Epidemiology
Rectovaginal fistulas make up about 5% of all anal fistulas. The overwhelming majority (88%) is due to delivery trauma and affects 0.1% of all vaginal deliveries (36). Further causes are chronic inflammatory bowel diseases (especially Crohn disease) with up to 2.1% and deep anterior resections with up to 10% (85, 24, 43, 56, 57, 69). Rectovaginal fistulas are increasingly encountered as complications in hemorrhoidal surgery and functional pelvic floor disorders, particularly where staplers or foreign body materials are concerned (3, 27, 35, 49, 64).
Classification
There is no standard classification of rectovaginal fistulas. The present classifications rely on cause, size and location. Another classification differentiates between simple and complicated fistulas: Crohn fistulas and radiation induced fistulas are classified as complicated.
For the surgical procedure, it is recommended to differentiate between high and low fistulas: high fistulas require an abdominal procedure, while low fistulas may be treated via an anal, perineal or vaginal approach. Since the assessment of a possible perineal defect also influences the surgical strategy, it is worth noting the classification by Fry et al. (26, 19, 40, 41, 52):
I Perineal defect without fistula
II Perineal defect, fistula in lower third of vagina
III No perineal defect, fistula in lower third of vagina
IV No perineal defect, fistula in middle third of vagina
V No perineal defect, fistula in upper third of vagina
Etiology
While most rectovaginal fistulas are traumatic in origin, other causes include inflammatory processes and postoperative complications after pelvic surgery (12, 18, 72, 75, 85).
Postpartum rectovaginal fistulas
- 88% of all rectovaginal fistulas (75)
- Cause: Traumatic vaginal dilatation with tearing of the perineum and rectovaginal septum (29)
- 5% of all vaginal deliveries result in third or fourth-degree perineal tears. Risk factors include: High birth weight; forceps delivery, especially in older pregnant women (4, 37)
- In about 95% of the women affected primary repair of the perineal tear, carried out immediately postpartum, results in good outcomes. (72)
- 1% to 2% of all higher-grade perineal tears (grade IV: complete tear of skin, perineum, anal sphincter, and rectal mucosa), dehiscence of the primary repair and inadequate care results in rectovaginal fistula. (36)
- Rare: Spontaneous healing of the fistula during the early postpartum period (36, 68)
- Common in postpartum fistulas: Sphincteric lesions concurrent with fecal incontinence (19, 40, 41, 52)
Rectovaginal fistulas through local infections
- Especially arising from cryptoglandular infections and bartholinitis (33, 92)
- Rare: Tuberculosis (72), lymphogranuloma venereum (47), amoebiasis (22), schistosomiasis (45), Inflammatory changes/erosions by foreign bodies such as retained IUDs (2, 6, 10, 34, 38, 67, 70), misuse of suppositories containing ergotamine or nicorandil (59, 65, 73)
- Also: HIV and associated infections (1, 60, 74), Behcet syndrome (13, 15)
Rectovaginal fistulas after rectum resection
- Caused by iatrogenic perforation of the vagina and the use of staplers
- In up to 10% of all low rectal anastomoses (43, 51), e.g. in malignancy, pouch-anal anastomosis in chronic inflammatory bowel disease (23, 25) and proctocolectomy in polyposis coli (55)
- Other risk factor: Pre- or postoperative radiochemotherapy; fistula formation in up to 6.5% of cases (16, 42, 46)
- Most important risk factor: Use of staplers, e.g. accidental involvement of the vaginal wall after previous hysterectomy (5, 39, 43, 56, 57, 69, 80, 89), but also anastomotic failure which - initially non-apparent - results in small pelvis abscess, which then drains through the vagina (50, 76)
Rectovaginal fistulas after other rectal operations and procedures in the lesser pelvis
- Transanal tumor ablation (anterior rectal wall), stapled hemorrhoidectomy, but also surgery for pelvic floor dysfunction (lowering, rectal prolapse, rectocele, incontinence) with a staplers or mesh implants
- Increased postoperative fistula formation after stapled hemorrhoidopexy, usually by including the posterior vaginal wall (3, 8, 17, 30, 31, 32, 53, 63), after technically demanding procedures such as STARR ("stapled transanal rectal resection") or TRANSTAR ("transanal stapled resection") (7, 27, 58, 62, 63, 64, 78) as well as after mesh implants in pelvic floor disorders (14, 35)
Symptoms and diagnostic work-up
The diagnosis of rectovaginal fistula rests on the patient’s medical history and clinical examination (44): Discharge of air and/or mucus, possibly also stool, via the vagina. Questions about previous operations and obstetric complications are vital, as are questions about the psychological strain on the affected women.
Most rectovaginal fistulas are located at the level of the dentate line and communicate with the posterior vaginal fornix. The fistula usually displays a slightly curved tract along the upper margin of the sphincter. The clinical examination must include inspection of the rectum and vagina. Further diagnostic work-up must be performed before any surgical measures and especially in case of unclear findings: Colonoscopy, CT, MRI. With appropriate experience, endoscopic ultrasound can visualize sphincter lesions very well and should complement rectal digital examination and manometry (77, 79).
Treatment options
Adequate treatment of rectovaginal fistulas always requires surgery, though this presents the surgeon with a challenge. Essentially the procedure is the same as in high transsphincteric anal fistulas.
Local conditions such as location and size of the fistula and tissue conditions, such as inflammation and sphincteric lesions have a decisive impact on treatment choice (71). The most common procedure is excision of the fistula with suture of the sphincter and closure of the rectal defect by advancement flap.
In 2010 Pinto et al. published a review of the various techniques (66). In almost all procedures the initial success ("fistula healing") at first attempt is only 60% and reveals marked differences regarding fistula etiology. Rectovaginal fistulas occurring postpartum or as surgical sequelae were cured in up to 70% of cases, while this rate dropped to only 44% in Crohn fistulas. Thus, revision surgery is not uncommon in definitive fistula management.
Endorectal closure
The endorectal closure of rectovaginal fistulas comprises transanal fistula excision with suture of the sphincter and subsequent covering of the suture line with an advancement flap of the mucosa/submucosa or full-thickness rectal wall, in isolated cases also by an anoderm advancement flap. The procedure was described in 1969 by Belt (9) and corresponds to the flap principle in high anal fistulas (61). The success rates of this technique vary between 50% and 70 %.
Transperineal closure
In transperineal procedures, access is gained via the rectovaginal space. After releasing the rectum from the vagina, the anterior rectal wall and posterior vaginal wall are repaired separately; this is followed by augmenting the rectovaginal septum by adapting the levator limbs. The most important aspect of the procedure has to do with the fact that any necessary sphincteroplasty may be performed during the same operation (54, 71, 84).
One downside is the relatively large perineal wound with its risk of wound healing disorders. Since the success rate of around 80% (21, 82) is good, the guidelines also recommend the transperineal procedure for fistula closure and concurrent sphincter repair.
Wound management and perioperative complications
Immediate complications include postoperative bleeding and urinary retention, although these complications are much more common after hemorrhoid surgery. Postoperative urinary retention is caused by inadequate analgesia and excessive intravenous fluid regimen (83, 90). There is a risk of local infections with secondary dehiscence of suture lines, which is why adequate drainage of deeper wound areas must be ensured. Regarding postoperative bowel movement, the stool should be kept soft, e.g. by taking mild laxatives.
Relevant postoperative complications include dyspareunia due to vaginal constriction or scarring (86), which affects about 25% of sexually active patients (21, 91).
Stoma construction
Anal fistula surgery rarely requires an ostomy, whereas it is much more common in rectovaginal fistula. By itself the surgical technique in rectovaginal fistulas does not mandate an ostomy, rather the indication should be based on the actual findings. Patients primarily affected are those with marked destruction of the anal canal and resulting fecal incontinence. In fistulas following rectal anastomosis and Crohn fistulas, the indication should be rather generous (11, 20, 28, 48, 81, 87, 88).