Complete absence of the inferior vena cava presenting as a paraspinous mass.

Dilatation of the azygos-hemiazygos venous system presenting as paravertebral masses may be seen in intrahepatic and extrahepatic portal vein obstruction, anomalous pulmonary venous return, occlusion of the superior and inferior vena cava, persistence of the left superior vena cava, hepatic vein obstruction, elevation of central venous pressure as in congestive heart failure, pericardial effusion, constrictive pericarditis, pregnancy, and isolated aneurysms of the azygos vein.' a: Although prominence of the azygos vein is a wellknown finding with infrahepatic interruption of the inferior vena cava or persistence of the supracardinal vein, it has not been described to our knowledge in complete absence of the inferior vena cava.-