Intestinal ultrasound assessment of Crohn’s disease activity and complications: correlation with clinical, biochemical, and cross-sectional imaging findings

Background Crohn’s disease (CD) is a chronic inflammatory bowel disorder with variable clinical presentation and disease course. Accurate, non-invasive assessment of disease activity is crucial for guiding management and follow-up. Intestinal ultrasound (IUS), particularly the International Bowel Ultrasound Segmental Activity Score (IBUS-SAS), has emerged as a promising imaging tool. Objective To evaluate the role of IUS and IBUS-SAS in assessing disease activity in CD patients, compare its performance with the Crohn’s Disease Activity Index (CDAI) and laboratory biomarkers (CRP, fecal calprotectin), and validate findings with cross-sectional imaging (CT/MRI). Methods This prospective study included 28 patients with pathologically proven Crohn’s disease (18 males, 10 females; mean age 30 years). All patients underwent IUS with IBUS-SAS scoring, laboratory testing (CRP and fecal calprotectin), and CDAI evaluation. A subset of 20 patients also underwent CT/MRI. Statistical analysis included correlation coefficients, ROC curve analysis, and Cohen’s kappa for inter-modality agreement. Results IUS identified active disease in 67.9% of patients. The mean IBUS-SAS was 47.1 ± 28.9, with strong correlations to CDAI (rs = 0.915, p < 0.001), fecal calprotectin (rs = 0.828, p < 0.001), and CRP (rs = 0.823, p < 0.001). ROC analysis demonstrated excellent diagnostic performance, with an AUC of 0.978. An IBUS-SAS cut-off of 24.5 predicted clinical activity (CDAI > 150) with 90% sensitivity and 87.5% specificity, while a cut-off of 38 predicted moderate-to-severe activity (CDAI > 220) with 100% sensitivity and 84.6% specificity. Agreement between IUS and CT/MRI was substantial to almost perfect for most parameters (κ = 0.77–1.00), except perianal disease, which was missed by IUS. Conclusion IUS with IBUS-SAS is a reliable, non-invasive tool for evaluating disease activity and complications in Crohn’s disease, showing strong correlation with CDAI and biomarkers, and high agreement with cross-sectional imaging. Its use may facilitate routine monitoring, though limitations exist in obese patients and in detecting deep pelvic or perianal disease, where MRI remains superior.