 Patients who present for the first time to Emergency Room with renal colic due to a distal ureteral calculus as diagnosed with spiral CT scan and KUB will be randomized to receive Xatral 10mg po once a day or placebo once discharged from the ER. The purpose of this study is to assess if patients treated with Xatral will have a higher spontaneous passage rate of their ureteral stone than those treated with placebo. 