The kidneys are in the back of the upper abdominal cavity, one on either side of the spine. The right kidney is situated lower than the left kidney to allow space for the liver.
The kidneys are bean-shaped organs that filter the blood and excrete waste from the human body in the form of urine. They are each about four to five inches long and have roughly one million nephrons, or microscopic filters. In addition to waste excretion, kidneys also help regulate blood pressure, regulate red blood cells, keep water levels balanced and regulate the amount of acid in the body.