Magnetic resonance imaging evaluation of small intestinal Crohn's disease.

Imaging evaluation in patients with Crohn's disease is based on morphological abnormalities, traditionally disclosed by barium studies including conventional enteroclysis, and more recently by cross-sectional imaging. A major prerequisite for optimal image quality and a more confident diagnosis is the adequate luminal distension of the bowel, which is usually achieved by administering an intraluminal contrast agent through a nasojejunal catheter. Magnetic resonance enteroclysis is a new technique that combines the advantages of volume challenge with state-of-the-art ultrafast pulse sequences, resulting in an excellent demonstration of the anatomy of the small bowel. Magnetic resonance enteroclysis compares favourably with conventional enteroclysis in detecting, localising and assessing the extent of involved small bowel segments. Luminal narrowing and extramural manifestations or complications of the disease can also be accurately assessed by the technique. Imaging features including the presence of deep ulcers, extensive wall thickening and mesenteric lymph nodes exhibiting marked gadolinium enhancement correlate strongly with disease activity. Although the clinical utility of magnetic resonance enteroclysis in Crohn's disease has been widely recognised, its routine application is currently limited to academic centres. Its clinical indications may include follow-up studies of known disease, the classification of Crohn's disease subtypes, an estimation of disease activity and a determination of the extramucosal extent and spread of the disease process.