Urinary tract infection (UTI) is one of the most common bacterial infections in childhood, affecting 8 % of girls and 2 % during the first 8 years of life. Up to 6 months of age, the prevalence is higher in boys than in girls (see also chapter “UTI and VUR”). In school age UTI is two- to fourfold more prevalent in girls and up to 5 % of all girls contract a UTI during their school years (Brandstrom and Hansson 2014).