P0477 Perianal Crohn’s fistula in the absence of luminal disease -natural history, time to progression to luminal disease and management in contemporary clinical practice: An ECCO-CONFER case series
Authors: Basnayake K , Raine T , Drobne D , Nardone O M , Jauregui-Amezaga A , Gawron-Kiszka M , Geldof J , Mahajna H , Cooney R , Ribaldone D , Festa S , Saibeni S , Bezzio C , Reenaers C , Filip R , Gojdičová A , Zagórowicz E , Pugliese D 
Published: January 2025

Abstract

Background
Isolated perianal fistulae (IPAF) without concurrent luminal disease is an uncommon presentation of Crohn’s disease (CD), posing unique diagnostic and management challenges. IPAF in CD often show complex features, such as secondary tracts and abscesses, and respond poorly to standard treatments for crypto-glandular fistulae1. Data on the natural history, progression to luminal disease, and effective management of IPAF in CD remain limited. This study examines contemporary diagnostic evaluation, clinical course, and outcomes for patients with IPAF lacking luminal CD at diagnosis.

Methods
We collected retrospective data on adult patients diagnosed with IPAF with the absence of luminal CD confirmed on at least one imaging-based diagnostic investigation within twelve months of diagnosis. Data collected included demographics, imaging and endoscopic findings, fistula classification2, surgical and medical treatments, treatment response3,4, and follow-up details.

Results
Data collection is ongoing. An interim analysis of complete data available at the time of this abstract included 40 patients (22 males, 55%). (Table 1).
The mean age was 33.9 years (±13.8). Complex PAF was present in 33 patients (83%). Baseline evaluation included a median of 2 fistula investigations and 2 luminal investigations per patient (from ileocolonoscopy, MRI, video capsule endoscopy, computed tomography enterography, intestinal ultrasound (IUS), and faecal calprotectin).
Combined surgical and medical therapy was used in 32 patients (80%), including Seton placement (n=27, 68%) and fistulotomy (n=17, 43%). Medical treatments included antibiotics (mean: 2.7 courses), immunomodulators (n=20, 50%), and biologics (n=29, 73%, primarily anti-TNF: n=26, 65%). (Table 2)
The median follow-up was 90 months (IQR: 36.75–115.5 months). Clinical remission was achieved in 19 patients (48%), while 12 (30%) reported clinical response with residual changes on imaging. Subsequent luminal disease developed in 20 (50%) with a median time to detection of luminal disease of 3.9 years.

Conclusion
In contemporary practice, diagnosis of IPAF remains rare and typically involves at least 2 diagnostic evaluations for luminal disease, including ileocolonscopy. Use of anti-TNF therapy in this cohort is common, with reported outcomes broadly in line with results seen in PAF in context of luminal disease. Future research should prioritize clinical outcomes, optimal diagnostic and monitoring guidelines, and the potential of new biologics or combination therapies to enhance response in this unique population.

References
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2.American Gastroenterological Association Medical Position Statement: Perianal Crohn’s Disease. Gastroenterology. 2003;125(5):1503-1507. doi:10.1016/j.gastro.2003.08.024
3. Present DH, Rutgeerts P, Targan S, et al. Infliximab for the Treatment of Fistulas in Patients with Crohn’s Disease. N Engl J Med. 1999;340(18):1398-1405. doi:10.1056/NEJM199905063401804/ASSET/FC9EF8AB-479C-43F9-94B6-9D1D480BA526/ASSETS/IMAGES/LARGE/NEJM199905063401804_T4.JPG
4. Panes J, Bouma G, Ferrante M, et al. INSPECT: A Retrospective Study to Evaluate Long-term Effectiveness and Safety of Darvadstrocel in Patients With Perianal Fistulizing Crohn’s Disease Treated in the ADMIRE-CD Trial. Inflamm Bowel Dis. 2022;28(11):1737-1745. doi:10.1093/IBD/IZAB361