MRI of perianal crohn's disease

Perianal disease is a common complication in Crohn's disease and imaging helps the clinician in the diagnosis and decisions regarding therapeutic strategy. Pelvic MRI is the recommended imaging modality because of its accuracy and advantages compared to other imaging techniques. Specific sequences and planes are mandatory for adequate assessment of perianal Crohn's disease. It is important to understand the perianal anatomy to adequately describe the anatomical location and extension of fistula. Other aspects in the assessment of perianal disease on MRI include the assessment of fistula activity, presence of abscesses and proctitis, and assessment of response to therapy. This chapter provides an overview of technical MRI features, pelvic anatomy, and different aspects of perianal Crohn's disease on MRI for an adequate diagnostic workup.