Back spasms started tonight kidney area to buttocks. 2nd round of antibiotics even though urine clean because of lingering symptoms. Spasms cause??

Needs evaluation. Back spasms could be caused by other problems besides just infection. If you're already on a second round of antibiotics and your urine tests are 'clear' -I would start to look for other causes. Sometimes disease of the spine can cause these spasms, or there could be a muscle or nerve problem. There are medications specifically for muscle spasms, so I hope you can find relief ASAP. Call doctor now.