The kidneys are bean-shaped organs located near the back, just above the waist. Each kidney is about the size of a clenched fist and weighs about ¼ pound in an adult. Inside each kidney, blood moves through tiny filters called nephrons. There are about 1 million of these tiny filtering units in each kidney. Nephrons make it possible for two healthy kidneys to filter the body's entire blood supply every two minutes.
Kidneys perform several important functions:
- They regulate water. To function properly, your body must have the right amount of water. Kidneys remove excess amounts of water from the body or retain water when the body needs more.
- They produce hormones. These hormones circulate in the blood and regulate blood pressure, make red blood cells, and absorb calcium from the intestine.
- Healthy kidneys remove waste products. Minerals, such as potassium and sodium, are needed by the body's cells so they can function properly. These minerals must be kept at specific levels so the kidneys excrete excess amounts in urine. Calcium and phosphorous levels, important minerals needed for bone formation, are also regulated by the kidneys. Wastes, such as urea and creatinine, are made when the body breaks down protein, such as meat. Many waste products act like a poison if they are not removed from the body. With poor kidney function, waste products are not removed and the amount of creatinine and urea rises in the blood.