Membranous obstruction of the inferior vena cava in the United States.

The pathogenesis of membranous obstruction of the inferior vena cava (MOVC) is unclear. Although the lesion is rare in the United States compared to Japan, India, and black South Africa, it has been responsible for 23% of cases of hepatic outflow obstruction we have encountered in the ethnically heterogeneous indigent population of Los Angeles. Most patients with MOVC are male. In contrast, recent series of patients with Budd-Chiari Syndrome (BCS) have demonstrated a female predominance. Compared to BCS without involvement of the inferior vena cava (IVC), patients with MOVC have more chronic symptoms. Large truncal collaterals, particularly on the back, strongly suggest MOVC. In patients without this sign, a high index of diagnostic suspicion is required. Chronic hepatitis B infection occurs with increased frequency in these patients. Chest radiograph may show an enlarged azygous shadow. Liver-spleen scan is not helpful, and the liver biopsy is frequently nondiagnostic. A useful screening procedure for hepatic outflow block is transhepatic portal pressure measurement demonstrating aberrant hepatic veins with pressures higher than in the portal vein and, occasionally, hepatofugal portal flow. Transcardiac membranotomy appears to be symptomatically effective in patients with MOVC and at least one patent hepatic vein. It is not known whether this operation will prolong life and prevent the development of hepatocellular cancer, which may occur in up to 48% of these patients. The correct therapeutic approach has not been established for those patients whose lesion is not amenable to surgery because of extensive IVC occlusion or absence of patent hepatic veins.