A urinary tract infection (UTI) is an infection anywhere in the urinary tract. The urinary tract includes the kidneys, bladder and urethra (the tube from which urine passes out of the bladder). UTIs are common in children of all ages, but are especially common in children who are still in nappies.
https://www.rch.org.au/kidsinfo/fact_sheets/Urinary_tract_infection_UTI/

