INTRODUCTION — An anorectal fistula is an inflammatory tract or connection between the epithelialized surface of the anal canal and, most frequently, the perianal skin or perineum. It often evolves from a spontaneously draining anorectal abscess. Perianal fistulous disease has significant implications for patient quality of life as sequelae range from minor pain and social hygienic embarrassment to frank sepsis.
The management of the anorectal fistula (also called fistula-in-ano) remains one of the most challenging and controversial topics in colorectal surgery. Surgery is the mainstay of therapy with the ultimate goal of draining local infection, eradicating the fistulous tract, and avoiding recurrence while preserving native sphincter function [1,2]. The surgical approach depends on several factors, such as the etiology, location, type, and duration of the fistula, as well as previously performed procedures and preoperative sphincter function.
This topic will discuss the surgical management of anorectal fistulas. The causes, clinical manifestations, diagnosis, and classification of anal fistulas are discussed elsewhere. (See "Anorectal fistula: Clinical manifestations, diagnosis, and management principles" and "Perianal Crohn disease".)
FISTULA ANATOMY — Over 90 percent of anorectal fistulas develop from a cryptoglandular abscess originating from the crypts of Morgagni, which are located between the two layers of the anal sphincter (figure 1). As such, most internal openings of the fistula are located around the anal glands surrounding the dentate line [3,4].
Fistulas that occur between the anal orifice and the dentate line are referred to as anal in origin, while fistulas that originate above the dentate line are rectal in origin. Less commonly, fistulas can occur between the anal canal or rectum and the vagina or bladder. (See "Urogenital tract fistulas in females".)
The course of an anorectal fistula follows one of four paths: intersphincteric (45 percent), transsphincteric (30 percent), suprasphincteric (20 percent), or extrasphincteric (5 percent), before exiting at the perianal skin (figure 2 and figure 3) [5]. (See "Anorectal fistula: Clinical manifestations, diagnosis, and management principles", section on 'Classification'.)
ANATOMY OF THE ANAL REGION — A thorough knowledge of the anatomy of the anal canal, ischiorectal fossa, perirectal tissues, and sphincteric muscles is imperative before proceeding with any operative procedure to treat an anorectal fistula. The following is the anatomical description of the anal region [6-8].
Anal canal — The anal canal begins at the anorectal junction and ends at the anal verge (figure 1 and figure 4). The anal verge is demarcated at the site where the squamous epithelium lining of the lower anal canal becomes continuous with the skin of the perineum. Anteriorly, the middle third of the anal canal is attached by dense connective tissue to the perineal body, which separates it from the membranous urethra and penile bulb in males and from the lower vagina in females. Laterally and posteriorly, the anal canal is surrounded by loose adipose tissue within the ischiorectal fossas. Posteriorly, the anal canal is attached to the coccyx by the anococcygeal ligament, a midline fibroelastic structure that may possess some skeletal muscle elements and that runs between the posterior aspect of the middle portion of the external sphincter and the coccyx. Just above this is the raphe of the levator ani muscle, the fusion of the two halves of iliococcygeus, which merges anteriorly with the puborectalis muscle.
Ischiorectal fossa — The ischiorectal fossa is triangular in shape and bounded by the skin inferiorly, the obturator internus muscle laterally, and the inferior surface of the levator ani as its anterior and medial border. Posteriorly, the ischiorectal space is continuous to the sacrotuberous ligament and the gluteus maximus muscle with the potential space in the buttock deep to the muscle. Superiorly, the ischiorectal fossa is sealed off by the origin of the levator ani from the inner surface of the obturator internus and the continuity of the inferior fascia of the pelvic diaphragm with the obturator fascia. Anteriorly, the ischiorectal fossa is separated from the superficial perineal space by the attachment of the perineal fascia to the posterior border of the urogenital diaphragm. The ischiorectal fossa continues forward for a short distance above the urogenital diaphragm and the lower border of the pelvic diaphragm until these two diaphragms join. The left and right ischiorectal fossas communicate posteriorly, above a portion of the external anal sphincter that extends posteriorly to attach to the coccyx (figure 5).
Internal anal sphincter — The internal anal sphincter is a well-defined ring of obliquely orientated smooth muscle fibers that is continuous with the circular muscle of the rectum and terminates at the junction of the superficial and subcutaneous components of the external sphincter (figure 1). The lower portion of the sphincter is crossed by fibers from the conjoint longitudinal tendon that pass into the submucosa of the lower canal.
External anal sphincter — The external anal sphincter is an oval, tube-shaped complex composed mainly of skeletal muscle fibers. The muscle consists of deep, superficial, and subcutaneous parts but should be considered as a single functional and anatomical entity (figure 1).
The uppermost fibers of the external anal sphincter blend with the lowest fibers of puborectalis muscle. The fibers from the upper third attach anteriorly into the superficial transverse perineal muscles, and posteriorly the fibers are attached to the anococcygeal raphe. The majority of the fibers of the middle third of the external anal sphincter surround the lower part of the internal sphincter. The middle third is attached anteriorly to the perineal body and posteriorly to the coccyx by the anococcygeal ligament. The fibers of the lower third of the muscle lie below the level of the internal anal sphincter and are separated from the lowest anal epithelium by the submucosa layer.
The transverse perinei and bulbospongiosus muscles fuse with the external sphincter in the lower part of the perineum. The perineal body attaches the external anal sphincter muscle to the surrounding structures and is an imbrication of muscle fibers in females in comparison to a central tendinous insertion in men. Also, in females, the anterior and lateral portion of the external anal sphincter is significantly shorter and is oriented in a horizontal plane. In males, the external sphincter is more anular and is separate from the central point of the perineum, so that there is a surgical plane of cleavage between the external sphincter and perineum [9].
Anal mucosa — The upper part of the anal canal is lined by mucosa similar to the rectum, while the lower portion is lined by stratified epithelium similar to the skin of the perianal region. The line around the anal canal that can be traced by following the anal columns is the pectinate line (also called the dentate line or mucocutaneous line) (figure 1). This line represents the change in epithelium as well as lymphatic drainage, blood supply, and venous drainage. The pectinate line is palpated or visualized approximately 2 cm above the anal opening.
At the junction of these two types of lining are the anal columns, longitudinal and wider at the distal end, while fading at the proximal end of the canal. They are united distally by thin membranes called anal valves. Between the bases of the longitudinal columns and the anal valves are anal sinuses, rudimentary anal glands (also called crypts or ducts), which open into the anal sinuses (figure 1). An infection of an anal sinus and gland can develop into an abscess. The abscess develops a fistula that can extend from the anal canal into the perianal musculature, the ischiorectal fossa, and the skin.
PREOPERATIVE EVALUATION
Initial visit — Appropriate management and long-term success of treating the fistula begins with the first patient encounter in the surgeon's office or emergency room. The internal and external openings of the fistulous tract need to be identified. The external opening may be seen on external examination; the typical appearance is a small, dimpled area of granulation tissue that drains pus or blood on manual compression. The internal opening may be identified by anoscopy with manual compression over the external opening. Proctoscopy is also indicated in the presence of rectal disease, such as Crohn disease or other suppurative conditions.
A digital rectal examination is performed on every patient to assess for an indolent or incompletely drained abscess (figure 6). In contrast, most patients will not tolerate even gentle probing of the fistula track in the office setting.
Imaging — There are multiple imaging options for the evaluation of anorectal fistulas. The choice of which modality, if any, to implement is dependent on equipment availability, radiologist expertise, patient tolerance, cost, and the proposed management strategy [10]. (See "Anorectal fistula: Clinical manifestations, diagnosis, and management principles", section on 'Imaging studies'.)
The anatomy of most fistulas can be determined in the operating room without preoperative imaging. If the internal openings and extent of sphincter involvement are difficult to identify, intraoperative radiographic studies can be helpful. We commonly use three-dimensional ultrasound intraoperatively to evaluate recurrent or complicated fistulas. Hydrogen peroxide can be used with this technique to outline the fistula tract.
Informed consent — The major postoperative risks of surgical management of anorectal fistulas include fecal incontinence and recurrences, which should be addressed when discussing treatment options. Fistulas located in the lateral position, complex fistulas, those with horseshoe extensions, and those with lack of identification of the internal opening have an increased risk of recurrence [11]. The risk of postoperative incontinence is higher with anterior fistulas in women, high anal fistulas, previous fistula surgery, and fistulotomy with or without setons [11].
SURGICAL PLANNING — The overall goal of surgery is to eradicate the fistula, preserve anal sphincteric function, and prevent a recurrence. The tremendous variability of patient factors and the heterogeneity of anorectal fistulas require a greater need for surgical "judgment" than in most colorectal diseases.
While most cryptoglandular fistulas are treated surgically, combined medical and surgical therapy is required if the fistula is secondary to Crohn disease. (See "Perianal Crohn disease" and "Anorectal fistula: Clinical manifestations, diagnosis, and management principles".)
Staged approach — If drainage persists beyond 6 to 12 weeks after the initial incision and drainage of an anorectal abscess or other septic process, an anorectal fistula is suspected, for which further surgery is indicated (algorithm 1) [1].
In our practice, all patients suspected of a fistula undergo an examination under anesthesia to determine whether the fistula is simple or complex based on the extent of anal sphincter muscle involvement and other characteristics of the fistula. Patients with a simple fistula, who otherwise have no risk factors for incontinence, should undergo a primary fistulotomy (see 'Simple fistulas' below). Patients with a complex fistula, or who are at high risk for incontinence, should have a draining seton placed to preserve the sphincter mechanism and help eradicate the septic focus. In six or more weeks, a second sphincter-sparing procedure can be performed after drainage diminishes (algorithm 1). (See 'Draining setons' below.)
Procedure selection — The procedure selected for an individual patient should be based on a thorough physical examination of the anal region. The key technical component of all operative procedures is the identification and curetting of the internal opening to ensure adequate drainage [12]. No single operative technique is appropriate for the treatment of all anorectal fistulas; hence, the judgment and experience of the surgeon must guide the treatment decisions [12-15].
The surgical management of the anorectal fistula depends on the location of the fistula in relation to the external anal sphincter (Parks' classification) and the amount of the sphincter complex involved with the fistulous tract (figure 2). Clinical experience has shown that fistulotomy is an effective procedure for simple submucosal, intersphincteric, and low-sphincteric fistulas, while staged procedures are a better approach for complex fistulas [12].
In a retrospective review of 9536 fistulas treated in Italy over 15 years (5520 simple and 4016 complex), the overall healing rate of simple fistulas was 81.1 percent (91.9 percent sphincter-cutting versus 65.1 percent sphincter-sparing) [16]. Fistulotomy was the most frequently used procedure, although its popularity waned over the years, with a concomitant increase in the use of sphincter-sparing approaches. The overall healing rate of complex fistulas was 69.0 percent (81.1 percent sphincter-cutting versus 61.4 percent sphincter-sparing). There was a trend toward technology-assisted procedures, although the healing rate for such procedures was lower than that of technology-free procedures (55 versus 72.5 percent).
Simple fistulas — Most fistulas are simple (minimal involvement of the external sphincter muscle) and classified as low-lying transsphincteric (Parks' type 2 and involving <30 percent of anal sphincter complex) and intersphincteric fistulas (Parks' type 1) (picture 1) [1]. The traditional approach to treatment is primary fistulotomy [15]. (See 'Procedures for simple fistulas' below.)
Complex fistulas — A complex fistula refers to those fistulas that have a high risk of treatment failure and cannot be safely treated by routine fistulotomy. An anal fistula is defined as complex in the following situations:
●Any fistula involving more than 30 percent of the external sphincter
●Suprasphincteric fistulas
●Extrasphincteric or high fistulas, proximal to the dentate or pectinate line
●Women with anterior fistulas
●Fistulas with multiple tracts
●Recurrent fistulas
●Fistulas related to inflammatory bowel disease
●Fistulas related to infectious diseases, including tuberculosis and HIV
●Fistulas secondary to local radiation treatments
●Patients with a history of anal incontinence
●Rectovaginal fistulas (see "Rectovaginal and anovaginal fistulas")
Primary fistulotomy alone is inadequate treatment of complex fistulas because of the high risk of postoperative incontinence, so sphincter-sparing approaches are necessary [12,15,17]. Sphincter-sparing procedures include endoanal advancement flaps, fibrin glue, fistula plugs, the modified Hanley procedure, ligation of the intersphincteric fistula tract (LIFT), or diversion [12,18,19]. The choice of procedures is dictated by fistula anatomy as well as surgeon preference (algorithm 1):
High transsphincteric fistula — In our practice, we prefer to treat high transsphincteric fistulas (Parks' type 2 and involving >30 percent of the anal sphincter complex) with either an endoanal advancement flap or LIFT. We perform LIFT when the primary (internal) opening has migrated distal to the dentate line or if the patient has preexisting incontinence. When the primary opening is at the dentate line, either endoanal advancement flap or LIFT can be performed.
Suprasphincteric fistula — Suprasphincteric fistulas (Parks' type 3) should be treated with endoanal advancement flaps. LIFT is not an option, because there is no intersphincteric fistula tract.
Extrasphincteric fistula — Extrasphincteric fistulas (Parks' type 4) are typically not of cryptoglandular origin but are instead caused by cancer or Crohn disease. These fistulas are rare but difficult to treat. Surgical options include proctectomy or fecal diversion.
Horseshoe fistula — Horseshoe fistulas can be managed initially by drainage of the lateral sites with setons and a midline seton from the posterior primary opening to the deep postanal space. The lateral setons can be removed after 12 weeks, and the primary opening can be managed by an endoanal flap or a snug seton (ie, modified Hanley procedure). (See 'Modified Hanley procedure' below.)
Recurrent fistula — Recurrent fistulas that involve the sphincter complex typically warrant a pelvic magnetic resonance imaging (MRI) scan to clarify anatomy and a seton for drainage. Subsequently, they can be managed according to their classification as described above.
PERIOPERATIVE PREPARATION
Preoperative preparation — In our practice, patients are advised to maintain a clear liquid diet for 24 hours prior to surgery and take two enemas the morning of surgery, if tolerated. We also advise patients to discontinue all drugs that can prolong bleeding (eg, aspirin-containing medications, nonsteroidal anti-inflammatory drugs). A mechanical bowel preparation is only required for patients undergoing a planned simultaneous sphincter reconstruction or extensive rotational flap.
Intraoperative preparation — The position of the patient and adequate administration of anesthesia are key components for performing the described operative procedures.
Antibiotics — The benefit of preoperative antibiotics has not been established for anorectal surgery. In our practice, broad-spectrum antibiotics are administered intravenously before the start of the procedure. (See "Antimicrobial prophylaxis for prevention of surgical site infection in adults".)
Anesthesia — The choice of anesthetic is determined by the preference of the patient and surgeon and the general medical condition of the patient. Options include a general anesthetic or locoregional anesthesia, such as a four-quadrant pudendal nerve block with 0.25% bupivacaine. Most patients will do well with a local anesthetic supplemented with intravenous medication for a light sedation. At the conclusion of the procedure, local injection of a long-acting local anesthetic provides several hours of comfort after the procedure. (See "Subcutaneous infiltration of local anesthetics" and "Procedural sedation in adults outside of the operating room: General considerations, preparation, monitoring, and mitigating complications".)
Position — Appropriate positioning facilitates visualization of the internal opening. The lithotomy position is the preferred position for patients with a posterior external opening and when performing advancement flaps, ligation of the intersphincteric fistula tract (LIFT) procedures, and diversions. Patients with anterior external openings, Crohn disease, and most patients with obesity are positioned in the prone jackknife position [1].
Anal examination — The anal examination is an important component of all fistula procedures. Palpation of the anal canal, the fistula tract, and surrounding structures is performed to determine the amount of anal sphincter muscle involved (figure 6). The anal canal is gently dilated digitally, the pectinate line is visualized, and the anal crypts are examined for evidence of inflammation and an internal opening.
Internal opening identification — The identification of the internal opening of the fistula is another key element common to all fistula procedures. Lack of identification of the internal opening is one reason for failure of any given technique [20]. Dilute hydrogen peroxide or dilute povidone iodine is infused via an angiocatheter into the external opening of the fistula while examining the anal canal with an anoscope. Visualization of hydrogen peroxide bubbles or povidone iodine at the internal opening confirms the internal location of the fistula.
PROCEDURES FOR SIMPLE FISTULAS — The following procedures are used to treat simple fistulas. The key technical component of all operative procedures is the identification and curetting of the internal opening to ensure adequate drainage [12]. All procedures include dilatation of the anal canal and anoscopy.
Fistulotomy — Fistulotomy involves laying open the fistula tract in its entirety. It is an effective treatment for simple anal fistulas that results in healing in over 90 percent of patients [21,22]. It is critical to assess all patients' incontinence score prior to fistulotomy. In patients with preexisting incontinence, fistulotomy is contraindicated in all situations (algorithm 1).
Critical elements — A probe is inserted into the internal opening and gently passed along the fistula tract to the external opening. An incision is made over the entire length of the fistula using the probe as a guide. The tract is gently curetted, and an absorbable stitch is used to marsupialize the tract to promote healing. The wound is gently packed with a petroleum-based gauze and covered with a sterile dressing [23]. We prefer to marsupialize the tract as it may speed up wound healing.
The most critical step in this procedure is to identify and curette the internal opening to reduce the risk of recurrence. In a randomized trial of primary fistulotomy for perianal abscesses in 52 patients, persistent fistulas occurred in seven patients (25 percent) treated with incision and drainage compared with no recurrences in 24 patients treated with a fistulotomy (figure 7 and picture 2) [20].
Outcomes — Patients should be observed for a minimum of six months following the procedure before determining a treatment failure or success [24]. The most concerning potential complication of a fistulotomy is incontinence from procedure-related damage to the external anal sphincter. The divided muscle fibers retract, and the result is solid fecal, liquid fecal, or gas incontinence. The reported rates of incontinence are highly variable, ranging from 0 to 82 percent [25-27]. Nevertheless, when fistulotomy is used for simple anal fistulas in properly selected patients, the risk of fecal incontinence is minimal or none [21,22].
Recurrence rates for an anorectal fistula treated with a fistulotomy are generally reported to be low, with success rates ranging from 79 to 100 percent [20,23,25,26,28-31]. In an observational study with median 76 months' follow-up, the three-year recurrence rate for 109 patients with a low-lying simple fistula treated was 7 percent [31].
PROCEDURES FOR COMPLEX FISTULAS — The following procedures are used to treat complex fistulas. All procedures include dilatation of the anal canal, anoscopy, and identification of the internal opening. (See 'Intraoperative preparation' above.)
Draining setons — A draining (or noncutting) seton is placed primarily for drainage. It does not cut through the sphincter. For complex fistulas, including those that traverse more than 30 percent of the sphincter, are proximal to the dentate line, or are high transsphincteric fistulas, draining setons are used at the time of the first operation to preserve the sphincter mechanism and help eradicate the septic focus [32].
Critical elements — A draining seton is typically inserted during an examination under anesthesia procedure when the fistula is determined to be complex and/or the patient is at high risk for fecal incontinence. To identify the track, a probe is inserted into the external opening and advanced passively along the track until it exits the internal opening. A suture is then tied to the probe and pulled through the fistula track. The suture is used to pull a seton through the fistula track. Silastic vessel loops are the best material for draining setons. A yellow vessel loop is preferred to other colors for its size [33].
The ideal length of a draining seton is tight enough so as not to get in the way of bowel movements but loose enough not to erode through the skin (picture 3). Because the knot that secures the seton circle will inevitably enter the track, it should be as small as possible (two squared throws of the tie; cut the ends close to the knot for both the tie and seton) (picture 3). Patients with setons that are too small, too tight, too loose, too long, too numerous, or secured incorrectly can be miserable due to chronic irritation from the setons [33].
Properly placed draining setons can be left in place indefinitely, as long as they are effective in relieving symptoms, or they can be removed at the time of the definitive fistula repair with one of the following methods ≥6 weeks from the time of seton insertion.
A draining seton can also be converted to a snug (cutting) seton by incising the skin bridge and subcutaneous tissue between the seton and sphincter muscle, allowing the seton to slowly migrate through the muscle over time. (See 'Fistulotomy by snug setons' below.)
Fistulotomy by snug setons — A snug seton, also referred to as a "cutting" seton, is a reactive suture or elastic that is placed through the fistula tract and tightened at regular intervals. It slowly cuts through the tract, causing scarring, thus preventing the wide disruption of the anal sphincter associated with fistulotomy.
Critical elements — The internal opening is identified and a probe inserted between the internal and external openings as previously described. The skin bridge is opened completely between the internal and external openings, and a small piece of braided silk or an elastic vessel loop is pulled through the fistulous tract. This seton is secured snugly around the sphincter muscle (figure 8). For a snug seton to work properly, the skin bridge and subcutaneous tissue between the seton and muscle must be completely divided (picture 4).
Patients are examined at monthly intervals, and the seton is tightened until the deep space is obliterated. The seton promotes granulation tissue formation and allows the edges of the wound to become firm before the sphincter is divided. The seton will slowly divide the fistulous tissue tract on the leading edge of the seton while allowing healing to occur on the trailing edge and preserving sphincter continuity and theoretically preserving sphincter function. Incontinence occurs not because the sphincter muscle is divided but when the muscle fibers retract and the space in between is filled with scar tissue.
There is wide variation in the amount of time that snug setons remain in situ. Shortened periods between seton tightening may result in poor outcomes. From basic biology principles, significant collagen deposition and fibrosis occur over a period of four to six weeks, so setons that cut through more rapidly than this may not provide adequate time for scarring to occur [28].
Outcomes — The two most important complications of a fistulotomy with a snug seton are recurrence and incontinence. The success rates for snug setons range from 82 to 100 percent; however, long-term incontinence rates can exceed 30 percent [26,27,29,30,34,35].
In one multicenter study, 200 consecutive patients had loose setons placed and exchanged regularly; all fistulas eventually cleared with a recurrence rate of 6 percent [36]. However, leaving draining setons indefinitely may result in low-grade incontinence of gas, mucous, or fluid discharge and have an adverse impact on quality of life [37].
A retrospective analysis (n = 59) of the long-term results of a snug seton as a treatment for high cryptoglandular fistulas revealed primary and secondary healing rates of 93 and 98 percent, respectively [34]. Normal or near-normal continence was maintained in 78 percent of patients; 13.5 and 8.5 percent of patients, respectively, developed moderate and severe incontinence. Mean continence score was significantly worse in women than men.
A randomized trial compared the risks of incontinence of a modified snug seton technique, which includes the repair of the internal anal sphincter and directing the seton through the intersphincteric space, with the conventional snug seton technique in 34 patients with high transsphincteric fistulas [38]. There was no significant difference in incontinence rates, resting anal manometric pressures, healing rates, or recurrence rates between the two techniques.
Advancement flaps — The endoanal and endorectal advancement flaps preserve the anal sphincter by closing off the internal opening of the fistula by a mobilized flap of healthy tissue consisting of mucosa and submucosa, with or without the internal sphincter [39]. The flap provides tissue coverage of tract internal opening and allows the tract to heal and close (figure 9).
Endoanal and endorectal advancement flaps are the preferred approach for complicated anorectal fistulas without coexisting incontinence [40]. Not all anorectal fistula patients are candidates for mucosal flap advancement. Very high fistulas, for example, are technically challenging to treat by this technique. Additionally, anal stenosis, active proctitis, and inflammatory bowel disease are relative contraindications due to high complication and failure rates [41].
Critical elements — The key component of this procedure is to create a flap that includes the mucosa, submucosa, and a portion of the circular muscular fibers that is sufficient to cover the internal opening. The base of the flap proximally should measure at least twice its width at the apex. The flap is raised by making a curvilinear incision around the dentate line. The incision should not extend more than one-third of the anal canal circumference to prevent stricture formation. If dilute epinephrine is used to control bleeding, care should be taken not to raise a flap that is too thin. A thin flap may result in ischemia and may not provide sufficient integrity to adequately cover the internal opening and prevent recurrence.
After the fistulous tract is curetted and debrided, the flap is advanced and sutured in place. We prefer to anchor the center and most cephalad portion of the underside of the flap first; then, the lateral portion of the flap is secured with a running or interrupted suture.
Outcomes — A variety of endoanal advancement flap techniques exist and, in experienced hands, have low-to-moderate recurrence rates (0 to 40 percent), depending in part on patient population, and tolerable incontinence rates ranging from 0 to 12.5 percent [31,42-46]. The wide range in outcomes is due to heterogeneity in patient populations, technique, and experience.
In a retrospective single-institution study, 58 of 98 patients underwent endorectal advancement flap for a cryptoglandular fistula and the rest for inflammatory bowel disease-associated fistulas [47]. At 7±3 years after surgery, primary healing occurred in 72 percent of patients; additional flaps or other treatment increased the overall healing rate to 93 percent. Patients with Crohn disease had lower healing rates than those with cryptoglandular fistulas (87 versus 98 percent). More patients had normal continence after than before surgery (57 versus 43 percent).
Modified Hanley procedure — The modified Hanley procedure is a sphincter-preserving procedure for the treatment of horseshoe abscesses and fistulas (picture 4) [48]. (See "Perianal and perirectal abscess", section on 'Horseshoe'.)
The modified Hanley procedure is performed in difficult cases of anorectal fistulas, including patients with:
●Horseshoe fistulas
●Ischiorectal fistulas
●Deep postanal abscesses with fistulas
●Recurrent fistulas
Critical elements — The key components of this technique are to identify and drain all fistulous tracts. A probe is inserted through the internal opening into the deep space abscess cavity. An incision is made in the posterior midline, initially avoiding the superficial external sphincter. The midline incision is then deepened parallel to and through the fibers of the superficial external sphincter, thereby unroofing the deep space for drainage. A probe is then guided through the internal opening to exit through the midline surgical incision. The walls of the deep space are inspected to identify limbs of the horseshoe abscess fistula.
If a deep postanal abscess or extension into the ischiorectal fossa is identified, we prefer to use a modified Hanley technique for definitive management with draining lateral setons and a snug seton in the posterior midline.
A counterincision is made over the appropriate site with the subsequent incision, drainage, and curettage of all of the fistulous tracts. Next, the seton is attached to the midline probe and retrieved through the internal opening and secured to itself with a 0 silk suture. The underlying perianal skin and anoderm between the primary midline opening and the secondary midline surgical incision are removed to allow subsequent tightening of the seton. A Penrose drain is placed in the tract and removed 24 to 48 hours after surgery [49].
Outcomes — In a retrospective review of 23 patients with high transsphincteric horseshoe fistulas treated by a modified Hanley procedure using snug setons, 91 percent had complete healing within eight months, and no incontinence was reported [48]. This procedure requires months of postoperative care but is safe and effective.
Fibrin sealant — Fibrin sealant is a minimally invasive treatment option for anal fistulas. A mixture of fibrinogen, thrombin, and calcium ions forms a clot that is injected into the fistula tract, and within 10 to 60 seconds the fistula is potentially sealed [50,51]. This approach avoids sphincter division, but long-term results have not been encouraging (picture 5).
Critical elements — A catheter is typically inserted through the external opening and advanced to the internal opening. At the internal opening, a seal is created with fibrin, and then 2 to 5 mL of fibrin sealant is injected as the catheter is withdrawn. At the external opening, another plug is created, resulting in a dumbbell-shaped seal.
Outcomes — The recurrence rate for fistulas repaired with fibrin glue alone ranges from 14 to 69 percent, depending on the complexity of the fistula, duration of observation, and technical aspects, such as debridement of the fistulous openings [18,19,52].
Fibrin sealant injections are occasionally used to treat complex fistulas. The main benefit is sphincter preservation. But overall, it is not very effective. Fibrin glue extravasation from within the fistula tract and failure to identify and completely fill all branches of the tract with glue are the likely explanations for long-term failure.
Fistula plug — The biosynthetic fistula plug is made of lyophilized porcine small intestinal mucosa. It does not generate a foreign body reaction or necessitate disruption of the anal sphincter, and it eliminates the risk of sphincter dysfunction associated with other procedures, such as fistulotomy and setons [12,53]. The fistula plug was designed to ameliorate postoperative incontinence in high-risk fistula patients, such as fistulas with high internal openings, anterior fistulas, or those that transverse significant portions of sphincter muscle (picture 6). However, the use of fistula plugs, especially in high or complex fistulas, has waned due to reported low healing rates of <50 percent [54].
Critical elements — If setons were previously placed in the fistula tract, they are left in place at the start of the operation to aid in visualizing the tract and subsequent fistula plug placement. (See 'Fistulotomy by snug setons' above.)
Once the anatomy of the fistula is confirmed, the fistula plug is prepared by immersion into isotonic saline. A 2-0 silk suture is introduced into the internal opening and pulled through the entire length of the fistula tract with the assistance of the previously placed silastic seton or a lacrimal probe. With the suture coursing through the fistula tract, the tapered end of the fistula plug is attached and the plug is pulled into the fistula from the internal opening toward the external opening until snug.
Excess fistula plug material is trimmed from both ends. The fistula tract length is determined by subtracting the length of trimmed excess plug material from the original plug length. The fistula plug is fixed and buried within the internal sphincter at the internal opening by a large figure-of-eight stitch with an absorbable suture. Care is taken to avoid occluding the external opening of the tract, thereby preserving a route for external drainage.
Outcomes — Initial reports of the fistula plug were favorable, particularly in high-risk fistula patients in whom treatment with fistulotomy, snug setons, or mucosal advancement flaps were ineffective or caused unacceptably high incontinence rates. Later observational studies had conflicting results [55-59]. A 2016 systematic review identified six studies, which reported healing rates between 15.8 and 72.7 percent at a follow-up ranging between 2 and 19 months [60]. Plug extrusion occurred in 8.5 percent of patients. Six percent of patients reported deterioration in continence.
A prospective cohort study comparing the fistula plug technique with fibrin glue found that the fistula plug closure was significantly more successful than fibrin glue closure at three months (success rate 87 versus 40 percent) [55]. A follow-up study that included the original fistula plug cohort found that the success rate of the fistula plug remained high at 83 percent at two years [56]. However, the success achieved in these earlier reports has not been replicated in subsequent retrospective studies [57,58]. A retrospective review of 26 patients with 30 anal plugs found that 86.7 percent of fistulas recurred after a mean follow-up of 59 weeks [59].
A randomized trial of 60 patients with a high perianal fistula (transsphincteric, upper two-thirds of the sphincter complex) compared a fistula plug with an advancement flap [61]. At 11 months, patients treated with a fistula plug had a higher rate of recurrence (71 versus 52 percent) and lower rates of postoperative soilage (29 versus 48 percent). However, these differences were not statistically significant, indicating that the number of patients in the trial was too small to detect significant differences of this magnitude. Another trial of 94 patients with transsphincteric fistula reported a higher recurrence rate at 12 months after a fistula plug than after an advancement flap (66 versus 38 percent) [62]. Patients in both groups experienced similar improvements in anal pain and quality of life; fecal incontinence did not change (incontinence) after treatment. (See 'Advancement flaps' above.)
Another randomized trial of 304 patients with transsphincteric fistulas compared fistula plug with another technique of the surgeon's choice. At 12 months, the fecal incontinence quality-of-life score and healing rate were similar between the two groups, whereas the complication rate at six weeks and overall cost were higher in the fistula plug group [63].
Ligation of the intersphincteric fistula tract — Ligation of the intersphincteric fistula tract (LIFT) is a sphincter-sparing procedure for complex transsphincteric fistulas first described in 2009 (figure 10 and picture 7). This approach is performed through the intersphincteric plane. The procedure is based on the secure closure of the internal opening and removal of infected cryptoglandular tissue [14,64,65].
Critical elements — The intersphincteric tract is identified and isolated by meticulous dissection. Once isolated, the intersphincteric tract is hooked using a small, right-angled clamp. The tract is ligated close to the internal sphincter and then divided distal to the point of ligation.
Hydrogen peroxide is injected through the external opening to confirm the division of the correct tract. The external opening and the remnant fistulous tract are curetted to the level of the proximity of the external sphincter complex. Finally, the intersphincteric incision is loosely reapproximated with an absorbable suture. The curettaged wound is left opened for dressing [14].
A modification to the LIFT technique unroofs the fistula from the internal opening, therefore eliminating the intersphincteric wound. In one study, outcomes of the modified LIFT were comparable to those of the original LIFT with shorter operative time [66].
LIFT can be used to treat both simple and complex fistulas. Fistula tract longer than 3 cm, previous procedures, and obesity have been associated with LIFT failure [67,68].
Outcomes — Outcomes data vary depending on the type of fistulas [14,21,64,67,69,70]. Meta-analyses report that the standard LIFT procedure achieved fistula healing in 61 to 94 percent of patients in four to eight weeks, with low morbidity (14 percent) and rare fecal incontinence (1.4 percent) [71-73]. Various modifications to the standard LIFT procedure do not appear to affect its performance [68,74]. Horseshoe fistula, Crohn disease, and previous fistula surgery predict failure of the LIFT procedure [73].
LIFT has been compared with advancement flap in randomized trials:
●In a randomized trial of 39 patients with complex fistula who failed previous fistula operations, patients treated by the LIFT approach had similar probability of recurrence at 19 months compared with patients undergoing an anorectal advancement flap (2 of 25 [8 percent] versus 1 of 14 [7 percent] patients) [75]. However, patients undergoing the LIFT procedure had a statistically shorter time to return to work (one versus two weeks) and no difference in incontinence scores.
●In a randomized trial, mucosal advancement flap was compared with LIFT in 70 patients with high transsphincteric fistulas [76]. Mucosal advancement flap and LIFT achieved similar primary healing rates of 91.4 and 94.3 percent after similar mean time to healing of 32 days (flap) and 23 days (LIFT). At one year, 65.7 percent of patients after mucosal advancement flap and 74.3 percent after LIFT remained recurrence free.
Diversion — In our practice, we rarely create a diverting stoma to facilitate the treatment of cryptoglandular anorectal fistula disease. Select patients with severe anorectal Crohn disease, reoperative rectovaginal fistulas, extrasphincteric fistulas, perineal necrotizing fasciitis, and radiation-induced fistulas may require diversion to heal a persistent fistula. Fecal diversion alone is effective in these select patients, but long-term success following reanastomosis is low because of recurrence from the underlying disease [77]. There are no parameters to identify those in whom a successful outcome is likely.
POSTOPERATIVE MANAGEMENT — Patients are routinely discharged home the same day as the procedure. Pain is managed by nonsteroidal anti-inflammatory medications or opioids, depending on the extent of the procedure.
Our general postoperative instructions are as follows:
Activity
●Activity as tolerated.
●No lifting over 20 pounds for two weeks.
●No strenuous exercise, running, or aerobics for two weeks.
●No driving for 48 hours post-surgery and none while taking narcotics.
●Do not use a doughnut-shaped pillow.
Diet
●Consume a high-fiber diet.
●Add a dietary fiber supplement two to three times a day in juice, coffee, or a noncarbonated beverage.
●Drink two liters of water or an electrolyte-balanced drink daily.
Hygiene
●Soak the anal opening in a sitz bath of warm water for 15 minutes three times a day and after each bowel movement.
●Use moist cotton pads or moist towelettes rather than toilet tissue.
●Place a cotton ball between buttocks at the anal opening.
Bowel management
●Take two tablespoons of mineral oil for the first five nights; discontinue for loose stools.
●If no bowel movement for 72 hours, or if severe straining occurs, take one tablespoon of milk of magnesia every four to six hours until relief.
●If constipation continues for 48 hours after beginning milk of magnesia, then consume 10 ounces of magnesium citrate.
●Slight bleeding with bowel movements is expected. Contact office for excessive amounts (one-half cup) of blood.
Follow-up — Office-based anoscopy is performed at three and six months following the procedure. Failure of the procedure is defined as patient complaints of persistent drainage, anoscopic identification of persistent abscess or external fistula opening, or development of abscess or infection requiring additional surgery. The risk of these complications is described above with the discussion of specific procedures.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Anal abscess and anal fistula".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Anal abscess and fistula (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Anorectal fistulas are a heterogeneous group of disorders that can cause significant pain, social impairment, hygienic disdain, and, rarely, sepsis. Surgery is the mainstay of treatment for cryptoglandular fistulas unrelated to Crohn disease, other infectious processes, or malignancy, yet no one procedure is universally efficacious and safe. (See 'Introduction' above.)
●At 6 to 12 weeks after treatment of an initial anorectal abscess or other septic process, patients with persistent drainage should undergo an examination under anesthesia to confirm the diagnosis of a fistula; surgical treatment may be initiated in the same setting. (See 'Staged approach' above.)
●For patients with no existing incontinence or risk factors for future incontinence, we suggest a primary fistulotomy, rather than a sphincter-sparing procedure, for a well-drained, low-lying (<30 percent of sphincter complex) transsphincteric and intersphincteric simple fistula (Grade 2C). In these patients, fistulotomy results in healing in over 90 percent of patients with minimal or no de novo fecal incontinence. In patients with preexisting incontinence, however, fistulotomy is contraindicated in all situations. (See 'Fistulotomy' above.)
●For patients with existing incontinence or concerns for future incontinence, and/or patients with a complex fistula, a draining seton is placed before a second sphincter-sparing procedure is performed after another six or more weeks. The choice of the secondary procedure is dictated by fistula anatomy and surgeon preference (algorithm 1):
•For patients with a high transsphincteric fistula (≥30 percent of sphincter complex), we perform either an advancement flap or the ligation of the intersphincteric fistula tract (LIFT) procedure. We prefer LIFT for fistulas with an internal opening distal to the dentate line and for patients with preexisting incontinence. (See 'Advancement flaps' above and 'Ligation of the intersphincteric fistula tract' above.)
•For patients with a suprasphincteric fistula, we perform an advancement flap. Such fistulas have no intersphincteric tract and therefore cannot be treated with LIFT. (See 'Advancement flaps' above.)
•Extrasphincteric fistulas are typically not of cryptoglandular origin but instead caused by cancer or Crohn disease. These fistulas are rare but difficult to treat. Surgical options include proctectomy or fecal diversion. (See 'Diversion' above.)
•We perform either the modified Hanley procedure, which involves a posterior midline incision and unroofing of all fistulous tracts, or an advancement flap for patients with horseshoe fistulas (Grade 2C). (See 'Modified Hanley procedure' above.)
•Patients with a recurrent fistula require a pelvic magnetic resonance imaging (MRI) scan to clarify anatomy and a seton for drainage. Further surgical treatment is dictated by fistula anatomy as outlined above. Options include modified Hanley procedure, snug seton, and advancement flap. (See 'Recurrent fistula' above.)
●Fibrin sealant and fistula plug are less effective but remain sphincter-sparing options for treating anal fistulas. (See 'Fibrin sealant' above and 'Fistula plug' above.)
