Why are bladder infections more common in younger girls?

Prior to puberty, girls are more susceptible to bladder infections. This is because the urethra (which is the opening to the bladder) is in such close proximity to the rectum. Bacteria from the rectum are what cause the vast majority of bladder infections in girls. (That’s why young girls should be taught to wipe from front to back after they have a bowel movement.) It is the introduction of estrogen that begins the process of strengthening the wall between the vagina and bladder, replacing the “bad” bacteria with the “good” bacteria, and building up the tissue of the urethra, which then becomes a stronger barrier and helps prevent the remaining “bad” bacteria from entering the bladder. (Yes, sometimes our bodies seem to serve as the backdrop for a superheroes cartoon.)