MR enterography in the management of patients with Crohn disease.

Crohn disease is a complex pathologic process with an unpredictable lifelong course that includes frequent relapses. It often affects young patients, who are most vulnerable to the potential adverse effects of repeated exposure to ionizing radiation from computed tomography performed for diagnosis and surgical planning. The small intestine is the bowel segment that is most frequently affected, but it is the least accessible with endoscopic techniques. Magnetic resonance (MR) enterography has the potential to safely and noninvasively meet the imaging needs of patients with Crohn disease without exposing them to ionizing radiation. Appropriate use of MR enterography requires a carefully crafted protocol to depict signs of active inflammation as well as complications such as bowel obstruction, fistulas, and abscesses. Interpretation of MR enterographic images requires familiarity with the imaging signs and mimics of active bowel inflammation and stenosis. Although MR enterography currently is helpful for management in individual patients, the standardization of acquisition protocols and interpretive methods would increase its usefulness for more rigorous, systematic assessments of Crohn disease treatment regimens.