Role of magnetic resonance imaging in evaluation of the activity of perianal Crohn's disease

Aim: To evaluate the diagnostic ability of contrast-enhanced Magnetic Resonance Imaging (MRI) in assessment of the activity of perianal fistulas in Crohn's disease (CD) patients, compared to clinical data. Materials and methods: Fifty CD patients (25 men; mean[SD] age: 40.4[12.6] years) with known or suspected perianal fistulas underwent perianal space MRI. Radiological activity of disease was measured as the percentage increase (PI) of ROI values of fistulas in relation to ROI values of healthy local fat, after contrast administration. Clinical activity of disease was defined according to Perianal Disease Activity Index (PDAI) and Fistula Drainage Assessment (FDA). Results: Forty-two patients presented perianal disease at MRI (55 fistulas identified). An association between both fistula's PI and PDAI (Pearson's coefficient 0.512, p < 0.0001) and between PI and FDA (p = 0.003) was demonstrated. Areas under ROC curves of PI values in relation to PDAI and FDA were respectively 0.876 [95% CI = (0.743-1.00), p < 0.001] and 0.784 [95% CI = (0.588-0.980), p = 0.003]. A cut-off value of PI, calculated on these preliminary data, correctly classified more than 90% of fistulas. Conclusions: Contrast-enhanced MRI with PI calculation offered practical information about activity of perianal fistulas and might be helpful in providing a comprehensive evaluation of CD perianal disease. (C) 2011 Elsevier Ireland Ltd. All rights reserved.