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Anal Fistula / Abscess

Bradley Champagne, MD
Assistant Professor of Surgery
Case Medical Center
Cleveland, Ohio

 

Introduction
The appropriate management and long-term success of treating fistulous abscess disease begins with the first patient encounter in the office or emergency room. It is an uncomfortable and typically embarrassing experience for the patient and a thorough sincere explanation of the problem is imperative. A detailed history of the present illness and full review of systems will provide insight into the true etiology of the problem and impact treatment strategies. Multiple patient encounters, two-stage treatment plans and recurrence are commonplace and need to be discussed during the first interaction. Treating an abscess is relatively straight-forward and will be addressed in this manuscript. However, eradicating anorectal fistulae are both challenging and often frustrating for both the surgeon and the patient. The tremendous variability of patient factors and heterogeneity of anorectal fistulae impart the need for surgeon “judgement” more than in most colorectal dieases.  More recently, the emergence of less invasive approaches have likely reduced incontinence rates but at what cost? These options and the more traditional approaches to anorectal fistulae will be discussed.  
 
 
Anorectal Abscess
The typical presentation of acute anal abscess is constant severe peri-anal pain that is augmented with activity or pressure. If the abscess has ruptured patients will report foul smelling drainage and typically state that their pain subsided after the drainage ensued. Patients can be examined in both prone or the left lateral position and the classic presentation of erythema, warmth, induration, and fluctuance is commonly found. If tolerable, gentle anoscopy may reveal purulence from the primary opening but it is not mandatory to perform this step.  Importantly, high intersphincteric, deep post-anal and supra-levator abscesses may present with similar complaints of intense throbbing pain, but without peri-anal inflammation. In these cases, digital examination of the anal canal or vagina may reveal a tender mass. If patients with an ischioanal abscess that tolerate a digital exam, palpating the deep post-anal space is crucial and may reveal an occult deep post-anal space abscess or horseshoe fistulae.
 
The foundation of treatment of all anorectal abscesses is surgical drainage. The diagnosis is usually rapidly made and the procedure can be safely carried out either in the office, emergency room, or operating room. The patient is placed in the prone jackknife or left lateral position and the area surrounding the abscess cavity is prepped with an antiseptic solution and then anesthetized with an injection of 1% lidocaine. It is preferable to inject slowly with a 3-5 ml syringe and 25-27 gauge needle. A stab incision is made with an 11 or 15 blade scalpel at the point of fluctuance in closest proximity to the anal verge.  Larger cavities may require digital or hemostat-assisted exploration to break-up any undrained abscesses. If at any point during the procedure it becomes evident that the abscess cavity is too large to be drained in the office setting or the patient is too uncomfortable, the patient should be taken directly to the operating room for a complete exam under anesthesia. After the initial drainage, a small mushroom drain (#12 or 14 pezzer) can be placed. Others advocate making a cruciate incision and then excising the skin flaps but this is often not necessary.  Either of these techniques will allow any undrained pus to be expelled. The patient is provided with pain medications and a follow-up appointment in one to two weeks at which point the drainage catheter is removed. Antibiotics are not required unless the patient is immunocompromised, has a prosthetic device or valve, or if the abscess has not been completely drained.
 
Although this procedure is effective in resolving the acute abscess, the patient is at risk for developing chronic anal fistula or recurrent perianal sepsis, or both. These conditions occur in 35 to 50 percent of patients after a first-time perianal abscess.1  In a recent study, recurrence of perianal sepsis or chronic anal fistula was observed in approximately one-third of patients during a mean follow-up of 38 months after incision and drainage of a first-time perianal abscess. Age younger than 40 years significantly increased risk of recurrence. The presence of diabetes appeared to lower risk. Gender, smoking history, perioperative administration of antibiotics, and HIV status were not risk factors for chronic anal fistula or recurrence of perianal sepsis.1
 
Intersphincteric, supralevator, and deep post-anal abscesses (DPAS) may not present with the classical presentation of an anorectal infection. These are best treated in the operating room where a thorough exam can be performed. For intersphincteric abscesses, the internal sphincter is divided from its lower end to the dentate line and hemostasis is achieved. Supralevator abscesses are fortunately rare and require careful determination as to their cause. If it is a result of upward extension of an intersphincteric abscess, the abscess should be drained directly into the rectum, however if it is a result of an ischioanal abscess it should be drained via the ischioanal fossa. Supralevator abscesses that are caused from extra-pelvic disease such as Crohn’s disease, diverticulitis, or appendicitis should be approached with circumspection. Cross-sectional imaging with CT scans or contrast studies are useful in determining their origin. These abscesses may be initially drained via the rectum or the ischioanal fossa; however, the offending organ must be addressed, usually via laparotomy.2,3  Considering that only one third to one half of abscesses lead to fistula formation, the addition of a fistulotomy to the initial procedure is often unnecessary and can potentially lead to incontinence and recurrence.
 
Fistula Treatment
As stated above, after the abscess is treated patients may develop chronic drainage and an anorectal fistulae. A small dimpled area of granulation tissue with drainage of pus or blood on manual compression is the most common presentation. Patients typically will not tolerate even gentle probing of the fistula track in the office setting but anoscopy and proctoscopy may help discover the internal opening and the presence of rectal disease. The internal openings are often seen at the dentate line at the origin of the anal gland. Intraoperatively dilute peroxide may be infused via an angiocatheter into the external opening while examining the anal canal with an anoscope. Bubbling of the peroxide at the internal opening confirms the location of a fistula. Goodsall’s rule, stating that posteriorly based external openings tract to the posterior midline while anterior openings tend to tract radially is often useful in predicting the course of the fistulous tract.
 
Although anorectal fistulae are commonly encountered, treatment of this condition remains one of the most challenging and controversial topics in colorectal surgery. Perianal fistulous disease is responsible for a range of clinical effects ranging from minor pain and social hygienic embarrassment to frank sepsis; and has vast implications in patient quality of life. Management of anorectal fistulae is encumbered by several individualized factors such as etiology, location, type, duration, as well as previously performed procedures and pre-operative assessments of sphincter function. Surgery is the mainstay of treatment for anorectal fistulae4, with the ultimate goal of draining local sepsis, eradicating the fistulous tract, and avoiding recurrence while preserving native sphincter function. 5
 
Traditional Treatment of Anorectal Fistulae
Since Parks classified anorectal fistulae in 1976, surgical treatment has been predicated upon several points of conventional surgical wisdom. 6 After drainage of acute abscess and sepsis, traditional surgical treatment begins with identification of internal and external openings of the fistulous tract.4  Over ninety percent of anorectal fistulae result from cryptoglandular abscess originating from the crypts of Morgagni,7,8 and most internal openings of the fistula reside around the anal glands surrounding the dentate line. Fistulae will then course on one of four paths: intersphincteric (45%), transphincteric (30%), suprasphincteric (20%), or extrasphincteric (5%) before finally arriving at a perianal external opening. 6  Occasionally, small fistulae will be limited to submucosal planes. In addition to cryptoglandular fistulae, Crohn’s disease and iatrogenic surgical fistulae (e.g. - ileal pouch and rectovaginal fistulae) are other causes of fistulae that require specialized treatments.
 
Following drainage of acute sepsis and identification of the fistula tract’s internal and external openings, a curative surgical procedure is typically performed.  Unfortunately, no single surgical approach adequately addresses all types of anorectal fistulae. 9 Countless surgical techniques have been described to treat anorectal fistulae depending upon the location, severity, chronicity of the fistula as well as a host of functional characteristics related to each patient. Traditionally, well-drained, low-laying simple intersphincteric fistulae are treated with simple fistulotomy. Fistulotomy is the centuries-old “gold standard” 9 which involves laying open the fistula tract in entirety.4 Overall fistula recurrence following fistulotomy ranges from 0 to 21%, with high, although widely variable, rates of resultant incontinence (0 to 82%).10-12
 
Anterior fistulae present a therapeutically challenging subgroup and convey higher rates of post-fistulotomy incontinence due to the natural anatomical attenuation of the external sphincter muscle and perineal body, especially in women.7,8  For fistulae that transverse longer distances of sphincter, such as high transphincteric or more proximal, fistulotomy conveys high rates of post-operative incontinence and alternative surgical treatments are necessary. For these “complex” fistulae, cutting setons are used to slowly divide fistulous tissue tracts on the leading edge of the seton while allowing healing to occur on the trailing edge whereby preserving sphincter continuity and theoretically preserving sphincter function.   This technique can be applied successfully when treating a deep post-anal abscess (DPAS) with horseshoe fistulous extension. Leaving a cutting seton from the internal primary opening to the DPAS with draining setons laterally from the DPAS to the ishioanal space is very effective. 
 
Overall, success rates for cutting setons range from 82 – 100%, however, long-term incontinence rates can exceed 30%. In light of unacceptably high rates of long-term incontinence, several alternative treatments have been developed.13-15
 
Endoanal advancement flaps are attractive options employed to treat complex fistula. Following adequate drainage and identification of the fistulous tract, mucosal advancement flaps are raised adjacent to the internal opening to provide tissue coverage of tract opening and subsequently allow the tract to heal and close. A variety of techniques exist, and in experienced hands, have low recurrence rates (0 to 36%) and tolerable incontinence rates ranging from 0 to 12.5%.16-18  Not all anorectal fistulae patients are candidates for mucosal flap advancement. Very high fistulae, for example, are technically challenging to treat with mucosal advancement flaps. Additionally, anal stenosis, active proctitis, and inflammatory bowel disease are relative contraindications due to high complication and failure rates.19 Lastly, success rates for mucosal advancement flap surgery outcomes are highly variable, likely indicating the importance of a surgeon’s expertise with these exacting procedures.
 
In the era of minimally invasive surgery and the notion that “less is more”, recent introduction of synthetic biological materials has brought a bevy of new techniques to treat anorectal fistulae. A variety of FDA-approved fibrin based glue materials have been used to treat difficult fistulae. Fibrin glue injection through the fistula tract offers a minimally invasive and expeditious treatment whereby sparing sphincter division. Early success rates for difficult fistula rates approach 60 to 70%20-26, however long-term fistula recurrence approaches 69-100%.24,27,28 Fibrin glue extravasation from within the fistula tract, and failure to identify and completely fill all branches of the tract with glue are the putative explanations for long-term failure.29 Nonetheless, the non-invasive and safe treatment profile of fibrin glue renders it a reasonable first-line treatment despite the high failure rate.27 Similar glue experiences have been reported substituting polymerized bovine serum albumin and glutaraldehyde (BioGlue Surgical Adhesive, CryoLife, Inc., Kennesaw, GA).30
 
The controversy associated with fistula treatment techniques is rooted within the balance of the therapeutic index – highly efficacious techniques, such as fistulotomy, have unfavorably high rates in incontinence. Unfortunately, safer techniques, such as fibrin glue and advancement flaps sacrifice fistula recurrence for lower rates of post-operative incontinence.
 
In 2005, a biosynthetic plug of material was introduced by Cook Surgical for treatment of anorectal fistula.. The fistula plug technique, which tunnels the plug inside the fistula tract, avoids sphincter division and subsequently avoids sphincter dysfunction and incontinence. The fistula plug was designed to ameliorate post-operative incontinence for high-risk fistulae, such as fistulae with high internal openings, anterior fistulae, or those which transverse significant portions of sphincter muscle.
 
Initial reports of the fistula plug were favorable, most notably in high risk fistulae which conventional treatment with fistulotomy, cutting setons, mucosal advancement flaps were ineffective or caused unacceptably high incontinence rates.  Johnson, et al published their initial series of 25 patients with high transphincteric or deeper cryptoglandular fistulae prospectively assigned to undergo treatment with fibrin glue (n=10) or fistula plug (n=15).37 At an average follow-up of approximately 3 months, fistula plug closure of anorectal fistula was successful in 87% of the fistula plug cohort, whereas fibrin glue closure was successful in 40% of the fibrin glue cohort (p < 0.05).  Long-term follow-up data was republished in 2006 by Champagne, which included the original fistula plug cohort for a total study population of 46 patients.38  At two years follow-up (range 6 to 24 months), the fistula plug had an 83% success rate. 
 
In 2007, Van Koperen reported on patients (n=17) with “difficult” high perianal fistulas, defined as those coursing through the upper 2/3 of the external sphincter complex.39 In this complicated re-operative cohort, 41% (7 of 17) of fistulae were healed at a mean follow-up of 7 months (range, 3-9 months).
 
Ellis et al retrospectively reported their fistula plug experience (n=19) compared to a historical group receiving either mucosal or anodermal advancement flap (n=95). 9 At a median follow-up of 10 (range 6 to 22) months, fistula plug success rate was 88%, while the advancement flap success rate was 67.4% (p > 0.05). The underpowered study is hindered by its retrospective nature and dissimilarity between groups.
 
Despite favorable initial reports, there has been no level 1 evidence of actual benefit, and controversy exists regarding indications and technique. Furthermore, studies published in 2009 have not demonstrated the same success that was achieved in earlier reports. Safar and colleagues had a success rate of only 13.9% with the Surgisis plug for complex anal fistulas.45 Likewise Christoforidis et al. compared the Surgisis plug to the endorectal advancement flap and reported a 32% success rate in the plug group.46 Prospective randomized studies with a homogenous technique are needed to help clarify these differences
 
Conclusion/Comments:
As with other colorectal diseases the options to treat anorectal fistulae haveexpanded over the last decade. We need to weigh the balance of incontinence, recurrence, and cost when we consider which technique to offer our patients.
 
Currently, for short intersphincteric and transphincteric uncomplicated fistula tracts fistulotomy is preferable. Deep post-anal space abscesses with horseshoe extension can successfully be managed by a modified Hanley technique or advancement flap. Patients with longer tracts or pre-existing incontinence can be successfully managed with either endorectal advancement flaps or the Surgisis fistula plug. It is important to explain both options, their reported success rates, complications and let the patient decide. Ideally, the reported success rates discussed with the patient should be from your own institution or practice.

 

References
 
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