Benign Anorectal: Rectovaginal Fistulas

Obstetric injury is the most frequent cause of acquired rectovaginal fistulas but infection and other forms of trauma may also result in these fistulas. After an obstetric injury, the fistula may be manifest immediately but more frequently appears 7–10 days after delivery. Fistulas occur most often after a thirdor fourth-degree laceration. Inadequate repair, breakdown of the repair, or infection may result in fistula formation. In developed nations, rectovaginal fistulas occur after 0.06%–0.1% of vaginal deliveries.1–3 In developing countries, however, the incidence of rectovaginal and vesicovaginal fistula after childbirth is almost 3 times higher, with more than half of these fistulas being larger than 4 cm in diameter.4,5 In these countries, prolonged labor, causing necrosis of the rectovaginal septum, leads to the formation of a fistula. Disease processes may also cause rectovaginal fistulas. Cryptoglandular infection may result in an abscess spontaneously draining into the vagina resulting in a fistula. Rectal and gynecologic malignancies may result in fistulas as a result of local extension of the tumor or secondary to treatment with radiotherapy. Women with inflammatory bowel disease, Crohn’s disease more frequently than ulcerative colitis, may develop rectovaginal fistulas. In a 23-year population-based study of patients with Crohn’s disease in Olmsted County, MN, 88 fistulas developed in 59 patients.6 Eight (9%) of the fistulas were rectovaginal fistulas. Over a period of approximately 30 years, 90 of the 886 women seen at St. Mark’s Hospital with Crohn’s disease and an intact rectum developed a rectovaginal fistula.7 Operative trauma may also result in a rectovaginal fistula. Complications of rectal or vaginal surgery usually result in fistulas opening low in the rectum. High fistulas are most frequently complications of low stapled colorectal or ileoanal anastomoses. In one series of 140 patients undergoing low anterior resection for rectal carcinoma, four (2.9%) developed a rectovaginal fistula.8 The mechanism is usually that a portion of the posterior vaginal wall is included in the anastomosis or that an abscess secondary to an anastomotic leak drains into the vagina. Pouch vaginal fistulas are reported in 3%–12% of patients.9–12 Rectovaginal fistulas are also a complication of neovaginal construction for congenital abnormalities or as sex-change procedures.13 Fistulas have also been reported after vaginal dilatation of a radiated vaginal cuff, fecal impaction, viral and bacterial infection in human immunodeficiency virus patients and sexual assault.14–17 Congenital rectovaginal fistulas occur but are outside the scope of this chapter.