Liver Sonography by Duplex and Color Doppler

Portal Hypertension

Cirrhosis is the most important cause of portal hypertension in the Western world. The best way to think of “portal hypertension” is to understand what creates portal pressure. Portal pressure is the product of portal venous flow and resistance to flow. The causes of portal hypertension can be categorized based on this formula. Etiologies causing primary increased flow include arterioportal fistula (which may be congenital, post-traumatic, atherosclerotic, or due to erosion of a hepatic artery aneurysm into the portal vein) and splenomegaly (for example, due to myelofibrosis). The better-known category of primary increased resistance is traditionally divided into pre-hepatic, intra-hepatic, and post-hepatic causes. Pre-hepatic causes include portal or splenic vein thrombosis and extrinsic compression of the portal vein. Intra-hepatic causes are based on the location of the increased resistance, that is, presinusoidal, sinusoidal/mixed, or post sinusoidal. Presinusoidal causes of portal hypertension include parasitic infections (such as schistosomiasis), sarcoidosis, myeloproliferative diseases, primary biliary cirrhosis, primary sclerosing cholangitis, and certain toxins. Sinusoidal causes include alcoholic hepatitis/cirrhosis and cryptogenic cirrhosis (cause unknown). Post-sinusoidal causes include veno-occlusive disease and hepatic vein obstruction (such as Budd-Chiari syndrome). Post-hepatic causes of portal hypertension include constrictive pericarditis, inferior vena cava obstruction, and severe right heart failure/tricuspid insufficiency.