The renal vein is a blood vessel that carries deoxygenated blood away from the kidneys. Each kidney has its own renal vein, which drains blood into the inferior vena cava, a large vein that returns blood to the heart. The renal vein plays a crucial role in maintaining the body's fluid and electrolyte balance by transporting waste products filtered by the kidneys. In addition to carrying blood, the renal vein also helps regulate blood pressure and volume. It is connected to the renal artery, which supplies oxygenated blood to the kidneys for filtration. Proper functioning of the renal vein is essential for overall kidney health and effective waste removal from the body.