What is the best treatment for a fistula at ano?

Treatment of Fistula in Ano

Surgical drainage with incision is the definitive treatment for fistula in ano, with the specific surgical technique determined by fistula complexity and sphincter involvement to minimize recurrence while preserving continence. 1, 2

Initial Assessment and Diagnosis

• Perform a focused medical history and complete physical examination, including digital rectal examination, to identify the fistula tract and assess complexity 3, 2
• Check serum glucose, hemoglobin A1c, and urine ketones to screen for undetected diabetes mellitus, which is a common comorbidity 2
• Request imaging (MRI, CT scan, or endosonography) in cases of atypical presentation, suspected occult supralevator abscesses, complex anal fistula, or perianal Crohn's disease 3, 2

Surgical Management Algorithm

Simple Low Fistulas (Not Involving Sphincter Muscle)

• Perform fistulotomy at the time of abscess drainage for subcutaneous fistulas that do not involve sphincter muscle 3, 1
• Keep the incision as close as possible to the anal verge to minimize the length of the potential fistula while providing adequate drainage 1
• Simple intersphincteric and low transsphincteric fistulas treated with fistulotomy achieve healing rates higher than 95% with low recurrence 4

Complex Fistulas (Involving Sphincter Muscle)

• Place a loose draining seton rather than performing immediate fistulotomy to prevent incontinence 3, 1, 2
• Only sphincter-saving techniques should be used for complex anal fistulas 4
• Ligation of the intersphincteric fistulous tract (LIFT) and rectal advancement flaps provide optimal outcomes with healing rates of 60-90% 4
• Novel techniques including fistula laser closure (FiLac) and video-assisted anal fistula treatment (VAAFT) are safe with reported healing rates of 65-90% 4

Critical Intraoperative Decision Point

• Avoid probing to search for a fistula if one is not obvious, as this may cause iatrogenic complications 3, 2
• All fistula tracts should be curetted and irrigated with hydrogen peroxide and metronidazole 5

Timing of Surgery

• Base the timing of surgery on the presence and severity of sepsis 3, 1, 2
• Patients with sepsis, immunosuppression, diabetes, or diffuse cellulitis require emergent drainage 1
• In fit, immunocompetent patients with small perianal abscesses without systemic signs of sepsis, outpatient management can be considered 3, 1

Antibiotic Therapy

• Antibiotics are not routinely indicated for adequately drained anorectal abscesses in immunocompetent patients 2
• Administer antibiotics in the presence of sepsis, surrounding soft tissue infection, or immunocompromised status 3, 2
• When indicated, use empiric broad-spectrum antibiotic therapy covering Gram-positive, Gram-negative, and anaerobic bacteria 2, 6
• Consider sampling of drained pus in high-risk patients or those with risk factors for multidrug-resistant organisms 3, 2
• Topical metronidazole cream combined with 5% lidocaine applied 3 times daily for 4 weeks may enhance healing in acute fissures associated with fistulas, with healing rates of 86% versus 56% with lidocaine alone 3, 7

Risk Factors for Recurrence and Failure

• The risk of recurrence after drainage alone can be as high as 44% 1
• Inadequate drainage, loculations, horseshoe-type abscess, and delayed time from disease onset to incision increase recurrence risk 1
• For LIFT procedures specifically, collection, fistula tract size more than 5 millimeters, and failure to ligate the tract in one attempt are associated with failure 8
• Average time to diagnose recurrence is approximately 99 days, with most recurrences occurring within the first few months 8

Common Pitfalls to Avoid

• Do not perform immediate fistulotomy on fistulas involving sphincter muscle, as this significantly increases incontinence risk 1, 2
• Do not probe aggressively for occult fistulas during initial drainage, as this creates iatrogenic tracts 3, 2
• Ensure complete drainage with adequate incision size, as incomplete drainage is a major cause of recurrence 1