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16 The Seton in Anal Fistula Management 253
tightening, which led to the cutting of the fistula, followed by a skin excision and
ligation of the fistula channel. In addition to this surgery procedure, the Hippocratic
school doctors introduced into the medical practice a chemical cauterization of
fistula, which was performed in several ways: by burning sulfur powder over an
open fistula; by pulling of the linen thread fiber, wrapped like a wick soaked with the
spurge juice and sprinkled with sulfur powder into the fistula channel, which was left
for 5 days; as well as by injection into the fistula channel of sulfur and saltpeter
myrrh powder. Before the injectio n of the mixtures, a probe was placed into the
opening of fistula, which showed the way and facilitated the injection.
Based on the same principles, the roman Aulo Cornelio Celso (25 BC–45 AD),
the Middle Eastern physicians Albucasais (936–1013 AD) and Avicenna
(980–1037), the medieval physician John of Ardene (1307–1392) or the French
renaissance surgeon Ambroise Pare (1510–1592) and many others described a
variety of methods to treat fistulae, in particular with setons.
Fistula treatment has not changed much over the centuries, and still today the use
of the seton is a fundamental resource in the management of a perianal fistula.
3 To Put or Not to Put
In front of a perianal abscess, an adequate drainage is often needed. Slightly over one
in four (28%) surgeons would always place a seton if an internal opening and tract
were found during incision and drainage, whi le one in six (16%) would never
consider this option. A large proportion of respondents would place a seton only
in selected cases, depending on the characteristics and location of the abscess (Ratto
et al. 2019).
However, if a surgeon should search for a fi stula at the time of the initial incision
and drainage of an abscess is still controversial and even if positive results of
fistulotomies during abscess drainage have been reported, results seem to depend
on the surgeon’s experience. If the surgeon is not familiar with anorectal anatomy or
pathology, or concomitant risk factors (i.e., anterior fistula in women) are present,
the anal fistula should not be searched for (Abcarian 2011). Perianal abscesses are
thought to result in fistula in more than 50% of cases. Therefore, if a drainage site of
an abscess does not heal in 2–3 months or breaks down after healing, a fistula should
be strongly suspected, and the patient should be further evaluated with imaging
(transanal ultrasound, magnetic resonance imaging).
Surgical treatment of fistula-in-ano is dictated by the amount of sphincter
involvement, and internal and external anal sphincter preservation is in the
interest of continence maintenance. In fact, in t he last 25 years, the percentage
of sphincter cutting procedures has been decrease d from 98% to less than 50%
(Blumettietal.2012).
There are a variety of reasons to use setons in the management of anal fistulas.
They serve mainly to drain the track preparatory to an attempted repair (bridge to
sphincter preserving techniques), as a way of staging a fistulotomy, or to set the stage
for spontaneous healing. The intent is to allow decompression of the sepsis in the
254 J. Martellucci and M. L. Vuolo
track, and this means that accessory tracks and cavities are drained, and the acute
inflammation associated with the primary track is allowed to subside. This procedure is also intended to stimulate a foreign body reaction and induce a slow
division of the track. Unfortunately, until now, no proof of this mechanism has
ever been published and if the use of seton is really useful in improving secondary
surgery results or necessary as a bridge to other surgery has not yet been proven by
comparative studies.
Moreover, sometimes fistulas are already adequately drained by their track
without the need of a seton and the seton generates an enhanced primary track
fibrosis that can theoretically negatively affect the outcome of future treatments. On
the contrary, it has been postulated by several reports that the seton should lead to a
better outcome of ligation of the intersphincteric fistula tract (LIFT) or advancement
flap procedures, because it enables better identification of the intersphincteric tract
by allowing maturation of the tract around the seton (Shanwani et al. 2010; Tan et al.
2011, 2012).
4 To Cut or Not to Cut
Seton-based techniques are popular methods for treating anal fistulas. Using seton
converts an inflammatory reaction to a foreign body reaction with subsequent
perisphincteric fibrosis. These techniques are categorized as cutting (tight) and
non-cutting (loose) regarding their mechanism of action.
The cutting seton and the two-stage fistulotomy are the most commonly used
techniques based on this simple surgical principle (García-Aguilar et al. 1998).
Loose seton works as a drain, which may remain in place for a long time.
Sometimes, it makes the fistula persistent by stimulating fibrosis around
it. Division of the muscle encircled by the fistula is then performed as a second
procedure (two-staged fistulotomy) or the fistula tract treated with other sphinctersaving procedures, usually between 6 and 12 weeks after seton placement. On the
contrary, by periodic tightening around the tissue encircled by the fistula, the cutting
seton gradually transects the muscle by pressure necrosis. It needs to be tightened
several times after surgery and may cause severe pain and results in fecal or gas
incontinence due to a short time for healing of the sphincter after cutting it. Different
techniques for tightening the seton, including knots and rubber bands, are reported.
Length of time between tightening is typically reported and varies widely from paper
to paper, often generating heterogeneous and not comparable results.
The utility of cutting seton has been well-established. However, in recent times,
some large case seri es reported to use this procedure in less than 10% of the cases
(Kelly et al. 2014).
This could be related to the development and the availability of new sphincter-
saving techniques and greater attention to functional outcomes. In fact, the incidence
of fecal incontinence after treatment with primary fistulotomy or tight seton is often
reported as similar and related to the complexity of the fistula.
16 The Seton in Anal Fistula Management 255
On the contrary, treatment with loose seton as a bridge to other sphincter-saving
techniques may result in higher rates of recurrence or persistence of the fistula tract
or orifice.
Moreover, proponents of the cutting seton argue that they do not need a second
operation, whereas those in favor of the loose seton argue that the cutting seton
produces unnecessary pain and divides the sphincter in an uncontrolled way.
Although many advocate that loose seton placement should be the gold standard
in the management of complex fistula, existing literature reporting the outcomes of
anal fistula treatment with the placement of a loose seton consists of small/medium
volume case series with limited follow-up and conflicting results when compared to
other techniques, leaving to the surgeon the choice of the best treatment based on
personal experience and patients’ characteristics.
5 What Kind of Seton to Use?
The choice of material for the cutting seton was influenced by several considerations. The use of different mater ia ls i ncl ud in g sil ico ne, s il k, r ubb er bands, stainless steel wire, catheters, cut strips from surgical gloves, and sutures has been
described, all of which are fixed in place by some kind of knot or knot-free
connections (Subhas et al. 2012).
The correct use of setons minimizes the symptoms from the seton itself and
optimizes its effectiveness (Bolshinsky and Church 2018). The characteristics of the
main types of seton are shown in Table 1.
Nowadays, the selection of the type of seton is often based on personal prefer-
ences, and the advantages and disadvantages of the different seton techniques have
not been clearly established by clinical trials.
Table 1 Kind of setons in use and main characteristics
Local
reaction and
fibrosis Tolerability
Nylon/
polypropylene
(monofilament)
Silk
(polyfilament)
Silicone/rubber
band (vessel loop)
Surgical drains
(Penrose,
Nelaton)
Medicated seton xxx x xxx xx xx xxx
Knot-free x xxx x xx xxx xxx
x xx xx xxx x x
xx xxx xx xxx xx x
x xxx x xx x x
x xx x xx xx xx
Ability
to
section Drainage
Risk of
loss or
breakage Cost
256 J. Martellucci and M. L. Vuolo
0 or 1 nylon or polypropylene were commonly used in clinical practice. Poly-
filament (i.e., silk) is theoretically predisposed to higher bacterial colonization, but
this is not reflected in the clinical outcome.
Although there was no significant difference in the outcomes comparing silk and
polypropylene sutures, the number of patients requiring multiple sessions was higher
in the silk suture group, with a longer duration of seton placement. In addition, it was
observed that the requirement for fistulotomy was quite high in most patients
undergoing silk seton placement as it failed to transect after a certain level. However,
even if polypropylene material provided a better cut, it caused a significantly higher
amount of pain compared to silk seton especially during daily activities, which was
persistent even during defecation and rest (Akici and Ersen 2020).
Rubber, silicone, silastic vessel loops, or bands have been used but mainly as
loose setons in acute sepsis or in semi-permanent setons in complex Crohn’s/
radiotherapy fistulae. However, these materials have more elasticity, and so the
cutting and fibrotizing actions are less predictable.
The use of a knotted loose seton for complex anal fistulas can cause perianal
discomfort and reduced quality of life. There are several commercially available
alternatives with a knot-free closure mechanism. When compared with a conventional loose seton, the knot-free seton was associated with improved tolerability and
greater perianal comfort with significantly less burning sensation and pruritus.
However, besides these advantages, there are also some inconveniences associated
with the knot-free loose seton, particularly, the closure mechanism as a potential
weak point (Verkade et al. 2020). In fact, the incidence of loss of seton (LOS) is
significantly higher in patients with knot-free loose setons.
Reinterventions after seton placement are frequent in clinical practice, but the
exact incidence of LOS in patients is unknown.
Medicated setons are also described, especially in Ayurvedic practice. This
technique (Kshara sutra) has ancient origins and involves the use of surgical linen
thread smeared with an alkaline caustic solution of herbs. A prospective randomized
trial by Ho et al. comparing ayurvedic cutting seton and fistulotomy for low fistulain-ano concluded that the chemical seton was more painful than conventional
fistulotomy and there was no difference in time to wound healing, complications,
or functional outcome (Ho et al. 2001).
6 Draining Seton as the Only Treatment
(A Pathophysiological Paradox?)
Could a high transsphincteric fistula close spontaneously after the removal of a loose
seton maintained for a few months? Even if the negative answer to this question
seems obvious, due to the structural fibrosis of the tract around the seton, it
anecdotally happens that some patients treated by placement of a draining seton,
followed by removal at an interval or after the loss of seton, will experiencing
resolution or significant amelioration of their symptoms.
16 The Seton in Anal Fistula Management 257
In the 76 patients reported in the study of Daodu and colleagues (2018), the
external portion of the fistula and any residual abscess cavity was unroofed to the
edge of the external sphincter and all granulation tissue curetted. The sphincter
muscle was not divided. A doubled large vessel loop was then passed through the
fistulatractandtiedandtheknotadditionallysecuredwitha2-0silktie.Seton
removal was planned after 6 months for those patients who were symptom free. In
this experience, 56 patients (73.7%) experienced complete symptom resolution
after the removal of the seton. Fourteen (18.4%) had significant amelioration of
symptoms with no additional surgical management required. Six (7.9%) had
persistent severe symptoms, and two went on to another attempted definitive
procedure. Only five (7.8%) patients experienced the recurrence of the fist ul a
after seton removal after a mean follow-up time of 63 months. The average time
to recurrence was 25.2 months.
Emile et al. (2017) reported 251 patients with high transsphincteric fistula that
were treated with loose seton placement. Fistulectomy was conducted from the
external orifice until the point where the track passed beneath the external anal
sphincter muscles. A 1 silk thread was placed loosely around the remaining part of
the track and the anal sphincter muscles. Seton was removed after 3 months upon
complete healing of the superficial wound and when there were no signs of perianal
discharge. Patients were followed for a median period of 16 months. The recurrence
of FIA was recorded in 26 patients (10.3%) of patients after a mean duration of
12.2 3.9 months of seton removal. Significant risk factors for recurrence were
previous fistula surgery, anterior anal fistula, and presence of secondary tracks or
branches as supralevator extension and horseshoe fistula.
Similarly, Eitan and colleagues (2009) reported the results of 41 patients in which,
after excising the anal mucos a and opening of the inter-sphincteric space with an
attempt to preserve the internal anal sphincter as much as possible, a loosely tied
no. 1 prolene or rubber seton is placed to encircle the remaining internal and external
anal sphincter. The seton was removed after a minimal period of 3 months, leaving a
tract for spontaneous healing. After a mean follow-up duration of 5.1 years, fistula
persistence was recorded in eight (19.5%) patients.
Moreover, Subhas and colleagues reported healing of the high transsphincteric
fistula tract in 75% of patients with a simple progressive migration technique
(Subhas et al. 2011). It consists of the daily rotation of the 0 silk seton by the patient,
pulling the knot through the fistula tract. In 38% (9 patients), seton completely
worked their way to the surface, requiring no further surgery. In another 38%
progressive migration was extensive enough to allow a simple incision of superficial
skin bridge. In the remaining 25% (6 patients), they opted for alternative techniques.
A similar approach was reported by Kelly (Kelly et al. 2014), in whom a suture seton
was tightened every 6–8 weeks, in preparation for a superficial or “controlled”
fistulotomy. Healing occurred in 94% of patients with only minor disturbances in
anal sphincter function in 4% of patients.
The mechanism by which a drainage seton may act as a definitive treatment of
anal fistula is still not clear; it could be because the seton gradually erodes its way
through the fistula tract and anal sphincter muscles or because the internal opening
258 J. Martellucci and M. L. Vuolo
Table 2 Results of fistula treatment after seton removal
No. of patients
Daodu et al. 76 6 months 63 months 11 (14%)
Emile et al. 251 3 months 16 months 26 (10%)
Eitan et al. 41 3 months 61 months 8 (19%)
Time before
removal Follow-up
Persistence or
recurrence
may move distally in the anal canal outside of the high-pressure zone, allowing the
tract to heal.
According to these results (Table 2), the recurrence rate is comparable to the rates
of other popular and effective sphincter preserving techniques such as LIFT or
advancement flaps. From another point of view, if these data will be confirmed by
large randomized trials, there would be no difference in selected cases between
simply removing the seton or submit the patient to further surgical treatment, with an
increased risk of surgical complications or continence impairment. As evident,
however, existing literature reporting the outcomes of anal fistulae treatment with
the sole placement of a loose seton consists of small volume retrospective case series
with limited follow-up. The success rate of the loose seton removal for complex
fistula-in-ano may fall over time. Counseling before seton removal should emphasize that, although most patients do not require sphincter division and some are cured
by this technique, many patients may develop further sepsis that usually requires
surgery (Buchanan et al. 2004).
7 Seton 2.0: New Perspectives
The concept of re-routing a fistula tract with a seton was previously reported, aiming
to reduce the functional impairment of cutting setons or in the treatment of high
complexity fistulas such as the rectovaginal, horseshoe, or Crohn’s related, aiming to
drain large tracts without large incisions or to simplify the main tract.
Pinedo et al. (2010) adapted the same principles in 18 patients with transsphincteric fistulas. The external part of the track was laid open to the outer surface
of the external sphincter and an internal sphincterotomy was performed to lay open
the intersphincteric element of the track. A loose elastic seton was inserted in the
remaining track through the external sphincter and removed when the internal
opening had migrated to the anal verge. All setons were eventually removed after
a median of 4 months; however, it is not clear how many fistulas healed, although
there was deterioration in anal control reported.
Lim et al. (2012) described a similar modification of the loose seton technique.
The primary track was re-routed into the intersphincteric space, by dividing the
mucosa and internal sphincter below the internal opening and placing a seton around
the external sphincter in the intersphincteric plane, before closing the internal opening,
mucosa, and divided internal sphincter over the seton. A total of 53 patients were
treated by this technique, with a reported recurrence rate of 13% and incontinence
16 The Seton in Anal Fistula Management 259
reported by two patients. However, the follow-up was mostly done by telephone
contact, and no clinical assessment was made to confirm the healing of the fistula.
Following the same principles, Omar et al. (2019) described a similar technique.
After the excision of the fistula tract until the external anal sphincter (EAS) fibers, a
1 silk seton was inserted. Then patients were randomized into tw o groups: in group
1 (conventional drainage seton group), the 2 ends of the silk suture were tied loosely
around the remaining part of the fistula tract, EAS, and IAS. In group 2 (EAS-sparing
seton), after passing the silk suture through the remaining part of the tract, dissection
into the intersphincteric plane was carried out then the silk suture was rerouted
across the intersphincteric plane and tied around the IAS only, sparing the EAS
muscles. The point where the fistula tract was passing through the EAS was closed
with a readsorbable 3/0 suture. Patients treated with external anal sphincter-sparing
seton after re-routing of the fistula tract achieved quicker healing and less postoperative pain than those with conventional drainage seton. However, postoperative
complication and recurrence rates were comparable in both groups.
A comparison of the two approaches (internal vs external anal sphincter
rerouting) was reported by Abdelnaby et al. (2019). In this study they randomized
two groups of patients. In group I, after the seton was introduced inside the fistula
tract, it was rerouted by dissection in the intersphincteric plane and was tied loosely
around the EAS, sparing the internal anal sphincter (IAS) fibers. The internal fistula
opening was excised and was closed by the advancement of an elliptical mucosal
flap. Patients were then examined under anesthesia after 4–6 weeks to confirm
healing of the flap and absence of internal opening, and then the loose seton was
cut, without dividing any EAS fibers. In group II, after the seton was introduced inside
the fistula tract, it was re-routed by dissection in the intersphincteric plane and was tied
tightly around the IAS, sparing the EAS. The seton was kept in place until it fell
spontaneously after cutting through the IAS fibers. The drained mucosal flap technique
was associated with a significantly lower incidence of fecal incontinence, even if with
longer operative time and longer time to complete healing compared to rerouting seton
around the IAS. The success rates of both techniques were comparable.
Despite the results of these studies, based on small numbers, weak outcome
measures, and follow-up methods, the concept of rerouting the fistula tract may
represent an intriguing option for further research.
8 Uncomfortable Questions (How to Do It)
Although the seton can claim a long hist ory, there are still many daily clinical
activity questions:
• I want to put my seton but I’m not able to find the internal orifice. Can I do it?
• Can my seton be misplaced?
• How many setons I have to put in the same tract? How long should it be?
• Is there something wrong if my seton is in place but new external openings
appeared?
260 J. Martellucci and M. L. Vuolo
The answers to many of these questions are still conditioned by personal experience and expertise. For sure, a correct use of seton is essential to benefit from its
effects, minimizing discomfort. Emerging data from ultrasonographic or videoassisted fistuloscopic studies on recurrences or ineffective setons suggests that
seton misplacement is more frequent than supposed, as well as a nonoptimal use
of setons (too long, too tight, too many setons in the same tract, too small, too big,
too many knots, etc.).
The surgeon should avoid opening up communication between a diseased and an
intact space as this maneuver is likely to extend the septic process. After the previous
drainage of the abscess, a finger in the rectum may help to identify the fibrotic tissue
around the internal fistula opening. Peroxide or other solutions can be injected into
the external orifice to better identify the internal orifice during anoscopy. Preoperative or intraoperative endoanal ultr asound should also be considered for internal
orifice identification and evaluation of sphincteric tissue involvement. Internal
orifice should be expected at 6 or 12 o’clock according to Goodsall’s rule. It suggests
that if the pe rianal skin opening is posterior to the transverse anal line, the fistulous
tract will open into the anal canal in the midline posteriorly, sometimes taking a
curvilinear course. A perianal skin opening anterior to the transverse anal line is
usually associated with a radial fistulous tract. If despite all these measures the
internal orifice is not identified, its artificial creation should be avoided in order
not to create false iatrogenic tracks.
Once the internal orifice is suspected or demonstrated, a probe is passed gently
and passively along the track, using enough force to make the probe move but not
forcing it past resistance. The probe should be used to explor e the track, inserting and
withdrawing in different planes and different directions until the route of the fistula
becomes obvious. Once the track has been identified, its relationship to the anal
sphincters can be assessed. This is done by palpating the track through the skin and
assessing the thickness of the tissues superficial to the track. The seton can be then tied
to the probe or inserted through the eye of the probe and pulled through the track.
The external opening of the fistula should be enlarged to prevent it from
narrowing around the seton, and the diameter of the seton must be suitable for the
track to be drained. Drainage must be adequate to completely depressurize the track.
The ideal length of a seton is tight enough to have a low pro file so as not to get in the
way of toileting but loose enough not to erode the skin. Because the knot that creates
the seton circle will inevitably enter the track, it should be as small as possible. This
means just two throws of the tie, squared, and cutting the ends of the tie and the seton
close to the knot (Bolshinsky and Church 2018).
9 What Patients Should Know
Often patients undergoing seton placement have many questions and doubts. They
usually find the answers themselves, in daily life. Questions about medication,
dressing, hygiene, daily life activity, return to work, sexual activity, or complications
are common, and surgeons should provide useful information after surgery:
16 The Seton in Anal Fistula Management 261
• What to expect : the fistula will continue to drain. The volume of drainage may
increase at first and should lessen as healing occurs. Discomfort with prolonged
sitting and certain activities may be noticed. Many individuals are able to return to
work and resume routine activities the day after their procedure. Some people
require a week off from work if the surgery is more extensive. Generally, within
1–2 weeks, surgical discomfort is minimal. Sexual activity is not forbidden. From
about 2 weeks after surgery, patients could return to sexual intercourse if they feel
comfortable, taking care to not dislodge the seton.
• Diet and medications: a normal diet can be early resumed after surgery. It is very
important to prevent constipation after surgery, and fibers or stool softeners could
be considered. Excessive straining due to constipation may cause seton dislodg-
ment or further complications or damages.
• Personal care: excessive bathing and wiping of the perineal area are not necessary
and may increase discomfort. The area should be kept clean and dry. Ladies’
sanitary towels may be useful (thin variety). After at least 4 weeks, the seton
could be gently rotated during a bath, to prevent it from getting crusted with
bodily fluids and to help fistula tract migration towards the distal anal canal.
• Seton breakage: occasionally, the seton can break or may become displaced and
fall out. If this occurs, it is not an emergency. If the patient finds it, he can take it to
the surgeon to assess whether it has fallen intact (fistulotomy completed) or
broken. In the second case, repositioning can be considered.
10 Conclusions: Seton in Guidelines
The role of the seton for the treatment of anal fistula is variably reported in
international guidelines (Table 3). Many of these suggest a cautious use of the
cutting seton, while loose seton is usually considered as a bridge for sphinctersaving procedures. Seton for intersphincteric or low transsphincteric fistulas is
widely considered unnecessary, considering fistulotomy as the main treatment.
However, looking at the heterogeneity of the studies on this topic, the variability of the results and their methodology usually retrospective and with short
follow-up often performed by phone remains the impression that although the
seton is an ancient treatment, its role in fistula management can still be further
explored.
The evidence supporting the use of setons in the management of anal fistulas was
comprehensively reviewed in the original position statement on anal fistula
(Maksimovic and Maksimovic 2013).
Essentially a seton can be used in three main ways in the treatment of an anal
fistula, with myriad variations of technique between published series. The seton
can be inserted and tied loosely over the sphincter to drain the track and allow
sepsis to settle before it is removed, in the hope that the fistula will heal (loose
seton). The seton can be used to divide the sphincter muscle slowly to eradicate
the fistula (cutting seton), and the seton can be used as a long-term drain to
provide palliation.
262 J. Martellucci and M. L. Vuolo
Table 3 The use of seton in international guidelines
European Society of Coloproctology (ESCP)
2018
Systematic review and consensus (de Groof
et al. 2016)
German Society Guidelines 2017 (Ommer
et al. 2017)
Association of Coloproctology of Great
Britain and Ireland (ACPGBI) Position
Statement 2018 (Williams et al. 2018)
American Society of Colorectal Surgeon
(ASCRS)
Practice guidelines 2016 (Vogel et al. 2016)
The use of the cutting seton is not advised
because of the risk of incontinence
No consensus, highest level of evidence 2a
Loose seton placement is an effective
treatment reducing the chance of recurrent
abscess formation
Consensus, highest level of evidence 2a
Chronic loose seton drainage is an important
alternative treatment for complex perianal
fistula
Consensus, highest level of evidence 2a
Some surgeons advise a loose seton before
surgery aiming at cure
No consensus, highest level of evidence 2a
The most important function of the seton
drainage is preparation for subsequent
definitive treatment of high anal fistulas
demonstrated during abscess drainage
Evidence level: 2a
Recommendation grade: B
Consensus strength: strong consensus
A loose seton, used as a sole treatment,
results in fistula healing in only a small
proportion of patients. Higher healing rates are
achieved by staged fistulotomy after a period of
seton drainage
Evidence: Level III
A loose seton can be used to treat “high” and
complex anal fistulas with a low risk of
diminishing anal control
Recommendation: Grade B
A tight seton (cutting) inserted into a
transsphincteric fistula will result in healing in
upwards of 90% of patients. There is some risk
of diminishing anal control that is influenced
by the height of the internal opening and the
amount of muscle encompassed in the seton
Evidence: Level III
A tight seton can be used to treat selected
“high” and complex anal fistulas where other
techniques are either not suitable or have
failed. The patient should be counseled
carefully
Recommendation: Grade B
A cutting seton may be used with caution in
the management of complex cryptoglandular
anal fistulas
Grade of recommendation: Wweak
recommendations based on moderate-quality
evidence, 2B
(continued)