Fistula-in-ano is an abnormal connection between the anal canal and the skin around the anus. It is often the result of a previous or current perianal abscess. The fistula usually originates from infected anal crypts internally and tracks to the perianal skin externally. The majority of the fistulas are cryptoglandular in origin, but Crohn’s disease, malignancy, radiation, trauma, or unusual infections may also produce fistulas. Diagnosis is usually made by physical examination of the perianal region and sometimes aided by procedures such as a fistulogram, proctoscopy, or sigmoidoscopy. An opening of the fistula may be observed, and the perianal region may be tender and erythematous. An induration may be felt, and malodorous discharge may be seen coming out of the fistula. Imaging studies such as a CT scan or MRI are only indicated for deep and complex anal fistulas. Fistulas are classified by their relationship to parts of the anal sphincter complex and are divided into intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric. These classifications help determine treatment decisions and operative planning. Definitive treatment aims to prevent both recurrence and sphincteric injury, and surgery is almost always necessary to cure an anal fistula. An intersphincteric fistula is treated by unroofing or removing the fistulous tract. A transsphincteric or suprasphincteric fistula is treated by placing a drain through the fistula. An extrasphincteric fistula is treated based on anatomy and etiology. We present the case of an 18-year-old male diagnosed with a fistula-in-ano. Fistulectomy was performed by threading the tract and excising it to prevent a recurrence.
Fistula-in-ano or anal fistula is an abnormal connection between the anal canal and the perianal skin. It is often the result of a previous or current perianal abscess that leaves a narrow tunnel behind.1 The fistula usually originates from infected anal crypts internally and tracks to the perianal skin externally. The majority of the fistulas are cryptoglandular in origin, but Crohn’s disease, malignancy, radiation, trauma, or unusual infections may also produce fistulas.2, 3 We present the case of an 18-year-old male diagnosed with a fistula-in-ano. Fistulectomy was performed by threading the tract and excising it to prevent a recurrence.
Focused History of the Patient
The patient is an 18-year-old male with a recent history of perianal abscess for which he completed an initial course of antibiotics. Despite medication, he subsequently noticed external perianal leakage and presented to our clinic for surgical evaluation.
The patient had identifiable drainage from an anomalous tract exiting in the perianal region.
Examination of anal fistulae commonly reveals a tender, inflamed, and indurated external opening in the perianal skin, or a palpable bulge indicating an anal fistula ending in a blind pouch just under the skin layer.1 Occasionally, a palpable cord may be appreciated. If further exploration of the fistula is desired by the clinician, a fistula probe may be used under general anesthesia to gently examine the fistula tract starting at the external opening, or anoscopy may be used to assess the internal origin.
This patient’s presentation did not indicate the need for preoperative imaging. Typically, imaging studies such as a CT scan or MRI are only indicated for deep and complex anal fistulae. These studies may characterize the anatomic course of the fistula tract and identify any anal sphincter involvement that might inform treatment planning and operative strategy.
Anorectal fistulae, or fistulae-in-ano, most commonly result from a prior anal abscess, where ongoing inflammation and infection leads to the expansion of anal crypts toward the skin exteriorly. The vast majority of anal fistulae are cryptoglandular in origin, but less commonly the pathogenesis may be attributed to Crohn’s disease, foreign bodies, obstetric injury, malignancy, or radiation.2, 3 Undiagnosed anal fistulae will typically result in worsening of symptoms, including pain with defecation and movement, pruritis, and purulent and/or malodorous discharge, and prompt a patient to seek medical attention. Lack of prompt surgical intervention may result in significant pain, expansion of the abscess, and more serious infection including sepsis.
Options for Treatment
Surgical intervention is indicated for nearly all symptomatic anal fistulae, with the exception of certain patients with Crohn’s disease.1 Fistulotomy involves incision and drainage of the fistula tract and is the traditional standard of care for the majority of anal fistulae.4 Fistulectomy may also be performed, involving complete excision of the fistula tract. The surgical options available are determined by the classification of the fistulae by type, size, location, duration, and the surgical history of the patient. Special attention is given during procedural planning and selection to attempt to preserve anal sphincter function and continence.
The Parks’ classification system is used to assess the anatomic relationship between the fistula and the external anal sphincter and to guide operative planning.4, 5 Fistulae are classified by their relationship to parts of the anal sphincter complex and are either intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric.
An intersphincteric fistula begins between the internal and external sphincter muscles, passes through the internal sphincter muscle, and opens very close to the anus. A transsphincteric fistula begins between the internal and external sphincter muscles, crosses the external sphincter muscle, and opens an inch or more away from the anus. A suprasphincteric fistula begins between the internal and external sphincter muscles, extends above, and crosses the puborectalis muscle, proceeding downward between the puborectalis and levator ani muscles, and opening an inch or more away from the anus. An extrasphincteric fistula begins at the rectum, proceeds downward through the levator ani muscle, and opens into the skin surrounding the anus.
The majority of anorectal fistulae are considered simple fistulae classified as Parks type 1 and 2, with intersphincteric and low-lying intersphincteric involvement, respectively.1, 4Additionally, fistulae due to more rare etiologies such as inflammatory bowel disease, rectovaginal fistulae, and certain infections such as HIV or TB are classified as complex, as they are associated with higher rates of treatment failure.1
Primary fistulotomy is routinely performed for most simple fistulae, and is associated with 90% treatment success.6 Fistulectomy is another first-line option depending on surgeon preference that has been shown to have similar outcomes in patients with simple anatomy.7 In patients with complex fistulae or patients who have any risk of incontinence, a staged approach is preferred, involving an initial seton drain placement for six or more weeks possibly followed by a sphincter-sparing surgical procedure.4 Surgical options for complex fistulae are determined by anatomy and surgeon preference and include the LIFT procedure, an advancement flap, a diversion or proctectomy, and a modified Hanley procedure.4, 8, 9 Patients with Crohn’s disease warrant concomitant medical and surgical management using the above options to achieve optimal treatment outcomes.10
Rationale for Treatment
The goal of surgical intervention for anorectal fistulae is to eliminate any abscesses or infectious foci while removing or closing the anatomic space formed by the fistula tract, without injury to sphincteric function or continence.
Patients with any history of fecal incontinence are not candidates for primary fistulotomy, and treatment options for complex fistulae should be used.4
The patient underwent a successful primary fistulectomy for a simple anorectal fistula. The external sphincter was located, and a probe was inserted to navigate internally and identify the internal origin. As the entire fistula tract was visualized, fistulectomy was performed to excise the tract as a whole. Hemostasis was achieved and the wound was allowed to heal by secondary intention to allow for granulation tissue development and skin regeneration.
The subject of surgical treatment of anorectal fistulae has historically remained controversial within the colorectal surgery literature. Preoperative patient selection for various treatment options has long been debated but has recently become more refined with the improved anatomic classification of perianal fistulous disease and the advent of new treatment options.
The classification system developed by Parks, Gordon, and Hardcastle in 1976 has had a significant impact on the management of anorectal fistulae. The anatomical designations drawn from over 400 cases in the study helped to stratify the degree of predicted operative complexity.5 As a result of the classification, suprasphincteric and extrasphincteric involvement were separated as anatomic features associated with significantly higher rates of treatment failure with fistulotomy alone.11–13 This led to the later development of multi-staged sphincter-conserving treatment strategies that have decreased rates of complications related to incontinence.13, 14 At this time, the Parks system remains the most commonly used classification system that dictates which evidence-based approach is likely to be the most effective for individual patients based on anatomy and surgical preference.
For simple fistulae, including Parks’ Type 1 and Type 2, many surgeons view fistulotomy and fistulectomy as comparable operative choices for repair. While some studies have suggested a shorter duration of healing and shorter operative times with fistulotomy with marsupialization,15, 16 a meta-analysis of six randomized controlled trials performed in 2016 by Xu et al. did not detect any statistically significant difference between the two procedures in terms of recurrence or overall complications.7 Currently, the choice between fistulotomy and fistulectomy is often based on intraoperative evaluation and surgeon preference.17 Patients are typically followed for a minimum of 6 months before determining treatment success or failure.18 Recurrence rates for fistulectomy and fistulotomy are comparably low at 7% after 3 years,19 and treatment success rates vary from 79–100%.19–22
Complex fistulae typically require a multi-staged approach, starting with a seton drain placement into the fistula canal for six weeks. This initial step involves dilatation of the anal canal under anesthesia, anoscopy, and identification of the internal opening. A draining seton is placed into the fistula with the intention of eliminating septic foci and reducing inflammation to facilitate the second planned operation.23 Alternatively, a snug seton or a “cutting” seton is also used as a form of step-wise fistulotomy with an adequate allowance of time between intervals to allow for appropriate scarring and prevent the sudden loss of sphincter tone that might otherwise occur intraoperatively. The cutting edges of the seton are tightened at monthly intervals with close follow-up to incise small portions of the fistula tract with the cumulative effect over time resulting in the complete or near-complete incision of the tract. It is critical that the intervals between cuts are no shorter than one month, as appropriate scarring typically occurs over a period of 4–6 weeks.24 The use of snug setons remains debated. Some studies have suggested success rates of 80–100%, but included incontinence rates of greater than 20–30%.25–28 One multicenter study of 200 patients demonstrated that all eventually achieved clearing of the fistula tract with a 6%recurrence rate.29
Alternative secondary procedures have been proposed for complex fistulae based on subtype and anatomic involvement. Advancement flaps using tissue from local mucosa and submucosa are used to cover and close the internal opening of the fistula, allowing it to heal and close, and this method is a preferred option for patients without preexisting incontinence.30, 31 Recurrence ranges from 0–40% for advancement flap procedures with relatively improved incontinence rates of 0–12%.19, 3235 The modified Hanley procedure is a more extensive sphincter-preserving operation requiring months of postoperative care but resulting in improved results for patients with horseshoe fistulae or recurrent disease. A retrospective review of 23 patients undergoing a modified Hanley procedure for horseshoe perianal fistula demonstrated complete healing in 91% of patients with none reporting incontinence.36 The LIFT procedure, or ligation of the intersphincteric fistula tract, was first described in 2009 for the treatment of anorectal fistulae and involves ligating the fistula tract close to the internal opening with subsequent distal division and curettage and reapproximation of the intersphincteric wound.4 While outcomes vary depending on the extent and severity of the disease, two meta-analyses have suggested treatment success rates of 61–94% with minimal to no incontinence.37, 38
Other less invasive alternatives have been proposed including fibrin sealants and fistula plugs, and while these options may be of benefit to patients at high risk of incontinence, they have been associated with poor efficacy.39, 40 Finally, diversion remains an option for severe or recalcitrant disease, distorted anatomy due to radiation, or select patients with Crohn’s disease, but is generally avoided whenever possible.4
Operations to correct fistulous disease of the anus and rectum are typically same-day procedures with minimal immediate morbidity. Postoperatively, patients benefit from limited exertional activity with high-fiber diets and sitz baths, and they are followed at 3 and 6 months for the determination of recurrence or treatment success.4
- Small probe or small straight mosquito or clamp
- Cautery or blade
Nothing to disclose.
Statement of Consent
The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.
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- Xu Y, Liang S, Tang W. Meta-analysis of randomized clinical trials comparing fistulectomy versus fistulotomy for low anal fistula. SpringerPlus. 2016;5(1). https://doi.org/10.1186/s40064-016-3406-8
- Limura E, Giordano P. Modern management of anal fistula. World Journal of Gastroenterology. 2015;21(1):12-20. https://doi.org/10.3748/wjg.v21.i1.12
- Garg P. A new understanding of the principles in the management of complex anal fistula. Medical Hypotheses. 2019;132. https://doi.org/10.1016/j.mehy.2019.109329
- Taxonera C, Schwartz DA, García-Olmo D. Emerging treatments for complex perianal fistula in Crohn’s disease. World Journal of Gastroenterology. 2009;15(34):4263-4272. https://doi.org/10.3748/wjg.15.4263
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