EP918 - Clinical efficacy and safety of the bared external anal sphincter (BEAS) in high horseshoe-shaped anal fistula

Purpose/Background: High horseshoe-shaped anal fistula (HHAF) is a complex disease manifesting in the perianal region, typically requiring surgical intervention for treatment. However, the current therapeutic approaches are significantly challenged by the high rates of postoperative recurrence and anal incontinence. To overcome the limitations of traditional surgical approaches, we introduces the bared external anal sphincter (BEAS) technique. Our study aims to evaluate the differences in clinical efficacy between BEAS surgery and the modified Hanley procedure in a real-world setting.

Methods/Interventions: This study is a single-center, prospective cohort study to be conducted in a tertiary hospital in China, aimed at tracking the short-term clinical efficacy and safety of patients with HHAF who undergo BEAS surgery and modified Hanley surgery from November 2023 to September 2024. Utilizing data from the prospective database of this tertiary referral hospital, the study seeks to provide insights into the clinical outcomes of these surgical treatments. The steps of BEAS surgery are shown in Figure 1. The primary outcome of this study is the wound healing rate within six months, while the secondary outcomes include the time to return to work/activities, the maximum Visual Analog Scale Pain Score (VAS-PS) within the 1 to 5 days post-surgery, and the Cleveland Clinic Florida Incontinence Score (CCF-IS) and Quality of Life in Anal Fistula Questionnaire Score (QoLAF-QS) at 1 month, 3 months, and 6 months postoperatively. P< 0.05 was statistically significant, and all statistical tests are bilateral.

Results/Outcomes: During the study period, a total of 18 patients completed the 6-month follow-up. There were no statistically significant differences in gender, age, or BMI between the two groups. The primary outcome measure, 6-month wound healing rate, showed no statistically significant difference between the groups. Regarding secondary outcomes, there was no significant difference in the time required for patients to return to work. Postoperatively, both groups exhibited a significant increase in VAS-PS, CCF-IS, and QoLAF-QS scores, which gradually decreased over time; however, there were no statistically significant differences in these score metrics at any time point. Baseline characteristics and detailed outcome measures are presented in Figure 2.

Conclusion/Discussion: This study is the first cohort study to evaluate the differences in therapeutic outcomes between BEAS surgery and the modified Hanley procedure. By conducting a detailed observation of the efficacy and treatment results of these two surgical methods, this study aims to reveal their differences in clinical effectiveness and provide evidence-based support for future randomized controlled trials (RCTs). Currently, the evaluation of this study is based on a relatively small sample size, which allows us to preliminarily conclude that the BEAS surgical approach exhibits comparable safety and efficacy to conventional methods in the treatment of high transsphincteric anal fistulas. However, for more robust conclusions, further research with larger sample sizes is necessary to generate statistically more reliable and valid data.

Figure 1
(a) IS approach. (b) LES approach. The dissection of LES approach is along the outer edge of the EAS to bare the EAS. (c) Exposure of DPIS and DPAS. Expose DPIS and DPAS to reach the fistula through IS approach and LES approach, respectively. (d) Determination of the internal opening location (e) Musculomucosal flap and EAS advancement. Advance the musculomucosal flap and the EAS to ensure that the internal opening can reach the lower edge of the EAS without tension. Subsequently, close the IS approach using interrupted sutures while maintaining the LES approach. (f) Postoperative drainage. Maintain the LES approach opening, and pack the fistula tract with povidone-iodine gauze for postoperative drainage. Place a seton from the fistula tract to the LES approach for continuous drainage. IS=Intersphincteric; LES=Lateral-external-sphincteric; EAS=external anal sphincter; DPIS=deep intersphincteric space; DPAS=deep postanal space.

Figure 2
Baseline characteristics and detailed outcome measures.