When my kitty had a UTI they prescribed him Amoxi-Drops for 14 days and gave him a sub-q fluids. Right before he was supposed to be done his meds, he started peeing blood again and I had to take him back and they gave him two one week course of Cefa-Drops and it cleared it right up.
Both times they did UA's and he had blood and protein in his urine, but no bacteria. It's not say there was none, it just might have been diluted. He is now on Purina UR canned only and cannot eat dry food again.