What is the treatment for infection secondary to vaginal rectal fistula?

Treatment for Infection Secondary to Vaginal Rectal Fistula

Immediate surgical drainage of any associated abscess is the essential first step, followed by placement of a non-cutting seton and adjunctive antibiotic therapy—antibiotics alone without surgical drainage will fail. 1, 2

Initial Management: Control the Sepsis

The priority is surgical intervention to drain the infection:

• Perform urgent surgical drainage of the intersphincteric or perirectal abscess under anesthesia to control sepsis before any other treatment 1, 2
• Place a loose, non-cutting seton during the initial drainage procedure to maintain ongoing drainage and prevent recurrent abscess formation 1, 3
• Avoid probing for fistula tracts during the acute infection phase, as this risks iatrogenic complications and sphincter injury 4

The World Society of Emergency Surgery emphasizes that attempting definitive fistula repair during active infection leads to treatment failure and complications 1, 2

Antibiotic Therapy: Adjunctive, Not Primary

Antibiotics are necessary but insufficient as monotherapy:

• Start broad-spectrum antibiotics covering gram-positive, gram-negative, and anaerobic bacteria after surgical drainage 2, 5
• Metronidazole is FDA-approved for anaerobic bacterial infections including gynecologic infections and intra-abdominal abscesses, which are the typical pathogens in rectovaginal fistulas 5
• Continue antibiotics for 1-2 weeks as adjunctive therapy, not as primary treatment 2
• Obtain cultures of drained pus in high-risk patients (immunocompromised, diabetes, recurrent infections) or those with risk factors for multidrug-resistant organisms 4

A critical pitfall: relying on antibiotics without adequate surgical drainage has high failure rates and promotes antibiotic resistance 2, 6

Subsequent Management After Infection Control

Once sepsis is controlled and inflammation subsides:

• Avoid definitive surgical repair until the infection has completely resolved and inflammation has subsided for several weeks to months 1, 7
• Consider diverting colostomy or ileostomy for severe symptoms, large fistulas, or to allow healing in complex cases 7, 6
• For Crohn's disease-related fistulas, consider anti-TNF therapy (infliximab) after adequate drainage and sepsis control, as this is FDA-approved and proven effective in placebo-controlled trials 4, 2
• Immunosuppressive agents (azathioprine, 6-mercaptopurine) may help maintain fistula closure but are slow-acting and should not be started until sepsis is completely resolved 4, 1

Definitive Repair Options (After Infection Resolution)

The approach depends on fistula complexity and location:

• For simple, low fistulas: transanal advancement flap or local repair techniques have success rates of 75-100% 7, 8
• For complex or recurrent fistulas: interposition of healthy, well-vascularized tissue (Martius flap using labial fat pad) improves outcomes 7, 6
• For high rectovaginal fistulas: transabdominal approaches may be necessary 7, 9

Critical Pitfalls to Avoid

• Never delay surgical drainage while continuing antibiotics alone—this leads to treatment failure and spread of infection 1, 2
• Never attempt definitive fistula repair during active infection or inflammation, as this dramatically increases failure rates 1, 7
• Never start immunosuppressive therapy before complete surgical drainage of sepsis, as this risks serious infectious complications 1
• Never perform fistulotomy for high or complex fistulas involving significant sphincter muscle, as this causes incontinence 4, 3

Monitoring and Follow-up

• Assess clinical response by monitoring decreased drainage and symptom improvement 3
• Consider MRI or endosonography to evaluate fistula tract inflammation after initial treatment 3
• Long-term follow-up for at least 12 months is essential, as recurrence rates are significant (25-33% in some series) 2, 3, 6

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