Renal veins carry deoxygenated blood away from the kidneys, according to Healthline. Renal veins separate into two parts as the blood vessel enters the left and right kidney. These veins branch off the inferior vena cava, one of the major blood vessels in the human body as shown by a diagram from the American Medical Association.
Healthline also states the renal veins perform other important functions. Two sections of the renal veins connect to different parts of the kidney. The posterior and anterior portions of the blood vessel drain the back and front of the kidneys, respectively. These two branches of the renal vein are responsible for draining blood from the ureter. The ureter moves urine away from the kidney and towards the bladder to perform an important function of the excretory system, according to ScienceDaily.
Two major problems can develop in the renal veins. WebMD reveals that a blood clot in the kidney, known as renal vein thrombosis, can be life-threatening and should be treated as soon as possible. The Mayo Clinic states that this type of blood clot can lead to nephrotic syndrome, a condition that lets too much blood protein into urine. Another serious condition in the renal veins is called nutcracker syndrome, according to Healthline. This disorder occurs when two arteries compress the renal vein and make it too narrow.