A kidney stone can be as tiny as a grain of sand, and you can pass it in your pee without ever knowing. But a bigger one can block your urine flow and hurt a lot. Some people say the pain can be worse than childbirth. They usually consist of calcium oxalate but may be composed of several other compounds. 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 ...