Kidneys

Your kidneys are bean-shaped organs, each about the size of your fist. They are located near the middle of your back, just below the rib cage.

Your kidneys filter blood. The filtering occurs in tiny units inside your kidneys called nephrons. One kidney has about a million nephrons. They remove waste products and extra water, which become urine. The urine flows through tubes called ureters to your bladder, which stores the urine until you go to the bathroom.

The wastes in your blood come from the normal breakdown of active tissues and from food you eat. After your body has taken what it needs from the food, waste is sent to the blood. If your kidneys did not remove these wastes, the wastes would build up in the blood and damage your body.