Japanese Practice Guidelines for Anal Disorders II. Anal fistula

Anal fistulas usually result from an anal gland infection in the intersphincteric space, which is caused by bacteria entering through the anal crypt (cryoptglandular infection). Reports of anal fistulas have been as high as 21 people in 100,000. Anal fistulas are 2-6 times more prevalent in males than females, with the condition occurring most frequently in patients in their 30s and 40s. Anal abscess symptoms include sudden onset of anal pain, swelling, redness, and fever. Purulent discharge or intermittent perianal swelling and pain are most often consistent with anal fistula symptoms. Methods for diagnosing anal fistulas include visual inspection, palpation, digital examination, anoscopic examination, barium enema, fistulography, as well as imaging, such as ultrasound, CT, and MRI. Parks classification is widely adapted in the West; however, Japan usually employs Sumikoshi classification. Antibiotics should be administered in cases of perianal abscess with surrounding cellulitis, or concomitant systemic disease, or those not alleviated by incision and drainage. The site and size of incision and drainage depend upon the abscess type and location. Incisions should be performed taking care not to damage the sphincter muscles and with possible future fistula surgery in mind. As spontaneous recovery is rare, except in the case of children, surgery is the principle approach to anal fistulas. Several approaches are utilized for anal fistulas. A specific procedure may be chosen depending upon curability and anal function. Postsurgical outcomes vary from study to study. Fecal incontinence may occur after fistula surgery, but reports vary.