Crohn's disease of the small bowel: evaluation of ileal inflammation by diffusion-weighted MR imaging and correlation with the Harvey-Bradshaw index

This study was undertaken to determine the diagnostic capabilities of diffusion-weighted magnetic resonance imaging (DWI) in detecting ileal inflammation in Crohn's disease (CD), and to verify the correlation between the DWI sequences and the Harvey-Bradshaw index (HBI). Twenty patients with an endoscopic-histological diagnosis of CD of the terminal ileum and MR enterography with DWI sequences and HBI were retrospectively selected. Disease activity was visually evaluated on the DWI sequences. In quantitative analysis, the apparent diffusion coefficient (ADC) of the terminal ileum was compared with that of normal ileal loops. Pearson's r was used to verify the correlation between the DWI findings and the HBI. On visual assessment, the accuracy, sensitivity and positive predictive value of DWI for the detection of inflammation were 100 %. In the quantitative assessment, the ADC value of the disease-active terminal ileum was significantly lower (p < 0.00001) than that of normal ileal loops. A correlation was found between visual assessment of the terminal ileum with the DWI sequences and HBI; no correlation was found between ADC of the terminal ileum and HBI. DWI sequences may be useful in differentiating actively inflamed small bowel segments from normal small bowel in CD. Though partial, the correlation between DWI sequences and HBI confirms the utility of this technique in the study of patients with CD.