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

Abstract

Background

The primary goal of anal fistula treatment is eradication of the fistula while preserving continence and minimizing the risk of recurrence. Although fistulotomy is effective for simple fistulas, management of complex trans-sphincteric fistulas remains challenging. Sphincter-sparing techniques show variable outcomes, with high recurrence rates and risk of incontinence. This study evaluated a hybrid technique combining core-out fistulectomy with trans-sphincteric laser ablation to improve healing while preserving sphincter function.

Material/Methods

This retrospective pilot study included 20 adult patients with magnetic resonance imaging (MRI)-confirmed trans-sphincteric fistulas (<6 mm diameter) treated between August and November 2024 at a tertiary referral center. Patients with inflammatory bowel disease, malignancy, or abscess were excluded. The fistula tract was surgically excised from the skin to the sphincter complex, and the trans-sphincteric portion was ablated using a 1470-nm diode laser. The primary outcome was fistula healing; secondary outcomes were healing time, complications, recurrence, and time to return to work.

Results

Twenty patients (12 males; mean age 40.5 years) underwent the procedure. The overall healing rate was 90% (18/20). Mean healing time was 6.4 weeks, with a mean follow-up of 9.9 months. Two patients experienced recurrence. No significant postoperative complications or continence disturbances were observed. The mean time to return to work was 8.9 days, and all patients resumed normal daily activities the day after surgery.

Conclusions

Core-out fistulectomy combined with trans-sphincteric laser ablation appears to be a safe and effective treatment for selected trans-sphincteric fistulas. Larger prospective studies with longer follow-up are needed to confirm these findings.

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

This single-center, retrospective study evaluated the outcomes of the combined technique in patients with trans-sphincteric anal fistulas. All procedures were performed by a single European Board-certified coloproctologist at Ozel Aktif International Hospital, Yalova, Turkey between August and November 2024.

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.

Figure 1.

Schematic details of the procedure.

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.

Figure 2.

Perianal Fistula Disease Severity Score (PFDSS).

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.

Table 1.

Patient demographics and clinical data.

Patient	Age (yearrs)	Sex	BMI	Smoking status	Comorbidities	Number of prior surgeries	If applicable previous surgeries		Fistula duration (weeks)		Suppuration
1	52	M	38	Current	DM, HT, RA	0	NA		2		Yes
2	42	F	25	Current	–	2	Abscess drainage, seton placement		40		Yes
3	60	M	24	Never	–	2	Abscess drainage		104		No
4	59	M	23	Current	–	1	Abscess drainage		60		Yes
5	48	M	23	Never	–	0	NA		10		Yes
6	41	F	32	Current	–	2	Abscess drainage		96		No
7	30	M	33	Never	–	0	NA		20		Yes
8	50	M	29	Never	HT	1	Abscess drainage		12		No
9	45	F	36	Never	–	2	Abscess drainage, seton placement		82		Yes
10	25	F	24	Never	–	1	Abscess drainage		40		No
11	37	M	27	Never	–	1	Abscess drainage		5		No
12	43	M	23	Never	–	0	NA		22		Yes
13	29	F	19	Current	–	0	NA		30		Yes
14	19	M	35	Current	–	1	Abscess drainage		16		No
15	33	F	27	Current	–	1	Abscess drainage		23		No
16	22	F	20	Current	–	1	Abscess drainage		5		No
17	50	M	29	Never	HT	0	NA		19		Yes
18	40	M	34	Current	–	1	Abscess drainage		33		No
19	37	M	31	Never	–	2	Abscess drainage, seton placement		52		Yes
20	45	M	28	Current	–	1	Abscess drainage		8		No
Patient	Presence of seton	Tract length (mm)	Surgery duration (minutes)	Pathology specimen	Healing time (weeks)	Follow-up time (months)	PFDSS	Recurrence	Time to recurrence (weeks)	Return to work (days)	Return to daily routine (days)
1	None	58	25	Chronic Inflammation and fistula tract	7.0	12	0	0	NA	13	1
2	Yes	36	19	Chronic Inflammation and fistula tract	6.0	12	0	0	NA	4	1
3	None	38	20	Chronic Inflammation and fistula tract	8.0	11	0	0	NA	8	1
4	Yes	37	23	Chronic Inflammation and fistula tract	5.0	11	0	0	NA	9	1
5	None	35	17	Chronic Inflammation and fistula tract	nan	11	2	1	5	20	1
6	None	44	24	Chronic Inflammation and fistula tract	7.0	11	0	0	NA	10	1
7	None	49	27	Chronic Inflammation and fistula tract	6.0	11	0	0	NA	9	1
8	None	43	20	Chronic Inflammation and fistula tract	8.0	11	0	0	NA	11	1
9	Yes	52	30	Chronic Inflammation and fistula tract	10.0	10	0	0	NA	15	1
10	None	40	25	Chronic Inflammation and fistula tract	9.0	10	0	0	NA	14	1
11	None	39	23	Chronic Inflammation and fistula tract	8.0	10	0	0	NA	7	1
12	None	37	27	Chronic Inflammation and fistula tract	3.0	10	0	0	NA	6	1
13	None	36	22	Chronic Inflammation and fistula tract	5.0	9	0	0	NA	5	1
14	None	45	30	Chronic Inflammation and fistula tract	5.0	9	0	0	NA	3	1
15	None	42	19	Chronic Inflammation and fistula tract	4.0	9	0	0	NA	8	1
16	None	38	18	Chronic Inflammation and fistula tract	7.0	9	0	0	NA	9	1
17	None	41	23	Chronic Inflammation and fistula tract	6.0	8	0	0	NA	8	1
18	None	53	25	Chronic Inflammation and fistula tract	8.0	8	0	0	NA	6	1
19	Yes	42	23	Chronic Inflammation and fistula tract	nan	8	2	1	3	15	1
20	None	37	20	Chronic Inflammation and fistula tract	4.0	8	0	0	NA	5	1

M – Male; F – Female; DM – diabetes mellitus; HT – hypertension; RA – rheumatoid arthritis; NA – not applicable; PFDSS – perianal fistula disease severity score.

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

Managing complex anal fistulas is challenging, and there still is no widely-accepted standard treatment method. It is difficult to both preserve anal sphincter function and achieve non-recurrence. We addressed this issue by combining 2 techniques: laser ablation and core-out excision. This hybrid treatment method was used in 20 patients, and successful healing was achieved in 18 (90%) of them during a mean follow-up of 9.9 months.

Previous studies evaluating the effectiveness of LAFT resulted in varying primary healing rates from 20% to 89%, with follow-up times ranging from 6.3 to 60 months [10,13–26] (Table 2). The surgical techniques are similar to laser ablation, but differ mainly in terms of closure or non-closure of the internal opening and excision or non-excision of the external orifice. In terms of internal opening, most of the studies did not use sutures; however, in the studies by Brabender et al, Serin et al, Wolicki et al, and Nordholm-Carstensen et al, it was sutured in all of the cases, while Giamundo et al sutured 27 out of 175 cases [13–18]. Wilhelm et al performed a flap repair of the internal opening. In our study, we performed a simple excision of the internal orifice followed by suturing [18].

Table 2.

Studies on LAFT.

	Number of [atients	Primary healing rate (percent)	Follow-up time (months)	Preoperative imaging	Use of bridging seton	Modality for internal orifice
Ozturk et al [10]	50	82	12	MRI	Yes	No closure
Wilhelm et al [18]	117	64.1	25.4	Proctosigmoidoscopy & endoanal ultrasonography	Yes	Flap closure
Dönmez et al [22]	27	89	22	Proctosigmoidoscopy & MRI	None	No closure
Terzi et al [23]	103	28	40	Proctosigmoidoscopy & MRI	None	No closure
Lauretta et al [19]	30	33.3	11.3	Endoanal ultrasonography	Yes	No closure
					(in 26 patients)
Marref et al [24]	69	45.6	6.3	Not routinely used	Yes	No closure
Stijns et al [25]	20	20	10	MRI	Yes	No closure
					(In 15 patients)
Alam et al [21]	20	55	7.1	Not specified		No closure
de Bonnechose et al [26]	100	44.6	13.6	Not routinely used	Yes	No closure
Brabender et al [13]	18	22	29	Not routinely used	None	Sutured
Isık et al [20]	100	62	48	MRI	Yes	No closure
Serin et al [14]	35	42.9	11	Proctosigmoidoscopy & MRI	None	Suture closure
Wolicki et al [15]	83	74.7	42	Endoanal ultrasonography & MRI (If necessary)	Yes	Suture closure
					(In 65 patients)
Nordholm-Carstensen et al [16]	66	44.1	19	Endoanal ultrasonography	None	Suture closure
Giamundo et al [17]	175	66.8	60	Proctosigmoidoscopy & endoanal ultrasonography & MRI (if needed)	Yes (In 16 patients)	Suture closure in 27 patients, no closure in 148 patients
Present study	20	90	9.9	MRI	4 patients had setons	Suture closure
	Modality for external orifice	Etiology		Fistula type			Reccurence rate (percent)
		Fistula associated with Crohn’s disease	Cryptoglandular fistula	Intersphincteric	Suprasphincteric	Trans-sphincteric
Ozturk et al [10]	No excision	0	50	10	0	40	18.0
Wilhelm et al [18]	Excised	13	104	8	6	103	12.0
Dönmez et al [22]	No excision	Not specified	27	14	5	7	11.11
Terzi et al [23]	No excision	0	103	56	11	29	60.0
Lauretta et al [19]	No excision	0	30	0	0	30	66.7
Marref et al [24]	No excision	6	63	2	11	56	54.4
Stijns et al [25]	No excision	0	20	6	0	14	80.00
Alam et al [21]	No excision	20	0	1	1	18	45.0
de Bonnechose et al [26]	No excision	10	90	0	13	87	55.4
Brabender et al [13]	No excision	4	14	5	14	1	78.0
Isık et al [20]	No excision	0	100	10	8	80	38.0
Serin et al [14]	No excision	0	35	21	2	12	57.1
Wolicki et al [15]	Excised	2	81	Not specified	Not specified	Not specified	21.7
Nordholm-Carstensen et al [16]	Excised	11	55	2	59	5	55.9
Giamundo et al [17]	No excision	0	174	18	5	152	21.7
Present study	Core-out excision of the fistula tract	0	20	0	0	20	10.00

The studies were placed in the table according to publication date. MRI – magnetic resonance imaging of the perianal region; BMI – body mass index.

External opening was another area that differed among the studies. While in most of the studies no excision was performed, Wilhelm et al, Wolicki et al, and Nordhom-Carstensen et al excised the external openings [15,16,18]. In the present study, we performed core-out excision of the external orifice based on 2 main concerns. The first concern was leaving patients with the burden of a chronic wound, which could have potential for malignant transformation. The second concern was raised in the study of Ozturk et al, commenting on “possible occurrence of anal sinuses in the soft tissue of patients treated with LAFT, as the skin closed with laser ablation; however, the soft tissue (fat tissue) did not undergo fibrosis and liquidation, which presented mimicking recurrence/non-healing” [10]. They recommended excision of the skin in the external opening. However, in addition to their recommendations, we performed excision of the entire fistula tract until the muscular sphincter complex.

The core-out excision worked in favor of shortening the fistula tract. The length of the fistula tract was associated with healing according to the study by Lauretta et al [19], in which patients with shorter tracts (eg, 28.5 mm) were cured, whereas patients with longer tracts (eg, 46 mm) did not respond to the laser treatment. Longer fistula tracts meant longer tract length in the non-muscular tissue, as the lengths of the sphincter muscle were similar. This finding also supports the use of our technique, in which excising the fistula tract in the non-muscular area shortens the tract overall. Also, laying open the excised area allowed for preventing abscess formation, as no dead space was created.

In the studies cited above, the treated populations were heterogeneous in terms of types of fistulae and the presence of Crohn’s disease. The studies on LAFT had a varying number of intersphincteric fistula patients, as detailed in Table 2. In our study, we excluded intersphincteric fistula patients, as this type of fistula could be treated by simple fistulotomy in most cases without additional patient costs, as highlighted by Isik et al [20]. In 8 of the studies, patients with Crohn’s disease were excluded and only patients with fistulas with cryptoglandular origin were included. While other studies enrolled varying levels of Crohn’s patients, Alam et al performed their study solely on Crohn’s patients [21]. We did not enroll any patients with Crohn’s disease, as we did not want to add another possible confounder. In a recent systematic review, anal fistula patients with Crohn’s disease had higher failure rates than anal fistula patients without Crohn’s disease (39.5% versus 31.4%) [4].

Other surgical methods such as LIFT and VAAFT are also viable ways to treat anal fistulas. In a study by Zahra et al, LIFT has a success rate of 75%, and Van Hoof et al also reported similar healing rates [27,28]. Van Hoof et al also reported that in some cases there were early recurrences and failures due to residual infection and blind tracts [28]. In a retrospective study by Chase et al, the VAAFT procedure was found to have low healing rates (22% of the cryptoglandular fistulas and 27% of the Crohn’s fistulas), especially for more complex fistulas [29]. They also reported that 6% of the patients developed incontinence, which is an important disadvantage when compared to LAFT and laser ablation methods.

Preoperative imaging is essential in detecting the type of fistulae, possible secondary tracts, and presence of abscess. Previous studies utilized proctosigmoidoscopy, MRI, and endoanal ultrasonography for this purpose. In our study, all of the patients underwent perianal MRI to be sure no second tracts were omitted.

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.