Magnetic Resonance Enterography for the Assessment of Crohnʼs Disease: Changing Imaging Paradigms?

Abstract

Purpose: Advances in the immunopathogenesis and therapy of inflammatory bowel disease (IBD) coupled with bolder definitions of disease control have led to increasing reliance on imaging. Increased awareness of the potential downstream effects of ionizing radiation has placed more emphasis on radiationfree imaging. We assessed the role of magnetic resonance enterography (MRE) in assessing small bowel Crohn's disease (CD). Methods: We conducted a retrospective review of 250 MRE studies performed between June 2009 and August 2011 at our institution. Clinical data including demographics, disease characteristics and therapy were obtained from electronic patient record review. Inflammatory markers, radiological investigations and ileocolonoscopy when performed within 90 days of MRE were recorded. MRE reports were recorded using accepted activity criteria - small bowel dilatation, stenosis, wall thickening, enhancement, mucosal irregularity, mesenteric inflammation, hypervascularity, lymph node enlargement, abscesses, fistulation and extraintestinal features. Results: Of 122 patients with IBD at time of MRE, 109 had CD. Seventy-one of 122 patients were female, mean age 34 (range 16-68) and median disease duration of 4 years (range 0-39). Abnormalities were noted in 77 MRE scans; 54 had active non-stricturing, 22 active stricturing and 1 fibrostenotic disease. Within the active groups, there were 7 fistulae and 4 abscesses in 7 patients. Ileo-colonoscopy was performed in 22 of these patients with 19/22 showing active colitis and raised CRP in 24/46 within 90 days of MRE. Treatment was increased in 61% of the active non-stricturing group, 9/33 to azathioprine, 11/33 to infliximab, 4/33 to surgery, 6/33 received 5-ASA with no change in the remaining 39%, of whom 4/9 had normal ileo-colonoscopy and 16/19 normal CRP. In 68% of active stricturing group, treatment was increased to azathioprine in 2, biologics (8) and 5 to surgery. Eight of 22 patients in this group had an elevated CRP and 5/8 had active colitis at ileo-colonoscopy. Of 31 normal MRE, treatment was not increased in 97%. Of these, CRP was normal in 25/29 and ileo-colonoscopy normal in 6/12. The fibrostenotic subject had normal CRP and mild colitis at colonoscopy, and proceeded to surgery. Of the abscess/fistula group 2 were referred for surgery, 3 started infliximab (fistula) and 2 were treated with antibiotics. Conclusion: The small bowel remains difficult to assess endoscopically. The choice of investigation will be driven by the clinical question, available expertise and economic factors. MRE adds to assessment of patients with CD, in addition to endoscopy and biological markers identifying patients with active disease where treatment escalation may result in meaningful benefit.