- Kidney: One of two bean-shaped organs that filter wastes from the blood and discharge these waste products in urine. The kidneys are located near the middle of the back. The kidneys send urine to the bladder through tubes called ureters.
- Kidney cancer: The most common type of urologic cancer. The kidneys are two large organs that sit in the back part of the abdominal cavity. The kidney's main function is to filter the blood and clean the body of excess water, salt, and waste products. Tumors of the kidney occur twice as often in men as in women and usually occur between the ages of 50 and 70.
- Kidney stone: A stone that develops from crystals that form in urine and build up on the inner surfaces of the kidney, in the renal pelvis or in the ureters. (Also see nephrolithiasis.