Seton tube placement involves passing a tube from the skin into the fistula entering the anal canal. Tube is then pulled through to the anal verge and joined to the skin end to form a loop.  It is left in situ for weeks to months to allow adequate drainage of the fistulous tract prior to fistulectomy. In some cases it is placed under tension (so-called "cutting seton") and periodically tightened such that it slowly pulls through to the outside via the sphincters allowing them to heal slowly behind the tube, reducing the risk of fecal incontinence.