Purpose <p>For treating complex transsphincteric fistula, a two-stage approach is usually administered: an initial seton placement followed by a sphincter-sparing procedure. However, success rates are not optimal. This study aimS to describe the modified transanal opening of the intersphincteric space (TROPIS), a single-staged procedure for managing transsphincteric fistula with or without concurrent anorectal abscess, and to compare its efficacy with the LIFT.</p> Methods <p>Thirty-six patients who presented with mid-high transsphincteric fistula with or without associated anorectal abscess and consented to the procedure from 2020 to 2023 were managed with modified TROPIS. The primary outcome measures were recurrent fistulas and fecal continence. These results were compared with our previous study data of 24 patients who underwent LIFT procedure from 2011 to 2013.</p> Results <p>Thirty-six patients received modified TROPIS; nine (25.0%) had an associated ischiorectal abscess. At the 8-month and 14-month follow-up, zero patients experienced fistula recurrence or fecal incontinence. In comparison with our previous study, 24 patients with transsphincteric fistula with or without associated abscess were treated with initial seton placement, then LIFT. With a follow-up range of 14–36&#xa0;months, five (20.8%) patients presented with recurrent fistulas; no patients experienced fecal incontinence. These results were statistically significant.</p> Conclusions <p>Our results reflect that modified TROPIS is a safe, simple, and effective procedure for treating patients with transsphincteric fistula with or without associated abscess. Patients healed with no fistula recurrence, which is significant in comparison with previous patients treated with LIFT. Modified TROPIS does not require an initial seton placement for managing transsphincteric fistula with associated abscess.</p>