For the patient in the preceding question, appropriate management includes which of the following?

c. Division of the internal anal sphincter using electrocautery, encircling the external sphincter with a seton

In young patients, transection of internal and external sphincter muscles in the posterior half, when performed in the course of a fistulotomy, does not always jeopardize anal continence. In older patients and in women, however, transection of the external sphincter muscle, particularly in the anterior half, risks incontinence. When external sphincter transection appears likely, some authors recommend the use of a seton. A seton is a suture that is drawn through a fistula. The rationale for using a seton is to create fibrosis. The seton is threaded through the fistulous track and tied over the muscles. In the second stage (average interval, 6 to 8 weeks), fistulotomy is performed. Incontinence after the proper use of seton is uncommon, even when the fistula is deep.