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 complete physical examination including digital rectal examination to identify the fistula tract and primary opening 3, 2
• Imaging (MRI, CT scan, or endosonography) should be obtained when there is atypical presentation, suspicion of occult supralevator involvement, complex fistula anatomy, or underlying Crohn's disease 3, 2
• Check serum glucose, hemoglobin A1c, and urine ketones to screen for undetected diabetes mellitus, which is a common comorbidity 2

Surgical Management Based on Fistula Type

Simple Low Fistulas (Not Involving Sphincter Muscle)

• Fistulotomy is the procedure of choice for simple intersphincteric and low transsphincteric fistulas, achieving healing rates higher than 95% with low recurrence 4
• For subcutaneous fistulas identified during abscess drainage, immediate fistulotomy can be performed at the time of drainage 3, 2
• Keep the incision as close as possible to the anal verge to minimize the length of any potential fistula tract 1

Complex Fistulas (Involving Sphincter Muscle)

• Only sphincter-saving techniques should be used for complex fistulas to prevent incontinence 4
• Place a loose draining seton rather than performing immediate fistulotomy when sphincter muscle is involved 3, 1, 2
• 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 Principles

• Curettage of all fistula tracts followed by irrigation with hydrogen peroxide and metronidazole reduces infection and improves healing 5
• Avoid probing to search for a fistula if one is not obvious, as this causes iatrogenic complications and false tract formation 3, 2
• Ensure complete and accurate drainage, as inadequate drainage is a major risk factor for recurrence (up to 44%) 1

Antibiotic Therapy

• Antibiotics are not routinely indicated for adequately drained fistulas in immunocompetent patients 2
• Administer antibiotics when sepsis is present, surrounding soft tissue infection exists, or in immunocompromised patients 3, 2
• Empiric broad-spectrum coverage should include Gram-positive, Gram-negative, and anaerobic bacteria when indicated 2, 6
• Sample drained pus in high-risk patients or those with risk factors for multidrug-resistant organisms 3, 2

Common Pitfalls to Avoid

• Do not perform immediate fistulotomy on fistulas involving sphincter muscle, as this significantly increases the risk of fecal incontinence 1, 2
• Delayed time from disease onset to surgical intervention increases recurrence risk 1
• Horseshoe-type abscesses and loculations require more extensive drainage with potentially multiple counter incisions to prevent recurrence 2
• In patients with failed previous repairs, strongly suspect underlying Crohn's disease, which markedly reduces surgical success rates and may require medical management first 7

Special Considerations

• For anovaginal fistulae (often from obstetric injury), delay surgical correction until inflammation and infection have completely subsided, and evaluate anal sphincter function preoperatively 7
• Fistulas secondary to inflammatory bowel disease, neoplasia, radiation, or anastomotic leaks may require fecal stream diversion either as an adjunct to repair or as definitive treatment 7
• The presence of diabetes, immunosuppression, or diffuse cellulitis requires emergent drainage rather than delayed management 1