Review ArticlesMRI of Perianal Crohn Disease Technique and InterpretationSantillan, Cynthia S. MD∗; Huang, Chenchan MD†; Eisenstein, Samuel MD‡; Al-Hawary, Mahmoud M. MD§Author Information ∗Department of Radiology, University of California, San Diego, CA †Department of Radiology, New York University Langone Health, New York, NY ‡Department of Surgery, University of California, San Diego, CA §Department of Radiology, University of Michigan Health System, Ann Arbor, MI. Address correspondence to Cynthia S. Santillan, MD, University of California, San Diego Medical Center, 200 West Arbor Dr 8756, San Diego, CA 92103 (e-mail: [email protected]). Received 26 October, 2020 Accepted 13 November, 2020 Santillan should have listed as “Consultant for Alimentiv”. The remaining authors report no conflicts of interest. Topics in Magnetic Resonance Imaging: February 2021 - Volume 30 - Issue 1 - p 63-76 doi: 10.1097/RMR.0000000000000268 Buy Metrics Abstract Magnetic resonance imaging (MRI) has emerged as the imaging method of choice for evaluation of perianal fistulizing disease. As treatment of Crohn disease and associated perianal fistulas has evolved to include a combination of systemic treatments and surgical interventions, perianal MRI provides critical information to guide treatment selection and timing. Radiologists need to be familiar with the normal regional anatomy to accurately describe perianal fistulas and any associated complications which can then be used to classify fistulas based on several available classification systems. Following treatment, MRI can provide information that suggests treatment success or failure. We propose a perianal fistula reporting template that includes the necessary information to convey fistula complexity, guide treatment, and evaluate treatment response. This review article will also discuss the postoperative appearance of many treatments currently used for management of perianal fistulizing disease and some associated complications. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.