As difficult as it is to acquire in small children (bags, cotton wool and worse, catheters), urine checking is essential in kids, especially when a child has an unexpected fever.
An annual urine review in children is a suggested screen to pick up after silent kidney disease. If the urine is found to be infected, it is usually due to a Urinary Tract Infection (UTI). Recurrent UTIs does, more so than in adults, raise the possibilities of some abnormalities in the renal tract. Further testing will indicate if any abnormalities are found or infections become frequent.