The bladder is a hollow, flexible pouch in your pelvis. Its main job is to store urine before it leaves your body. Your kidneys make pee. Tubes called ureters carry the pee from your kidneys to your bladder. When you use the bathroom, the muscles in your bladder push the urine out through a tube called the urethra.
You get bladder cancer when cells inside of it grow out of control. Over time, a tumor forms. It can spread to nearby fat and tissue. In severe cases, it can spread to distant parts of your body, including your lymph nodes, bones, lungs, or liver.