Assessment of disease activity with magnetic resonance enterography in pediatric Crohn's Disease

Objectives and study: Magnetic Resonance Enterography (MRE) is considered the imaging test of choice in children affected by Crohns Disease (CD) in order to study the small bowel. Few studies in literature analyze the correlation between disease activity evidenced by MRE and the standardized reference indices of activity in a pediatric population. The primary aim of our study was to determine whether MRE can be used to evaluate the activity of disease in a pediatric population affected by CD, studying the correlation between the activity index obtained by means of MRE and the standardized reference indices commonly used in clinical practice. We also compared MRE and endoscopy in their definition of disease localization. Methods: We recruited 39 CD pediatric patients who underwent 79 MRE at the time of diagnosis or during follow-up. At the same time of MRE, serum C-reactive protein (CRP), fecal calprotectin and the clinical activity index for pediatric CD (PCDAI) were performed. To evaluate the correlation of these parameters with disease activity on MRE, we applied a Pediatric Magnetic Resonance Index of activity, called P-CDMRI, which includes 11 parameters, for a total score ranging from 0, suggestive of remission, to 25, indicative of the maximal disease activity. Forty-five MRE performed within two months from a full endoscopic examination were used to evaluate the concordance on disease location and activity as detected by the two methods. The Simplified Endoscopic Score for Crohn’s disease (SES-CD) was used to evaluate endoscopic activity. Spearman correlation coefficients have been calculated between P-CDMRI and PCDAI and CRP and fecal calprotectin levels. We also considered the correlations between PCDAI the two most important RME variables, using the Kruskal Wallis test. p ≤0,05 values were considered statistically significant. Correlation coefficient values were interpreted as follows: 0.0, not correlated; 0.2, weakly correlated; 0.5, moderately correlated; 0.8, strongly correlated; and 1.0, perfectly correlated. MRE and endoscopy concordance in disease localization was evaluated with Cohen k statistics. Results: the P-CDMRI significantly correlated with the clinical (PCDAI, r = 0,690, p<0,001), laboratory (CRP, r = 0,436 p<0,001; fecal calprotectin, r = 0,390 p=0,008) and endoscopic (SES-CD, r = 0,445 p=0,003) indexes of activity. We observed a good concordance in the localization of the involved gastrointestinal tracts between MRE and endoscopy (K= 0,630 p<0,001). However, some discrepancies were observed, probably due to a better sensibility of endoscopy in detection of superficial lesions and a more precise evaluation of transmural involvement by MRE. Conclusion: Our study suggests that P-CDMRI is a good indicator of disease activity in CD pediatric patients, with significant correlations with the most commonly used clinical, laboratory and endoscopic parameters; it may thus be used to evaluate CD activity during the follow-up as well as the response to therapy. However, studies with a larger population of patients should be warranted to confirm these results. Disclosure of interest: “None Declared”.