The kidneys, each about the size of a fist, play three major roles:
- removing waste products from the body, keeping toxins from building up in the bloodstream
- producing hormones that control other body functions, such as regulating blood pressure and producing red blood cells
- regulating the levels of minerals or electrolytes (e.g., sodium, calcium, and potassium) and fluid in the body
After the blood has circulated through the body, it passes into the kidneys. The kidneys filter waste products and excess salt and water out of the blood, and pass these out of the body as urine. The kidneys also make hormones that control blood pressure, as well as maintain bone metabolism and the production of red blood cells. It's a serious problem when the kidneys stop working. Waste products that build up in the body cause imbalances in chemicals needed to keep the body functioning smoothly.
There are many different types of kidney diseases. Kidney diseases can lead to end-stage renal disease (ESRD), a condition in which the kidneys fail to work normally. People with only one working kidney can live a normal life, since one kidney can do the work of two, but when both kidneys are no longer able to clear the body of waste, a person with kidney failure needs to receive dialysis or a kidney transplant.