What Causes Pain In Flank Along With Lower Back?

Male 23....Sir I was diagnosed with urinary tract infection..I have flank pain at times at the left side and sometimes lower back pain. No other symptoms as such. Urine flows easily. Urinalaysis says pus cells of abt 20-25 cells/HF is present. Is it the upper tract infection(kidneys) or the lower. If it is uppertract infection then the antibiotics applicable for lower tract infection is sufficient!? Anyways I am taking citralka and Ofloxacin tabs. Other symptoms rathar than pain is not yet present.