A bladder fistula is when an opening forms between the bladder and some other organ or the skin. Most often the bladder opens to the bowel ("enterovesical fistula") or the vagina ("vesicovaginal fistula").
How Does the Bladder Usually Work?
The bladder is a balloon-shaped organ that stores urine, which is made in the kidneys. It is held in place by pelvic muscles in the lower part of your belly. When it isn't full, the bladder is relaxed. Nerve signals in your brain let you know that your bladder is getting full. Then you feel the need to pee. The brain tells the bladder muscles to squeeze (or "contract").
Female urinary tract
Male urinary tract