Your kidneys are bean-shaped organs, each about the size of your clenched fist. They are located near the middle of your back, just below the rib cage. The kidneys are sophisticated reprocessing machines. Every day, your kidneys process about 180 liters of blood to excrete about 2 liters of waste products and extra water.

The wastes in your blood come from the normal breakdown of active tissues and from the food you eat. Your body uses the food for energy and self-repairs. 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 accumulate in the blood and damage your body.

Nephron:
Actual removal of wastes occurs in tiny units inside the kidneys called nephrons, it is a single filtering unit. Each kidney has about a million nephrons.