Concurrent duplication and azygos continuation of the inferior vena cava.

Duplication of the inferior vena cava and azygos continuation of the inferior vena cava arise from separate embryologic anlage. The former arises from persistence of both supracardinal veins and the latter from arrested development of the right subcardinal vein. Individually these entities are uncommon, but their occurrence together in one patient is exceedingly rare. A patient with both these anomalies of the venous system concurrently is described. This combination has been reported only once before in the radiologic literature.