The causes and consequences of chronic hepatic venous outflow obstruction.

The causes of chronic hepatic venous outflow obstruction are membranous obstruction of the inferior vena cava (group 1), hepatic venous ostial obstruction (group 2) and partial hepatic venous ostial obstruction (group 3). At the H. F. Verwoerd and Kalafong Hospitals, Pretoria, 155 cases have been diagnosed, almost all in the first group. Over 50% of the patients in this series had hepatocellular carcinoma; this association appears to be a constant finding world-wide. The most likely cause is a chronic hepatocaval thrombosis with organisation, leading to fibrous stenosis or membranous occlusion of the involved veins.