When a kidney stone becomes trapped in the ureter, it may remain there until your doctor removes it. Or, it eventually may move downward and pass on its own. It can take hours, days or weeks for a stone to pass.
As a rule, the smaller the stone, the more likely it is to pass on its own. The larger the stone, the greater the risk that it will remain trapped in the ureter. A trapped stone can significantly obstruct the flow of urine.