P0496Longitudinal assessment of intramural fat accumulation (fat halo sign) in patients with Crohn’s disease: prevalence, predictive factors, and impact on disease outcomes

Abstract Background The prevalence of Intramural Fat Accumulation (IFA) within the intestinal submucosal wall, as detected by Magnetic Resonance Enterography (MRE), along with its clinical significance and potential to predict disease outcomes in Crohn’s Disease (CD) remain poorly understood. This study sought to determine the prevalence of IFA, explore its associations with clinical and radiological features, and evaluate its predictive value for adverse outcomes over a 12-month follow-up. Methods This prospective observational study included CD patients with at least one MRE between June 2020 and June 2025. All MRE were evaluated by a single radiologist for the presence of IFA. The extent and wall thickness of the diseased segment, creeping fat, T2 hyperintensity, comb sign, lymphadenopathies, stenosis and fistulas were also reported. Data from patients with multiple MRE were analyzed to identify factors associated with the persistence, loss, or gain of IFA over time. Results A total of 172 CD patients were included. IFA was detected in 15% of patients, predominantly localized in the ileum (73%). Its presence was significantly associated with creeping fat (p = 0.016) and increased bowel wall thickness (p = 0.001). At the second MRE, persistence of IFA was significantly correlated with baseline IFA thickness (p = 0.001), DWI restriction (p = 0.048), creeping fat (p = 0.019) and comb sign (p = 0.048). No significant correlation was observed between IFA and the need for hospitalization or surgery after 12 months. Baseline T2 hyperintensity (p = 0.034) and contrast enhancement patterns were associated with IFA loss (0.018), while previous surgery showed a trend toward predicting IFA gain (p = 0.055). Conclusion IFA is a structural marker in CD associated with specific radiological features, but it does not predict adverse clinical outcomes at 12 months. References: 1. Erol, M. Y. & Algin, O. Detection of intramural fat accumulation by 3D-Dixon-Caipirinha-Vibe and the contribution of this technique to the determination of the chronicity of Chron’s disease. Magn Reson Imaging 85, 93–101 (2022). 2. Fullard, K. J., Souto, R., Dill, T. & Lochhead, A. Intramural fat in association with inflammatory bowel disease (IBD). Pathology 45, S67 (2013). 3. Jones, B. et al. Submucosal Accumulation of Fat in Inflammatory Bowel Disease. J Comput Assist Tomogr 10, 759–763 (1986). Conflict of interest: Usai, Alessandra: No conflict of interest Dr. Favale, Agnese: advisory board for abbVie Balestrieri, Antonella: No conflict of interest Soddu, Paola: No conflict of interest Ibba, Ivan: No conflict of interest Demurtas, Mauro: No conflict of interest Italia, Angelo: No conflict of interest Onali, Sara: Consultant/lecture fees to: Abbvie, Alfasigma, MSD, Takeda, J & J, Galapagos, Pfizer, Eli Lilly Saba, Luca: No conflict of interest Fantini, Massimo Claudio: MCF has acted as a consultant for: AbbVie, AlfaSigma, Celgene, Celltrion, Gilead, Pfizer, MSD, Bristol-Meyer, Takeda, Johnson & Johnson, Roche, Galapagos, Biogen, Sandoz, Eli-Lilly, Lionhealth, Teva, Giuliani, Dr Falk Pharma, Sanofi he has received financial support for research from Johnson & Johnson and Pfizer.