Editorial: Seton Use in Perianal Fistulising Crohn's Disease. Authors' Reply

We thank Mr. Anand and Mr. Tozer for their interest in our study [1, 2] and for their ongoing contributions to the field of perianal fistulising Crohn's disease (PFCD) through the TOpClass consortium. Several important considerations were raised in their editorial that require further explanation.

We agree that a limitation of our retrospective study was our inability to assess for abscess recurrence directly. However, most patients with clinically relevant abscesses present to hospital or undergo surgical drainage. Since each of these parameters was included in our composite primary endpoint of major adverse fistula outcomes (MAFO), we believe it is likely that our study captured most clinically relevant abscesses. Despite this, we acknowledge that subclinical abscesses, those that drain spontaneously, or those that are less severe and treated with antibiotics alone would have been missed. Therefore, future prospective studies with patient-reported outcome measures and access to point of care imaging modalities such as endoanal or transperineal ultrasound would help to determine more accurately if the rates of abscess recurrence differ substantially based on the presence of setons.

There are a number of variables that clinicians should consider when selecting potential candidates to forgo seton placement. First, our study design included patients who initiated their first anti-TNF therapy for active perianal Crohn's disease. As a result, our study population mainly comprised patients who were early on in their disease course. Second, we observed a potential protective role of setons (although not statistically significant) in a subgroup of patients with abscesses detected by pre-treatment MRI. As a result, the ability to forgo seton insertion may be most applicable for patients with first presentation PFCD without an abscess, or those with an abscess that drains spontaneously and where the goal of treatment is curative. Due to a paucity of literature pertaining to patterns of PFCD on initial presentation and the natural history of PFCD in the era of biologic therapies, it is unclear what proportion of patients with new PFCD would meet these criteria.

Future studies characterising the breadth of variability in PFCD complexity and severity, along with the proportion with associated abscesses in modern day PFCD at the time of disease onset, will help to determine the proportion of patients who might be suitable to forgo seton insertion. Finally, due to the potential for residual uncontrolled confounding, our results should be interpreted with caution. As a result, we agree with Mr. Anand and Mr. Tozer that future randomised controlled studies are needed to confirm our findings.

The authors declarations of personal and financial interests are unchanged from those in the original article [2].

Jeffrey D McCurdy: conceptualization, writing – original draft. Blair Macdonald: writing – review and editing. Greg Rosenfeld: writing – review and editing. Talat Bessissow: writing – review and editing. Vipul Jairath: writing – review and editing. David H. Bruining: writing – review and editing. Siddharth Singh: writing – review and editing.

This article is linked to McCurdy et al. papers. To view these articles, visit https://doi.org/10.1111/apt.70081 and https://doi.org/10.1111/apt.70094.