Most people have two kidneys. These are located on the back side of the body, with one on each side just below the rib cage. The kidneys filter the blood, eliminating waste products and turning them into urine.

Urine drains out from each kidney through a tube called a ureter and into the bladder, where the urine is stored and then expelled via the urethra.

Blood is transported to the kidney through a blood vessel called the renal artery. Once the blood has been filtered by hundred of tiny filters called nephrons, it travels throughout the rest of the body through the renal vein.

The kidneys also help balance fluids, salts, and minerals in the body and keep the blood pressure at an appropriate level.

The kidneys are inside a fibrous envelope called the Gerota's fascia and are surrounded by a layer of fat. The outer part of the kidney is called the renal cortex. The inner part that collects urine is called the medulla. In the upper part of each kidney there is a small gland called the renal gland, which produces important hormones.