A. Usui1, Y. Ishiyama1, A. Nishio1, M. Kawamura1, Y. Kono1, G. Ishiyama1 1Sapporo Ishiyama Hospital,Sapporo, HOKKAIDO, Japan
Introduction: Horseshoe fistulas are deep posterior anal fistulas which extend into the ischiorectal space in the shape of a horseshoe, involving muscle structure associated with continence. Surgical management is challenging due to its complex configuration and sphincter involvement. Failures in surgery for horseshoe fistulas often are attributed to insufficient drainage of the fistula or unsuccessful eradication of the fistula. These issues can be resolved with complete fistulotomy, which has been discredited for its high rate of incontinence, but recent studies have shown severance of the superficial external sphincter does not affect continence. We have chosen complete fistulotomy as the initial procedure of choice for horseshoe fistulas and divided the procedure in two stages to avoid impairment of sphincter function.
Methods: A retrospective review of 139 patients who underwent surgery for horseshoe fistula using this method between 2014 and 2017 was conducted. Incisions for the initial surgery were placed along the extended fistula arms so that the lateral tracts of the horseshoe were deroofed. The large open wound allowed a wider view enabling the eradication of fistula walls with a direct vision of the sepsis origin, as well as easier drainage. A loose seton was placed in the primary tract through the fistula origin which was laid open in the second surgery after the lateral wound was partially healed.
Results:
Fistula tracts extended into the supralevator space in 14 of the patients. An upward intersphincteric extension to the submucosa of the rectum was observed in 15. Twenty-one patients (15.1%) had undergone previous surgery intended to cure a lower anal fistula, implying the difficulty in accurate diagnosis for deep posterior anal fistulas.
All patients were followed up for a median of 22 months (range 3-53) and recurrence was observed in 12. In all but 1 patient, recurrence occurred as a superficial residual infection with the sepsis origin cured. Recurrence rate was 5.41% in those with tracts extending only to the ischiorectal fossa. Those with fistula extending higher intersphincterically had a significantly higher recurrence rate. Furthermore, patients who resided further than 50km from the hospital and could not visit the outpatient clinic frequently also had a significantly higher recurrence rate, indicating wound observation for premature closure is crucial in preventing recurrence. In regard to anal sphincter function, no patient had any continence issues including minor problems at the end of the follow up period.
Conclusion:Managing horseshoe fistula with the two-stage complete fistulotomy approach allows for complete eradication of the fistula tract without compromising anal sphincter function.