Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Seek prompt reassessment if urinary symptoms return.
Keeping a record of fever, symptoms, urine culture results, antibiotics, and imaging can help clinicians recognize patterns.
And for anyone, someone who:
Routine follow-up is especially useful for children with repeated UTIs, abnormal imaging, constipation, urine holding, weak urine flow, or ongoing wetting.
A pediatric urologist or kidney specialist may be involved when infections are recurrent or the urinary tract may not be working normally.
The article also says
Symptoms often begin to improve after effective treatment starts.
Contact the treating clinician if symptoms are not improving as expected, fever continues, the child becomes more unwell, or vomiting prevents medicine from staying down.
The clinician may contact the family when the culture is complete.
The result may confirm the infection, show that a different antibiotic is needed, or suggest that the sample was contaminated.
Do not change treatment without discussing the result with the treating clinician.
A repeat urine culture is not always needed after a child has recovered from an uncomplicated infection.
It may be appropriate when symptoms continue, the infection returns, or there are other clinical concerns.
Every sign above is quoted from the sofidex article on Bladder infections in children. If you are not sure, err upward — it is always reasonable to be checked.