[Imaging diagnosis of perianal fistula in Crohn disease]

Anal fistula is the most common perianal lesion in Crohn disease (CD), which usually is complicated and difficult to treat, and has a high recurrence rate and serious influence on the quality of life of patients. Inaccurate or incomplete intervention may result in irreversible damage. In order to achieve the best outcome, an optimal disease assessment is crucial. Many imaging modalities are useful for the evaluation of perianal fistulas in CD, which may help confirm the diagnosis, accurately classify the disease, plan the most suitable treatment, and monitor the efficacy. Magnetic resonance imaging (MRI), endoscopic ultrasonography (EUS) and anal endosonography (AES) are considered to be the suitable options for evaluation of the initial perianal fistula, both in terms of sensitivity and specificity, while MRI is more suitable for monitoring the curative efficacy. Fistulography (by X ray or CT) is generally less applied due to inferior soft tissue performance, radiation exposure, etc. This paper reviews the various imaging modalities, analyzes their advantages and disadvantages in order to assist clinicians in selecting the most appropriate examination individually.