Non-perforating small bowel Crohn's disease assessed by MRI enterography: Derivation and histopathological validation of an MR-based activity index

Abstract

ObjectivesTo develop and validate a qualitative scoring system for enteric Crohn's disease activity using MR enterography (MRE). MethodsMRE was performed in 16 patients (mean age 33, 8 male) undergoing small bowel resection. Mural thickness, T2 signal, contrast enhancement, and perimural oedema were scored qualitatively (0–3) at 44 locations. Transmural histopathological scoring of acute inflammation (AIS) was performed at all locations (score 0–13). MRI parameters best predicting AIS were derived using multivariate analysis. The MRI activity index was applied to 26 Crohn's patients (mean age 32, range 13–69 years, 15 male) and correlated to terminal ileal biopsy scores of acute inflammation (“eAIS” score 1–6). Receiver operator characteristic curves were calculated. ResultsMural thickness (coefficient 1.34 (95% CI 0.36, 2.32)], p=0.007) and T2 signal (coefficient 0.90 (95% CI −0.24, 2.04) p=0.06) best predicted AIS (AIS=1.79+1.34*mural thickness+0.94*mural T2 score [R-squared 0.52]). There was a significant correlation between the MRI index and eAIS (Kendall's tau=0.40, 95% CI 0.11–0.64, p=0.02). The model achieved a sensitivity of 0.81 (95% CI 0.54–0.96), specificity of 0.70 (0.35–0.93) and AUC 0.77 for predicting acute inflammation (eAIS ≥2). ConclusionsA simple qualitative MRI Crohn's disease activity score appears predictive against a histopathological standard of reference.