I recently ( 2 days back ) had my second incident of frank hematuria , i was administered antibiotics and just like last time which happened abt 3ys and 9 months ago , blood stopped immediately. The Ultra sound then had shown normal sized kidneys and everything was normal. However this time Ultra sound revealed a smaller left kidney ( 9.3 * 4 cm) as against 12.4 * 5.3 cm for right kidney, further some mild cortical irregularity was indicated near left pole. I was advised a CT scan which confirmed a scared left kidney of reduced size.with marked cortical thining along inferior pole.Right kidney showed normal morphology .KIDNEYS show normal excretion and concentration of contrast of , ureters show normal course and caliber.No distortion. few prominent lymph nodes are noted in para aottic region lagest 1.5 * 1.1 cm.
You seemed to pyelonephritis or infection of left kidney.... And left small because of old healed kidney.... Even no treatment available for scarred small kidney. Now you may have 2nd infection or may be stone... Get urine routine, culture and repeat ultrasound without wasting time.  If infection then antibiotics in the main treatment. Choice of antibiotic may be guided by urine culture.