The left renal vein and the right renal vein make up the renal veins that drain the kidney. They begin at the hilum of the kidney where three to six tributaries unite. The kidney is connected to the inferior vena cava via the renal veins. The renal arteries are behind the veins, which is unlike most other veins in the abdomen that rest beside of behind the arteries.
The left renal vein joins the inferior vena cava by flowing between the aorta and superior mesenteric artery. It crosses ahead of the aorta. The left renal vein is longer than the right and takes on the left inferior phrenic vein, left suprarenal vein, left testicular and ovarian vein, and left second lumbar vein. This is unlike the body’s right side veins, which drain right into the inferior vena cava.