Characteristics and post-operative outcomes of surgery for fistula-in-ano managed at a tertiary care hospital in Sri Lanka: a retrospective study

Abstract

Objectives

Management of fistula-in-ano is associated with recurrence and, occasionally, with anal incontinence. We investigated the clinical characteristics and outcomes of fistula-in-ano.

Methods

We included patients with fistula-in-ano managed at a tertiary care center (2016–2021). We collected clinical characteristics and 1-year outcomes using questionnaires. The chi-square test was used in statistical analysis.

Results

In total, 284 patients (231 men, 81.3%; median age 39.5 [range: 7–73] years) were included. Most patients had simple fistulae (n = 191, 67.3%). Transphincteric (n = 110, 38.7%) fistulae were the most common type, followed by intersphinteric fistulae (n = 103, 36.6%). Fistulotomy (n = 157, 55.3%) was the most common procedure. Follow-up details were traceable in 157 (55.3%) patients. At 1 year, the overall healing rate was 88.5% (n = 136). There was no association between type of surgical procedure and incontinence. The mean Vaizey score, used to assess anal incontinence, was 0.84 (range: 0–14). Incontinence was observed in 32 patients (20.9%), and flatus incontinence was the most common type (n = 17, 53.1%). Complex fistulae were associated with higher recurrence rates than simple fistulae (32.6% vs. 2.8%).

Conclusion

The healing rate in surgical treatment of fistula-in-ano was 88.5%, with acceptable complication rates. There was no association between surgical procedure type and incontinence.

Keywords

Anal fistula fistulotomy incontinence surgery recurrence retrospective study

Introduction

Fistula-in-ano is a benign condition that is commonly encountered in surgical practice. This condition has been described in the medical literature for over 2500 years.¹ The reported incidence of fistula-in-ano is approximately 8.6 per 100,000 population.^2,3 Fistulae can be classified as simple and complex. Simple fistulae are more common and easy to treat.^2,3 However, complex and recurrent fistulae often present with numerous recurrences requiring multiple interventions.⁴ Thus, it remains challenging to achieve a long-term cure for fistula-in-ano through operative treatment while minimizing postoperative complications.

Repeated interventions increase morbidity owing to an increased risk of anal sphincter injury leading to irreversible anal incontinence.⁵ Anal incontinence is a serious complication that can affect patients’ long-term quality of life.⁶ Wide variation in the rate of incontinence (up to 40%) has been reported based on the anatomy of fistulae and the intervention done.⁷ However, most patients have minor post-operative incontinence.⁷ Furthermore, complex and recurrent fistulae may be associated with a medically treatable cause such as tuberculosis, Crohn’s disease, or actinomycosis.⁸

Several international reports on the clinicopathological characteristics, classification, treatment, and outcomes of anal fistulae have been published, including studies from India.^9–11 In neighboring Sri Lanka, however, the patterns of anal fistulae have not been widely studied. Therefore, recent patterns of fistula-in-ano in Sri Lanka warrant investigation. We aimed to investigate the largest cohort of fistula-in-ano treated at a single tertiary care center in Sri Lanka and to describe the clinicopathological characteristics, epidemiology, treatment, and outcomes of fistula-in-ano in the country.

Methods

We conducted a retrospective analysis of all consecutive patients who underwent surgery for fistulae-in-ano (2016–2021) at the Professorial Surgical Unit in the National Hospital of Sri Lanka. All assessments and investigations were performed by a senior consulting colorectal surgeon or senior surgical trainee under supervision. Data including clinical details, demographic characteristics, anatomy of fistulae, type of interventions, and complexity of the fistula were prospectively entered into a computerized database. Fistulae with multiple external openings; high transphincteric, suprasphincteric, and extrasphincteric fistulae; and/or those with high blind extensions or horseshoe tracts were defined as complex fistulae.^12,13

We assessed the anatomy and complexity of fistulae using endoanal ultrasonography. Selected patients also underwent sigmoidoscopy prior to examination under anaesthesia.^14,15 During examination under anesthesia, a segment or the entire tract of fistulae was sent for histopathological evaluation to identify a specific etiology. Intervention or surgical treatment was based on the anatomy of the fistula and its etiology. Interventions included seton fistulotomy, fistulectomy, fistula plug insertion, ligation of intersphincteric fistula tract (LIFT procedure), and drainage procedures for abscesses. These procedures were performed in a single setting or as a staged procedure depending on the complexity of the fistulae. Selected patients with large pararectal cavities underwent insertion of irrigation tube(s) for a short period to irrigate the cavity.¹⁶

Histopathological data and outcomes were recorded in the computerized database. The degree of incontinence was measured objectively using the Vaizey score, which is a widely accepted and validated measure of anal incontinence.¹⁷ The Vaizey score comprises four questions used to assess the degree of incontinence (solid, liquid, gas, lifestyle alteration) in addition to the need for medication and use of incontinence pads. The frequency of each type of incontinence is rated on a scale ranging from 0 (never) to 4 (always or at least once a day) such that the sum of the frequencies add up to a total score ranging from 0 to 24.¹⁷ Higher scores indicate higher levels of incontinence.

Data were analyzed using IBM SPSS version 20 (IBM Corp., Armonk, NY, USA). The Pearson chi-square test was used to assess the associations. Statistical significance was determined at an alpha of 0.05. Ethics approval was obtained from the Ethics Review Committee of the National Hospital of Sri Lanka (No: AAJ/ETH/COM/2016, date: 7 July 2016). All data were anonymized and de-identified prior to the analysis. Informed consent was not required because this was a retrospective study using anonymized data. The reporting of this study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.¹⁸

Results

A total of 284 patients were operated and 640 surgical procedures were performed over the 6-year study period. Most patients were men (n = 231, 81.3%). The mean patient age was 39.5 (range: 7–73) years. Most patients were in the age group 31–40 years (Figure 1).

Figure 1.

Number of patients diagnosed with fistula-in-ano in each age group.

Patients’ symptoms associated with fistula-in-ano included perianal pain or perianal discharge; the mean duration of symptoms was 11.7 months (range: 1 week to 12 years). Most patients had no associated comorbidities (90.5%); 5.1% of patients had diabetes mellitus and 3.2% had hypertension.

The type of fistulae was available in 276 patients. Transphincteric fistulae were the most common type (n = 110, 38.7%), followed by intersphincteric fistulae (n = 103, 36.6%) (Figure 2). Internal opening was commonly found at the 6 o’clock position (n = 129, 47.8%). The level of internal opening was below and at the dentate line in 117 (41.2%) and 112 (39.4%) patients, respectively. Most patients had one external opening (n = 178, 62.7%) and the commonest site was at the 6 o’clock position (n = 53, 20.3%) (Figure 3).

Figure 2.

Location of the fistula tract.

Figure 3.

Position of external opening of fistula-in-ano.

Simple fistulae (n = 191, 67.3%) were more frequently found than complex fistulae (n = 85, 29.9%). Among patients who had concomitant abscesses or collections (n = 12), intersphicteric collections were commonly observed (n = 8, 66.7%) and superficial collections were seen in three (25%) patients. Sphincter defects were observed in 31 patients (10.9%). Additionally, other concomitant anal conditions were seen among 38 (13.4%) patients; among them, hemorrhoids were the commonest (n = 21, 55.3%) coexisting condition.

The most common operative procedures performed in patients with fistula-in-ano were fistulotomy, fistulectomy, and LIFT. Approximately 44.7% (n = 127) of patients underwent only one surgical procedure whereas 157 (55.3%) patients required additional procedures. Fistulotomy was done in 157 (55.3%) patients, including repeat procedures in some patients. Furthermore, fistulectomy was performed in 47 (16.5%) patients. Cutting seton was applied in 113 (39.8%) patients. In addition to the main surgical procedures, irrigation tube insertion was performed in 38 (13.4%) patients who had pararectal cavities associated with fistula-in-ano.

Follow-up details were traceable in 157 (55.3%) patients. At 1 year, 88.5% (n = 139) had complete healing with no recurrence. The healing rates of fistulotomy and fistulectomy were 93.8% and 88.9%, respectively (Tables 1 and 2). Among patients who were followed up at 1 year, the mean duration of healing was 2.67 months (range: 2 weeks to 24 months; standard deviation ±3.79 months). Post-operative incontinence was assessed using the Vaizey score. Patients’ scores ranged from 0 to 14, with a mean score of 0.84 (Figure 4). Of 157 patients who were followed up, 32 (20.9%) complained of incontinence; among them, incontinence to gas was predominant (n = 17, 53.1%). Incontinence to liquid stool was reported by 16 patients (50.0%) whereas only five (15.6%) patients were incontinent to solid stool. Of the 96 patients who underwent fistulotomy, 16 patients developed recurrence (p = 0.010). Occurrence of incontinence was unrelated to surgical procedures. Among patients with incontinence, 18 had simple fistulae and 13 had complex fistulae. The age of the patient had no correlation with the healing of fistulae or with incontinence.

Table 1.

Comparison of different surgical procedures used in the treatment of fistula-in-ano.

	Fistulectomy	Fistulotomy	LIFT procedure	Cutting seton insertion
Total surgeries performed, including repeat procedures	47	157	5	113
Subsequent surgeries	Fistulotomy = 3Cutting seton = 8	Fistulectomy = 4Cutting seton = 51LIFT = 4	Fistulotomy = 1	Fistulotomy = 6Fistulectomy = 5
Sex ratio	36:11	130:27	4:1	90:23
Follow-up	27 (57.4%)	96 (61.1%)	5 (100%)	29 (25.7%)
Healed after surgery	24 (88.9%)p = 0.949	90 (93.8%)p = 0.010	4 (80%)p = 0.543	27 (93.1%)p = 0.014
Incontinence following surgery	6 (22.2%)p = 0.854	22 (23.2%)p = 0.383	1 (20%)p = 0.959	14 (48.3%)p = 0.444
Recurrence (in follow-up)	2 (7.4%)p = 0.467	16 (16.7%)p = 0.010	0p = 0.413	5 (8.5%)p = 0.361

Note: p value is in comparison with other interventions.

LIFT, ligation of intersphincteric fistula tract.

Table 2.

Comparison of anal incontinence and recurrence rates between simple and complex fistulae.

Fistula type	Anal incontinence observed			Recurrence observed
Simple	18	58.1%	p = 0.071	3	16.7%	p < 0.001
Complex	13	41.9%	p = 0.071	15	83.3%	p < 0.001

Figure 4.

Number of patients who developed various types of anal incontinence.

Recurrence was observed in 18 out of 157 patients who were followed up; of these, 15 patients (83.3%) had complex fistulae (p < 0.001). Among patients with recurrence, most had undergone fistulotomy (n = 16, 88.9%). The rate of recurrence was higher in the group that underwent fistulotomy versus those who had other procedures but this was not statistically significant (Table 1).

In our cohort, 12 patients (11 men) had Crohn’s disease; of these, 58.3% (n = 7) had transphincteric tracts. All patients with Crohn’s disease had one internal opening, and the number of external openings ranged from 1 to 7. Notably, 7 out of 12 patients required more than one surgery. The median number of surgeries performed in patients with Crohn’s disease was two (range: 1–11). In addition to surgical management, medical management for Crohn’s disease was commenced or continued. Follow-up details were traceable in only nine (75%) patients; among them, only four patients (44.4%) had complete healing. In post-operative follow-up, five of seven patients complained of incontinence and two patients underwent stoma creation; therefore, incontinence was not assessed in these patients.

Discussion

In this study, we analyzed the operative experience in a single surgical unit including 640 anal fistula procedures in 284 patients. Commonly performed surgeries included fistulectomy and fistulotomy. Most patients (55%) underwent more than one surgical procedure. During follow-up, patients were mainly evaluated for healing of the fistula, complications, and recurrence. Complete healing was achieved in 88.5% of patients who underwent surgical treatment.

A study conducted by Farag et al. on fistulotomy in which fistulae were laid open, allowing healing from the base, aggressive fistulotomy led to postoperative incontinence but inadequate treatment resulted in recurrence.¹⁹ In our study, of the 96 patients who were followed up after fistulotomy, 22 patients developed incontinence, and recurrence was noted in 16 patients (p = 0.010). However, the rates of complication were comparable between fistulectomy and seton insertion.

In a study by Seyfried et al., fistulectomies with primary sphincter reconstruction had a lower recurrence rate than the aforementioned techniques.²⁰ Of 27 patients who were followed up after fistulectomy, incontinence was present in six (22.2%); however, recurrence was present in only two (7.4%) patients. In a recent study by Roig et al., among 75 patients who underwent fistulectomy and sphincter reconstruction, 10.6% had incontinence and recurrence was seen in 26.6%.²¹

In our study, cutting seton was used in 113 patients; the limited follow-up details showed that 23.2% had incontinence. In comparison, Vatansev et al.²² used a cable tie cutting seton in 32 patients and 15.6% had incontinence. In a similar study, Chuang-wei et al.²³ observed incontinence in 24.1% of patients.

According to Garg at al.,²⁴ use of an anal fistula plug has high rates of healing; however, owing to an unsustained healing rate, this has been discontinued since 2012. Omar et al.²⁵ also stated that recurrence rates with a fistula plug were high. Therefore, a similar method was adopted during the early part of our study and later discontinued. In the present study, the LIFT procedure was performed five times and successful healing was achieved in four cases. A systematic review of LIFT showed that the original LIFT procedure had a recurrence rate of 9.7%; no recurrence was noted in the modified procedures.²⁶

The type of fistula influences post-operative fecal incontinence and recurrence and can determine the estimated amount of muscle loss during surgery. Visscher et al. stated that incontinence and quality of life were comparatively more affected after surgery for complex fistulae than for simple fistulae.²⁷ We found that among patients with incontinence, 18 had simple fistulae and 13 had complex fistulae. In our cohort, selected patients with troublesome incontinence underwent anorectal ultrasound and manometry; however, these investigations were not done routinely owing to resource constraints.

The management of an abscess includes drainage of pus or fluid collection, and the cavity should be kept empty by ensuring continuous drainage during the postoperative period.^24,28 Thus, abscesses are drained and associated cavities are completely curetted. In the study center, associated cavities are treated by inserting irrigation tubes and injecting 0.5% to 1% sodium hypochlorite solution as an antiseptic until the cavity is fully contracted.¹⁶

Prolonged placement of draining setons is the preferred management of anal fistula in Crohn’s disease. Similarly, fistulotomy and insertion of seton was performed in most of our patients in addition to medical management. Hermann et al. suggested that surgical management should be combined with medical measures including azathioprine and biological agents such as infliximab or adalimumab (anti-tumor necrosis factor antibody).^29,30

Several limitations are present in this study. A considerable proportion of the study population was lost to follow-up and was not traceable despite proper documentation of contact details; thus, the reasons for the defaulting of treatment could not be determined. According to a study by Garg et al., performing preoperative magnetic resonance imaging in all patients improved the healing rate in fistula surgery.²⁴ However, this is not feasible in our healthcare system owing to financial restrictions and limited resources, in which complex imaging is mainly reserved for patients with cancer. During follow-up, a few patients (n = 6, 3.8%) sought traditional treatment options, which may have affected the outcome of surgical management. Despite these limitations, the results of this study are likely to have acceptable generalizability owing to the large catchment population and referrals from most parts of Sri Lanka.

Conclusion

At our center, the healing rate in the surgical treatment of fistula-in-ano was 88.5%, with acceptable complication rates. Notably, there was no association between the type of surgical procedure and incontinence.

Footnotes

Authors’ contributions

UJ, VS, and DNS formulated the concept and design of the study and the acquisition and analysis of data; collected, analyzed, and interpreted the data; drafted the article, revising it critically for important intellectual content and approved the final version to be published. All authors have read and approved the final version of the manuscript.

Availability of data and materials

The data used in the above analysis are available on reasonable request from the corresponding author.

Declaration of conflicting interest

The authors declare that there is no conflict of interest.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

ORCID iD

Umesh Jayarajah

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