What is UTI? Urinary tract infection is generally found in kids age 5-9. There is a bacteria in the Human body which flushes out during pee or Urination. But if it stays inside the body than it starts growing in the urinary tract and even can move to the kidney, Urinary bladder, and ureters and cause infection. And because of these two most known and common infections in kids can be found called, kidney infection and bladder infection.