Anal Fistulotomy

Abstract

Fistula-in-ano is a chronic abnormal communication between the anal canal and, usually, the perianal skin. It can be described as a hollow tract that is lined with granulation tissue and connects a primary opening inside the anal canal to a secondary opening in the perianal skin. It usually originates from the anal glands and is frequently the result of a previous anal abscess. Anal fistulae present with pain, swelling, pruritus, skin irritation, and purulent or bloody drainage. Most anal fistulae are diagnosed based on clinical findings, but complex and deep anal fistulae usually require imaging studies such as CT scan or MRI to delineate the tract. Fistulae are categorized based on their relationship to the anal sphincter complex. An intersphincteric fistula tracks through the distal internal sphincter and intersphincteric space to an external opening near the anal verge. A trans-sphincteric fistula extends through both the internal and external sphincters. A suprasphincteric fistula originates in the intersphincteric plane and tracks up and around the entire external sphincter. An extrasphincteric fistula originates in the rectal wall and tracks around both sphincters to exit laterally, usually in the ischiorectal fossa. Currently, there is no medical treatment available and surgery is almost always necessary. A simple intersphincteric fistula can often be treated with fistulotomy or fistulectomy, while trans-sphincteric and suprasphincteric fistulae are treated by placement of a seton to maintain drainage and induce fibrosis. Extrasphincteric fistula treatment depends on the anatomy and etiology of the fistula. We present the case of a 1-year-old male with a history of recurrent perianal infection, which led to the development of an anal fistula. The anal fistula was noted to be superficial and a fistulotomy was performed.

Case Overview

Background

Fistulae are abnormal connections between two epithelialized surfaces. Anal fistula formation occurs secondary to chronic inflammation, as is true for many types of fistulae. The list of conditions that may incite this inflammatory state is extensive but includes trauma, inflammatory bowel disease, malignancy, acne inversa, and sexually transmitted infections, among others.¹ The most common cause, however, is recurrent perianal abscess from infected anal glands, which accounts for approximately 80% of anal fistulae.¹ 

Focused History of the Patient

History taking for the patient with suspected perianal fistula should include:

• Has the patient experienced episodes of perianal abscesses before? If so, how frequently?
• Has the patient received surgical drainage or other procedure for perianal abscesses or fistula before?
• Does the patient exhibit any signs consistent with undiagnosed inflammatory bowel disease?
• A sexual history may be appropriate if a sexually transmitted infection etiology is suspected.

Physical Exam

When a perianal fistula is suspected, a close assessment of the affected region for expression of pus or fluctuance should be performed. The intensity and extent of redness, pain, and edema should be noted. The rectal exam should be performed to 1) assess the sphincter tone, 2) detect the presence of scar tissue and notching that may indicate the internal opening of a fistula tract, and 3) identify a mass if neoplasm is suspected. A thorough examination of the anal canal and distal rectum may require examination under anesthesia due to the potential for exquisite perianal pain.

Imaging

Imaging modalities are typically not necessary for simple anal fistulae. For more complex tracts, rigid sigmoidoscopy and proctoscopy may be useful in identifying the internal opening of the fistula. Moreover, these techniques may be useful in the diagnosis of underlying causes of anal fistula other than perianal abscess, including Crohn’s disease or rectal neoplasia.² MRI, CT, and endoanal ultrasound are highly effective at delineating fistula anatomy and can be of value with complex fistulae. In addition, these imaging modalities are useful in identifying secondary tracts that, if not addressed, can increase the risk of recurrence.³

Natural History

In practice, the risk of complications for an anal fistula is related to its classification; more superficial fistulae typically pose a less immediate risk of complication due to their ease of treatment, while more complex, difficult-to-treat fistulae can lead to numerous sequelae including chronic pain, sepsis, sphincter damage, and incontinence.^4, 5 However, the natural history of all untreated anal fistulae is similar, with persistent pain, infection, and possible progression to sphincteric damage and sepsis.⁶

Options for Treatment

Preferred fistula management is always surgical, as recurrent infection, pain, and risk of sepsis are the norm. The type of fistula, however, will dictate the appropriate surgical technique. For fistulae that have superficial tracts, as depicted in this case, simple fistulotomy with healing via secondary intention is appropriate.⁷ If the surgeon notes significant fibrosis surrounding the superficial tract, fistulectomy may be preferred over fistulotomy. This is a matter of surgeon preference, with both approaches showing similar efficacy.⁸

While standard surgical fistulotomy is highly effective and is the standard of care for superficial anal fistulae, numerous interventions may be considered for more complex fistulae such as ligation of intersphincteric fistula tract (LIFT), anal fistula plugs, fibrin glue injections, laser-closure, video-assisted anal fistula treatment (VAAFT), and adipose-derived stem cells.⁹ These procedures for complex fistulae have different success rates, and procedure selection should take this into consideration. The goal of surgical management is to eradicate the risk of sepsis, permit tract healing, and preserve sphincter function.

Rationale for Treatment

Perianal fistulae secondary to recurrent abscess formation are non-healing lesions by definition and thus require surgical intervention. Delay in surgical management can lead to the complications described above, including persistent pain, sepsis, sphincter damage, and incontinence. 

Special Considerations

The rate of recurrence following fistulotomy is related to the depth and complexity of the fistula structure, with rates in a study by Li et al. ranging from 1.8% with superficial fistulae to 13.6% in high anal fistulae.¹⁰ The following considerations may help reduce the risk of recurrence:

• Proctoscopy prior to fistulotomy is important, as studies have shown an increased risk of recurrence when surgery is done in the presence of unidentified proctitis.^11, 12
• Definitive mapping of fistula anatomy including internal opening, and surveillance for secondary tracts, should be completed prior to fistulotomy.
• Forceful use of a probe should be avoided in identifying fistula tracts, as damage secondary to aggressive probing may increase the risk of recurrence or development of new, iatrogenic fistulae.
  

Discussion

While superficial anal fistulae are readily treated with fistulotomy, complex anal fistulae remain a challenge for clinicians due to their high recurrence and complication rates. Complex anal fistulae were classified by Parks et al. as intersphincteric, trans-sphincteric, suprasphincteric, and extrasphincteric, each of which has a unique preferred surgical approach and risk profiles.¹³ The simplest of anal fistulae avoids the sphincter muscles of the anus altogether, such as in the present case, and can be easily treated with fistulotomy or fistulectomy. Fistulectomy may be preferred in deeper anal fistulae that still remain superficial to the sphincter muscles or for fistulae with infiltrating fibrosis. This is at the discretion of the surgeon, with both approaches having comparable efficacy and recurrence rates.⁸

Here, the fistulotomy of a superficial anal fistula was performed on a 1-year old male with recurrent perianal abscess. The operation was started by palpating for the internal fistula opening, followed by gentle probe delineation and threading of the tract. Electrocautery was utilized to open the fistulous tract, with a curette dissection of fibrous and necrotic tissue performed to minimize the risk of recurrence. Electrocautery was again utilized for hemostasis, and wound dressing was applied with healing by secondary intention. Standard postoperative care consists of stool softeners, topical antibiotics, and appropriate analgesics followed by a 1-week follow-up. If possible, follow-up should be extended until complete wound healing. If performed properly and in a timely fashion, the fistulotomy for superficial anal fistulae is a highly effective treatment approach, which can readily improve patient comfort and quality of life.

Equipment     

• Local anesthetic
• Probes
• Methylene blue, hydrogen peroxide
• Seton (Silastic vessel loop, suture)
  

Disclosures

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.