Post-operative recurrence (POR) of Crohn’s disease (CD) remains a major challenge, affecting up to 80% of patients within 10 years after surgery. Conventional endoscopy struggles to distinguish early inflammatory recurrence from post-surgical ischemic changes, delaying effective treatment. Virtual chromoendoscopy (VCE) offers precise visualisation of mucosal and vascular changes. The PROSPER study aims to develop and validate a novel endoscopic score integrating advanced imaging features to predict early POR in CD.

This analysis is part of the international, multicentre, prospective PROSPER study (NCT06505304). Adult CD patients undergoing ileocolic resection were enrolled pre-operatively or within 3 months post-operatively and underwent endoscopic assessment at 3 or 6 months after surgery, guided by faecal calprotectin levels (cutoff 150 µg/g). Endoscopic videos were obtained using white-light and VCE modalities —TXI, RDI, and NBI with the Olympus (EVIS-X1) platform, and i-scan1 and OE mode 1–2 with the Pentax (INSPIRA) platform— following a standardised protocol. A three-round modified Delphi process defined the PROSPER domains: two in-person consensus meetings and an online survey (Qualtrics platform) where experts rated each feature. Consensus required >75% agreement. Seven core experts participated in both the first (10 videos) and second (15 videos) rounds, scoring the colon proximal to the anastomosis, the anastomotic region (including anastomotic line, ileal inlet, ileal body, and, when present, blind loops), and the neo-terminal ileum. All anastomotic configurations -end-to-end, end-to-side, side-to-end, side-to-side, and Kono-S- were assessed. Inter-rater agreement was evaluated using Fleiss’ κ, Gwet’s AC1/AC2, and ICC(2,k).

Mucosal and vascular domains were selected, including erosions, superficial and deep ulcers, villi morphology, vessel dilatation, and bleeding (Table 1). Agreement across both in-person rounds was moderate to substantial for features in the neo-terminal ileum and colon proximal to the anastomosis (AC1/AC2 = 0.61–0.78) and lower for the anastomotic region (fair to moderate), particularly for villi and erosions (AC2 ≈ 0.40–0.50). Ulcers and vascular patterns showed higher reproducibility (AC1 ≈ 0.70–0.80). Moderate agreement was observed for the anastomosis type (κ 0.51). The Delphi survey confirmed selected domains, with over 80% expert agreement on inclusion and weighting.

The novel PROSPER score is a multimodal tool integrating advanced imaging for comprehensive assessment of the anastomosis, showing  good inter-expert agreement across most domains. These results support its feasibility for detecting early POR. The next phase will involve real-life validation.