Background Radiological evaluation plays a critical role in the investigation of inflammatory bowel disease (IBD). Primarily, its role is in diagnosing lesions in the small bowel from the distal duodenum to the terminal ileum. Repeated exposure to ionising radiation is a concern particularly for those patients with early onset IBD who will require multiple diagnostic imaging procedures. MRI of the small bowel has been made possible with the development of rapid scanning techniques.
Aims To assess the reliability of MRI in assessing extent and activity of IBD.
Methods Over a one-year period all patients being investigated for suspected IBD or patients with existing IBD who required reassessment of small bowel disease, underwent MRI small bowel with enteral and intravenous contrast. T1 and T2 weighted images pre contrast with T1 volumetric images following intravenous contrast were obtained within weeks of concurrent upper GI endoscopy and ileocolonoscopy. Comparison of MRI findings was made with endoscopic findings and histopathology of biopsies obtained. Kappa's coefficient was used to determine correlation.
Results MRI small bowel was carried out in 58 patients (27 female; 31 male) (mean age 13.4 years (6–17years)); 34 patients had an MRI as part of the primary evaluation for suspected IBD; 3/34 patients did not have features of IBD on MRI examination or on endoscopic evaluation; 17/31 patients had Crohn's disease (CD), 9/31 had ulcerative colitis and 5/31 had IBD-unclassified. Of 17 patients with CD, 13 had features of small bowel disease on MRI small bowel study (76%); 1 patient with CD had isolated MRI small bowel changes (ileitis) without endoscopic or histology changes; 4 patients had a diagnosis of CD based on MRI small bowel changes where it was impossible to classify colitis detected on endoscopy/histopathology alone. MRI small bowel study was performed on 24 patients with pre-existing CD; 15/24 had MRI changes (63%). There was significant agreement between active ileal CD on MRI and histopathology/gross endoscopy.
Conclusion In the investigation of paediatric IBD, MRI small bowel may offer an alternative method of detecting small bowel disease. MRI ileal disease agrees closely with histopathology and/or gross endoscopy. The absence of radiation and the potential to identify subtle inflammation, active inflammation in strictured areas, extraintestinal manifestations, and colorectal disease offer distinct advantages over fluoroscopic studies.