Objective: Assessment of disease extension and activity is crucial to guide therapy in Crohn disease. The objective of the current study was to determine the accuracy of Magnetic Resonance (MR) for this assessment.
Design: 50 patients with clinically active (n=35) or inactive (n=15) Crohn disease underwent ileocolonoscopy (reference standard) and MR. T2-weighted and pre- and post-contrast-enhanced T1-weighted sequences were acquired. Endoscopic activity was evaluated by CDEIS; in addition endoscopic lesions were classified as absent, mild (inflammation without ulcers), or severe (presence of ulceration).
Results: The comparison of intestinal segments with absent, mild and severe inflammation demonstrated a progressive and significant (p<0.001) increase in the following MR parameters: wall thickness, post-contrast wall signal intensity, relative contrast enhancement, presence of edema, ulcers, pseudopolyps and lymph node enlargement. Independent predictors for CDEIS in a segment were wall thickness (p=0.007), relative contrast enhancement (p=0.01), presence of edema (p=0.02), and presence of ulcers at MR (p=0.003). There was a significant correlation (r=0.82, p<0.001) between the CDEIS of the segment and the MR index calculated according to the logistic regression analysis coefficients. The MR index had a high accuracy for the detection of disease activity (area ROC curve 0.891, sensitivity 0.81, specificity 0.89) and for the detection of severe lesions (area ROC curve 0.978, sensitivity 0.95, specificity 0.91) in the colon and terminal ileum.
Conclusion: The accuracy of MR for detecting disease activity and assessing severity brings about the possibility of using MR as an alternative to endoscopy in the evaluation of Crohn disease.