Purpose: A study of 523 fistulas of cryptoglandular origin operated on between January 1985 and December 1991 at the Lehigh Valley Hospital was undertaken for the purpose of establishing whether the "so-called" simple fistula-in-ano has a favorable outcome. High transsphincteric fistulas with or without high blind tract, suprasphincteric, extrasphincteric, and horseshoe fistulas as well as fistulas associated with inflammatory bowel disease were excluded.
Methods: Four-hundred sixty-one patients with anal fistulas classified as simple fistulas-in-ano (uncomplicated transsphincteric, low and high blind track intersphincteric) were studied retrospectively. There were 310 males and 151 females with an average age of 42 years and mean follow-up of 34 months.
Results: Thirty (6.5 percent) patients developed recurrent fistulas: 16 (53.3 percent) because of missed internal openings at initial surgery, six (20 percent) attributed to missed secondary tracks, five (16.7 percent) because of premature fistulotomy wound closure, and three (10 percent) because of miscellaneous factors.
Conclusion: All so-called simple fistulas-in-ano may not have readily detectable primary openings and may possess secondary tracks which preclude their behavior as simple fistulas.