Anal Fistula in Crohn’s Disease

Transmural bowel inflammation in Crohn’s disease (CD) is associated with the development of fistulas, which are tracts or communications that connect two epithelial-lined organs. Common sites for fistulas connect the intestine to bladder (enterovesical), to skin (enterocutaneous), to bowel (enteroenteric), and to the vagina (enterovaginal). Anorectal fistulas (often called fistula in ano or cryptogenetic fistulas) is defined by an abnormal communication between the epithelialized surface of the anal canal and (usually) the perianal skin, and represent one of the major perianal complications of CD. The lifetime risk for developing a fistula in CD patients is approximately 25–50 %, while rectovaginal fistulas accounted for 9 %. The development of perianal fistulas can result in considerable morbidity and inaccurate diagnosis before treatment may lead to irreversible functional consequences.