P498 An expert Delphi consensus: Early identification of patients at risk of Crohn's disease in perianal fistulas and abscesses (PREFAB) and identification and management of isolated perianal Crohn's disease (ipCD) - Part B, ipCD
Authors: Hanna L , Munster L , Dige A , Lundby L , Buskens C J , Hart A L , van der Bilt J D W , Tozer P J ,   The TOpCLASS perianal Crohn's disease Consortium . The Dutch Initiative on Crohn and Colitis (ICC) and the Initiative on Crohn and Colitis Surgery (ICC-S). This abstract is a partner to the PREFAB abstract with the same authorship
Published: January 2024

Abstract

Background
In clinical practice, some patients with ‘idiopathic’ perianal fistulae (iPAF) and no evidence of luminal IBD are labelled ‘isolated perianal Crohn’s disease’ (ipCD) and treated with IBD-directed therapies. However, there are no accepted criteria to guide which patients should be diagnosed as ipCD, or how they should be managed. This project aimed to provide a definition of ipCD, strategies for management, and a platform for building further understanding of this group.

Methods
An expert panel of IBD gastroenterologists, surgeons and radiologists took part in a Delphi consensus on ipCD. The first-round was an electronic survey, probing: 1) personal experience of ipCD; 2) how fistula histology may influence ipCD diagnosis; 3) patient and fistula features suggestive of ipCD; and 4) suggested management of patients with suspected-ipCD. Responses informed the creation of clinical criteria for ipCD, and statements on ipCD management, which were discussed, amended, and agreed-upon at a second-round virtual consensus meeting. Consensus was predefined as ≥70% ‘strongly agree’ or ‘agree with minor reservation’.

Results
&gt;30 specialists participated. In round 1: 93% agreed ipCD is a separate Crohn’s phenotype; 83% reported having treated ipCD patients with IBD medical therapies; 73% agreed iPAF patients with fistula histology suggestive of ipCD could be labelled as histologically-confirmed ipCD; and 93% agreed histologically-confirmed ipCD with complex fistulation should be treated with IBD medical therapy (e.g., biologics). However, there was no consensus on the appropriateness of IBD medical therapy for simple fistulae. For iPAF patients without histological evidence of IBD, the panel agreed factors suggestive of ipCD. These included: family history of IBD, symptoms of IBD extraintestinal manifestations, co-existent/previous perianal lesions (fissures, anal stricture, tags), and certain fistula features. Factors were used to produce a criteria to diagnose ipCD and identify patients appropriate for a trial of medical therapy. If a trial of therapy is pursued, the panel agreed careful discussion of the risks of treatment, and known-unknowns, when treating ipCD. Optimised anti-TNF is preferred first-line (82% agreement) with a careful review of treatment response, and contemporaneous MRI, at 6-12 months (93% agree).

Conclusion
ipCD is a contentious label and standardisation of the diagnosis could help us better assess this group and their treatment outcomes. We present a suggested criteria for diagnosing this group, and a pragmatic approach to trialling biologic therapy. Key to managing this group is honest discussion regarding the known-unknowns of ipCD treatment, to manage patient expectations and support a joint decision-making approach.