One of a pair of organs in the abdomen. The kidneys remove waste and extra water from the blood (as urine) and help keep chemicals (such as sodium, potassium, and calcium) balanced in the body. The kidneys also make hormones that help control blood pressure and stimulate bone marrow to make red blood cells.
Last updated: 2016-01-06
Source: The National Cancer Institute's Dictionary of Cancer Terms (http://www.cancer.gov/dictionary)