Pyuria or presence of pus in urine may indicate infection or UTI or
Renal stones.Since your Ultrasound was normal,most probably
renal stones are out of consideration.But presence of pus (purulence),a urine culture report has to indicate the causative organism of such infection.Most of the reports include the name of the organism,out of which E.Coli,being most common,if not S.aureus,Klebsiella and other bacteria or virus.