What is the Role of Diffusion-weighted Imaging in Ileocolonic Crohn's Disease?

To the Editor: We read with great interest the article by Kim et al, published in the January issue of Inflammatory Bowel Diseases. The study design, excluding most of colonic segments (transverse, descending, and sigmoid colons) and operated patients from their statistical analysis, led difficult to draw any conclusion regarding the role of diffusion-weighted magnetic resonance imaging (DW-MRI), in ileocolonic Crohn’s disease (CD). We agree partially with the authors concerning the fact that there is no real additional value in performing DWMRI to increase the detection of ileocolonic CD lesions using qualitative analysis, i.e., diffusion-weighted imaging hyperintensity. Most of the authors focused on the qualitative parameter of DW-MRI to detect and assess inflammatory lesions. Accordingly, Kim et al confirmed that the accuracy of diffusion-weighted imaging hyperintensity is similar to the performances of injected sequences and could also be a marker of severity. Additional studies are warranted to confirm previous data showing that diffusion-weighted sequences could be an alternative to injected sequences to limit side effects and patients’ discomfort. We consider that the quantitative analysis using the apparent diffusion coefficient (ADC) is the main strength of DWMRI performed with no bowel cleansing and no rectal enema in CD. Our team and others previously showed that the Clermont score is highly correlated to the Magnetic Resonance Index of Activity and to the simplified endoscopic score for CD in the terminal ileum. In addition, we reported that segmental ADC is highly correlated to the Magnetic Resonance Index of Activity in colonic segments, which could mean that ADC use could decrease the number of false positives. We will present at the European Crohn’s and Colitis Organization congress, the preliminary results of a prospective study showing that ADC and Clermont score were highly effective in detecting endoscopic ulcerations in the colon and the terminal ileum, respectively. The conclusion of Kim et al should not be misinterpreted and should not discourage IBD physicians to conduct further studies interesting in DW-MRI in CD. DW-MRI is a well-tolerated, reproducible, and non– time-consuming tool, which could be repeated to monitor CD activity both in daily practice and in clinical trials. Further investigations should be performed to confirm that the quantitative parameters (ADC and Clermont score) are able to assess therapeutic response and that DW-MRI could be generalized for the management of patients with CD.