Diffusion-weighted MRI in inflammatory bowel disease.

Cross-sectional MRI is an attractive alternative to endoscopy for the objective assessment of patients with inflammatory bowel disease (IBD). Diffusion-weighted imaging is a specialised technique that maps the diffusion of water molecules in biological tissues and can be done without intravenous gadolinium contrast injection. Diffusion-weighted imaging further expands the capability of traditional MRI sequences in IBD. However, the use of quantitative parameters, such as the apparent diffusion coefficient, is limited by low reproducibility. The Nancy score is a luminal disease activity index applied in diffusion-weighted imaging, and comprises only qualitative parameters. The score is accurate in Crohn's disease and ulcerative colitis, and requires no fasting or bowel preparation for assessment of colonic disease. However, deficiency of anatomic detail limits the use of diffusion-weighted imaging for assessment of intra-abdominal Crohn's disease complications. The contribution of such imaging in the prediction of disease course and treatment response in patients with IBD remains to be determined.