Estrogens and Urinary‐Tract Infection

Abstract

The effects of estrogen on the risk of urinary-tract infection (UTI) in women has been the subject of many studies in both humans and experimental animals. Often, these studies have come to seemingly contradictory results: some have suggested an increased risk attributable to estrogen and others that estrogens may be preventative. In part, this confusion arises because the physiological effects of estrogen on different anatomic parts of the urinary tract differ depending on the specific effect and the outcome measured. For example, in the absence of estrogen, the periurethral and vaginal microflora, which is usually predominated by hydrogen peroxide-producing lactobacilli and few Escherichia coli, changes dramatically to a flora with few or no lactobacilli but many E. coli [1]. This change in flora is associated with a markedly increased risk of recurrent E. colibladder infections. In a randomized, placebo-controlled trial of topical intravaginal estrogen cream in such women, both the reestablishment of the normal lactobacillus-dominant vaginal flora and reduced rates of UTI were demonstrated in estro-