrombosis, splenomegaly, splenic atrioventricular fistula) and intrahepatic (schistosomiasis, congenital hepatic fibrosis, idiopathic portal fibrosis, myeloproliferative disorder, sarcoid, graftversus-host disease) etiologies. Sinusoidal portal hypertension is a consequence of cirrhosis of any etiology. Postsinusoidal hypertension can also be divided into intrahepatic (vascular occlusive disease) and posthepatic (Budd-Chiari, congestive heart failure [CHF], IVC webs) etiologies. In evaluating patients with suspected portal hypertension, an enlarged portal vein on routine abdominal ultrasonography may suggest portal hypertension but this is not diagnostic. Doppler ultrasound allows identification of vascular occlusion and the direction of portal venous flow. CT and MR angiography are useful for evaluating portal venous patency and anatomy. The most accurate method for measuring portal hypertension is hepatic venography. This procedure introduces a balloon catheter directly into the hepatic vein where free hepatic venous pressure (FHVP) is measured. The hepatic vein is then occluded by inflation of the balloon allowing measurement of the wedged hepatic venous pressure (WHVP). The hepatic venous pressure gradient (HVPG) may then be calculated by subtracting the FHVP from the WHVP (HVPG = WHVP - FHVP). Clinically significant portal hypertension is defined as HVPG greater than 10 mm Hg.