The human body normally has two kidneys. These fist-sized organs are located in the back part of the abdomen, just below the rib cage, on either side of the spine. Their primary function is to filter the blood and remove waste from the body.
The kidneys also help maintain the proper fluid balance in the body. The kidneys filter all the blood in the body around 12 times an hour, removing excess fluid and waste and manufacturing urine. Occasionally, someone is born with just one kidney or loses a kidney due to disease or injury. The body functions well with just one kidney in these instances, but at least some kidney function is necessary for life.