Outcomes of Transanal Advancement Flap Repair and Hybrid Seton Placement in 84 Patients With Transsphincteric Anal Fistula

Introduction

Transsphincteric anal fistulas are a particularly challenging subset of anorectal disorders due to their complex anatomy and proximity to critical sphincter muscles. These fistulas, which traverse both the internal and external sphincter muscles, can result in significant morbidity and diminished quality of life if not properly managed [1]. The principal challenge in their treatment lies in achieving complete fistula healing while preserving continence and minimizing postoperative complications [2,3]. The incidence of anorectal fistulas is estimated to be approximately 8.6 cases per 100 000 individuals annually, with higher prevalence rates in males. Fistulas are commonly classified using the Parks classification into intersphincteric, transsphincteric, suprasphincteric, and extrasphincteric types. Diagnosis relies on a combination of clinical examination and imaging, with magnetic resonance imaging (MRI) considered the standard method due to its high sensitivity in delineating fistula tracts and detecting associated abscesses. Proper classification and diagnosis are essential to guide appropriate management and optimize surgical outcomes [4].

A variety of surgical techniques have been developed to address transsphincteric fistulas, with transanal advancement flap repair (TAFR) and seton-based approaches among the most widely used [5]. The TAFR technique involves mobilization and advancement of a rectal mucosal flap to cover the internal fistula opening, promoting healing while attempting to preserve sphincter function [2]. Neverthless, the hybrid seton placement (HSP) technique employs an approach using a combination of cutting and draining seton stitches to progressively divide and heal the fistula tract while maintaining sphincter integrity [6]. Previous studies have reported healing rates of approximately 75% for transanal advancement flap and 87% for hybrid seton procedures, both associated with relatively low risk of incontinence [7,8].

Various surgical techniques have been described for the treatment of transsphincteric anal fistulas, including different types of seton placement [6,9,10], TAFR [2], ligation of the intersphincteric fistula tract (LIFT) [11], fibrin glue application [12], video-assisted anal fistula treatment (VAAFT) [13], and fistula tract laser closure (FiLaC) [14]. However, there is a lack of comprehensive studies in the literature comparing the superiority of these methods. As a result, determining the most effective and reliable technique for managing this often challenging condition remains a persistent concern for colorectal surgeons.

Among the various surgical options for transsphincteric anal fistulas, TAFR and HSP are 2 frequently used techniques. TAFR aims to preserve sphincter integrity by covering the internal opening with a mobilized mucosal flap, while HSP combines drainage and gradual fistula tract closure using a staged seton stitch approach. Given their technical differences and distinct healing mechanisms, it is essential to evaluate and compare their effectiveness and effect on functional outcomes. To objectively assess postoperative continence and quality of life, standardized scoring systems such as the Cleveland Clinic Incontinence Scoring (CCIS), which evaluates the severity and frequency of incontinence, and the Fecal Incontinence Quality of Life (FIQL) scale, which measures the psychosocial impact of incontinence, are widely utilized in clinical studies and surgical outcome comparisons [15,16].

Therefore, this retrospective study from a single center included 84 patients who underwent surgery for transsphincteric anal fistula between July 2022 and December 2024 using TAFR and HSP and aimed to evaluate postoperative outcomes.

Material and Methods

ETHICS APPROVAL:

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study was approved by the Local Ethics Committee of Gazi University (reference: 14.01.2025–95). Written informed consent was obtained from all patients before the surgical procedures.

STUDY DESIGN:

This retrospective observational study included a total of 84 patients with transsphincteric anal fistula who underwent TAFR or HSP between 2022 and 2024 at our tertiary institution.

DIAGNOSIS AND PREOPERATIVE EVALUATION:

All patients included in the study were diagnosed with transsphincteric anal fistula using a combination of clinical and radiological assessment. The diagnosis was initially suspected based on physical examination, including inspection and digital rectal examination to identify the fistula’s external and internal openings. To confirm the diagnosis and assess the extent and complexity of the fistula tract, pelvic magnetic resonance imaging (MRI) was performed in all cases. MRI was used to delineate the trajectory of the tract, its relationship with the sphincter complex, and to detect any associated abscesses, including their size and location. The classification of the fistulas was based on the Parks system.

Prior to surgery, all patients underwent a thorough clinical evaluation, including detailed medical history, physical examination, and routine preoperative laboratory testing, to ensure fitness for surgery. Group allocation was determined by the surgeon based on clinical factors and personal preference; no randomization was performed. All patients provided written informed consent for both the surgical procedure and the anonymous use of their clinical data for scientific purposes.

SURGICAL PROCEDURES:

Hybrid Seton Placement: HSP was performed as described by Ege et al [6]. Briefly, the fistulous tract was gently probed and the portion outside the sphincter was laid open and curetted. A double-strand elastic seton stitch, prepared from a thin circular strip of a surgical glove, was then placed through the sphincter tract and tied over itself without excessive tension. This provided a slow and stable cutting action, eliminating the need for postoperative adjustments (Figure 1). A loose seton stitch was used for patients with complex fistula anatomy or accompanying abscesses, and was not routinely applied in all HSP cases.

Transanal Advancement Flap Repair: In patients selected for TAFR, surgery was performed under regional anesthesia in lithotomy or jack-knife position. After excision of the mucosal component of the internal opening and curettage of the fistula tract, the internal opening was closed at the muscular level using absorbable sutures. The integrity of the closure was verified by instillation of hydrogen peroxide through the external opening to ensure there was no leakage. Subsequently, a U-shaped rectal mucosal flap was advanced to cover the internal opening and secured with absorbable sutures, while care was taken to ensure adequate vascularity and a tension-free closure. In TAFR, a loose seton stitch was always placed initially to mature the tract (Figure 1).

DATA COLLECTION:

Patient data were retrospectively collected from medical records of individuals who underwent surgical treatment for transsphincteric anal fistula. Demographic characteristics, type of surgical intervention, and follow-up durations were recorded. Functional outcomes were assessed using the Cleveland Clinic Incontinence Score (CCIS) and the Fecal Incontinence Quality of Life (FIQL) scale [15,16]; both were completed at the 6-month postoperative follow-up and were filled out in a manner allowing direct comparison with preoperative baseline values. Additionally, recurrence, incontinence status, and anal soiling were documented.

POSTOPERATIVE EVALUATION AND FOLLOW-UP:

All patients were evaluated through routine outpatient follow-up visits conducted at the 1^st postoperative week, 1^st month, and 6^th month. Patients were followed for a minimum of 6 months and up to a maximum of 24 months. In cases where changes in clinical findings were observed after the 6^th month, patients were re-evaluated and their condition was reassessed accordingly. In the TAFR group, postoperative care included fecal suppression with oral diphenoxylate-atropine combination (2.5/0.025 mg) for the first 3 days, accompanied by a clear liquid diet during this period. At the 1^st postoperative week, a gentle digital rectal examination was performed to evaluate the integrity of the advancement flap. In the HSP group, patients were advised to consume a high-fiber diet that avoided spicy and irritant foods. The seton stitch typically fell off spontaneously by the 1^st month of follow-up. In rare cases where spontaneous detachment did not occur, the remaining fibrotic tissue was incised and the seton stitch was removed under local anesthesia in an outpatient setting.

INCLUSION AND EXCLUSION CRITERIA:

The study included adult patients aged 18 years and older who underwent either TAFR or HSP for transsphincteric anal fistula. Anal fistula types other than transsphincteric fistulas were excluded from the study. Most patients included in the study had previously undergone loose seton placement and were subsequently scheduled for routine second-stage surgery. Patients other than these, who had undergone additional surgical procedures that could affect sphincter function, were excluded from the study, as were patients with rectovaginal fistulas or those with fistulas secondary to Crohn’s disease. Individuals with comorbidities or psychological conditions that could potentially affect continence or quality of life assessments were also excluded.

STATISTICAL ANALYSIS:

All statistical analyses were performed using SPSS Statistics Version 23.0 (IBM Corp., Armonk, NY, USA). The distribution of continuous variables was assessed using the Kolmogorov-Smirnov test. Descriptive statistics were expressed as mean±standard deviation (SD) for normally distributed variables, and as median with minimum and maximum values for non-normally distributed variables. Categorical variables are presented as frequencies and percentages.

Comparisons between the 2 surgical groups were conducted using the independent samples t test for normally distributed continuous variables, and the Mann-Whitney U test for non-parametric data. For within-group comparisons (preoperative vs postoperative), paired sample t tests or Wilcoxon signed-rank tests were used, depending on the distribution of the data. Categorical variables were analyzed using the chi-square test or Fisher’s exact test as appropriate.

A post hoc power analysis, based on the observed difference in FIQL scores, demonstrated that the study had greater than 80% power to detect clinically meaningful differences between groups at a significance level (α) of 0.05. Additionally, effect sizes were calculated for the main outcome measures to assess the clinical relevance of findings. A P value of less than 0.05 was considered statistically significant.

Results

PATIENT DEMOGRAPHICS AND SURGICAL DISTRIBUTION:

Of 84 patients, 21 (25%) were female and 63 (75%) were male, with a mean age of 45.1 years (range: 21–69) (Table 1). TAFR was performed on 36 patients, while 48 patients underwent HSP.

POSTOPERATIVE FUNCTIONAL OUTCOMES:

Among the 2 surgical groups, anal soiling was significantly more frequent in patients treated with HSP compared to those who underwent TAFR (P=0.035). No statistically significant differences were observed between the groups in terms of recurrence rates (6.2% vs 11.1%, P=0.45) or any of the 4 types of fecal incontinence evaluated: solid, liquid, gas, and overall. Both surgical approaches demonstrated comparable outcomes regarding continence and recurrence, with the exception of a higher incidence of soiling in the HSP group. Healing rates were 93.7% and 88.8% for TAFR and HSP, respectively (P=0.46). (Table 2)

CONTINENCE EVALUATION (CCIS SCORES):

At baseline, 23.8% of patients had some degree of fecal incontinence, as indicated by CCIS scores ranging from 0 to 8. Following surgery, this proportion increased to 27.4%, with postoperative CCIS scores ranging from 0 to 13. Most patients (n = 61) had no change in incontinence status. However, 11 patients experienced a deterioration, while 12 patients showed an improvement in their continence scores. There was no statistically significant difference in CCIS score improvement between the TAFR and HSP groups (P=0.6586) (Figure 2).

QUALITY OF LIFE ASSESSMENT (FIQL SCORES):

Both surgical groups demonstrated statistically significant improvements in FIQL scores after surgery (P<0.001 for both TAFR and HSP). Patients in the TAFR group had an increase in mean FIQL score from 54.33 to 106.56, while those in the HSP group improved from 56.50 to 99.98. Although both techniques effectively enhanced quality of life, the magnitude of improvement was significantly greater in the TAFR group (52.22 vs 43.48, P=0.0129), suggesting a potential advantage of TAFR over HSP in this regard (Figure 3).

Discussion

This study aimed to evaluate and compare the clinical outcomes of 2 widely used surgical techniques – TAFR and HSP – in the management of transsphincteric anal fistulas. Both TAFR and HSP demonstrated favorable clinical outcomes in the management of transsphincteric anal fistulas. While no significant differences were observed between the 2 techniques in terms of recurrence rates or fecal incontinence subtypes (solid, liquid, gas, overall), patients in the TAFR group had a significantly lower incidence of anal soiling. Postoperative healing rates were comparable. FIQL scores significantly improved in both groups after surgery, but the degree of improvement was greater in the TAFR group, suggesting a better effect on patients’ quality of life. Although a small proportion of patients experienced worsening of continence based on CCIS scores, no statistically significant differences in CCIS score changes were found between the 2 surgical methods. Although many studies in the literature have shown that both surgical options yield favorable outcomes and improve patients’ symptoms, no clear superiority has been demonstrated among the various surgical techniques used in the treatment of anal fistulas. There are only a limited number of studies comparing seton placement and TAFR [17], and to date, no study has compared HSP with TAFR.

In the study by Jafar et al, TAFR was associated with lower rates of recurrence and wound infection compared to seton placement [18]. In our study, however, no statistically significant difference was observed in recurrence rates between the 2 groups.

Many studies in the literature have reported that HSP and other seton techniques are associated with low complication rates and high healing rates [6,18]. Similar outcomes were observed in our study. Consistent with the findings of Gulen et al, a significant improvement in FIQL scores was also detected [19]. In contrast to these results, studies by Hamalainen et al and Richie et al reported high recurrence and incontinence rates with cutting seton techniques [20,21].

In the study by Jayarajah et al, a significant improvement in FIQL scores was observed following surgical intervention; however, a decline in CCIS scores was also reported, indicating an increase in minor incontinence symptoms. In contrast, our study demonstrated a significant improvement in FIQL scores, with no statistically significant change in CCIS scores. Furthermore, the TAFR group had superior functional outcomes, with significantly higher FIQL scores [22].

Our study found that both TAFR and HSP are effective surgical options for managing transsphincteric anal fistulas, with comparable outcomes in terms of continence preservation. However, TAFR was associated with significantly less postoperative anal soiling than HSP. These findings are in line with the broader literature supporting TAFR as a sphincter-preserving technique that maintains high healing rates and minimizes complications. Jarrar et al reported that advancement flap repair achieved a healing rate of 88% in complex fistulas and emphasized its advantage in preserving continence and avoiding the morbidity associated with cutting seton stitches [23]. In our study, although recurrence rates were comparable between the 2 groups, the lower incidence of anal soiling and the greater improvement in quality-of-life scores observed in the TAFR group suggest a potential functional advantage. These findings support the use of both techniques as viable options, but indicate that TAFR may be preferable in patients where postoperative continence and comfort are of particular concern.

In a large-scale study with a 10-year follow-up, Diaz et al demonstrated that fistulectomy combined with endorectal advancement flap repair yielded a success rate of 76.2%, with most recurrences (90.3%) occurring within the first postoperative year. Importantly, deterioration in continence over time was mild and not significantly associated with prior anal surgeries or fistula complexity. These results show that the advancement flap technique remains both effective and safe in the long term. In our study, short-term observations similarly revealed that TAFR offers advantages in preserving continence and enhancing patient quality of life. Therefore, TAFR may be considered the preferred approach in patients where long-term continence preservation and reduced postoperative morbidity are clinical priorities [24].

This study has several limitations, including its retrospective design, limited follow-up duration, small subgroup sizes, and the exclusion of complex fistula cases such as those related to Crohn’s disease. These factors may affect the generalizability and statistical power of the findings. Future studies should include larger, more diverse populations with longer follow-up periods and randomized designs to better assess long-term outcomes and guide optimal treatment selection.

Conclusions

Both TAFR and HSP are effective and safe surgical options for the treatment of transsphincteric anal fistulas, demonstrating low recurrence rates and no significant increase in postoperative incontinence. However, the TAFR group had a lower rate of anal soiling and greater improvement in quality-of-life scores, indicating a potential functional advantage. These findings support the use of either technique, with TAFR potentially offering greater benefit for patients prioritizing continence preservation and postoperative comfort.