The kidneys are a pair of organs on either side of the spine in the lower abdomen. Each kidney is about the size of a fist. Attached to the top of each kidney is an adrenal gland. A mass of fatty tissue and an outer layer of fibrous tissue (Gerota's fascia) enclose the kidneys and adrenal glands.

The kidneys are part of the urinary tract. They make urine by removing wastes and extra water from the blood. Urine collects in a hollow space (renal pelvis) in the middle of each kidney. It passes from the renal pelvis into the bladder through a tube called a ureter. Urine leaves the body through another tube (the urethra). The kidneys also make substances that help control blood pressure and the production of red blood cells.

Types of Cancer

Several types of cancer can start in the kidney. Renal cell cancer is the most common type of kidney cancer in adults. This type of cancer may be called renal carcinoma or hypernephroma. Another type of cancer, transitional cell carcinoma, affects the renal pelvis in the kidney and the ureter. It is similar to bladder cancer and is often treated like bladder cancer. Wilms' tumor is the most common type of childhood kidney cancer. It is different from adult kidney cancer and requires different treatment.