A magnetic resonance enterography index for assessing small bowel Crohn’s disease activity

BACKGROUND: This study aimed to construct a magnetic resonance imaging (MRI) index for assessing transmural inflammatory activity in the small intestine of patients with Crohn’ disease which enables rapid and non-invasive quantitative assessment of Crohn’s disease inflammation. METHODS: In this prospective study, magnetic resonance enterography (MRE) was performed to examine 29 consecutive patients with Crohn’s disease who had undergone ileocolonoscopy in the Jingling hospital of Nanjing. This diagnostic study was not registered on a clinical trial platform. We grade the T2 signal ratio and T1 enhancement ratio with a score of 0 to 3. The ratios were calculated as follow: terminal ileal inflammation of intestinal T2 signal intensity/adjacent normal intestinal T2 signal intensity (T2 ratio 1), terminal ileal inflammation intestinal T2 signal intensity/vertical muscle T2 signal intensity (T2 ratio 2), the fifth phase of the inflamed intestinal T1 signal intensity/noncontrast intestine T1 signal (T1 ratio 3), and the fifth phase of inflamed intestinal T1 signal intensity/adjacent normal intestinal T1 signal (T1 ratio 4). Wall thickness, lymph nodes, perimural T2 signal, comb sign, and ulceration were graded from 0 to 3. the simple endoscopic score for Crohn’s disease (SES-CD) from 0 to 12 was used to assess Crohn’s disease activity as a reference. The study calculated the correlations between the MRE activity index and endoscopic activity scores and derived the MRE index model to assess Crohn’s disease activity. RESULTS: The MRE index model (a T1 ratio 4 score of 1.52 + an ulceration score of 2.03) had a sensitivity of 0.962, a specificity of 0.667, and an area under the curve (AUC) of 0.968 [95% confidence interval (CI): 0.921–1.000]. The intraclass correlation coefficient (ICC) for the interobserver agreement of the MRE index was 0.921 (95% CI: 0.833–0.963). CONCLUSIONS: The study derived an MRE index with good sensitivity to inflammatory changes in the small bowel. The index could be used to assess Crohn’s disease activity of the small bowel.