My son had a double kidney infection it took 5 days to get his wbc count from 36,000 to 9,000 they saw fluid around his kidneys the first day but they redone a ultrasound and they said it came back normal,any ideas on what could have caused this?

I do not understand what you meant by double kidney infection. Did you mean your son have infection of both kidneys (bilateral pyelonephritis). During acute infection, sometimes we see fluid around the kidneys by either ultrasound or CT scan. Because of your son's age, only 3 years old, so I wonder if he has an underlying congenital abnormality such as vesicoureteral reflux or UPJ abnormality?