Bladder cancer (also called bladder cancer or bladder carcinoma) occurs when cells in the bladder begin to grow out of control. The bladder is a hollow, balloon-shaped organ that stores urine and is located in the lower abdomen.

The bladder has a muscular wall that allows it to enlarge to store urine produced by the kidneys and to contract to expel urine from the body. There are 2 kidneys, one on each side of the spine, above the waist. The bladder and kidneys work together to remove toxins and waste from the body through urine in the following ways:

Tiny tubes in the kidneys (renal tubules) filter and clean the blood.
These tubules remove waste products and make urine.
Urine passes from each kidney to the bladder through a long tube called the ureter.
The bladder stores urine until it leaves the body through a tube called the urethra.