Use of Penrose drains to treat certain anal fistulas: a primary operative seton.

In 20 selected patients with a complex anal fistula, a seton consisting of a 1/4- to 5/8-inch Penrose drain was passed through the anal fistulous tract and then sutured to maintain tension. This elastic seton not only provides drainage of the fistulous abscess but also, by pressure necrosis of the enclosed sphincter muscle, "cuts through" the muscle and accomplishes primary fistulotomy or, when placed without tension, serves as a marker for later fistulotomy. All 20 patients had a good result. One patient complained of occasional leakage of mucus. Two others were periodically incontinent of loose stools but were socially continent and employable. Use of a seton should be considered in patients with complex fistulas that involve the puborectal muscle.