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64 M. P. Gosselink and H. Baharlou
Table 2 Incision and drainage with fistula treatment of cryptoglandular anorectal abscess
Recurrence
Author Year
Waggener et al. (1969) 1969 67 N.S. 9
McElwain et al. (1975) 1975 1000 43 4
Lai et al. (Eisenhammer
1978)
Ramanujan et al. (1984) 1984 323 36 2
Hebjørn et al. (1987) 1987 20 12 10
Schouten et al. (1991) 1991 36 43 3
Tang et al. (1996) 1996 24 23 0
Ho et al. (1997) 1997 24 16 0
Li et al. (1997) 1997 39 25 3
Knoefel et al. (2000) 2000 66 40 4
Oliver et al. (2003) 2003 100 12 5
Saber et al. (2016) 2016 100 N.S. 5
Galanis et al. (2016) 2016 100 12 6
Number of
patients
1983 32 5 0
Follow-up duration
(months)
(%)
abscess or
fistula
were excluded because the fistula tract could not be found, or in how many patients the
transsphincteric tract was assumed to be too high for fistulotomy .
The surgical management of the associated fistula should be carried out with great
care to avoid unnecessary damage to the sphincters with its potential risk of
alterations in fecal continence. Uneducated probing in the cavity of the abscess
could cause false routes. Furthermore, when the tissues are edematous and friable,
confident assessment of the amount of sphincter involved may be difficult.
A Cochrane systematic review of six randomized controlled trials on this topic
revealed that a small numbe r of patients may get transient incontinence following
abscess drainage with fistula treatment (Malik et al. 2010). In these patients the longterm effect of sphincter damage and associated fecal incontinence is still uncertain.
This is especially the case in patients with a high transsphincteric ischiorectal
abscess where the use of abscess drainage with fistula treatment is very controversial. None of the included studies provided information regarding the height of the
fistulous abscess. It is also important to realize that even in patients with a visible
internal opening, during rectal exam, the majority of patients will never develo p a
perianal fistula (Ho et al. 1997; Tang et al. 1996).
In a recent study, Rojansakul et al. described another technique to eradicate the
intersphincteric origin of the fistulous anorectal abscess in the acute setting (Rojanasakul
et al. 2021). They investigated primary closure of the internal opening via an
intersphincteric approach. They could easily identify the intersphincteric tract in 66 of
the 86 patients during the primary operation. In the remaining 20 patients the
intersphincteric space was explored in order to close the internal opening. The recurrence rate was 17% after 90 days follow-up. These results are very promising, especially
because more than half of the patients had high transsphincteric fistulous abscess. In
addition, no deterioration of fecal incontinence was observed after the intervention.
5 From Abscess to Fistula 65
Some surgeons advocate seton placement to avoid sphincter damage in the acute
setting of anorectal abscess, when the internal opening is easily identified; however,
a seton placed at this stage will definitely lead to a perianal fistula. As mentioned
earlier, even if an internal opening is clearly visible during emergency treatment, a
substantial proportion of these patients will have no further problems after incision
and drainage (Ho et al. 1997; Tang et al. 1996). However, an exception is the high
interspincteric superlevatoric abscess. In these cases the intershpincteric space must
be opened for adequate drainage (Onkelen van et al. 2013a; Zhang et al. 2016).
It seems evident that the anorectal abscess and fistula are part of a spectrum of the
same disease process. The driver of ongoing inflammation in the intersphincteric
space is still unclear. According to the cryptoglandular hypothesis, the persistence of
anal gland epithelium and associated mucus production might contribute to the
recurrence of anorectal sepsis. However, during fistula surgery no remaining anal
gland tissue with mucin-producing cells can be found (Mitalas et al. 2012). The
involved crypt is typically located in the transitional zone, where the dentate line
indicates the active changeover from columnar to squamous varieties, through the
process of squamous metaplasia (Herfs et al. 2011). This transition zone is prone to
chronic inflammation in the case of tissue damage. The local chronic inflammation
could lead to tissue stem cell failure or change in the differentiation pattern of
epithelial stem cells, explaining the non-healing character of anorectal fistulous
abscesses. It would be of interest to investigate if injection of stem cells in the
acute stage would have the same benefits as treatment with stem cells in
cryptoglandular fistulas (Zhou et al. 2020; Garcia-Arranz et al. 2020).
Taking into account that more than half of the patients treated with incision and
drainage alone will not develop further recurrence, the most important question
remains: Which patients are at risk of developing a perianal fistula after abscess
drainage? Shanan et al. performed a large retrospective study in a busy district
general hospital (Sahnan et al. 2019). Over an 11-year period 1826 patients with a
cryptoglandular anorectal abscess were identified. After a median follow-up of
45 months 14.9% of patients developed a perianal fistula. Shanan et al. looked at
risk factors such as gender, location of abscess, diabetes mellitus, and age. The only
independent predictor was that women are more likely to develop a persistent
perianal fistula following anorectal abscess drainage compared to men. This finding
was confirmed in another study from the same group, identifying 148,286 patients
with cryptoglandular disease in a national database (Sahnan et al. 2017). The rate of
fistula formation after initial treatment of the anorectal abscess in this study was
15.5%. Again, female sex was a significant independent predictor of fistula formation after drainage, with women 18% more likely to develop a fistula following an
abscess. This finding was also observed by Hämäläinen et al., showing that anterior
abscesses in females are exceptionally prone to fistula formation (Hämäläinen and
Sainio 1998). They could not explain this fi
nding but suggested that anatomical
aspects of the anorectum may play a role.
The national database study by Shanan et al., also found a higher risk for fistula
formation in patients aged 41–60 years with an ischiorectal or intersphincteric
location of the initial abscess (Sahnan et al. 2017). Sözener et al. also found that
ischiorectal and intersphincter ic abscesses had a higher risk of progression to fistula
66 M. P. Gosselink and H. Baharlou
than perianal abscesses (Sözener et al. 2011). This is of importance because it
suggests that the indication for fistulotomy in patients with perianal abscess may
be weaker than previously thought. However, a more recent study did not find a
significant correlation between location of the anorectal abscess and perianal fistula
formation (He et al. 2020). Two studies also found younger age significantly
increased the risk of disease recurrence (Hamadani et al. 2009; Gokce and Gokce
2020). Neither study could confirm female gender as a risk factor. Two other studies
looked into risk factors for perianal fistula recurrence following anorectal abscess
drainage, finding only a significant association between BMI and perianal fistula
recurrence (Gokce and Gokce 2020; Lu et al. 2019). Patient weight was unfortunately not included in the two studies by Shanan et al. (2017, 2019).
It was initially thought that detection of enteric organisms in the anorectal abscess
was associated with an increased risk of subsequent fistula formation (Eykyn and
Grace 1986). However, a recent case series of 164 patients found no statistically
significant association between the presence of gut-derived organisms and the development of a fistula or recurrent anorectal abscess at 1-year follow-up (Xu et al. 2016).
Furthermore, a multivariate double-blind, randomized trial showed that antibiotic
treatment after abscess drainage offered no protection against subsequent fistula
formation (Sözener et al. 2011). These findings are in line with two recent studies
that revealed the absence of viable bacteria in the perianal fistula tract (Onkelen van
et al. 2013b; Tozer et al. 2015). In contrast, a recent randomized trial of 307 patients
evaluated the role of antibiotics after incision and drainage of the anorectal abscess,
finding significant protection against fistula recurrence within 3 months of follow-up
(Ghahramani et al. 2017). In this study, metronidazole and ciprofloxacin were prescribed for 7 days postoperatively. With only a 3-month follow-up period, it remains
unclear if postoperative antibiotic administration would also decreasefistula formation
in the long term. Of note, men had a higher risk than women for fistula development
after incision and drainage in this study (Ghahramani et al. 2017).
In conclusion, anorectal abscesses and perianal fistulas are considered two phases
of the same disease. It is still unclear why some patients completely heal after
incision and drainage of the anorectal abscess and others go on to develop a perianal
fistula. To elucidate the many aspects of the abscess-fistula sequence, a better
understanding of the glandular infection arising from the anal crypts is necessary.
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5 From Abscess to Fistula 67
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fistula-in-ano following
Classification of Anal Fistula and Abscess
Useful Features to Address the Treatment
Pankaj Garg
Contents
1 Introduction . ..... . ............... ............................................................. 70
2 Purpose and Attributes of a Classification ................................................... 71
3 Overview of Anal Fistula Classifications . ...... . . ........................................... 71
4 Anal Fistula Classifications ................................................................... 74
4.1 Parks Classification ..................................................................... 74
5 St James’s University Hospital MR Imaging Classi fication ............ ..................... 76
5.1 Strong Points ............................................................................ 77
5.2 Weak Points ............................................................................. 77
6 Garg Classification . . . ......................................................................... 78
6.1 Grade I: LOW – Single Tract (Intersphincteric or Transsphincteric) .... ..... ..... ... 79
6.2 Grade II: LOW – Multiple Tracts or Associated Abscess or Horseshoe Tract
(Intersphincteric or Transsphincteric) .... . . . . . ....... . . . . ...... . . . . ....... . . . . ....... . . 79
6.3 Grade III: HIGH – Single Tract (Intersphincteric or Transsphincteric) or
Associated Comorbidities (Anterior Fistula in a Female or Already
Damaged/Weakened Sphincter, Post-Radiotherapy, Crohn’s Disease) ............... . 79
6.4 Grade IV: HIGH – Multiple Tracts or Associated Abscess or Horseshoe Tract
(Intersphincteric or Transsphincteric) .... . . . . . ....... . . . . ...... . . . . ....... . . . . ....... . . 82
6.5 Grade V: Suprasphincteric or Supralevator or Extrasphincteric ..... .................. 84
6.6 Strong Points ............................................................................ 84
6.7 Weak Points ............................................................................. 87
7 Status of Extrasphincteric Fistulas ........................................................... 87
8 Evaluation of Existing Classifications on Long-Term Data ................................. 88
9 Conclusions ......................................... .......................................... 90
References .................... ................................ ................................ .... 91
6
P. Garg (*)
Colorectal Surgery, Garg Fistula Research Institute, Panchkula, India
© Springer Nature Switzerland AG 2022
C. Ratto et al. (eds.), Anal Fistula and Abscess, Coloproctology,
https://doi.org/10.1007/978-3-030-76670-2_7
69
70 P. Garg
Abstract
Classification is required for any disease so that the disease can be graded both for its
severity or complexity. Moreover, a treatment guideline could be provided according
to the grades of the classification. The process of classifying anal fistulas started in
1934, and since then, it has evolved a lot. The initial classifications categorized anal
fistulas broadly as fistulas above the anorectal sling or the fistulas below the anorectal
sling. However, in 1950s, the role of intersphincteric space in the pathogenesis and
spread of fistulas was discovered. Since then, a major change came in the direction of
classifying fistulas. All the subsequent classifications categorized fistulas primarily as
either intersphincteric or transsphincteric. These included commonly used Parks and
St James’s University Hospital classifications. However, the main drawback of these
classifications was that they did not guide the management of the disease. In the last
decade, a new classification known as Garg classification tried to remove this major
drawback. This classification divided fistulas primarily as low (involving less than
one-thirds of the external sphincter) and high (involving more than one-thirds of the
external sphincter). Apart from being the most comprehensive classificationtobe
proposed, Garg classification seems to have optimally addressed both the issues,
classifying fistulas on the basis of their complexity and acting as a guide regarding
the management of the disease. Among all classifications, the three most relevant
classifications, Parks, St James’s University Hospital, and Garg classifications, would
be discussed in detail.
Keywords
Anal fistula · Fistula-in-ano · Classification · Fistulotomy · Parks · Incontinence
1 Introduction
It is a common practice to classify a disease. A disease can be classified by staging or
grading. Although these terms are used interchangeably, there is a difference
between the two words.
Staging: It is classifying the spread of the disease through the body which may
involve the surrounding tissues or distant organs. It is usually applicable in cancers as the
latter can potentially spread all over the body. The most used staging system is TNM
staging system – T ¼ Tumor; N ¼ node involvement, and M ¼ metastatic spread.
Grading: It is classifying the aggressiveness of the disease . In cancers, this
denotes the aggressiveness of cancer cells based on how different they look from
normal cells (differentiation), how quickly they are growing and dividing, and how
rapidly they can spread.
On the other hand, in benign diseases, both the terms, staging and grading, can be
used. However, it seems prudent to use grading for benign diseases as classification
of a benign disease focuses more on aggressiveness of the disease rather than its
spread in the body.
6 Classification of Anal Fistula and Abscess 71
2 Purpose and Attributes of a Classification
The next question which assumes importance is the purpose and utility of classifying
a disease.
The purpose of any classification is that it should be clear on the following:
1. Severity of the disease: A classification should grade the disease in the increasing
order of severity or complexity. In comparison to the higher grade which repre-
sents complex disease, the lower grade of the disease is expected to be earlier
diagnosed and a simpler stage of the disease.
2. Management of the disease: The classification should support the physician on
the disease management. In comparison to the higher grade, the lower grade of
the disease is expected to be managed more easily.
3. Prognosis of the disease: The classification should also preferably indicate
information about prognosis of the disease. In comparison to the higher grade,
the lower grade of the disease is expected to have a better prognosis and vice
versa.
Apart from giving useful information on the above three points, a good classification should be simple, easy to handle, and comprehensive (it should cover all
variants of the disease). A disease should not be classified just for the sake of doing
classification. It is becoming a trend to propose classifications for several diseases
where none are needed.
3 Overview of Anal Fistula Classifications
Anal fistula is one of the peculiar diseases which has intrigued clinicians for several
centuries. Until now, very few diseases evoked so much fear, interest, respect,
confusion, and emotions among surgeons as anal fistula has done.
The first attempt to classify fistulas was done by Milligan and Morgan (1934).
They classified the fistulas according to the relationship of the fistula tracts to the
anorectal ring. The fistulas were divided in two categories, anal fistulas as those
situated below the level of the anorectal ring, and anorectal fistulas as those situated
above the anorectal ring. This was a good beginning because this categorization
clearly identified and categorized the “highly complex” fistulas as anorectal fistulas.
In the era of no advanced radiological techniques as support, this classification
helped surgeons to identify fistulas in which extreme caution needed to be taken.
The next major advancement was identifying and highlighting the importance of
the intersphincteric space in the pathogenesis and spread of fistulas by Eisenhammer
(1958). The significance of this finding cannot be overstated. The presence and the
involvement of the intersphincteric space is perhaps the main reason which makes
anal fistulas more complex and refractory to treatment than almost all fistulas in other
parts of the body. Moreover, this finding was of paramount importance because it
became the basis of almost every classification that had been proposed since then.
72 P. Garg
Taking clue from the findings of Eisenhammer, Steltzner in 1959 proposed a
classification which divided fistulas as intermuscular (fistulas present between internal and external sphincters), transsphincteric, and extrasphincteric (Steltzner 1959).
This simple classification became the basic framework of all classifications for the
next half a century till it was changed for the first time in 2017.
Goligher in 1961 highlighted the relevance of levator muscle plate in grading the
severity of anal fistulas (Goligher 1961). He divided high fistulas as ischiorectal
fistulas ( fistulas which are up to the ischiorectal fossa, but below the level of levator
ani) and pelvirectal fistulas (fistulas which cross levator muscle). The importance
and association of the levator muscle with fistula pathogenesis was indeed a landmark in fistula classification.
In 1968, Lilius published the concept of upward spread of fistulas in the
intermuscular (intersphincteric) plane in the rectal wall (Lilius 1968). This was
quite interesting and prophetic because more than five decades later, it was recognized that supralevator extension of fistulas was almost always in the intersphincteric
plane (Garg 2016).
In 1976, assimilating and integrating all advancements in the field, Parks et al.
proposed a classification in which the fistulas were classified based on anatomical
location and were divided as intersphincteric, transsphincteric, suprasphincteric and
extrasphincteric (Parks et al. 1976)(Table1). This was the most comprehensive
classification to be proposed till date (Table 2).ItwasknownastheParksclassification.
However, a simple version of Parks classification soon came into vogue and became
quite popular (Table 3). It is used even today by many surgeons and radiologists.
The next landmark development happened in early 1990s, and it was the emergence of MRI in the field of anal fistulas. This was a major advancement as it
confirmed the prevailing concepts and understanding about
fistulas adding significant information at the same time. Utilizing MRI to classify the fistulas, Morris et al.
proposed a new classification in 2000 which came to be known as St James’s
University Hospital (SJUH) classification (Morris et al. 2000). As this was the first
classification to be proposed after the arrival of MRI on the global stage, it was a
wonderful opportunity to raise the level and utility of fistula classifications. Unfortunately, this did not happen. They could have given a better and clinically relevant
classification which could have been more useful to the clinicians. But the new
proposed and published classification (SJUH) was just a minor modification of Parks
classification and had no additional clinical utility at all (Morris et al. 2000).
Moreover, this classification was not based and validated by any patient data.
Even though SJUH has been commonly used across the world, it is not because of
its usefulness but perhaps because of the lack of any better alternative.
In 2005, the Standard Practice Task Force published the categorization of anal
fistula into simple and complex types (Whiteford et al. 2005). This was not exactly a
classification, but it seemed like an “advisory” to surgeons of what are complex
fistulas (fistulas whose treatment posed a high risk for impairment of continence)
(Whiteford et al. 2005). So, this was not used much either by the surgeons or the
radiologists.
6 Classification of Anal Fistula and Abscess 73
Table 1 Evolution of anal fistula classifications
Year Proposer Advancement in classification
1934 Milligan and
Morgan
1958 Eisenhammer Highlighted the importance of the intersphincteric plane both in
1959 Steltzner Fistulas into three main groups:
1961 Goligher High ano-rectal fistulas divided into:
1968 Lilius Extended the concept of intermuscular (intersphincteric) fistula
1976 Parks et al. Divided fistulas primarily based on location as whether it is
2000 SJUH– Morris et al. Though MRI based, this was essentially the same as Parks
2005 Standard Parameters
Task Force
2017 Garg Classified fistulas based on the extent of sphincter involvement.
Fistulas classified according to the relationship of the tracts to
the anorectal ring:
Anal fistulas – those situated below the level of the ring
Anorectal fistulas – those situated above the ring
the pathogenesis and spread of fistulas
Intermuscular – between internal and external sphincters
Transsphincteric
Extrasphincteric
Ischiorectal – fistula extends to the top of the ischiorectal
fossa
Pelvirectal – fistula penetrates the levator ani muscles, ending
in the pararectal tissue
extension upward into the rectal wall
intersphincteric, transsphincteric, or extrasphincteric and
divided fistulas into four categories
classification with slight modification and it divided fistulas into
five categories
Divided fistulas in only two categories:
Simple – linear low fistulas
Complex – all other than simple
It graded fistulas according to their complexity and gave
management guidelines based on classification
The next classification was published in 2017 by Garg (2017a). This classification
was based on observation and analysis of 440 operated fistula patients, who had got
preoperative MRI (Garg 2017a). It was the first classification to categorize fistulas on
the basis of extent of the sphincter involvement (Garg 2018a). This classification was
a major advancement because of several reasons. First, it was the first to move
beyond classifying the fistulas on the basis of the anatomic location as mainly
intersphincteric and transsphincteric types (Garg 2018a). Second, it was based on
440 operated patients whose findings were correlated with preoperative MRI scans
(Garg 2017a, 2018a). Third, it was the first to grade the disease on the basis of the
severity. And fourth, most importantly, this was the first classification which provided clear guidance regarding the management of the disease (Garg 2017a).
So, the classification of anal fistulas has been quite interesting and has evolved
slowly but remarkably over the last nine decades.