A review of Magnetic Resonance Enterography classification and quantitative evaluation of active disease in patients with Crohn's disease.

Crohn's disease (CD) is a chronic inflammation of the gastro-intestinal system in which episodes of clinical worsening alternate with episodes of clinical regression. Monitoring of disease is mandatory to evaluate the efficacy of therapy and it is usually performed using a combination of clinical symptoms, laboratory tests, endoscopy and radiological exams, such as MR enterography or CT enterography. MR enterography should be preferred to CT enterography because of the absence of ionizing radiation, a very high soft tissue contrast, and a lower incidence of adverse events. In 2003, Maglinte introduced a radiological classification to identify patients in different stages of disease (active inflammatory, fibrostenotic and fistulising/perforating subtypes), based on following parameters: oedema, ulcers, stenosis, mural thickening, stratified contrast enhancement, engorged vasa recta, fistulae/abscess and mesenteric inflammation. In general, medical therapy is efficient in reducing inflammation while fibrotic disease and fistulising subtypes usually require surgery. Moreover, in patients with active CD it is important to quantify disease activity in order to adequately plan therapy and to monitor drug effects, by using some MR enterography indexes such as MaRIA score, Clermont index, and others. In this review we describe how to apply Maglinte's classification in MR enterography exams and how to quantify active disease.