Anal Fistulae

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Systematic review doi:10.1111/j.1463-1318.2008.01483.x

Surgical management of anal fistulae: a systematic review

A. I. Malik and R. L. Nelson

Colorectal Unit, Department of Surgery, Northern General Hospital, Sheffield, UK

Received 10 September 2007; accepted 12 September 2007

Abstract

Objective The anal fistula has been a common surgical

ailment reported since the time of Hippocrates but little

systematic evidence exists on its management. We aimed

to systematically review the available studies relating to

the surgical management of anal fistulas.

Method Studies were identified from PubMED, EM-

BASE, Cochrane Controlled Trials Register, ClinicalTri-

als.Gov and Current Controlled Trials. All uncontrolled,nonrandomized, retrospective studies, duplications or

those unrelated to the surgical management of anal

fistulas were excluded.

Results The search strategy revealed 443 trials. After

exclusions 21 randomized controlled trials remained

evaluating: fistulotomy vs fistulectomy (n = 2), seton

treatment (n = 3), marsupialization (n = 2), glue therapy

(n = 3), anal flaps (n = 3), radiosurgical approaches

(n = 2), fistulotomyfistulectomy at time of abscess

incision (n = 5) and intra-operative anal retractors

(n = 1). Two meta-analyses evaluating incision and

drainage alone vs incision + fistulotomy were obtained.

Conclusion Marsupialization after fistulotomy reduces

bleeding and allows for faster healing. Results from small

trials suggest flap repair may be no worse than fistulot-

omy in terms of healing rates but this requires confirma-tion. Flap repair combined with fibrin glue treatment of

fistulae may increase failure rates. Radiofrequency fistul-

otomy produces less pain on the first postoperative day

and may allow for speedier healing. Major gaps remain in

our understanding of anal fistula surgery.

Keywords Systematic review, fistula-in-ano, seton,

fistulotomy, fistulectomy, perianal abscess, glue therapy,

flap repair

Background and aims

Anal fistulae have been known as a common surgical

ailment for over two and a half millennia. One of the

earliest papers written by Hippocrates in 400 BC

described fistulotomy as well as his use of a cutting seton

made of horse hair wrapped with lint threads [1]. Current

management remains dependent on surgeon preference

between options like fistulotomy, fistulectomy and (loose

or cutting) seton insertion. Recently, newer sphincter-

saving approaches utilizing flaps, fibrin glue and plugs of

various types have emerged especially for dealing with

complex (high or trans-sphincteric) anal fistulae.The first meta-analysis was by Nelson who suggested

that recurrence was less likely if fistulotomy was per-

formed at the same time as incision of a perianal abscess

[2]. A more detailed meta-analysis by Quah et al. looked

at the same area [3]. They analysed data from five studies

again looking specifically at the role of fistulotomy at the

time of perianal abscess drainage. We feel pooling of data

from these analyses is open to question for reasons

explained in this article. To date there is no other

systematic evidence available evaluating global treatment

for anal fistulae. We reviewed all available randomized

controlled studies relating to the surgical management of

anal fistulae.

Method

Study search and selection

English and non-English randomized controlled trials

(RCTs) relating to the surgical management of anal

fistulae were identified from PubMED, EMBASE, Coch-

rane Controlled Trials Register, ClinicalTrials.Gov and

Current Controlled Trials. A high sensitivity, low speci-

ficity approach was utilized in order to reduce chances of

missing relevant studies. For example the search terms

used for PUBMED were (anal OR anus OR anorectal OR

in-ano) AND (fistul*) AND (randomized OR randomized

Correspondence to: Prof. R Nelson, Department of Surgery, Northern General

Hospital, Herries Road, Sheffield S5 7AU, UK.

E-mail: [email protected]

420 2008 The Authors. Journal Compilation 2008 The Association of Coloproctology of Great Britain and Ireland. Colorectal Disease, 10, 420430


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OR trial OR control*) with similar but slightly altered

terminology for compatibility with the other databases.

Selected articles and reviews were scanned for further

citations. To minimize publication bias a hand-search of

colorectal conference proceedings (ACPGBI and ASCRS)

for the previous 5 years was performed to detect any

unpublished studies with negative results. All uncon-

trolled, nonrandomized, retrospective studies, duplica-

tions, those unrelated to the surgical management of anal

fistulae or studies purely recruiting Crohns patients were

excluded.

Quality assessment

For assessment of study quality, individual study quality

assessment was made focussing on the presence or

otherwise of randomization, concealed allocation of

participants, blinded outcome assessment if feasible, and

description extent of follow-up attrition rates. For somestudies where clinical issues affecting randomization were

considered important, e.g. preoperative vs intra-operative

randomization, inclusion of high vs low fistulae and

patients with Crohns disease, this was also taken into

account.

Data retrieval and analysis

From each study the participants (fistula type, random-

ized, treated, followed up, dropouts) overall and per

group were assessed. We also extracted information on

outcomes and adverse events from each study. This

included but was not limited to rates of patient satisfac-

tion, postoperative pain and bleeding, fistula healing,

fistula recurrence, perianal abscess, repeat surgery for

fistula or abscess and incontinence.

Analysis was performed on an intention to treat basis.

Patients without end-points were not assumed to be

treatment failures. For analysis of outcomes in the

radiofrequency fistula studies, relative risks (RR), their

confidence intervals and the chi-squared test for hetero-

geneity were calculated. The calculations were performed

utilizing the RevMan version 4.2 software (http://

www.cc-ims.net/RevMan) courtesy of the Cochrane

Collaboration.

Results

Description of studies

The search strategy revealed 443 trials and two

meta-analyses. After the exclusions described above 21

randomized controlled trials remained evaluating: fistulo-

tomy vs fistulectomy (n = 2), chemical seton vs

fistulectomyfistulotomy (n = 2), cutting seton vs inter-

nal anal sphincter (IAS) preserving seton with mucosal

flap (n = 1), incision and drainage of perianal abscess-

fistula vsincision with fistulotomyfistulectomy at time of

abscess incision (n = 5), fistulotomy fistulectomy alone

vs fistulotomy fistulectomy with marsupialization

(n = 2), anodermal island flap vs fistulotomy or loose

seton insertion (n = 1), advancement flap vs fistulotomy

with sphincter reconstruction (n = 1), endoanal advance-

ment flap vs endoanal flap with antibiotic impregnated

sponge (n = 1), fibrin glue vs fistulotomy or loose seton

insertion (n = 1), fibrin glue with either intra-adhesive

antibiotic or surgical closure of primary opening or both

(n = 1), advancement flap vsadvancement flap with fibrin

glue obliteration of fistula tract (n = 1), radiofrequency

fistulotomy vs conventional fistulotomyfistulectomy

(n = 2) and Parks vs Scott retractors during fistula

surgery (n = 1). Both meta-analyses looked at incision

and drainage alone vs incision + fistulotomy for perianalabscess-fistula [2,3].

Quality of included trials

Only four studies mentioned the randomization method

utilized [47]. In the Gupta study, the operation theatre

nurse picked a sealed envelope after the patient arrived in

theatre [4]. Zbar et al. used random numbers [5] and

Perez et al. used computer generated randomization [6],

but it was unclear if these numbers were concealed from

the investigators prior to participant randomization and

hence could have been open to selection bias. The fourth

study utilized a research secretary to create randomization

sequences in blocks of four which were unknown to the

surgeons or patients and kept in sealed envelopes [7].

We found 13 of 21 studies reported the use of sealed

envelopes to conceal allocation of participants after

random numbers had been generated [4,718]. Only

one study by Hebjorn et al. [19] had blinded assessors

during postoperative follow-up. Losses to follow-up were

mentioned by nine of 21 trials [611,1820]. Five studies

had average follow-up beyond a year ranging from 13 to

42 months [4,6,13,17,20]. Eight RCTs had average

follow-up of 1 year [5,7,8,11,12,16,19,21] and the

remaining eight trials had less than 1 year follow-up[9,10,14,15,18,2224].

Fistulotomy vs fistulectomy

To date only two RCTs have looked at fistulotomy vs

fistulectomy (Table 1). An RCT from Mexico demon-

strated significantly larger IAS and external anal sphincter

(EAS) defects on endoanal ultrasound in 40 patients

randomized to fistulectomy compared with fistulotomy

A. I. Malik & R. L. Nelson Surgical management of anal fistulae

2008 The Authors. Journal Compilation 2008 The Association of Coloproctology of Great Britain and Ireland. Colorectal Disease, 10, 420430 421


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[22]. Whether the larger defect size with fistulectomy

translated into meaningful differences in clinical outcome

could not be ascertained as there are neither follow-up

data published nor were they obtainable from theauthors.

The one study which has looked further is by

Kronborg and was published over two decades ago. He

demonstrated shorter healing times (34 days vs 41 days)

with fistulotomy compared to fistulectomy (P < 0.02) in

47 randomized patients [21]. No significant differences

in repeat surgery, recurrence or incontinence rates were

shown.

Setons for the treatment of anal fistulae

Setons, in use for over two millennia by mankind, consist

of passing a suture through the fistula tract and tied

tightly as a cutting seton to perform a slow fistulotomy

over weeks. Alternatively a loose seton may be placed

which is thought to control infection and attendant

symptoms, and also may eventually cut out producing a

cure. Astoundingly to date there are only four RCTs with

randomization which have evaluated this technique and

none have looked at the clinically important question of

how plain cutting setons compare with gold-standard

fistulotomy in terms of recurrence and incontinence rates

[3,7,9,15].

Two studies have looked at chemical (Ayurvedic)

setons when compared with fistulectomy [8] or fistulot-omy [9] (summarized in Table 2). This is essentially an

ancient Indian cutting seton technique where linen

threads are coated with layers of latex and plant extracts

producing a strongly alkaline outer layer which cuts

through tissues chemically at a rate of 1 cm every 6 days.

The large multicenter Indian study by Shukla (n = 503)

showed longer healing with chemical setons compared to

fistulectomy but a lower recurrence rate (4% vs 11%) [3].

Losses to follow-up at 1 year were significant (59%) and

could have affected the findings if those who received

fistulectomy and healed completely were less likely to

return for follow-up when compared with those having

chemical setons.The 2001 Ho paper (n = 108) compared chemical

setons to fistulotomy in low anal fistulae. He found no

difference in healing times, complications or functional

outcome. There was more pain in the seton group during

the first 24 days postop but this became insignificant by

day 7 [9].

Zbar (n = 34) on the other hand, compared conven-

tional cutting setons vsinternal anal sphincter preserving

cutting seton in high trans-sphincteric fistulae [5]. The

latter procedure consisted of closure of the internal fistula

opening by a short mucosal flap, an IAS repair and

rerouting of the cutting seton through the intersphinc-

teric portion for EAS cutting. While improvements in

resting anal manometry were demonstrated, these were

not statistically significant and there were no differences

in postoperative Pescatori incontinence scores, recurrence

or healing times at 12 months.

The only other RCT evidence relates to the use of

loose setons in patients with complex fistulae as compared

with fibrin glue treatment in the Lindsey study [10] and

is described further on in this article.

Fistulotomy with incision of perianal abscess-fistula

The perianal abscess contributes significantly to emer-gency surgical workload and the large number of studies

in this area reflects ease of patient recruitment. We

identified five studies summarized in Table 3 (n = 408)

exploring incision and drainage alone of perianal abscess-

fistula vs incision combined with fistula surgery [11

13,19,20].

The Tang study randomized patients after an internal

opening was demonstrated in theatre prior to incision of

the abscess [11]. Hebjorn et al. performed incision of the

Table 1 Fistulotomy versus fistulectomy (n = 2).

Study, Year Participants n Interventions Outcome Follow-up

Kronborg,

1985 [21]

Simple fistulae 47 Fistulotomyvs

fistulectomy

Healing time: 34 days vs 41 days (P < 0.02)

Repeat surgery: 3 26 vs 2 21 (ns)

Recurrence: 3 24 vs 2 21 (ns)

Incontinence: 1 24 vs 3 21 (ns)

12 months

Belmonte Montes,

1999 [22]

Simple fistulae 40 Fistulotomy

vs fistulectomy

Defect size on ultrasound at 6 weeks:

Internal anal sphincter: 8.5 mm vs 9.08 mm (ns)

Internal and external sphincter: 9.25 vs 11.38 (P < 0.05)

6 weeks

n, study sample size.

Surgical management of anal fistulae A. I. Malik & R. L. Nelson

422 2008 The Authors. Journal Compilation 2008 The Association of Coloproctology of Great Britain and Ireland. Colorectal Disease, 10, 420430


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Table

2

RCTsevaluatingsetoninfistulasurgery(n=3).

Study,Year

Participants

n

Interventions

Outcome

Follow-up

Notes

Shukla,1991[8]

Uncomplicated

analfistulae

502

Chemicalsetonvs

fistulectomyor

fistulotomy

Healingtime:8vs4weeks(median)

Healingat12weeks:180265vs210237(P

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