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The infrarenal portion of the inferior vena cava is formed from the right supracardinal vein while the left supracardinal vein regresses. A duplicate inferior vena cava results from persistence of both the right and left supracardinal veins. Although such anomalies are generally asymptomatic, they have important clinical ramifications in certain settings (e.g., when pulmonary embolism occurs after filter placement in the right inferior vena cava because of the presence of a left inferior vena cava). They can also be a source of diagnostic uncertainty and make surgery more hazardous. Knowledge of caval anomalies can prevent misinterpretation of mediastinal masses, iliac occlusion with venous collaterals, and paravertebral lymph-node enlargement. In this patient, a complete resection of the renal-cell carcinoma, which was confined to the kidney, was successful.

N Engl J Med 2007; 356:e17.