eP413 - Cutaneous Advancement Flaps for Distal Anal Fistulas: An Expert Center's 20-year Experience and Outcomes

Purpose/Background: Anal fistulas are a common, yet challenging, disease. Many treatment modalities have been described over time, but data is inconsistent regarding their individual recurrence and associated incontinence rates. Mucosal advancement flaps are among popular techniques, with highly variable recurrence rate, between 0 and 52%. Cutaneous advancement flaps can also be used for a variety of fistulas with distal internal opening. However, this technique and associated outcomes are rarely found in existing literature. This study aimed to determine the efficacy of cutaneous flaps, based on an expert center’s 20-year experience, with determination of targeted patients and surgical technique details.Methods/Interventions: This is a retrospective study, reviewing a single colorectal referral center’s experience and expertise. Adult patients who presented with anal fistulas and internal opening distal to the dentate line, who had been treated with a cutaneous advancement flap from 2002 to 2022 were included. Patients with Crohn’s disease or rectovaginal fistulas were excluded. Surgical features were detailed, recurrence and postoperative incontinence were specifically studied. Recurrences were classified as early or late, depending if they occurred sooner or later than 3 months postoperatively.Results/Outcomes: This study represents the largest reported cohort of cutaneous advancement flaps for anal fistulas. 58 patients were ultimately included and analyzed. Mean age at surgery was 48.21 (SD 11.54) and mean BMI 29.14 (SD 5.91). Of all patients, 65.5% were women, 17.2% were smokers, 5.3% diabetics, 74.1% had had previous anal fistulas, and 77.6% abscesses. 19% of patients had undergone previous fistulotomy at some point, 15.5% had had mucosal advancement flap and 62.1% seton placement. Most patients (95.7%) presented with a unique fistula tract, with higher proportions of anterolateral (39.7%) and trans-sphincteric (44.8%) tracts. During cutaneous flap surgery, 31% had concomitant mucosal flap, 51.7% had partial or complete fistulectomy, 89.7% had internal sphincter plication, 29.3% complete fistula tract curettage, 32.8% excision of external opening and 27.6% excision of internal opening.Recurrence rate was 31% (10.3% early-recurrence, 20.7% late-recurrence), with a median follow-up time of 106 days overall and 524 days for the recurrence group. Median recurrence timing was 136 days. BMI was slightly higher among patients with recurrence (28.45 vs 30.73, p=0.05), and they tended to be more frequently immunosuppressed (11.1% vs 0%, p=0.09). More patients with recurrence had undergone complete curettage of fistula tract during flap surgery (20.0% vs 50.0%, p=0.03). Among all of patients’ characteristics and surgical details, no other factors were associated with recurrences.Overall postoperative incontinence rate was 13.8%, but this outcome was most probably underreported. Of all patients with recurrence, 77.8% had follow-up surgery, with a majority of mucosal flap redo (55.6%).Conclusion/

Discussion: Cutaneous advancement flaps should be considered in the therapeutic armamentarium of distal anal fistulas. It most typically involves internal sphincter plication. It can be done as a single technique, or in combination with mucosal flap and fistulectomy. Associated recurrence rate appears to be within other techniques’ averages overall, without clear advantage. Future research should focus on cutaneous flap as a first-line treatment for distal fistulas, to assess its efficacy for non-recurring disease."Table 1: Patients’ characteristics with vs. without recurrence

Table 2: Postoperative outcomes
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