A stone is a hard, solid mass that can form in the gallbladder, bladder, and kidneys. These types of stones have different causes and are treated in different ways.

Kidney stones form when minerals or acid salts in your urine crystalize. Most stones leave your body while you urinate. However, sometimes stones get stuck in the ureter, block the normal flow of the urine and cause symptoms. Stones can also be too big to leave the kidney. In both cases you may need treatment to remove the stone.