Characterization of Inflammation and Fibrosis in Crohn's Disease Lesions by Magnetic Resonance Imaging

OBJECTIVES: Measurement of the component of fibrosis in Crohn's disease (CD) may have important therapeutic implications. The aim of this study was to characterize the Magnetic Resonance Imaging (MRI) findings that are differentially associated with the presence of fibrosis and those associated with inflammatory activity, using the pathological analysis of surgically resected intestinal lesions as reference standard. METHODS: MRI studies with identical imaging protocol of 41 CD patients who underwent elective bowel resection within 4 months before surgery were reviewed. MRI evaluated wall thickening, edema, ulcers, signal intensity at submucosa at 70 s and 7 min after gadolinium injection, stenosis, and pattern of enhancement in each phase of the dynamic study and changes on this pattern over time. Pathological inflammatory and fibrosis scores were classified into three grades of severity. RESULTS: In all, 44 segments from 41 patients were analyzed. The pathological intensity of inflammation was associated with the following MRI parameters: hypersignal on T2 (P=0.02), mucosal enhancement (P=0.03), ulcerations (P=0.01), and blurred margins (P=0.05). The degree of fibrosis correlated with the percentage of enhancement gain (P<0.01), the pattern of enhancement at 7 min (P<0.01), and the presence of stenosis (P=0.05). Using percentage of enhancement gain, MRI is able to discriminate between mild-moderate and severe fibrosis deposition with a sensitivity of 0.94 and a specificity of 0.89. CONCLUSIONS: MRI is accurate for detecting the presence of severe fibrosis in CD lesions on the basis of the enhancement pattern.