Abstract Background Approximately 50-75% of patients with Crohn’s disease (CD) require surgery during disease course, yet post-operative recurrence (POR) may occur in 70% of patients within the first year (1). Early detection is crucial for guiding timely treatment and improving long-term outcomes. Intestinal ultrasound (IUS) is a safe, cost-effective, and patient-friendly non-invasive tool for assessing and monitoring CD activity (2). However, evaluation of POR, particularly at anastomotic site, remains challenging. While validated IUS scoring systems enable the assessment of CD activity (3), no scores are currently available to standardize POR assessment. We aimed to develop the first IUS score to predict POR in CD: the PROSPER-IUS score. Methods CD patients enrolled in the international, multicenter PROSPER study (NCT06505304) who underwent IUS at 3 and 6 months following ileocolic resection were included. Key IUS features relevant to POR were identified through a Delphi process during two in-person consensus meetings (Figure 1). Ten expert IBD-IUS readers independently scored 10 standardised videos evaluating selected features at neoterminal ileum, anastomotic site, colon, and, when present, blind loop. Interrater agreement for each feature was assessed using intraclass correlation coefficients (ICC) and Gwet’s AC1/AC2. Features to be included in the final PROSPER score were selected through an anonymised online survey. Consensus was defined as ≥ 75% agreement among participants. Results Overall, assessment of bowel wall thickness (BWT) and submucosal thickness demonstrated good agreement (ICC 0.7 and 0.62, respectively). Agreement for BWT at anastomosis was moderate (ICC 0.53), while it was good for the neoterminal ileum (ICC 0.61) and very good for ascending colon (ICC 0.93). Evaluation of bowel wall stratification and vascularization achieved excellent agreement across all segments. Assessment of ileal motility, inflammatory mesenteric fat (iFAT), and lymph nodes reached moderate-to-substantial agreement (AC1 0.57, 0.6 and 0.66, respectively). Finally, presence of fistulas, abscesses, spiculates and free fluid showed excellent agreement (Table). Following the online survey, most features achieved a score 80% for inclusion in the final score, except for submucosal thickness, ileal motility, and free fluid. Conclusion The novel PROSPER IUS score demonstrated good to excellent interobserver agreement across most evaluated domains, supporting its reliability for assessing POR in CD. A multicenter prospective validation study is currently underway, benchmarking the score against clinical biomarkers, endoscopic findings, and patient outcomes. These findings highlight its strong potential for future adoption in clinical practice and clinical trials. References: 1. Bernstein CN, Loftus E V, Ng SC, Lakatos PL, Moum B. Hospitalisations and surgery in Crohn’s disease. Gut. 2012 Apr;61(4):622–9. 2. Kucharzik T, Taylor S, Allocca M, Burisch J, Ellul P, Iacucci M, et al. ECCO-ESGAR-ESP-IBUS Guideline on Diagnostics and Monitoring of Patients with Inflammatory Bowel Disease: Part 1. J Crohns Colitis. 2025 Jul 3;19(7). 3. Yanai H, Feakins R, Allocca M, Burisch J, Ellul P, Iacucci M, et al. ECCO-ESGAR-ESP-IBUS Guideline on Diagnostics and Monitoring of Patients with Inflammatory Bowel Disease: Part 2. J Crohns Colitis. 2025 Jul 3;19(7). Conflict of interest: Verstockt, Bram: Research support from AbbVie, Biora Therapeutics, Celltrion, Landos, Pfizer, Sanofi, Sossei Heptares/Nxera and Takeda. Speaker’s fees from Abbvie, Agomab, Alfasigma, Biogen, Bristol Myers Squibb, Celltrion, Eli Lily, Falk, Ferring, Galapagos, Materia Prima, Johnson and Johnson, Pfizer, Sandoz, Takeda, Tillots Pharma, Truvion and Viatris. Consultancy fees from Abbvie, Alfasigma, Alimentiv, Anaptys Bio, Applied Strategic, Astrazeneca, Atheneum, BenevolentAI, Biora Therapeutics, Boxer Capital, Bristol Myers Squibb, Domain Therapeutics, Eli Lily, Galapagos, Guidepont, Landos, Merck, Mirador Therapeutics, Mylan, Nxera, Inotrem, Ipsos, Johnson and Johnson, Pfizer, Sandoz, Sanofi, Santa Ana Bio, Sapphire Therapeutics, Sosei Heptares, Takeda, Tillots Pharma and Viatris. Stock options Vagustim and Thethis Pharma. Dr. Zammarchi, Irene: No conflict of interest Allocca, Mariangela: No conflict of interest Bezzio, Cristina: No conflict of interest Banai Eran, Hagar: No conflict of interest Castiglione, Fabiana: Honoraria from: Takeda, AbbVie, Celltrion, Johnsson Johnsson, Cadigroup, Sandoz, Pfizer, Lilly, Lionhealth, Nestlè Cannatelli, Rosanna: No conflict Dal Buono, Arianna: speaker’s fees from AbbVie, Alphasigma, Ferring, Lilly, Janssen, and Celltrion Doherty, Glen: No conflict of interest Furfaro, Federica: Grant: IG-IBD Personal Fees: Pfizer, Biogen,J & J, Abbvie, Amgen, Janssen Lepore, Federica: No conflict of interest Lu, Cathy: Advisory board - Abbvie, JnJ, Takeda, Ferring, Merck, Celltrion, Pfizer Research Funding - Abbvie, JnJ Maconi, Giovanni: Personal Fees: Abbvie, Arena Pharmaceuticals, Alfa-Wasserman, Fresenius-Kabi, Gilead, Janssen Cilag, Roche Non-financial Support: Takeda, Abbvie, Alfa-Wasserman Nardone, Olga Maria: Advisory board fees from Eli Lilly, Nestlè, Janssen Speaker fees from AbbVie, Janssen, Eli Lilly, Ferring, Alfa Sigma, Recordati, Noòs, and Pfizer O’grady, John: No conflict of interest Piazza O Sed, Nicole: No conflict of interest Ricci, Chiara: No conflict of interest Ghosh, Subrata: None None None Iacucci, Marietta: Grant: Pentax, Olympus, Eli lilly,Helmsley Personal Fees: Pentax, Pfitzer, Janssen, EliLilly, J & J
Verstock et al. (Thu,) studied this question.