Obstetric

Obstetric injuries are the most common cause of rectovaginal fistulas, occurring in up to 88% of fistulas in published series (Lowry et al., 1988).

Episiotomy is commonly performed in the practice of obstetrics. Kozok (1989) reported that approximately 62% of vaginal deliveries in the United States required episiotomy (80% of nulliparous patients and 20% of multiparous patients). Approximately 5% of vaginal deliveries or 20% of episiotomies result in a rectal tear or anal sphincter disruption. Although the majority of perineal injuries are successfully repaired at the time of the delivery, dehiscence of an episiotomy repair can occur and is associated with infection, abscess, fistula, or sphincter disruption. Up to 1.5% of women who undergo an episioproctotomy develop a rectovaginal fistula. Such fistulas present either immediately postpartum from failed recognition of a fourth degree injury or 7 to 10 days following an apparently normal repair. Midline episiotomy with resulting third- or fourth-degree laceration produces the greatest risk for development of a rectovaginal fistula. Mediolateral episiotomy, more common in British obstetric practice, causes fewer tears into the rectum when compared with midline incision. Rectovaginal fistula following infection and dehiscence of an episiotomy most commonly occurs low in the rectovaginal septum but may extend much higher, especially in the case of a traumatic cloaca. Of paramount importance in these patients is an assessment of their degree of incontinence. Wise et al. (1991) noted that 27% of low rectovaginal fistulas had coexistent fecal incontinence, recommending a careful continence evaluation before embarking on a repair.

Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), specifically Crohn’s disease, is the second most common cause of rectovaginal fistulas and should be suspected in any instance where an attempt at repair has failed. Because ulcerative colitis is not a transmural disease, it usually does not cause such problems. Most commonly, a rectovaginal fistula from Crohn’s disease is located in the mid-rectovaginal septum. However, in patients with anorectal Crohn’s disease, a fistula can extend into the most distal aspect of the vagina or perineum. An anovaginal or rectovaginal fistula in Crohn’s disease is more likely to result in proctectomy or a defunctioning stoma than anal Crohn’s disease without rectovaginal fistula.

Infection

The most common nonobstetric infection causing a rectovaginal fistula is a cryptoglandular abscess located in the anterior aspect of the anal canal. Extension of such an abscess into the vaginal wall can result in fistula formation. Other infectious processes that may fistulize into the vagina include lymphogranuloma venereum, tuberculosis, and Bartholin’s abscess. Acquired rectovaginal fistula may be an early manifestation of human immunodeficiency virus infection in girls. Colovaginal fistula can result from diverticulitis, is usually located near the vaginal apex or cuff, and usually occurs in women who are postmenopausal and have previously undergone hysterectomy.

Prior Anorectal Surgery

Rectovaginal fistula can occur following surgeries that involve the posterior vaginal wall or the anterior rectal wall. These include procedures, such as vaginal hysterectomy, rectocele repair, hemorrhoidectomy, local excision of rectal tumors, and low anterior resection.

Cancer and Radiation Therapy

Rectovaginal fistulas can result from invasive cervical or vaginal cancer or from anal or rectal cancer. They also develop in up to 6% of women following pelvic irradiation for endometrial, cervical, and vaginal cancer and are dependent on the radiation dosage. Fistulas that present early, during radiation therapy, are more likely to be caused by destruction of the carcinoma, whereas fistulas that occur later are caused by radiation injury to the tissue. Late fistulas are commonly associated with a rectal stricture. In a patient with a history of pelvic cancer, determining whether the rectovaginal fistula is caused by recurrent cancer is critical. This often requires examination under anesthesia, with biopsies of the margins of the fistula. Rectovaginal fistulas caused by radiation usually occur within 2 years of the completion of the radiation. They are usually located in the mid or proximal vagina. Early warning signs of the development of a radiation-induced fistula include the passage of bright red blood per rectum, nonhealing rectal ulcerations, and anorectal pain.

Preoperative Preparation

Treatment of a rectovaginal fistula depends on the cause, location, and size of the fistula, as well as the condition of the involved tissues. Rectovaginal fistulas following obstetric trauma may spontaneously heal, whereas those associated with Crohn’s disease, cancer, or radiation injury have little chance of healing without surgical intervention. The tissues involved in a rectovaginal fistula should be given adequate time to heal following the acute injury. This allows maximum resolution of inflammation as well as a decrease in size of the fistula tract. Most authors recommend a waiting period of 8 to 12 weeks after the injury before attempting surgical repair, although immediate operative repair of a fourth-degree episiotomy dehiscence is recommended by some (Uygur et al., 2004). Fistulas associated with IBD are unlikely to heal if severe proctitis is present. Inflammation must be controlled by medical treatment, especially if the rectovaginal fistula is low because a reparative procedure is more likely to be successful if the proctitis has been controlled.

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