Causes

A rectovaginal fistula may form as a result of:

• Injuries during childbirth. Delivery-related injuries are the most common cause of rectovaginal fistulas. This includes tears in the perineum that extend to the bowel, or an infection of an episiotomy — a surgical incision to enlarge the perineum during vaginal delivery. These may happen following a long, difficult, or obstructed labor. These types of fistulas may also involve injury to your anal sphincter, the rings of muscle at the end of the rectum that help you hold in stool.
• Crohn's disease. The second most common cause of rectovaginal fistulas, Crohn's disease is an inflammatory bowel disease in which the digestive tract lining is inflamed. Most women with Crohn's disease never develop a rectovaginal fistula, but having Crohn's disease does increase your risk of the condition.
• Cancer or radiation treatment in your pelvic area. A cancerous tumor in your rectum, cervix, vagina, uterus or anal canal can result in a rectovaginal fistula. Radiation therapy for cancers in these areas can also put you at risk. A fistula caused by radiation usually forms within six months to two years after treatment.
• Surgery involving your vagina, perineum, rectum or anus. Prior surgery in your lower pelvic region, such as removal of your uterus (hysterectomy), in rare cases can lead to development of a fistula. The fistula may develop as a result of an injury during surgery or a leak or infection that develops afterward.
• Other causes. Rarely, a rectovaginal fistula may be caused by infections in your anus or rectum; infections of small, bulging pouches in your digestive tract (diverticulitis); long-term inflammation of your colon and rectum (ulcerative colitis); dry, hard stool that gets stuck in the rectum (fecal impaction); or vaginal injury unrelated to childbirth.