The role of 3-dimensional anorectal ultrasonography in the assessment of anterior transsphincteric fistula.

Purpose: The aim of this study was to evaluate the role of 3-dimensional anorectal ultrasonography in the choice of surgical technique according to the position of the fistulous tract in patients with anterior transsphincteric anal fistula.

Methods: A total of 33 patients (18 male) with anterior transsphincteric fistulas were evaluated by ultrasonography. The length of the external and internal anal sphincters, the position of the internal opening, the length of the compromised sphincter, and the percentage of sphincter muscle to be transected during surgery were measured, compared between sexes, and used in planning the surgery. Postoperative incontinence symptoms were quantified with a Wexner score.

Results: The external and internal sphincters were longer and the position of the internal opening was higher in males. The position where the tract crossed the external sphincter was in both sexes, but the percentage of compromised muscle was higher in females because of the smaller length of the external sphincter. Seton placement followed by fistulotomy or advanced flap repair were indicated in 11 of 18 males and 13 of 15 females as the tract crossed the external sphincter above 50.0%. The mean postoperative follow-up was 12 months. Overall, minor fecal incontinence symptoms were identified in 16 (48.0%) patients. Of these, 11 (73.0%) females and 5 (28.0%) males had a mean incontinence score of 2.9 and 3.0, respectively.

Conclusions: Three-dimensional ultrasonography was shown to be useful in the preoperative assessment of anterior transsphincteric fistulas by quantifying the length of muscle to be transected, contributing to the choice of a safe treatment approach and to the reduction of the rate of postoperative continence disorders.