Is magnetic resonance imaging a reliable diagnostic tool in the evaluation of active Crohn's disease in the small bowel?

GOALS: To evaluate the overall diagnostic accuracy of magnetic resonance imaging (MRI) in assessing the activity of Crohn's disease (CD) in the small bowel.

BACKGROUND: Cross-sectional imaging techniques are playing an increasing role in the evaluation of suspected CD. Advantages of MRI include a lack of ionizing radiation, the ability to provide dynamic information regarding bowel distention and motility, improved soft-tissue contrast, and a relatively safe intravenous contrast agent profile.

STUDY: Two reviewers searched MEDLINE, EMBASE, and other electronic databases to identify studies in which MRI imaging was evaluated for assessing the activity of CD in the small bowel from January 2001 to September 2011. Bivariate random-effects meta-analytic methods were used to estimate summary, sensitivity, specificity, and receiver operating characteristic curves.

RESULTS: MRI had a pooled sensitivity of 0.87 [95% confidence interval (CI): 0.77, 0.93] and a pooled specificity of 0.91 (95% CI: 0.81, 0.96). Overall, likelihood ratio (LR)+ was 9.5 (95% CI: 4.4, 20.6) and LR- was 0.14 (95% CI: 0.08, 0.26). In patients with high pretest probabilities, MRI enabled confirmation of active CD; in patients with low pretest probabilities, MRI enabled exclusion of active CD. Worst-case-scenario (pretest probability, 50%) posttest probabilities were 90% and 13% for positive and negative MRI results, respectively.

CONCLUSIONS: A limited number of small studies suggest that MRI has high sensitivity and specificity for diagnosis of active CD in the small bowel; MRI will likely also prove to be suitable as the primary modality for active CD imaging surveillance.