Sam,   If you are experiencing problems, you should contact your doctor. Xanac should not be stopped suddenly, but rather should be tapered off and only under the supervision of a doctor, so you should not just stop this medication.   According to Drugs.com, one of the side effects that you should contact the doctor about right away include "Urinating less than usual or not at all." Pain in the kidney area is not listed as a side effect, but that does not necessarily mean it is not a side effect.   I think the best for you would be to contact your doctor right away and let the doctor determine whether the medication should be changed or if additional medical test are needed.   Eileen