Abstract Background The optimal timing of intestinal ultrasound (IUS) after ileocolic resection for Crohn’s disease (CD) remains uncertain. Very early postoperative IUS (6 weeks) may be influenced by postoperative inflammatory–remodelling rather than recurrence. We prospectively assessed the value of bowel wall thickness (BWT) and faecal calprotectin (FC) at different postoperative timepoints following Kono-S anastomosis. Methods We enrolled consecutive ileal CD patients undergoing first ileocolic resection with Kono-S anastomosis between December 2023 and December 2024. All were low-risk for postoperative recurrence and received no prophylaxis. IUS (BWT, modified Limberg score, mesenteric fat, lymph nodes) and FC were performed at 4 (T1), 12 (T2), and 24 weeks (T3). Ileocolonoscopy was performed at T3. Endoscopic recurrence was defined as Rutgeerts ≥i2. Exploratory accuracy analyses used BWT 3 mm as a predefined threshold. Results Eleven patients were included. At 4 weeks, BWT 3 mm was observed in 10/11 (90.9%), with frequent mesenteric changes, consistent with postoperative rather than recurrent inflammation. At 12 weeks, BWT 3 mm persisted in only 2/11 patients, both of whom developed endoscopic recurrence (sensitivity 40%, specificity 100%). At 24 weeks, BWT 3 mm showed high specificity (100%) and moderate sensitivity (60%). FC showed a postoperative decrease from T1 to T3 but did not clearly differentiate recurrent from non-recurrent patients in this small, homogeneous cohort. Modified Limberg score, mesenteric fat and lymph nodes improved over time but did not provide further discriminative value. Conclusion Very early IUS at 4 weeks appears too premature to distinguish postoperative inflammatory changes from recurrence. From 12 weeks onward, BWT becomes informative, and at 24 weeks demonstrates excellent rule-in performance for endoscopic recurrence. In this low-risk, surgery-naïve cohort, BWT outperformed FC and other IUS parameters in identifying early recurrence, supporting IUS assessment after 8–12 weeks as a meaningful complement to endoscopic surveillance. References: 1. Castiglione F, Bucci L, Pesce F, et al. Bowel sonography for the diagnosis and grading of postsurgical recurrence of Crohn’s disease. Inflamm Bowel Dis. 2008;14(9):1240-1245. 2. Calabrese E, Maaser C, Zorzi F, et al. Bowel ultrasonography in the management of Crohn’s disease: a review with recommendations of an international panel of experts. Inflamm Bowel Dis. 2016;22(5):1168-1183. 3. Rispo A, Imperatore N, Testa A, et al. Diagnostic accuracy of ultrasonography in the detection of postsurgical recurrence in Crohn’s disease: a systematic review with meta-analysis. Inflamm Bowel Dis. 2018;24(5):977-985. 4. Bossuyt P, Ferrante M, Singh S. Biomarkers in postoperative recurrence of Crohn’s disease. Gastroenterology. 2023;164(7):1220-1238. Conflict of interest: Dr. Gridavilla, Daniele: No conflict of interest Colombo, Francesco: No conflict of interest Cataletti, Giovanni: No conflict of interest Guerci, Claudio: No conflict of interest Pennacchi, Luca: No conflict of interest Maconi, Giovanni: Personal Fees: Abbvie, Arena Pharmaceuticals, Alfa-Wasserman, Fresenius-Kabi, Gilead, Janssen Cilag, Roche Non-financial Support: Takeda, Abbvie, Alfa-Wasserman
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