What is the best course of action for an adult patient with a history of anorectal surgery and a previously successfully treated fistula with fistulotomy 6 months ago, now presenting with a new fistula?

Management of New Fistula After Previous Successful Fistulotomy

For an adult patient presenting with a new fistula 6 months after successful fistulotomy of a different fistula, proceed directly to surgical evaluation and treatment based on fistula complexity, as recurrent perianal fistulas require definitive surgical management with the specific approach determined by sphincter involvement. 1

Initial Assessment and Classification

Perform a focused physical examination with digital rectal examination to classify the new fistula and identify any associated abscess. 1 The key determination is whether this represents:

• A simple low fistula (subcutaneous or low intersphincteric not involving sphincter muscle)
• A complex fistula (involving sphincter muscle, high transsphincteric, suprasphincteric, or extrasphincteric) 1

Do not probe for occult fistula tracts during examination, as this risks iatrogenic complications. 1 The edema and anatomical distortion can lead to false tract creation.

Imaging Considerations

Request MRI, CT scan, or endosonography only if there is atypical presentation, suspicion of occult supralevator extension, or concern for complex anatomy. 1 Given this patient's history of previous anorectal surgery, imaging may be particularly valuable to:

• Define the relationship to the sphincter complex 1
• Identify any occult abscess requiring drainage 1
• Map the fistula tract before definitive surgery 1

Treatment Algorithm Based on Fistula Type

For Simple Low Fistulas (Not Involving Sphincter)

Perform fistulotomy as the definitive procedure, which achieves healing rates >95% with minimal recurrence. 2 This can be done as a single-stage procedure even in the setting of previous fistula surgery. 1

For Complex Fistulas (Involving Sphincter Muscle)

Place a loose draining seton initially rather than attempting immediate fistulotomy. 1 The WSES-AAST guidelines specifically recommend against fistulotomy when any sphincter muscle is involved due to continence risks. 1

After seton placement and drainage establishment, definitive options include:

• Fistulotomy with immediate primary sphincteroplasty: Achieves 84-96% healing rates with acceptable continence outcomes in selected patients 3, 4, 5
• Endorectal advancement flap: Success rate of 64% in Crohn's patients, approximately 80% in cryptoglandular fistulas 1
• LIFT procedure: Healing rates of 60-90% for complex fistulas 2
• Novel techniques (FiLaC, VAAFT): Healing rates 65-90% 2

Critical Factors Influencing Treatment Selection

History of recurrent fistula after previous surgery increases the risk of postoperative continence impairment 5-fold (RR=5.00,95% CI 1.45-17.27). 4 This patient's previous successful fistulotomy does not necessarily indicate recurrence, as the question states no other fistulas were observed 6 months ago—this appears to be a new, separate fistula.

High transsphincteric fistulas carry a 4-fold increased risk of continence deterioration compared to non-high fistulas. 3 One in five patients with high tracts experiences continence impairment. 3

Male sex and truly recurrent fistulas (same location) may have protective effects against postoperative incontinence, though larger studies are needed. 3

Antibiotic Considerations

Administer antibiotics only if there is:

• Associated abscess with surrounding soft tissue infection 1
• Signs of systemic infection or sepsis 1
• Immunosuppression or diabetes 1

For routine fistula without these features, antibiotics are not indicated after drainage. 1

Common Pitfalls to Avoid

Do not attempt to treat a complex fistula with simple fistulotomy at initial presentation. 1 The 2010 Cochrane review showed that while fistula treatment at abscess drainage reduces recurrence, it increases continence disturbances when sphincter muscle is divided. 1

Do not delay referral to a colorectal surgeon. 6 Longer time to referral is associated with impaired final continence outcomes. 6

Avoid probing for fistulas during acute presentation. 1 This creates iatrogenic tracts and complications.

Timing of Definitive Surgery

If abscess is present, drain immediately or within 24 hours depending on sepsis severity. 1 Young, fit patients without sepsis may undergo ambulatory surgery. 1

For definitive fistula repair without acute abscess, schedule electively after complete assessment and patient counseling regarding continence risks. 3, 4, 5