Clinical Efficacy of MR Enterography in the Diagnosis and Management of Crohnʼs Disease

Abstract

Purpose: Background: Assessing small bowel Crohn's disease (CD) activity is challenging as direct visualization is difficult and traditional radiographic studies can result in large cumulative radiation doses. MR enterography (MRE) is a rapidly evolving diagnostic technique performed without ionizing radiation. While prior studies evaluate the technical aspects of MRE, few address its clinical utility. Aim: To evaluate the clinical utility of MRE in patients with known or suspected CD at a single institution. Methods: Consecutive MRE performed between 1/1/09 and 9/30/09 were reviewed. All imaging was performed on a 1.5T clinical scanner with an 8-channel phased array body coil. Patients were scanned after ingestion of hyperosmolar oral contrast. High resolution T2 and T1 weighted pre- and post-contrast images were obtained. Studies performed for reasons other than known or suspected CD were excluded. Patient data including clinical course prior to MRE and subsequent management was abstracted from the medical record and a clinical disease activity score was derived. Each MRE was scored on a 4-point scale (1: active small bowel inflammation definitely absent, 2: probably absent, 3: probably present, 4: definitely present). A clinical efficacy score (CES) was also assigned to each MRE (range 0-3, from 0: not helpful, 1: confirmatory only, 2: contributory, led to change in management/diagnosis, 3: determined diagnosis/directly led to management change). Comparisons were made between groups to the correlation between MRE findings and clinical activity and impact of the MRE on management. Results: 50 of 57 MREs met inclusion criteria. MRE was ordered in 1 patient in clinical remission and showed no activity. 57% of clinically severe cases had MRE scores of 3 or 4 and 75% had definite activity. In mild to moderate cases by symptoms, MRE was unlikely to show active disease with 68% having MRE scores of 1 or 2. With regard to clinical efficacy, CES >2 in 74% while MRE was considered not helpful once. MRE had the greatest impact when it was employed to differentiate active CD from other non-functional diagnoses. In this group, CES =3 in 60%. In the group with established CD where MRE was used to assess activity, CES = 3 in 29%. Conclusion: MRE findings correlate well with clinical activity in patients with severe CD and those in remission. Most patients with clinically mild to moderate disease activity did not have active disease by MRE. In these patients, MRE prevented escalation of therapy and led to the work-up of alternate diagnoses. Overall, MRE was a useful tool in this clinical setting, leading to management change in 66% of cases without use of ionizing radiation.