Feb 6, - Everyone has them. But if they get into the urethra, they can end up in the bladder and cause an infection. Bladder infections are more common in women than men for several reasons. That causes the lining of the urethra to get thinner and may change the balance of bacteria in the vagina, making infections more likely. Aug 25, - Learn about UTI causes, treatments and self-care. Sexual intercourse may lead to cystitis, but you don't have to be sexually active to develop.