Many people pass the stone by themselves, totally symptoms free. But if the stone gets stuck in the ureter (shu1 niao4 guan3), it is extremely painful, and there will be blood in the urine, the worst thing is the whole kidney can get severe infection.

A good way to treat kidney stone (I can't say if it is the best or not) is ESWL (ti3 wai4 sui4 shi2), you can consult your doc about this.

The way to prevent kidney stone? Drink lots of water! It also helps in passing the stones. :)