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  PORTAL HYPERTENSION 1089-3261/01 $15.00 + OO NONCIRRHOTIC PORTAL HYPERTENSION Enrique Molina, MD, and K. Rajender Reddy, MD In the Western world, cirrhosis related to chronic hepatitis C and B and alcoholic cirrhosis are the most common causes for portal hyperten- sion. Noncirrhotic portal hypertension represents a relatively infrequent group of conditions that causes portal hypertension in the absence of cirrhosis. As with cirrhotic portal hypertension, most cases of noncir- rhotic portal hypertension are caused by increased portal venous outflow resistance, although, rarely, an increased flow in the portal circulation may be responsible. Ultimately, even in the cases in which there is a chronically increased flow (e.g., in arteriovenous fistulae), intravascular changes evolve, leading to increased resistance. Pathophysiologically, the causes for portal hypertension can be categorized into three groups based on whether the block to portal flow is at the portal venous level, in. the sinusoidal bed, or at the hepatic veins. Further, presinusoidal resistance to portal flow can occur either at an intra-hepatic site or at the extra-hepatic level; similarly, the postsinusoidal hepatic venous outflow blockage could be intra-hepatic or extra-hepatic (Table 1 . Although development of varices and subsequent bleeding from them are the main manifestations of portal hypertension from all causes, there are unique features related to noncirrhotic portal hypertension that are wor- thy of mention. The clinical manifestations of pre-sinusoidal portal hy- pertension characteristically are devoid of ascites and encephalopathy, whereas ascites is a cardinal feature of post-sinusoidal obstruction. The prognosis of portal hypertension caused by presinusoidal conditions is relatively better than that of any cause of portal hypertension. From the Center for Liver Diseases, University of Miami School of Medicine, Miami, Florida CLINICS IN LIVER DISEASE VOLUME 5 * NUMBER 3 AUGUST 2001 769  770 MOLINA REDDY Table 1, CAUSES OF NONCIRRHOTIC PORTAL HYPERTENSION Intrahepatic Presinusoidal Hypertension 1. Portal venule thrombosis Toxins Hypercoagulable states 2. Primary biliary cirrhosis 3 Primary sclerosing cholangitis 4. Sarcoidosis 5. Schistosomiasis 6. Congenital hepatic fibrosis 7. Noncirrhotic portal fibrosis 8. Nodular regenerative hyperplasia 9. Chronic biliary obstruction Extrahepatic Presinusoidal Hypertension 1. Portal, mesenteric, or splenic vein thrombosis 2. Intrasplenic arteriovenous fistula 3. Idiopathic splenomegaly, blood disorders, infiltrative disorders, and so forth Sinusoidal Hypertension 1. Perisinusoidal and hepatic fibrosis Hypervitaminosis A Noncirrhotic alcoholic liver disease Chronic active hepatitis Hemochromatosis 2. Peliosis hepatis 3 Infiltrative disorders Amyloidosis Malignancy Systemic mastocytosis Primary myeloproliferative disorders Chronic active hepatitis Acute hepatitis Acute fatty liver of pregnancy Post-sinusoidal Hypertension 1. Veno-occlusive disease Bone marrow transplantation Radiation Pyrrolizine alkaloids Noncirrhotic alcoholic liver disease Liver transplant rejection 2. Other hepatic venular lesions Extrahepatic Postsinusoidal Hypertension 1. Hepatic vein obstruction (Budd-Chiari syndrome) 2. Suprahepatic inferior vena cava thrombosis 3 Pulmonary hypertension 4. Constrictive pericarditis 5. Congestive heart failure  NONCIRRHOTIC PORTAL HYPERTENSION 771 The key parameters of portal pressure obtained indirectly, by cannu- lating the inferior vena cava and the hepatic vein with a balloon-tipped catheter, are the free hepatic vein pressure (FHVP), the wedged hepatic vein pressure (WHVP), and the hepatic venous pressure gradient (HVPG).5,22,37 he HVPG is obtained by subtracting the FHVP from the WHVP. This result closely correlates with the intrasinusoidal pressure. Besides clinical features, portal pressure determinations and hepatic histology provide information that help determine the cause of portal hypertension. Typically, the WHVP and HVPG are normal in presinusoi- dal portal hypertension but are elevated in sinusoidal portal hyperten- sion. Although postsinusoidal portal hypertension is also characterized by elevated WHVP and HVPG, in some cases the HVPG may be normal because of an increase in FHVP (e.g., in cardiac disease causing resis- tance to flow distal to the hepatic veins). INTRAHEPATIC PRESINUSOIDAL PORTAL HYPERTENSION Intrahepatic presinusoidal portal hypertension results from to an increase in resistance to portal flow caused by obliteration of the portal venules by thrombosis or inflammation. Thrombosis of portal venules can occur as a consequence of toxins (arsenic or vinyl chloride) causing small portal vein injury or is due to hypercoagulable states caused by antithrombin I11 deficiency, protein S deficiency, protein C deficiency, resistance to activated protein C, lupus anticoagulant, pregnancy, or use of oral contraceptives). Additionally, in the precirrhotic stages of primary biliary cirrhosis, primary sclerosing cholangitis, and chronic biliary stric- tures, inflammation or fibrosis can damage portal venules in the portal tract.= In such patients, occlusion of portal venules may lead to portal hypertension even before cirrhosis develops. Portal hypertension is rare as the initial presentation of primary biliary cirrhosis,Sl but develops in 47% of patients during follow-up.', 28 In sarcoidosis, portal hypertension can rarely occur as the result of compression of portal venules by granulomas and extensive fibrosis (Fig. l .l, Other mechanisms for portal hypertension in sarcoidosis include the development of secondary biliary cirrhosis, compression of the portal vein by perihilar lymph nodes, and portal vein thrombosis. The liver is usually enlarged, and the serum alkaline phosphatase level is elevated. Jaundice may occur, especially if bile duct destruction is Hepatic Schistosomiasis Hepatic schistosomiasis is probably the most prevalent chronic liver disease wor1d~ide.l~ ggs of Schistosoma mansoni deposited in the mes- enteric veins are trapped as the portal venules decrease in caliber (Fig. 2). The initial immunologic response leads to granuloma formation in  772 MOLINA REDDY Figure 1 Sarcoidosis. Epithelioid-cell granulomas observed in the portal tract that have caused an expansion. Figure 2. A granuloma is seen with the ovum of Schisfosoma mansoni. Hepatic lobular architecture is intact. Courtesy of Pablo Bejarano, MD, Miami, Florida.)  NONCIRRHOTIC PORTAL HYPERTENSION 773 the portal triads and later to portal fibrosis with dense deposits of collagen known as pipestem or Symmer’s fibrosis. Portal fibrosis causes presinusoidal portal hypertension presenting clinically as hepatomegaly, splenomegaly, esophageal varices, and other portosystemic collaterals. Congenital Hepatic Fibrosis Congenital hepatic fibrosis is an uncommon autosomal recessive malformation characterized by enlarged portal spaces containing abun- dant connective tissue and numerous, ectatic bile ducts (Fig. 3 . The main consequence is portal hypertension and bleeding from varices. Most patients bleed by the age of 5 to 20 years. Congenital hepatic fibrosis may be associated with Caroli’s disease and present with cholan- gitis. Other associations include adult polycystic kidney and liver disease and choledochal cysts.l, Portosystemic shunt is better tolerated in these patients with preserved hepatocellular function, although jaundice and encephalopathy may occur postoperati~ely.~~ Noncirrhotic Portal Fibrosis Splenomegaly with or without anemia, the so-called Ban t ’s syn- drome, is caused by a variety of diseases that present with splenomegaly, hypersplenism, and portal hypertension. In the 1960s, in India, a group of patients who developed splenomegaly without cirrhosis was de- scribed, and the syndrome was named noncirrhotic portal fibrosis Figure 3. Congenital hepatic fibrosis. Broad fibrous septa are seen containing epithelial lined structures of biliary srcin. There is no nodular regeneration that distinguishes this from cirrhosis.
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