Clinical relevance of transabdominal ultrasonography and magnetic resonance imaging in patients with inflammatory bowel disease of the terminal ileum and large bowel.

Background: Ileocolonoscopy represents the diagnostic standard in the work-up of patients with inflammatory bowel diseases (IBD). Patients are often reluctant to be colonoscoped because of the invasiveness and pain sensation during colonoscopy.
Aims: To compare the usefulness oftransabdominal ultrasound (US) and magnetic resonance imaging (MRI) in assessing disease extension and activity in patients with IBD restricted to the terminal ileum and large bowel.
Patients and Methods: 61 patients with IBD [37 Crohn's disease (CD) and 24 ulcerative colitis (UC)] were prospectively studied. All patients underwent clinical and laboratory assessment, ileocolonoscopy, transabdominal sonography, and MRI within 5 days. Involved bowel segments were defined as those with bowel wall thickness >3 mm and increased Doppler signal on US or contrast enhancement of the bowel wall on MRI. To compare disease activity endoscopic, MRI and US findings were graded with newly developed scores.
Results: The segment-by-segment analysis revealed an overall accuracy of 89% for US and 73% for MRI in identifying active IBD. The accuracy was better in patients with UC than in patients with CD for both US and MRI. The endoscopic activity index (EAI) correlated stronger with the US activity index (r = 0.884) than with the MRI activity index (r = 0.344). The correlation of US and MRI activity indices with EAI was better in patients with UC compared with patients with CD. All three imaging methods showed a significant correlation with clinical disease activity in patients with UC but not in patients with CD.
Conclusion: This study provides strong evidence that US should be considered as a first-choice method for follow-up of patients with IBD of the terminal ileum and large bowel.