MRI of Crohn?s Anoperineal Disease

Abstract

Anoperineal involvement is seen in up to 38% of patients with Crohn's disease. To adopt the best treatment strategy and avoid recurrences, it is important to obtain precise radiological information of the fistulous track. Magnetic resonance imaging provides precise information on the anatomy of the anal canal, the anal sphincteric complex, and the relationship of the fistula to the pelvic floor structures. In this article we review the anatomy of the anal canal, the pathogenesis of perianal fistula, different MRI sequences for the evaluation of fistula with emphasis on their imaging findings and an MR imaging based grading system for their classification.