Core-Out Fistulectomy Combined With Laser Ablation of the Trans-Sphincteric Fistula Tract: A Pilot Study of Efficacy and Safety

Introduction

The primary aim in the treatment of anal fistulas is to eradicate the fistula tract, prevent recurrence, and preserve continence. In low fistulas, fistulotomy remains the gold standard, with healing rates approaching 95% and minimal risk to sphincter function [1,2]. However, managing complex fistulas, which involve a greater portion of the sphincter complex, remains challenging and controversial.

Various sphincter-sparing techniques have been developed for complex fistulas, including seton placement, endorectal advancement flaps, ligation of the intersphincteric fistula tract (LIFT), fibrin glue, fistula plugs, video-assisted anal fistula treatment (VAAFT), and laser ablation of the fistula tract (LAFT) [3]. Despite these advances, no single technique offers consistently high healing rates while minimizing the risk of incontinence. A recent meta-analysis report ed failure rates of 28.6% for LIFT, 22.3% for VAAFT, 43.9% for LAFT, and 25.9% for endorectal advancement flap (EAF) techniques [4].

Another recently published systematic review with 24 studies and 1503 patients concluded that LAFT had a healing rate of 57.46% and a recurrence rate of 18.48% [5]. A recent RCT by Patel et al comparing laser versus open surgery for anal fistula showed 70% healing and 30% recurrence (and need for another surgery) for patients treated with laser [6]. According to the 2023 guidelines of the European Society of Coloproctology, laser therapy destroys the fistula epithelium and does not significantly affect the sphincter muscles [7]. Guidelines from the American Society of Colon and Rectal Surgeons (ASCRS) state that minimally invasive techniques using laser ablation or endoscopy have reasonable short-term healing rates (65%) but their long-term healing and recurrence rates are unknown [8].

To address concerns of recurrence and incontinence, we developed a novel approach that combines 2 existing strategies. As first introduced by Wilhelm et al in 2011, LAFT relies on obliterating the fistula tract and associated crypt glands using laser energy [9]. While techniques vary in terms of managing the internal and external openings, the main principle remains tract ablation. Our method standardizes the approach to the external and internal openings. Additionally, in LAFT, Laurette et al demonstrated that the length of the fistula tract has a significant effect on healing [10]. Fistula tracts shorter than 30 mm had a healing rate of 58.3% while longer tracts had a healing rate of 16.6% [10]. In our approach, we can address this limitation because the fistula tract is surgically excised from the skin up to the sphincter complex (core-out excision), and the portion traversing the sphincter is treated with laser ablation. Our combined method is designed to maximize fistula clearance while minimizing the risk of sphincter injury and postoperative incontinence.

This pilot study evaluated the effectiveness of core-out excision with sphincter-preserving laser ablation in patients with trans-sphincteric fistulas. The primary outcome was the healing rate, providing early insight into the feasibility and potential advantages of this approach. Secondary outcomes were time to healing, postoperative complications, and time to return to work.

Material and Methods

PATIENTS SELECTION CRITERIA AND THE STUDY POPULATION:

Patients were selected based on outpatient clinical examination and preoperative perianal MRI. Inclusion criteria were age ≥18 years, diagnosis of a primary trans-sphincteric fistula confirmed by MRI and physical exam, and fistula tract diameter <6 mm. Patients with or without prior surgery for anal fistula were included. Non-trans-sphincteric fistulas, fistula diameter >6 mm, concurrent perianal abscess, colorectal malignancy, or inflammatory bowel disease were excluded. All fistulas were classified according to the Parks classification [11]. This study was approved by the institutional review board of Istanbul Education and Research Hospital (January 2025, approval no. 2025.01.

SURGICAL TECHNIQUE FOR LAFT:

Surgery was performed under spinal anesthesia, with patients positioned in the modified lithotomy position. Metronidazole 500 mg intravenous was administered as antibiotic prophylaxis. A stylus was passed through the fistula to delineate the tract, followed by debridement of the internal opening. The tract was then excised en bloc from the skin up to the level of the sphincter complex. The excised specimen was submitted for pathological evaluation to confirm the total excision of the fistula tract up to the sphincter complex. The remaining intramuscular tract was treated using a 1470-nm diode laser at a power of 10 watts, applied for 6 seconds per centimeter in a withdrawal fashion (100–120 Joule/cm). The laser probe was carefully inserted through the tract and retracted in 1-cm increments. After laser ablation, the internal opening was closed with 3-0 Vicryl sutures. Hemostasis was achieved, and the wound at the external opening was packed with Bactigras. A schematic diagram of the procedure is provided in Figure 1. Bridging with seton was not routinely performed. However, 4 patients had a seton in place during the surgery.

The dressing was removed 12 hours later, and patients were discharged the following day. Before discharge, the first wound irrigation was supervised by the surgical nurse, and patients were instructed on continued daily wound care using running water at home.

FOLLOW-UP DATA:

Postoperative follow-up was conducted on day 10 and then every 2 weeks. For patients residing in other cities, standardized photographs were submitted via secure communication for remote wound assessment. Healing was defined as complete epithelialization without drainage. Healing was classified using the Perianal Fistula Disease Severity Score (PFDSS) (Figure 2) [12]. Recurrence was defined as the reappearance of fistulous discharge after initial healing. Complications such as persistent suppuration, infection, or delayed wound healing were documented during follow-up.

STATISTICAL ANALYSIS:

Statistical analyses were conducted using IBM SPSS Statistics for Windows, version 25 (IBM Corp., Armonk, N.Y., USA). Because our aim was to summarize the characteristics of the sample rather than testing hypotheses, descriptive statistics were used. Continuous variables are described using means and standard deviations for approximately normally distributed data, and medians and minimum-maximum values for non-normally distributed data. Categorical variables are summarized as frequencies (n) and percentages (%). All results are reported with appropriate units and are presented in tables/figures where relevant.

Results

A retrospective analysis was conducted on 20 patients diagnosed with trans-sphincteric anal fistulas, all located in the posterior region, and who underwent core-out fistulectomy combined with trans-sphincteric laser ablation of the fistula tract. The patient cohort had a mean age of 40.5 years (range: 19–60 years), with 12 males (60%) and 8 females (40%). The mean body mass index (BMI) was 28.0 kg/m2 (range: 19–38 kg/m2). Nine patients (45%) were current smokers, 4 (20%) were former smokers, and 7 (35%) had never smoked. Comorbidities were noted in 3 patients (15%), with 1 patient presenting with type II diabetes, hypertension, and rheumatoid arthritis, and 2 patients with hypertension alone. The patients’ demographics and clinical data are provided in Table 1.

The mean duration of the fistula before treatment was 32.9 weeks (range: 2–104 weeks). Suppuration was present in 9 patients (45%) at the time of intervention. The mean number of prior fistula or perianal abscess surgeries was 0.95 (range: 0–2).

The primary outcome was healing, defined as complete closure of the fistula tract without recurrence or non-healing, assessed over a mean follow-up period of 9.9 months (range: 8–12 months). Successful healing was achieved in 18 patients (90%) with a mean healing time of 6.4 weeks (range: 3–10 weeks). Two patients (10%, Patients 5 and 19) had scores of 2, thus experienced recurrence or non-healing, with recurrence occurring at 5 weeks and 3 weeks after treatment, respectively, according to the PFDSS. The 2 non-healing patients (both males, 37 and 48 years old) had no comorbidities and have never smoked.

Secondary outcomes included time to return to work and daily routines. The mean time to return to work was 8.9 days (range: 3–20 days), and the mean time to return to daily routines was 1.4 days (range: 1–3 days). Patients with recurrence (Patients 5 and 19) had longer recovery, with return-to-work times of 20 and 15 days, respectively, and return to daily routine times of 3 days for both. These 2 patients underwent seton placement, thus continuing their treatment outside of the study group. In the other patients, no serious complications (eg, subcutaneous sinuses, bleeding, signs of infection or pain) were reported.

Discussion

LIMITATIONS AND FUTURE DIRECTIONS:

This study has several limitations. First, the retrospective nature of this study is it main limitation. Second, the sample size was relatively small, with only 20 patients included. While the high healing rate observed is promising, a larger patient cohort is needed to validate the generalizability and robustness of these findings. Future studies with increased sample sizes would allow for more accurate statistical analysis and subgroup comparisons. Second, the mean follow-up period was 42.4 weeks, which may not be sufficient to fully assess long-term recurrence or late complications such as delayed incontinence or fibrosis. A longer follow-up is essential to evaluate the durability of healing and the safety profile of this hybrid technique over time. In a systematic review by Fuschillo et al, the mean follow-up durations for various techniques were 35.4 to 42.4 months, and a longer follow-up would have improved the results of our pilot study [4]. Third, all procedures were performed by a single surgeon. While this may reduce variability and bias in surgical technique, it also limits the reproducibility and generalizability of the results. Future multicenter studies involving multiple surgeons with varying levels of experience are necessary to assess whether similar outcomes can be achieved consistently across different clinical settings.

In future research, incorporating objective functional assessments such as standardized incontinence scores and quality of life metrics would provide a more comprehensive evaluation of treatment outcomes. Additionally, comparing this hybrid technique directly with other established sphincter-sparing procedures in randomized controlled trials would be valuable in determining its relative efficacy and safety.

Conclusions

This new hybrid method can be a good solution for select patients with primary trans-sphincteric fistulas that have a <6 mm diameter, no history of irritable bowel syndrome, and <2 previous anal fistula surgeries. This hybrid method has several advantages, such as a high healing rate, fewer complications, preserved sphincter function, and keeping the surgical area uncomplicated for future interventions if the patient needs a second operation.

This study provides preliminary evidence that our new hybrid method is a practical way of solving a complex problem using a combination of straightforward techniques that can be used without needing to learn complicated new methods. Longer follow-up and increased sample size are needed in further studies.