Magnetic resonance imaging of perianal fistulas.

Most cases of fistula-in-ano are nonspecific and result from inflammation of anal glands and crypts (cryptoglandular). The classification of cryptoglandular fistulas depends on the degree of involvement of the anal sphincter complex and determines the type of treatment. Studies have shown that preoperative MR imaging revealed important additional information compared with surgery alone and better predicts clinical outcome of patients with fistula-in-ano than initial surgical exploration. With the emergence of novel surgical treatments like MRI-guided surgery, laser, and adhesive treatments, MR imaging is a mainstay for preprocedural and intraoperative evaluation to ensure the adequacy of the procedure.