Timing of ligation of the intersphincteric fistula tract after loose seton drainage in complex anal fistulas

Abstract

BACKGROUND

The ligation of intersphincteric fistula tract (LIFT) is a well-established technique for complex anal fistulas; however, recurrence remains a concern, particularly when performed before complete resolution of residual infection.

AIM

To evaluate the role of interval magnetic resonance imaging (MRI) in determining definitive LIFT timing after loose seton drainage for complex anal fistulas.

METHODS

Between 2023 and 2025, 48 patients with anal fistulas were studied retrospectively to evaluate bridging loose seton placement followed by LIFT. Preoperative MRI was performed in all patients, while interval MRI was selectively used to assess residual abscess cavities and guide surgical timing. Patient demographics, comorbidities, fistula characteristics, and postoperative outcomes were analyzed. Functional outcomes were assessed using the Wexner incontinence score before and 2 months after LIFT.

RESULTS

Primary healing after LIFT was achieved in 91.7% of patients, while 8.3% (4 patients) experienced recurrence. In 9 patients with persistent abscess cavities, MRI was used to support surgical timing decisions and document regression of inflammatory findings. Recurrence occurred in 1 patient out of the 9 patients (11.1%) who underwent delayed LIFT after interval MRI and in 3 patients out of the 39 patients (7.7%) who underwent LIFT at the planned 8-week interval. Given the small sample size and baseline differences, these findings should be interpreted descriptively. No new continence disturbances occurred, and Wexner scores showed no significant change. Diabetes and cardiovascular disease were numerically more frequent among patients with recurrence but without statistical significance.

CONCLUSION

Interval MRI may assist definitive LIFT timing in selected patients with persistent inflammatory cavities after loose seton drainage. Prospective studies are needed to validate this approach.

Key Words: Complex anal fistula; Ligation of intersphincteric fistula tract procedure; Seton drainage; Optimal timing; Delayed intervention; Magnetic resonance imaging

Core Tip: This study suggests that timing of the ligation of intersphincteric fistula tract surgical procedure after loose seton drainage may be clinically relevant in selected patients with complex anal fistulas. Interval magnetic resonance imaging may help identify persistent inflammatory cavities that warrant postponement of definitive surgery. However, due to the overall small sample size and baseline differences observed between the groups evaluated in this study, no conclusions can be drawn regarding the superiority of delayed vs standard-timing ligation of intersphincteric fistula tract.

INTRODUCTION

Anal fistulas are a widespread and burdensome proctologic condition that frequently affects young adults, causing chronic pain, purulent discharge, and a lower quality of life[1]. Most arise from cryptoglandular infection, but their varied anatomy and proximity to the sphincter apparatus make management particularly challenging[2]. To standardize treatment planning, widely adopted frameworks, including the Parks classification and contemporary guidelines, are used to differentiate between simple and complex fistulas. Complex fistulas, defined by greater sphincter involvement and anatomical intricacy, pose a much greater risk of recurrence and postoperative incontinence compared to simpler cases[3]. Recent advances in imaging-guided classification further emphasize the importance of accurate grading to guide surgical strategy[4].

In response to the limitations of conventional techniques, Rojanasakul[5] introduced the ligation of intersphincteric fistula tract (LIFT) procedure in 2007 as a sphincter-preserving approach designed to treat transsphincteric fistulas without compromising continence. The technique involves dissection within the intersphincteric plane to identify, ligate, and divide the fistula tract at a point remote from both internal and external openings. This anatomical strategy aims to eliminate the fistula pathway while preserving the integrity of both sphincter muscles. Early findings demonstrated high healing rates with minimal impact on continence, positioning LIFT as an attractive first-line surgical treatment for select complex fistulas[6]. Since its introduction, LIFT has gained widespread popularity and has been incorporated into multiple treatment algorithms, particularly for patients in whom conventional fistulotomy poses a high risk of incontinence[7].

Despite initial enthusiasm, LIFT has shown highly variable long-term outcomes, with success rates in the literature ranging from 45% to 82% based on patient anatomy, technique, and characteristics[8]. A major cause of failure appears to be a residual abscess cavity, particularly when the procedure is performed before full resolution of the associated abscesses[9]. Anatomical factors such as a wide tract or branching extensions may limit the success of single-stage procedures. Without clear timing and selection criteria, recurrence remains unpredictable. These challenges have increased interest in tailored, staged approaches[10].

Given these limitations, many surgeons prefer a staged approach using loose seton drainage to control sepsis and allow tract maturation before definitive repair[11]. Although delayed LIFT following adequate drainage has been associated with favorable outcomes[12], objective criteria for determining the optimal timing of surgery remain poorly defined. Most of the published studies have relied on clinical assessment primarily, whereas the potential role of interval magnetic resonance imaging (MRI) in guiding surgical timing has received limited attention. To address this gap, we evaluated the clinical outcomes of a two-stage protocol incorporating loose seton drainage followed by selectively timed definitive LIFT, with interval MRI used as an adjunct to clinical assessment when indicated.

We hypothesized that interval MRI could identify patients with persistent residual inflammatory cavities who may require postponement of definitive surgery, while allowing patients with complete resolution of inflammation to proceed safely to LIFT. The primary aim of this study was therefore to evaluate the role of interval MRI as an adjunct to clinical assessment when determining the timing of definitive LIFT and its association with postoperative healing, recurrence, and continence outcomes.

MATERIALS AND METHODS

Study design and patient selection

This retrospective cohort study included adult patients with complex anal fistulas who underwent staged management consisting of loose seton drainage followed by the LIFT procedure at a single tertiary center between January 2023 and September 2025. Patients with Crohn’s disease, ulcerative colitis, horseshoe fistulas, extrasphincteric fistulas, or missing preoperative MRI data were excluded. Patients were also excluded if their fistulas spontaneously downstaged to subcutaneous, non-sphincter-involving tracts after seton drainage, or if the seton was expelled prematurely, resulting in spontaneous closure (Figure 1A). Following these criteria, a total of 48 patients were included in the final analysis (Figure 1B).

Figure 1 Patient selection and study flow. A: Patient selection flowchart; B: Study design flowchart. MRI: Magnetic resonance imaging; LIFT: Ligation of intersphincteric fistula tract.

All patients underwent pelvic MRI before surgery to evaluate the fistula anatomy, abscess cavity, and relationship with sphincter muscles. The decision to proceed to the LIFT procedure was based on MRI-confirmed regression of the abscess cavity and tract maturity. In 9 patients, the second-stage surgery was delayed beyond 8 weeks due to persistence of the abscess cavity on follow-up imaging.

Adequate drainage was defined clinically by the absence of active purulent discharge, fluctuance, or progressive induration around the fistula tract. Tract maturity was determined by stabilization of the fistula pathway without signs of ongoing acute inflammation. MRI was selectively used to confirm regression of residual abscess cavities in patients with persistent symptoms or equivocal clinical findings.

Loose seton placement

During the first stage, a non-cutting loose seton was placed under general or spinal anesthesia to drain the fistula tract and induce tract maturation. Care was taken to avoid rerouting of the fistula tract during seton placement, and the original anatomy of the tract was preserved to ensure accurate surgical planning. Antibiotics were administered perioperatively if an abscess cavity was present. Perioperative antibiotics were administered according to institutional protocol in patients with active abscess formation or surrounding cellulitis.

LIFT procedure

LIFT was performed after adequate drainage and regression of the abscess cavity. The timing was determined by the clinical resolution of sepsis and the success of the drainage. An interval of approximately 8 weeks was selected based on previously published recommendations that have suggested 6-8 weeks of drainage before definitive LIFT in the absence of ongoing sepsis[13]. MRI was used to confirm the absence of a residual abscess cavity when clinically indicated. LIFT was performed via a curved incision within the intersphincteric groove. The fistula tract was isolated via intersphincteric dissection, ligated using 2-0 polyglactin sutures, and excised distal to the ligature. No advancement flap or additional procedures were performed. All procedures were performed by the same colorectal surgeon experienced in fistula surgery.

Follow-up and outcome measures

Patients were followed for a median of 8 months (range: 2-18 months). Clinical evaluations were routinely conducted at postoperative weeks 2, 4, and 8. Pelvic MRI was selectively repeated in patients with ongoing drainage or suspected recurrence. Detailed data collected throughout the study included age, sex, MRI-classified fistula type, tract length, and maximum abscess cavity diameter. Systemic comorbidities such as diabetes mellitus, hypertension, chronic kidney disease, chronic obstructive pulmonary disease, and congestive heart failure were also documented.

Operative details such as the duration of seton placement and the time interval between the first and second stages were documented. Continence status was assessed using the Wexner incontinence score both prior to the initial operation and at 8 weeks following the LIFT procedure. Postoperative complications, including bleeding, wound infection, and recurrent or residual abscess formation, were noted. Primary healing was defined as the complete closure of the external opening with no clinical symptoms (pain or discharge) and no evidence of a remaining abscess or fistula upon examination. MRI was selectively repeated in cases with persistent symptoms. Recurrence was defined clinically as persistent or recurrent purulent drainage and/or reopening of the external fistula opening after initial healing. MRI was not routinely used to define recurrence but was selectively performed in symptomatic patients to evaluate suspected residual abscess cavities or recurrent fistula tracts.

Statistical analysis

Descriptive statistics are expressed as the mean ± SD or median (range). The distribution of continuous variables was assessed using the Shapiro-Wilk test. Variables that were not normally distributed were analyzed using Mann-Whitney U test (nonparametric test), whereas categorical variables were compared using Fisher’s exact test, as appropriate. Wexner scores were compared using the Wilcoxon signed-rank test. The association between recurrence and potential risk factors (age, fistula length, abscess size, comorbidities) was evaluated using Mann-Whitney U and Fisher’s exact tests. P < 0.05 was considered statistically significant. Due to the limited number of recurrence events, multivariable regression analysis was not considered statistically reliable. Statistical analyses were performed using SPSS version 29 (IBM Corp., Armonk, NY, United States).

RESULTS

Patient demographics and fistula characteristics

Forty-eight patients with complex anal fistulas underwent a two-stage surgical approach consisting of initial loose seton drainage followed by the LIFT procedure. The mean age was 45.8 years (range: 23-74 years), and 66.7% (n = 32) of the patients were male. Transsphincteric fistulas were the most common type (50%), followed by intersphincteric (39.6%) and suprasphincteric (10.4%). The mean fistula tract length was 38.5 mm, while the abscess cavity had a mean diameter of 29.0 mm. The mean interval between the first and second surgeries was 9.5 weeks, and the median follow-up duration was 8 months.

Recurrence and associated factors

Four patients experienced a recurrence, corresponding to an overall recurrence rate of 8.3% (Figure 2). Patients with recurrence tended to be older (mean age: 55.0 years vs 44.2 years), although this difference did not reach statistical significance (P = 0.075). Fistula length (P = 0.31), abscess cavity diameter (P = 0.46), and preoperative and postoperative Wexner scores (P > 0.48) were not significantly different between the recurrence and non-recurrence groups (Table 1).

Figure 2 Recurrence rate. Overall recurrence rate following the ligation of intersphincteric fistula tract procedure in the study cohort. Recurrence was observed in 4 of the 48 patients (8.3%).

Table 1 Analysis of risk factors for recurrence.

Variable	Recurrence, mean	No recurrence, mean	P value
n	4	44
Age	55	44.2	0.075
Fistula length in mm	38.1	38.5	0.313
Abscess diameter in mm	32	28.5	0.465
Preoperative Wexner score	3.3	2.05	0.490
Postoperative Wexner score	2.1	1.6	0.522

Continence outcomes

Following the LIFT procedure, the mean Wexner incontinence score dropped from 2.23 preoperatively to 1.72 at the 8-week follow-up. Although this reduction was not statistically significant (P = 0.33), continence remained stable after surgery (Figure 3, Table 2).

Figure 3 Distribution of Wexner incontinence scores before and after the ligation of intersphincteric fistula tract, commonly referred to as ligation of intersphincteric fistula tract procedure. Boxplots demonstrate preoperative and postoperative Wexner scores. Median values and interquartile ranges are shown. No statistically significant difference was observed between the two measurements (Wilcoxon signed-rank test, P = 0.33).

Table 2 Change in Wexner incontinence scores before and after ligation of intersphincteric fistula tract.

Preoperative Wexner score, mean	Postoperative Wexner score, mean	Mean difference	Wilcoxon P
2.2	1.7	-0.510	0.333

Association with chronic comorbidities

We also analyzed whether the presence of chronic systemic diseases was associated with recurrence. Among the 4 patients with recurrence, 1 patient had diabetes mellitus, 1 had hypertension, and 2 had chronic obstructive pulmonary disease. Although recurrence appeared to be numerically more frequent in patients with systemic comorbidities, none of these comparisons reached statistical significance (P = 1.0 for all).

Postoperative complications

Postoperative complications occurred in 8.3% of patients, specifically perianal abscess (n = 2) wound infection (n = 1), and bleeding (n = 1). There were no major complications such as incontinence, seton-related erosion, or the need for reoperation. Preoperative MRI identified residual abscess cavities in selected patients, which resolved after loose seton drainage, allowing definitive LIFT to be performed (Figure 4A and B). However, among the 48 patients analyzed, 9 of those patients continued to demonstrate persistent abscess cavities or sinus tracts on interval MRI obtained approximately 8 weeks after the seton placement. In these patients, the second-stage LIFT procedure was postponed for an additional mean duration of 6.2 weeks to allow further regression of inflammatory findings (Figure 4C and D). Recurrence occurred in 1 of the 9 patients whose LIFT procedure was delayed after interval MRI (11.1%) and in 3 of the 39 patients who underwent LIFT at the planned 8-week interval (7.7%).

Figure 4 Pre- and post-seton pelvic magnetic resonance imaging illustrating abscess cavity evolution in complex anal fistulas. A: Preoperative pelvic magnetic resonance imaging (MRI) showing an abscess cavity (orange arrow); B: Follow-up MRI showing resolution of the abscess cavity (orange arrow) after seton placement, and that the loose seton remained visible (white arrow); C: Preoperative pelvic MRI in a different patient showing an abscess cavity (orange arrow); D: Same MRI as in (C) showing a persistent abscess and sinus tract (orange arrow) despite ongoing drainage through a loose seton (white arrow).

DISCUSSION

The main finding of this study is that selective use of interval MRI provided additional information beyond clinical assessment when determining the timing of definitive LIFT in patients with persistent inflammatory findings. Following staged management with loose seton drainage and subsequent LIFT, primary healing after LIFT was achieved in 91.7% of patients, with an overall recurrence rate of 8.3%. These results align with multicenter series-determined healing rates of between 68% and 85%[14]. Furthermore, no new continence disturbances were observed, consistent with meta-analyses favoring LIFT over other techniques[15]. A staged approach can create better healing conditions for certain patients[16].

Previous reports of spontaneous fistula downstaging after seton placement could introduce selection bias in retrospective LIFT analyses if these patients are included[17]. Therefore, we excluded patients whose fistulas resolved or became superficial surgical intervention following seton loss. Because the LIFT procedure avoids sphincter division, it preserves continence. Our cohort experienced only rare and mild cases of incontinence, supporting earlier findings that LIFT results in minimal continence impairment[18,19]. Although complications are possible, patient factors such as smoking may contribute without impacting continence[20]. Furthermore, while posterior fistulas can be challenging to manage, they do not necessarily worsen outcomes[21].

Recurrence after LIFT is often linked to anatomical complexity or premature intervention. Operating prior to complete abscess resolution significantly increases failure risk due to residual infection[22]. Features such as high tracts or branching extensions also pose a risk[23]. While our study found a higher rate of recurrence among patients with comorbidities, this difference was not statistically significant, mirroring previous evidence that links this trend to impaired tissue perfusion and immune modulation[24].

Staged strategies are increasingly utilized for complex fistulas. In our cohort, loose seton drainage was followed by interval MRI assessment prior to definitive LIFT. In 9 patients, surgery was postponed due to persistent abscess cavities or sinus tracts which remained visible on follow-up imaging. Also in our cohort, the interval MRI contributed directly to the clinical decision-making by identifying persistent abscess cavities or sinus tracts in those 9 patients, which was the foundation of the decisions for postponement of definitive surgery. Beyond this role, the MRI examination also provided objective confirmation of regression of residual inflammatory findings before LIFT. Accordingly, we believe that interval imaging may help identify selected patients who could benefit from delayed definitive repair[25].

Patients in our study cohort with chronic systemic diseases appeared to have numerically higher recurrence rates compared to those without comorbidities; however, these findings should be interpreted cautiously given the limited number of recurrence events. Because comorbidities may delay healing and gradually impair continence, tailored care plans are essential for these patients[26]. Although our data do not permit definitive conclusions, these observations raise the possibility that patients with significant systemic comorbidities may benefit from a more individualized approach to surgical timing. Future prospective studies should evaluate whether extended drainage periods or additional imaging assessment before definitive LIFT could improve outcomes in these higher-risk patients. In our study, the mean Wexner incontinence score improved from 2.23 preoperatively to 1.72 at 8 weeks, indicating no significant functional impairment. This aligns with meta-analyses showing that LIFT maintains a low incontinence rate, frequently below 3%[27]. These findings support the continence-preserving advantage of LIFT, even in complex fistulas.

Of the 4 patients who developed recurrence, there were cases of favorable anatomy that allowed for repeat LIFT. While repeat LIFT procedures for recurrent disease are infrequently reported in the literature, our limited experience suggests that reoperation with the same technique may remain feasible in selected patients after adequate infection control and preservation of tract anatomy. In contrast to studies utilizing transperineal ultrasound for preoperative assessment, such as that by Murad-Regadas et al[28], our protocol incorporated MRI to confirm resolution of the abscess cavity. These recurrent cases are continuing to undergo clinical follow-up as a distinct cohort to evaluate future healing and continence.

MRI scans at 8 weeks revealed a persistent abscess or sinus tract in 9 patients, resulting in a mean surgical delay overall of 6.2 weeks. Recurrence occurred in 1 patient of the 9 who underwent delayed LIFT after interval MRI and in 3 patients of the 39 treated at the planned 8-week interval. Given the limited sample size and the fact that the delayed patients represented a selected subgroup with persistent abscess cavities on follow-up MRI, these observations should therefore be interpreted descriptively rather than as comparative evidence supporting one timing strategy over another.

From a practical perspective, our findings do not support routine interval MRI reassessment for all patients after loose seton drainage. However, patients with persistent drainage, ongoing perianal discomfort, induration, or equivocal clinical findings may benefit from repeat imaging to identify unresolved abscess cavities before definitive repair. Conversely, patients with complete clinical resolution of sepsis may be suitable candidates for definitive LIFT without additional delay. Given that systemic comorbidities may adversely affect healing, individualized perioperative strategies may be particularly relevant in higher-risk patients.

This study has several limitations. Its retrospective single-center design precludes causal inference, and subgroup analyses should be interpreted cautiously because of the limited sample size. Detailed MRI variables, secondary tract branching, and fistula complexity beyond the primary classification were not systematically recorded, preventing further evaluation of anatomical and imaging predictors of recurrence. In addition, objective inflammatory markers such as C-reactive protein and white blood cell count were not routinely incorporated into timing decisions, and the median follow-up of 8 months may have underestimated late recurrences.

CONCLUSION

Delayed LIFT following bridging seton drainage appears feasible in selected patients with persistent inflammatory findings after initial drainage. Unfortunately, patients requiring delayed surgery represented a subgroup with greater baseline inflammatory burden, precluding meaningful comparison with patients treated at the standard interval. Interval MRI may assist surgical timing decisions, but no conclusions can be drawn regarding the superiority of delayed vs standard-timing LIFT.