Assessment of Ileal Crohn’s Disease Activity by Gastrointestinal Ultrasound and MR Enterography: A Pilot Study

Introduction: In some cases, there may be a discrepancy between the symptomatology alleged by Crohn’s disease (CD) patients and the results of laboratory tests or imaging investigations. Ileocolonoscopy with biopsy is the primary investigation for diagnosing and monitoring CD patients. Cross-sectional imaging techniques such as CT or MR enterography (MRE) and intestinal ultrasonography (IUS) have been proposed as complementary methods to colonoscopy for a complete evaluation of this category of patients. This study aims to identify the role of IUS, contrast-enhanced ultrasound (CEUS) and MRE in evaluating ileal CD activity, using clinical severity scores (Crohn’s disease activity index—CDAI, Harvey–Bradshaw index—HBI) and faecal calprotectin or C-reactive protein (CRP) levels as reference methods. Materials and Methods: A total of 44 adult patients with ileal CD confirmed using an ileocolonoscopy with biopsy and histopathological examination were assessed by IUS, CEUS and MRE. The evaluation of the disease activity based on the results obtained from the cross-sectional imaging tests was carried out by using some severity scores available in the literature. The sensitivity and specificity of IUS + CEUS and MRE for differentiating active from inactive forms of CD were determined using CDAI, HBI, faecal calprotectin and CRP as reference methods. The accuracy of the results was assessed by the receiver operating characteristics method. The Pearson correlation coefficient was used to determine the types of correlation. A p-value less than 0.05 suggested a statistically significant relationship. Results: Compared to CDAI, the best correlation was identified for Limberg score (r = 0.667, 95% confidence interval (CI) [0.46, 0.8], p < 0.001), followed by MaRIAs score (r = 0.614, 95% CI [0.39, 0.77], p < 0.001). A sensitivity of 93.33% and a specificity of 71.43% (AUC = 0.98) were demonstrated in the case of Limberg score for differentiating patients with active disease from those in remission and for MaRIAs score a sensitivity of 100.00% and a specificity of 57.14% (AUC = 0.97). Regarding HBI, the best correlation was observed for MaRIAs score (r = 0.594, 95% CI [0.36, 0.76], p < 0.001). Also, faecal calprotectin showed the best correlation with MaRIAs score (r = 0.697, 95% CI [0.46, 0.84], p < 0.001), but in the case of CRP, there was only a weak correlation for all evaluated scores. Conclusions: Although magnetic resonance imaging does not appear to be superior to ultrasonography in terms of accuracy for differentiating active forms of CD from those in remission, the results of our study suggest that MRE associates a better correlation with clinical severity scores and faecal calprotectin levels compared to ultrasonography. More studies are needed to validate these results.