Risk factors for postoperative recurrence of anal fistula identified by an international, evidence-based Delphi consultation survey of surgical specialists

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Executive Summary

Postoperative anal fistula recurrence (AFR) remains one of the most significant challenges in colorectal surgery, with reported rates reaching as high as 40%. Recurrence leads to substantial medical and economic burdens, potentially compromising anal sphincter function and patient quality of life. This document synthesizes findings from an international, evidence-based Delphi consultation survey and associated expert commentaries to identify the critical risk factors for AFR across three domains: patient-related, fistula-related, and surgery-related.

A consensus reached by an international panel of surgical specialists identifies 14 core risk factors. The most critical factors include inflammatory bowel disease (IBD), undetected internal openings, and the presence of recurrent or complex fistula structures (such as horseshoe extensions). The findings underscore the necessity of accurate preoperative assessment—utilizing detailed clinical examinations and medical imaging—and rigorous postoperative care to mitigate recurrence risks. These identified factors provide a foundation for developing risk calculation tools and personalized intervention strategies for high-risk cohorts.

Methodology and Consensus Framework

The primary study utilized a two-round modified Delphi process to achieve international consensus. This structured interaction allowed experts to evaluate and re-evaluate potential risk factors identified from a systematic literature review.

Consensus Criteria

  • Expert Panel: 38 specialists from 13 countries across four continents participated in the first round; 31 completed the second round.

  • Evaluation Scale: A 9-point Likert scale (1–3: low importance; 4–6: not of critical importance; 7–9: of critical importance).

  • Consensus Threshold: Agreement was reached when at least 70% of the panel rated a statement as "of critical importance" (7–9) with a coefficient of variation (CV) ≤ 0.3.

Definition of Recurrence

Anal fistula recurrence was defined as the persistence or recurrence of symptoms or the development of recurrent perianal sepsis following surgical intervention.

Core Risk Factors for Recurrence

The Delphi process identified 14 risk factors that achieved international consensus. These are categorized into three primary domains:

1. Patient-Related Risk Factors

These factors pertain to the patient’s underlying health and systemic conditions.

  • Inflammatory Bowel Disease (IBD): Ranked as the highest risk factor overall.

  • Comorbid Colitis: The presence of proctitis or colitis significantly elevates recurrence risk.

  • Use of Immunosuppressants: Systemic medication that may hinder the body's healing response.

2. Fistula-Related Risk Factors

These factors describe the anatomical complexity and history of the fistula itself.

  • Undetected Internal Opening: Failure to identify the primary source of infection.

  • Recurrent Fistula: A history of previous recurrence is a major predictor of future failure.

  • Horseshoe Extension: Complex lateral extensions that are difficult to drain.

  • Suprasphincteric and Transsphincteric Fistula: Higher anatomical complexity involving the anal sphincters.

  • Location and Number of Fistulae: Multiple tracts or specific anatomical locations (e.g., high-positioned internal openings).

  • Height of the Internal Opening: Higher openings are associated with more complex surgical requirements and higher failure rates.

3. Surgery-Related Risk Factors

These factors relate to the surgical execution and the clinical history of interventions.

  • Surgeon Experience: The skill and experience of the operating specialist.

  • Previous Fistula Surgery: Past attempts increase odds of recurrence by two to three times, likely due to excessive scarring and distorted anatomy.

  • Type of Surgery: The specific technique chosen (e.g., sphincter-saving vs. laying-open).


Detailed Thematic Analysis

Anatomical Challenges and Identification

The identification of the internal opening is recognized as the most critical surgical step. Failure to locate or correctly treat this opening leads directly to recurrence. Expert commentary suggests that identification can be hampered by:

  • Inflammation of perianal crypts blocking the opening.

  • Excessive scarring and fibrosis from previous surgeries.

  • The formation of "false passages" or iatrogenic fistulas when surgeons use probes too aggressively.

The Role of Medical Imaging

The consensus and subsequent commentaries emphasize that clinical examination alone is often insufficient for complex or recurrent cases.

  • Preoperative MRI and Endoanal Ultrasound (EAUS): Essential for mapping pathologic anatomy, identifying secondary branches, and detecting abscess cavities.

  • Recurrence Limitations: Research indicates the sensitivity of EAUS is lower in recurrent fistulas compared to primary ones, making advanced imaging even more vital in secondary cases.

Surgical Principles vs. Cosmetic Concerns

A recurring theme in surgical failure is the over-emphasis on cosmetic outcomes at the expense of basic proctological principles. Experts argue that:

  • Satisfactory cosmetic results usually follow proper healing regardless of initial incision size.

  • Cosmetics should not prevent surgeons from the necessary removal or drainage of fistula tracts.

Postoperative Care and Healing

The "care domain" is often overlooked but critical to preventing relapse.

  • Healing Timeline: It takes at least six weeks for the anal canal to heal properly.

  • Monitoring: Weekly medical examinations during this period are recommended to identify complications early.

  • Hygiene: Daily rinsing of wounds and regular dressing changes are necessary to ensure the tract closes correctly from the base upward.

Study Strengths and Limitations

Strengths

  • Global Perspective: Inclusion of experts from four continents and 13 countries.

  • Methodological Rigor: Combination of a systematic literature review with a formal Delphi consensus and coefficient of variation (CV) analysis.

  • Multidisciplinary Influence: Representation from general, colorectal, and gastrointestinal surgical specialties.

Limitations

  • Demographic Bias: High proportion of male participants and limited representation from African institutions (all participants from a single country).

  • Specialty Scope: Lack of representation from non-surgical specialists, such as gastroenterologists or internal medicine specialists.

  • Patient Involvement: The study did not include patient representatives in the Delphi process.

Conclusion

The identification of these 14 risk factors provides an evidence-based framework for clinical decision-making. By accurately assessing patients preoperatively for IBD, anatomical complexity, and previous surgical history, clinicians can identify high-risk individuals who require specialized surgical approaches and more intensive postoperative monitoring. Future efforts should focus on incorporating these factors into validated risk-prediction tools to standardize care and reduce the international burden of anal fistula recurrence.