Letter: Re-Examining Seton Efficacy in Perianal Crohn's Disease—Considerations for Outcome Measurement and Clinical Interpretation

Abstract

We read with great interest the multicentre study by McCurdy et al. investigating the impact of setons on perianal fistula outcomes in patients with Crohn's disease (CD) receiving anti-TNF therapy [1]. This retrospective analysis provided valuable insights into current clinical practice. However, we wish to highlight methodological considerations that may influence the interpretation of these null findings.

First, the study defined “seton exposure” as the presence of ≥ 1 seton at anti-TNF initiation but did not address seton retention duration, a factor directly affecting fistula tract maturation. Prolonged seton drainage (≥ 8 weeks pre-biologic initiation) may improve fistula response rates by optimising local sepsis control [2]. In the absence of data on seton dwell time, the reported HR for major adverse fistula outcomes (1.23; 95% CI 0.68–2.21) may have underestimated therapeutic benefits in patients receiving adequate drainage periods.

Second, the propensity score model accounted for fistula complexity via MRI-based classifications but omitted key technical variables influencing seton efficacy. Consensus guidelines emphasise that seton positioning relative to fistula tracts (inter-sphincteric vs trans-sphincteric) and material type (cutting vs draining) significantly affect outcomes [3]. The lack of stratification by these parameters introduced unmeasured heterogeneity, particularly given the 17-year study span during which seton techniques evolved substantially.

Third, the definition of fistula remission (“clinical assessment”) lacks objective imaging confirmation. A considerable proportion of clinically quiescent fistulas exhibit persistent inflammation on MRI predictive of relapse. Incorporating radiographic endpoints (e.g., MAGNIFI-CD criteria) in future studies could enhance outcome validity [4].

Additionally, the study's exclusive focus on objective clinical endpoints overlooked the multidimensional nature of perianal fistula management. In clinical practice, sustained seton drainage frequently correlates with meaningful symptom alleviation, particularly reduced pain and improved daily function, even when complete anatomical closure remains elusive. By omitting patient-reported outcomes tracking pain severity, drainage frequency, or quality of life metrics, the analysis failed to capture critical dimensions of therapeutic success that directly influence treatment decisions and patient satisfaction. Therefore, future investigations should prioritise integrating both anatomical and patient-centric metrics such as the Fistula Quality of Life Index and visual analogue scale for pain to bridge this evidence gap. This would better align research outcomes with the complex goals of fistula care, where symptom control and functional restoration often outweigh idealised anatomical benchmarks.

In conclusion, while the authors provided important observational data on seton use in patients treated with anti-TNF agents, these findings should be interpreted within the study's methodological constraints. The clinical reality of perianal fistula management demands a more nuanced evaluation framework that simultaneously addresses technical surgical parameters (drainage duration, seton type), objective inflammatory resolution (via serial MRI assessments), and patient-experienced therapeutic benefits. Future prospective studies adopting this assessment model, particularly in high-risk subgroups with complex fistulas or recurrent abscesses, will better elucidate the true risk–benefit profile of seton maintenance during biologic therapy. Only through such comprehensive evaluation can we optimise the delicate balance between anatomical healing and functional restoration in this challenging patient population.