When to operate or not on a fistula in ano?

Management of Fistula-in-Ano: When to Operate and When Not to Operate

Operate on fistula-in-ano only when the patient is symptomatic, has no active abscess, has medically controlled proctitis (if Crohn's disease), and the fistula anatomy is clearly defined—otherwise, defer definitive surgery and focus on drainage alone. 1

When NOT to Operate (Contraindications to Definitive Fistula Surgery)

Absolute Contraindications

• Active abscess present: Never attempt definitive fistula repair when concurrent abscess exists—drain the abscess first with loose seton placement 1
• Active proctitis in Crohn's disease: Medical therapy must control rectal inflammation before any definitive fistula surgery, as active inflammation dramatically reduces healing rates 1
• Asymptomatic low anal-introital fistulae: These require no surgical intervention at all 1
• Acute/emergency setting: No additional fistula treatment modality should be performed during emergency abscess drainage 1

Relative Contraindications

• Crohn's Disease Activity Index (CDAI) >150: Avoid fistulotomy when systemic disease is poorly controlled 1
• Evidence of perineal Crohn's disease involvement: Extensive perianal disease increases failure risk 1
• Undefined fistula anatomy: Preferably have anatomically defined tract before definitive surgery 1
• Patient on steroids or immunosuppression: Higher risk of poor wound healing 2

Critical Pitfall to Avoid

Never probe to search for a fistula during acute abscess drainage—this creates iatrogenic complications and false tracts 1, 3, 4. If a fistula is not obvious without probing, simply drain the abscess and reassess later.

When TO Operate (Indications for Definitive Fistula Surgery)

Prerequisites for Definitive Surgery

All four criteria must be met 1:

1. Symptomatic patient (drainage, pain, recurrent infections)
2. No concomitant abscess (must be drained first if present)
3. Medically controlled proctitis (if Crohn's disease present)
4. Anatomically defined fistula tract (via MRI, endosonography, or examination under anesthesia)

Surgical Approach Based on Fistula Anatomy

For low/subcutaneous fistulas not involving sphincter muscle:

• Perform fistulotomy at time of abscess drainage 1
• This includes subcutaneous, superficial, or intersphincteric fistulas in lower third of sphincter 1

For fistulas involving any sphincter muscle:

• Place loose draining seton only—do NOT lay open the tract 1, 4
• This includes mid-to-high transsphincteric and all high fistulas 2
• Seton may be definitive treatment when combined with medical therapy, with removal at median 33 weeks 1

For high transsphincteric fistulas:

• Loose seton placement is the only appropriate option 2
• Fistulotomy carries unacceptable incontinence risk

Special Considerations for Crohn's Disease

Medical Optimization First

• Control luminal Crohn's disease with thiopurines, infliximab, or adalimumab before and after surgery 1
• Assess rectum for proctitis at time of any drainage procedure 1
• Most conservative approach should be adopted to avoid soft tissue damage and extensive scarring 1

Surgical Principles in Crohn's

• More than two-thirds have associated abscess requiring drainage before definitive intervention 1
• Concomitant perianal skin tags should NOT be treated surgically—this leads to chronic non-healing ulcers 1
• Success correlates with absence of rectal disease and quiescent disease elsewhere 5, 6

When Medical/Surgical Therapy Fails

• Consider diverting ostomy for refractory cases 1
• Proctectomy is last resort 1

Timing Considerations

Emergency drainage indicated for 3, 4:

• Sepsis, severe sepsis, or septic shock
• Immunosuppression
• Diabetes mellitus
• Diffuse cellulitis

Otherwise: Drain within 24 hours; young fit patients without sepsis may have ambulatory surgery 3, 4

Key Prognostic Factors

Better outcomes when 6, 7:

• Classical internal opening at dentate line present (74% primary healing vs 44% without)
• Rectum not involved in Crohn's disease
• Low-anal type fistula rather than anorectal

Worse outcomes when 4:

• Delayed time from disease onset to incision
• Inadequate drainage (recurrence up to 44%)
• Loculations or horseshoe-type abscess