15.1.1 Definition and Classification

RVFs are classified based on location, size, and etiology—a classification system that helps guide both diagnosis and operative intervention. RVF can occur anywhere along distal two-thirds of the anterior rectal wall where it is adjacent to the posterior vaginal wall, and is defined as a communication between the vagina and the rectum above the dentate line; in comparison, an anovaginal fistula is located below the dentate line. The terms “low” RVF and “anovaginal” fistula are sometimes interchangeably used. Most RVFs form between the dentate line and the posterior vaginal fornix. ¹ RVFs are further classified as “low” when they are at or slightly above the dentate line, “high” when the vaginal opening is behind or near the cervix, and “middle” if the fistula lies between these two areas (▶ Fig. 15.1). Regarding size, “small” fistulas are typically < 0.5 cm, “medium” are from 0.5 to 2.5 cm, and “large” fistulas are > 2.5 cm in diameter. Other classification schemes have been suggested based on etiology rather than location. ¹ The fistula may also be described as “simple” if it is small and direct, or “complex” if it is high, or due to radiation, malignancy, inflammatory bowel disease, or unintended complication of a pelvic anastomosis. The reality is that given the difficulty in curing some of these fistulas, the categorization of some of them as “simple” seems a misnomer.

15.2.1 Obstetric Injuries

RVF can acutely develop with a perineal tear or surgical episiotomy, or as a delayed complication of traumatic vaginal delivery. Risk factors for development of obstetric fistulas include episiotomy, third- and fourth-degree lacerations, prolonged labor, and high forceps deliveries. ⁴ It is estimated that episiotomy and third- and fourth-degree perineal lacerations occur in up to 5% of vaginal births. ⁵ About 10% of defects repaired in the acute setting fail; two-thirds of those that fail require reoperative intervention. ⁵ Approximately 0.05 to 0.1% of midline episiotomies lead to RVF, whereas up to 1% of third- and fourth-degree lacerations will be complicated by RVF often due to missed injuries, inadequate repair of an identified injury, or secondary infection of a repaired wound. ⁵ Prolonged labor results in persistent pressure on the rectovaginal septum resulting in ischemia of the septum, which can fistulize in the postpartum period. ^{4 , 6} The development of anal ulcers, anorectal abscesses after delivery, and sphincter injuries during delivery are also possible etiologies. When considering operative repair of RVF resulting from traumatic vaginal delivery, it is important to remember that almost half of obstetric injuries also involve the anal sphincter. ⁷

15.2.2 Neoplasm and Pelvic Radiation

Malignant RVF can be the result of a primary, recurrent, or metastatic neoplasm. Common solid neoplasms that cause RVF include colorectal, anal, cervical, uterine, and vaginal cancers. Blood cancers such as leukemia, aplastic anemia, and agranulocytosis can cause RVF but are rare. ⁸ Gynecologic malignancies treated with pelvic radiation can lead to RVF, ^{9 , 10 , 11} typically presenting 6 months to 2 years after treatment is completed; incidence is related to the dose of radiation delivered, ¹² but risk is increased in the setting of hypertension, diabetes mellitus, and previous abdominopelvic surgery. ¹¹ Radiation-induced proctitis can lead to mucosal ulceration with eventual erosion through the full thickness of the rectal and eventually vaginal wall. Patients with radiation proctitis typically describe rectal pressure and a constant urge to defecate; this tends to abate when the fistula forms, at which time complaints transition to feculent drainage from the vagina and persistent vaginitis.

15.2.3 Inflammatory Bowel Disease

The incidence of RVF in inflammatory bowel disease ranges from 6 to 23%. ^{3 , 13 , 14} Crohn’s disease, and specifically Crohn’s proctitis, is a more common cause when compared to ulcerative colitis, due to transmural inflammation and associated perianal disease. ¹⁵ Some success with medical management of RVF has been achieved in Crohn’s patients with use of metronidazole, ¹⁶ chemotherapeutic agents such as methotrexate ¹⁷ and cyclosporine, ¹⁸ and more recently with remicade ¹⁹ and other anti-TNF agents. The rate of failure to heal the fistula with any medical therapy remains high, and treatment is usually aimed at control of symptoms and stabilization of acute flares to optimize patients for eventual surgical intervention. ²⁰ There are reports of adenocarcinoma developing in the setting of chronic inflammation due to Crohn’s disease that may result in fistula formation, ¹³ as well as adenocarcinoma developing in chronic Crohn’s fistulas. Patients with longstanding fistulas-in-ano due to Crohn’s disease who do not heal with medical or surgical therapy are at risk for malignant degeneration and should be carefully examined in this setting. Behçet’s disease, while rare, can also cause RVF. ²¹

15.2.4 Infection

Pelvic infectious processes including diverticulitis, perirectal abscess due to cryptoglandular abscess, venereal disease, abdominal tuberculosis, and pelvic inflammatory disease can lead to RVF. Bartholin’s abscesses, as well as infections collecting in the pouch of Douglas, can drain through the rectovaginal septum. Colovaginal fistulas due to diverticulitis, masquerading as high RVFs, occur and are more prevalent in women who have undergone hysterectomy.

15.2.5 Trauma and Miscellaneous Causes

Operative trauma can lead to the inadvertent development of RVF. Both vaginal and rectal operations complicated by infections, wound breakdown, or anastomotic leak can lead to tissue infection, abscess development, ischemia, and fistula development. Low colorectal or coloanal anastomoses, specifically circular stapled anastomoses, ²² the procedure for prolapse and hemorrhoids, and stapled transanal rectal resections, ²³ run the risk of including the posterior vaginal wall in the anastomosis if the operating surgeon is not careful. Urogynecologic operations that involve mesh placement adjacent to the rectum and vagina also carry a risk of infection, with subsequent inflammation and fistula formation. Trauma to the vagina or anus from blunt and penetrating injuries can disrupt healthy tissue resulting in development of a fistula. Fecal impaction resulting in stercoral ulcer and pressure necrosis, ²⁴ prolonged pessary usage, ²⁵ and ergotamine suppositories ²⁶ have also been cited as causes of RVF.

15.4.1 Operative Timing

Timing and need for operative repair is guided by both the size and etiology of the RVF. More than half of small fistulas from obstetric trauma will heal spontaneously. Therefore, it is recommended to wait 3 to 6 months after delivery prior to operative repair ^{33 , 34} to allow resolution of acute inflammation, which may promote spontaneous healing the majority of the time. ³⁵ However, if a large tear is noted at the time of delivery, repair should be undertaken in the delivery room. ³⁶ If there is an infectious or inflammatory component to an RVF, draining seton placement may be beneficial to help clear the infection and allow contraction and fibrosis of the tract. Seton placement will allow time for medical optimization in patients with inflammatory bowel disease, provide symptomatic relief for poor operative candidates, or provide an interval of time needed for treatment of neoplasia as well.

15.4.2 Operative Approach

Operative repair can be performed through abdominal or local procedures, including perineal, vaginal, rectal, transsphincteric, or transsacral approaches. Regardless of the approach used, adequate mobilization of the vagina and rectum must be ensured to prevent undue tension on the repair and to avoid direct apposition of suture lines to try to limit recurrence. Fecal diversion can also help control symptoms and infection, promote healing, and may even be used for definitive management in poor operative candidates. Sphincter function should also be assessed and taken into consideration when planning a strategy for repair.

15.4.3 Perioperative Management

Smoking and Crohn’s disease are the most common risk factors for recurrence of RVF following operative repair, so preoperative smoking cessation and medical control of inflammatory bowel disease are encouraged. ³⁷ Mechanical bowel prep, vaginal cleansing, and perioperative antibiotics are recommended for both local and abdominal procedures. The bladder is decompressed with a catheter, and ureteral stent placement should be considered if difficult pelvic dissection is anticipated. Hospital stays are dependent on the extent of repair, operative blood loss, patient age, and comorbidities. Patients should postoperatively abstain from any vaginal penetration for 6 to 8 weeks.

15.4.4 Management of Recurrence

Approach to repairing recurrent RVF is guided by both the etiology of the fistula and the previous operative technique. Key to success is the introduction of new healthy tissue with adequate blood supply and debridement of all nonviable and infected tissues. Success rates approaching 90% can often be achieved despite the need for multiple repairs. ³⁷

15.5.1 Simple Fistulotomy

Anovaginal fistulas that do not have extensive involvement of the sphincter mechanism can be managed with laying open of the fistula tract and healing by secondary intention. This approach has been abandoned for higher RVFs as it is likely to impair fecal continence.

15.5.2 Conversion to Complete Perineal Laceration

One local approach for repair of fistulas with extensive anal sphincter defects and fecal incontinence is episioproctotomy with reconstruction of the anorectal-vaginal septum. This procedure should include excision of the fistula tract, division of the adjacent sphincters and perineal body, and then layered closure of all the tissues (▶ Fig. 15.2). This method is similar to the classic technique for closure of fourth-degree perineal lacerations following obstetric trauma, and leads to a high rate of healing of the fistula and improved fecal continence. ³⁸ This procedure is generally performed in lithotomy position, with a full-thickness incision made between the anus and vagina. The rectal mucosa, internal and external sphincters, and the vaginal mucosa are each closed separately. The sphincters may be closed in a single layer if dissection is difficult. Healing of this extensive repair may be promoted by proximal diversion of the fecal stream.

The Musset technique is a two-stage procedure in which a perineoproctotomy is performed followed by a layered closure 8 weeks later. Healing rates of 98 to 100% are reported and 75% of patients maintain sphincter function with this approach. ^{39 , 40} Patients who present with a cloacal defect can also be managed with a similar layered repair. ⁴¹ Some authors advocate sphincterotomy in the 5 o’clock position opposing the anterior repair if sphincter reconstruction is performed, ⁴² and others describe X-flap anoplasty to recreate the perineal body. ⁴¹

15.5.3 Fistula Excision with Layered Closure

Excision of the fistula with layered closure can be completed through a vaginal, rectal, perineal, or transsphincteric approach. Fistulas associated with sphincter defects are often approached through these techniques and muscle flaps utilized if there is significant tissue loss or damage.

In the perineal approach, the patient is in prone jackknife and a 180-degree curvilinear perianal incision just anterior to the anal verge, or Schuchardt incision, is used. The vagina is opened to the level of the lateral fornix and perineal dissection extended to healthy tissue at least 1 to 2 cm above the fistula and associated scar. Once the fistula tract is identified and transected, the levators are plicated, and the vagina, sphincter fibers, and rectal mucosa are closed in layers. Care should be taken to avoid direct apposition of suture lines; the vaginal side may be left open for drainage. The curvilinear incision is then closed in a V–Y flap fashion, reconstructing the breadth of a normal perineal body. ⁶ A transrectal approach has also been described which avoids the need for a perineal incision ⁸ but may require advancement of rectal mucosa to cover the defect left by excision of the fistula.

A transsphincteric approach can also be used. While first described to close rectourethral fistulas (RUFs), this technique can be used to fully expose more proximal tracts and reduce the need for transabdominal repairs. ⁴³ The patient is placed in prone jackknife position and the buttocks retracted laterally with adhesive tape. The incision extends from the anal margin to the midsacrum just to the left of midline. The mucocutaneous junction and sphincter muscles are marked with stay sutures. The rectal mucosa is then divided to expose the fistula, the fistula and surrounding scar tissue excised, and the vaginal opening is closed primarily. The incision in the anterior rectal wall is then transversely extended, full-thickness flaps are mobilized, and the rectum is closed using a “vest over pants” technique. The sphincter muscles are then reapproximated and the skin closed.