Absence of the inferior vena cava causing repeated deep venous thrombosis in an adult--a case report.

Agenesis of the inferior vena cava is an uncommon congenital vascular malformation. Although theoretically it may favor venous stasis, it is not normally associated with venous thrombosis. The authors found only three reports of the coexistence of both entities, and only one of these rules out the existence of associated hypercoagulability. They report the case of a patient with a history of repeated venous thrombosis. Magnetic resonance angiography and venography demonstrated complete agenesis of the inferior vena cava and persistence of a cardinal venous system with azygos and hemiazygos continuation, associated with right renal hypoplasia. Studies ruled out hypercoagulability syndrome, either primary or secondary to an occult neoplasm. The authors conclude that venous malformations, although rare, may cause thromboembolic disease, especially in young patients, and that magnetic resonance angiography is a useful diagnostic alternative to conventional phlebography.