Your kidneys remove waste and fluid from your blood to make urine. Sometimes, when you have too much of certain wastes and not enough fluid in your blood, these wastes can build up and stick together in your kidneys. These clumps of waste are called kidney stones. Kidney stones can grow to the size of a golf ball while maintaining a sharp, crystalline structure.
The stones may be small and pass unnoticed through the urinary tract, but they can also cause extreme pain as they leave the body.