The renal veins in the renal circulation, are large-calibre veins that drain blood filtered by the kidneys into the inferior vena cava. There is one renal vein draining each kidney. Each renal vein is formed by the convergence of the interlobar veins of one kidney.
Because the inferior vena cava is on the right half of the body, the left renal vein is longer than the right one.
Structure
One renal vein drains each kidney. A renal vein is situated anterior to its corresponding accompanying renal artery. The renal veins empty into the inferior vena cava, entering it at nearly a 90° angle. This is in contrast to the right side of the body, where these veins drain directly into the IVC.
In some individuals, the left renal vein passes posterior to the abdominal aorta instead of in anterior to it;