The kidneys are bean-shaped organs, each about 10 centimeters (4 inches) long. They are positioned in the back of the body behind the lower ribs. A healthy kidney is basically a filtering system. In fact, each kidney is made up of about a million filtering units called nephrons. As blood passes through the kidneys, it is "cleaned" - the body's waste products and excess fluid are removed. These waste products, along with the excess fluid, are then sent through the ureters to the bladder. Then they are passed out of the body as urine.
