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ANORECTAL 297
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Advancement Flaps
Patients with persistent or recurrent fissures after LIS are challenging
to manage. Repeat LIS is not recommended given the high risk of permanent incontinence, especially in patients without increased sphincter tone. These patients without evidence of increased sphincter tone
may benefit from a fissurectomy combined with a dermal advancement flap. Two common advancement flap techniques are the V-Y
flap and house flap. A V-Y flap is created from the perianal skin,
where the apex of the V is pulled proximally and sutured to the
proximal apex of the fissure (Fig. 5). In a house flap, the base of the
FIG. 3 Open lateral internal sphincter-
otomy. (From Wexner SW, Beck DE, eds.
Fundamentals of Anorectal Surgery. 2nd ed.
London: Saunders; 1998:214–215.)
FIG. 4 Closed lateral internal sphincterotomy.
FIG. 5 V-Y advancement flap. (From
Braasch JW, Sedgwick CE, Veidenheimer MC,
Ellis H, eds. Atlas of Abdominal Surgery.
Philadelphia: Saunders; 1991:199)
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FIG. 6 House advancement flap. (From
Liberman H, Thorson AG. How I do it. Anal stenosis. Am J Surg. 2000 Apr;179(4):325–9.)
pentagon-shaped flap is sutured to the proximal apex of the fissure,
while the external “house roof” is closed linearly (Fig. 6).
SPECIAL CONSIDERATIONS
LIS for patients with preexisting fecal incontinence or risk factors
should be offered cautiously so as not to worsen or permanently
induce incontinence. These would include women with obstetric
trauma or previous sphincter injuries.
When fissures are off midline, underlying disorders should be
considered such as Crohn’s disease, human immunodeficiency virus
(HIV), tuberculosis, anal cancer, sexually transmitted infections, or
other immunosuppressive or infectious etiologies such as human
papilloma virus (HPV) and syphilis. In such cases, biopsies and
cultures are helpful for diagnosis. Patients who are immunocompromised secondary to chemotherapy will often present with diarrhea;
nonoperative management and chemical denervation with Botox is
recommended.
Perianal morbidity is a common phenotype of Crohn’s disease,
and Crohn’s-related fissures generally should not be treated with
sphincterotomy. Medical management directed at the patient’s
Crohn’s disease will heal the majority of anal fissures. Patients who
are constipated should be treated with fiber supplementation and
increased hydration. Topical diltiazem and Botox denervation are
recommended for nonoperative management, with early involvement of gastroenterology.
Chen HL, Woo XB, Wang HS, etal. Botulinum toxin injection versus lateral
internal sphincterotomy for chronic anal fissure: a meta-analysis of randomized control trials. Tech Coloproctol. 2014;18(8):693–698.
Gandomkar H, Zeinoddini A, Heidari R, Amoli HA. Partial lateral internal
sphincterotomy versus combined botulinum toxin A injection and topical
diltiazem in the treatment of chronic anal fissure: a randomized clinical
trial. Dis Colon Rectum. 2015;58(2):228–234.
Nelson RL, Chattopadhyay A, Brooks W, Platt I, Paavana T, Earl S.
Operative procedures for fissure in ano. Cochrane Database Syst Rev.
2011;2011(11):CD002199.
Nelson RL, Thomas K, Morgan J, Jones A. Non surgical therapy for anal fis-
sure. Cochrane Database Syst Rev. 2012;2012(2):CD003431.
Steele SR, Madoff RD. Systematic review: the treatment of anal fissure.
Aliment Pharmacol Ther. 2006;24(2):247–257.
Stewart Sr DB, Gaertner W, Glasgow S, Migaly J, Feingold D, Steele SR.
Clinical practice guideline for the management of anal fissures. Dis Colon
Rectum. 2017;60(1):7–14.
Management of
Anorectal Abscess
and Fistula
Amy J. Thorsen, MD
pproximately 100,000 patients in the United States will seek care
for anorectal sepsis each year. The mean age of presentation is 40
A
years (range 20–60 years). Adult males are twice as likely to develop
an anorectal abscess and/or fistula compared with females. Anorectal
abscesses and fistulas can be thought of as two successive phases of
the same infectious process, with an abscess representing the acute
phase of infection and a fistula denoting the chronic phase of suppuration and fistulization. Thus it is not surprising that 30% to 70%
of anorectal abscesses are associated with a concomitant anorectal
fistula, and that 30% to 40% of patients develop an anorectal fistula
after undergoing treatment for an anorectal abscess.
Management of anal abscess and fistula includes four basic
principles: (1) control the septic process (drain the pus), (2) define
the involved anatomy, (3) treat the underlying process without
ANORECTAL 299
External sphincter
Intersphincteric space
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compromising sphincter function, and (4) minimize recurrence
risk. Although many presentations are straightforward, complex
and recurrent disease challenge even the most experienced surgeon.
It is crucial for surgeons managing this disease to understand the
regional anatomy, treat patients in the context of their comorbid
conditions (such as Crohn’s disease), and apply the appropriate
surgical technique. Improper management can lead to potentially
life-threatening sepsis or significantly impact a patient’s quality of
life by causing chronic discomfort and socially-inhibiting problems
with personal hygiene.
ANORECTAL ABSCESS
Etiology and Classification
The anal glands lie within the intersphincteric space and empty into
the rectum through 10 to 15 crypts of Morgagni located circumferentially at the dentate line. When this drainage is blocked, pressure
builds as the septic source grows and propagates along paths of least
resistance within or through the intersphincteric space. The potential
pathways of suppurative extension delineate the anatomic spaces of
anorectal sepsis: intersphincteric, submucosal, perianal, ischiorectal,
postanal (subdivided into superficial and deep by the anococcygeal
ligament), and supralevator space (Fig. 1).
The intersphincteric abscess, located at the site of the anal glands,
tracks craniocaudally between the sphincter layers. A submucosal
abscess represents the least extensive suppurative process, located
just beneath the mucosa above the dentate line. Perianal abscesses
descend through the intersphincteric space to the subcutaneous tissue around the anus and below the sphincter complex. The ischiorectal space encircles the external sphincter caudad to the levator ani
Supralevator space
Ischiorectal space
Submucosal space
BOX 1 Causes of Anorectal Abscess
Cryptoglandular
Iatrogenic (anorectal or genitourinary surgery)
Perineal trauma
Radiation injury
Inflammatory bowel disease
Acquired immunodeficiency syndrome
Invasive fungal infection
Hidradenitis suppurativa
Diverticulitis
Anal fissure
Osteomyelitis
Foreign body
Malignancy (carcinoma, adenocarcinoma, hematologic
malignancy)
Data from Becks DE, et al, eds. The ASCRS Textbook of Colon and Rectal
Surgery.2nd ed. New York: Springer-Verlag; 2011.
complex and medial to the ischial tuberosities; an ischiorectal abscess
occurs from the extension of sepsis laterally from the intersphincteric
space or caudally from the supralevator space. The postanal space is
located posteriorly, between the levators (cranially) and the external
sphincter (caudally); this space may be solely involved, or infection
may extend laterally to the ischiorectal fossa, forming the so-called
horseshoe abscess. The postanal space is divided into the superficial
and deep postanal spaces by the presence of the anococcygeal ligament. Deep postanal space infections may be missed if this ligament
is not penetrated during operative drainage. Supralevator abscesses,
located above the levators as the name implies, are caused by cranial
extension of cryptoglandular sepsis or by caudal extension of an
intraabdominal process, such as diverticular disease, that perforates
through the peritoneum.
Understanding the anatomic spaces of anorectal sepsis is imperative in deciphering the patient’s presentation and planning the
appropriate intervention that attains adequate drainage and reduces
complications such as systemic sepsis, recurrence, fecal incontinence, and complex fistula formation. Although the cryptoglandular
theory is believed to be responsible for the vast majority of anorectal
abscesses, it is crucial to identify contributing conditions or alternate
causes such as those displayed in Box 1. The impact of these factors
and etiologies on the nature of the disease and treatment strategy will
be discussed later in the chapter.
Internal sphincter
Presacral space
Supralevator space
Deep postanal space
Anococcygeal ligament
Perianal space
FIG. 1 Anal sepsis and fistula. Classification of anorectal abscess-
es by location. (A) Coronal view. (B) Sagittal view. (From Yeo CJ,
et al.Shackelford’s Surgery of the Alimentary Tract.ed 7. Philadelphia:
Saunders; 2007.)
Waldeyer’s fascia
Perianal space
Presentation and Diagnosis
Anal pain independent of defecation is the most common complaint,
given almost one-half of anorectal abscesses are in the perianal
space. Swelling and fever are often present. Associated symptoms
or medical history suggestive of or including inflammatory bowel
disease and immunocompromised status should also be gathered.
On anorectal examination, an indurated bulge with fluctuance and
cellulitis near the anal verge is indicative of perianal abscess. Intersphincteric abscesses are unique in their lack of external examination
findings but cause exquisite tenderness on digital rectal examination.
Ischiorectal abscesses typically have gluteal findings of induration,
tenderness, and fluctuance several centimeters away from the anal
verge without tenderness on digital rectal examination. Abscesses
limited to the postanal space may have localized tenderness posterior
to the anal verge, but without apparent induration or fluctuance.
Induration or fluctuance between the posterior anorectum and coccyx will be noted on bimanual examination. Supralevator abscesses
may have no anorectal findings unless there is a downward extension
of sepsis into the ischiorectal fossa; fluctuance above the levators
may be noted on digital rectal examination. Further evaluation with
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pelvic imaging should be considered to exclude their presence if a
supralevator component is suspected. Anoscopy, rigid proctoscopy,
and flexible sigmoidoscopy can be performed to evaluate the rectal
mucosa for inflammatory bowel disease, but it is often not tolerated
and should not be pressed. Patients who cannot tolerate an examination should undergo an examination under anesthesia (EUA).
The majority of patients with a suggestive history and physical
examination can be managed with bedside drainage or operative
evaluation and treatment. Radiologic imaging, however, is useful in
some acute situations and helpful with more chronic or recurrent
anorectal sepsis. CT is helpful in patients with associated abdominal
symptoms or findings or with the clinical suspicion of a supralevator
abscess. A pelvic CT scan should not be relied upon to exclude drainable anorectal infection; purulence can be present without definitive CT findings. Undrained anorectal infection can lead to severe
systemic infection and destruction of the anal sphincter complex,
resulting in functional morbidity. Endoanal ultrasound and MRI are
not generally available or tolerated in the acute setting of anorectal
abscess. Both, however, can be useful adjuncts in delineating the
anatomy of complex, multiple, or recurrent fistula-in-ano.
Operative Evaluation and Drainage
Surgical drainage remains the definitive treatment of anorectal
abscesses. Bedside drainage under local anesthesia using 1% lidocaine with dilute epinephrine is often well tolerated for perianal
abscesses and small ischiorectal abscesses. After infiltrating the area
with local anesthetic, a curved incision is made over the abscess. The
incision should be oriented over the side of the abscess closest to the
anal verge without transgression into the sphincter complex; this is
done so if a fistula forms (an estimated 50% occurrence), it is more
likely to have a simple, short tract. The temptation to drain an abscess
over its most fluctuant point or at the furthest point from the verge
should be avoided to prevent potential creation of a long fistula tract.
A hemostat or finger is used to probe the wound, breaking down
all loculations and defining the extent of disease. An ellipse of skin
at least 1 cm in size incorporating the initial incision is excised to
prevent premature closure of the skin. Hemostasis can be achieved
with direct pressure, silver nitrate, or local anesthesia with epinephrine. The cavity is irrigated, and dry gauze is applied externally with
the expectation of ongoing drainage. Packing the wound should be
avoided because it subjects the patient to more pain and slower healing without the benefit of improved resolution of sepsis.
Large ischiorectal abscesses and those that must be approached
transanally (intersphincteric, some supralevator, horseshoe, and
deep postanal space infections) are most appropriately done in
the operating room under monitored anesthesia care (MAC) or
general anesthesia. A preoperative antibiotic with gram-negative
coverage is administered. The anorectal region is best exposed with
the patient in the prone jack-knife position and the buttocks taped
widely apart, but the high lithotomy position is often adequate. A
headlamp to improve visualization is recommended. Commonly
used instruments include the Hill-Ferguson, Fansler, or Pratt bivalve
retractors, fistula probes, curettes, 16- or 18-gauge angiocaths, and
dilute hydrogen peroxide. The perianal region is inspected, noting
any induration, fluctuance, or dermatologic abnormalities. A digital
rectal examination is performed followed by anoscopy, looking for
mucosal bulging, induration, sphincter defects, or other abnormalities. A biopsy should be performed on ulcerations, suspicious
nodules, or perianal lesions to exclude neoplasia. A biopsy should be
performed on recurrent abscess or fistula tracts as well in an effort to
diagnose underlying inflammatory bowel disease, chronic infections
(such as tuberculosis or actinomyces), or the rare malignancy. If the
site of purulence is not obvious, an 18-gauge needle can be used to
aspirate in suspected areas. Culture data is rarely helpful, but it may
be so in patients with recurrent infections, nonhealing wounds, a
history of methicillin-resistant Staphylococcus aureus, or underlying
HIV infection in whom atypical microbes may be present.
For a large ischiorectal abscess, ipsilateral counterincisions can
serve to establish adequate drainage rather than a large incision that
resects overlying healthy tissue and prolongs healing unnecessarily.
Digital exploration of the abscess cavity is prudent to ensure that
extension into the postanal space or the contralateral fossa is not
present. Packing is usually unnecessary and impractical for the
patient to exchange. An alternate means of drainage utilizes a stab
incision overlying the abscess, as close to the anal verge as possible,
and the insertion of a 10- to 16-French mushroom catheter into the
cavity. The catheter is secured with an anchoring suture and left in
place for 1 week. The catheter is removed once a tract is well established, although it can be left in for prolonged periods in cases of
large or recurrent infections.
Drainage of a postanal space abscess deserves special note. A
radial incision is made from the posterior anal verge toward the
coccyx. Subcutaneous tissue is divided, and the underlying fibers
of the external sphincter are spread with a hemostat clamp. The
anococcygeal ligament is then divided to access the postanal space.
This fibrous ligament may take a bit of force to separate. A digit is
inserted to explore the extent of suppuration. If a horseshoe abscess
is present, elliptical counterincisions over the involved ischiorectal
fossa are created. Penrose drains can be looped between incisions
to maintain patency. If an underlying fistula is noted, a noncutting
seton is placed to prevent recurrent sepsis (Fig. 2). A second staged
procedure to later address the fistula can be planned.
Intersphincteric abscesses are addressed transanally. The mucosa
overlying the bulging/fluctuant anal canal is vertically divided with
cautery. This exposes the underlying internal sphincter muscle with
its circumferential transversely oriented muscle fibers. A fine-tipped
hemostat is passed through the internal sphincter into the suppurative intersphincteric space and directed cephalad. The internal
sphincter is divided over the hemostat with electrocautery. This
generally does not compromise fecal continence, but patients should
be informed of that small risk as part of informed consent. An alternative but less common method involves a stab incision at the anal
verge in the intersphincteric groove and insertion of a small mushroom catheter into the affected intersphincteric space. The catheter
is removed or backed out after sepsis has resolved.
The source of the supralevator abscess determines its treatment,
which is why preoperative imaging can be helpful when a supralevator component is suspected. Descending abdominal or pelvic sources
are typically addressed with CT-guided percutaneous drainage; more
complex or severe intraabdominal disease may warrant transabdominal surgery or fecal diversion. Ascending cryptoglandular sepsis
travels either through the intersphincteric space or through the levators from the ischiorectal fossa. The intersphincteric source is treated
with transanal or transrectal drainage; incorrect surgical drainage
through the ischiorectal fossa creates a suprasphincteric fistula. Conversely, the supralevator abscess with an ischiorectal source should
be drained via skin incision to drain the ischiorectal fossa; transrectal
drainage would be inappropriate and create an extrasphincteric fistula. A Malecot catheter may aid drainage of a supralevator abscess
when accessed through the ischiorectal fossa (Fig. 3).
Primary Fistulotomy
Fistulotomy at the time of incision and drainage of the anorectal
abscess was once a contentious issue. Proponents argued that the
presence of sepsis aided in defining the fistula tract; laying open
the tract would reduce recurrence. Edema and inflammation from
the suppurative process, however, may increase the risk of creating
a false tract when probing and can make it difficult to accurately
assess the degree of sphincter involvement. A general consensus
has been reached, however, that primary or “prophylactic” fistulotomy submits a majority of patients who would never have recurred
or developed a fistula to sphincterotomy and its attendant risks
of fecal incontinence. Primary fistulotomy should only be selectively performed in the most straightforward of superficial or low
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B
C
FIG. 2 (A) Horseshoe abscess shows that the deep postanal space is a window to the ischiorectal fossa bilaterally(arrows). (B) The deep postanal space is
drained through a radial incision in the posterior midline. A clamp is placed in the postanal space to ensure adequate drainage. If an internal opening is identified, a seton is placed through the fistula tract, encircling the posterior sphincter. (C) Counterincisions drain the ischiorectal fossa. Placement of Penrose
drains through the tracts ensures adequate drainage of the abscess cavities without significant soft-tissue loss. (Courtesy Gaio Lakin, PhD.)
transsphincteric fistulas, and provided that the anticipated benefit
of healing outweighs the potential risk of fecal incontinence. Care
must be taken to avoid creating false passages in the inflamed field
while searching for the internal opening. Once the tract is cannulated
with a fistula probe, the overlying tissue is divided and the wound
is left open to drain. Primary fistulotomy is contraindicated in the
elderly and in women with anterior fistulas, as well as in patients
with compromised fecal continence, Crohn’s disease, AIDS, and high
transsphincteric fistulas.
If a fistula is easily identified at the time of abscess drainage, an
alternative treatment option is partial fistulotomy and seton placement. Although this commits the patient to a second-stage procedure, draining seton placement should prevent recurrent anorectal
sepsis and, once healed, allow the surgeon to assess the patient’s
anorectal function and tolerance of a second-stage fistulotomy or
plan for a different fistula repair.
Antibiotics and the Immunocompromised Patient
Most patients do not require antibiotic therapy after surgical drainage; antibiotics in general do not improve healing, reduce recurrence,
or definitively decrease fistula formation after appropriate surgical
drainage. In certain populations, however, antibiotics are warranted.
Patients with large areas of cellulitis, signs of systemic sepsis or
shock, prosthetic heart valves, or various conditions of immunocompromise warrant prolonged oral or parenteral antibiotics. Immunocompromised patient groups include those with diabetes mellitus,
chronic corticosteroid use, acquired immunodeficiency syndrome,
bone marrow transplant recipients, and active chemotherapy.
In contrast with all other patients with anorectal infection, profoundly neutropenic patients are often not addressed with surgery.
The degree and duration of neutropenia is directly related to the
incidence and prognosis of anorectal infections. In general, patient
with absolute neutrophil counts (ANC) below 500 per cubic millimeter often do not mount sufficient immune response to develop
suppuration. Therefore, patients with a low ANC and without
fluctuance do not have a target for surgical drainage; prolonged,
broad-spectrum antibiotics are recommended. Efforts to correct the
neutropenia by holding chemotherapy and by administering neutrophil growth factors are employed. This vulnerable patient population
must be monitored closely, given that a suppurative process may
develop as the neutrophil count increases; imaging or EUA with
aspiration may be useful adjuncts to identify a drainable source. Progressive sepsis, obvious fluctuance, or expanding soft tissue infection
are indications for surgical evaluation, drainage, or debridement.
Necrotizing Perianal Skin Infection
Necrotizing perianal skin infections are destructive, life-threatening
infections that must be quickly differentiated from the more common anorectal abscess and infection on initial presentation because
immediate surgical debridement offers the only chance at survival.
Rapid development of severe anorectal pain that is out of proportion
to findings on examination is the classic harbinger of a necrotizing
infection. Risk factors include diabetes, chronic renal disease, obesity, smoking, underlying neurologic disease (such as dementia or
spinal cord injury) that prevents early detection or communication
of symptoms, and previous anorectal infections. Tender, irregular
red, violaceous, or black macules and blisters in the perianal region
are early signs of this dangerous process. These infections may be
associated with crepitus, induration, or gangrene. Septic shock and
electrolyte disturbances may develop. Anorectal sepsis with severe
systemic manifestations should be quickly recognized and evaluated
in the operating room; radical debridement of all nonviable tissue is
302 MANAGEMENT OF ANORECTAL ABSCESS AND FISTULA
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epithelializes. Although the cryptoglandular process is responsible
for the vast majority of fistulas, other etiologies can instigate chronic
inflammation and epithelialization along an abnormal communication between the skin and anorectum (see Box 1).
Although a perianal abscess is described by the anatomic space
in which it forms, an anal fistula is most commonly classified in
terms of its relationship to the internal and external anal sphincters.
In 1976, Park et al. published the classification system that is used
currently. Figure 4 depicts the four classes of fistulas. Each of these
fistula classes can be further complicated by the presence of circular
and/or high blind tracts that branch off the fistula tract into the
intersphincteric space or ischiorectal fossa, but do not drain inde-
No
Yes
pendently. Another type of fistula not included in the anorectal classification scheme is the superficial fistula, which is essentially a skin
bridge with an underlying subcutaneous tract that does not involve
the sphincter complex; this can be a result of scarring after recurrent infections and surgery, premature healing of an anal fissure, or
another process, such as hidradenitis.
Fistulas can be further categorized as “simple” or “complex” fistulas. A complex fistula has features that increase the risk of recurrence
and/or incontinence after intervention, either by its own anatomy or
by patient factors. Table 1 defines features of complex fistulas, which
includes most fistula classes except subcutaneous, intersphincteric,
or low transsphincteric fistulas.
Yes
FIG. 3 Drainage of a supralevator abscess(black ovals). On the right,
the supralevator abscess is associated with a transsphincteric fistula and
passage through the ischiorectal fossa; often there are associated findings
of an ischiorectal abscess. This abscess is drainedvia the skin and ischiorectal fossa; transrectal drainage would be inappropriate because it would
result in an extrasphincteric fistula. On the left, the supralevator abscess
is associated with an intersphincteric fistula and should be drained transrectally; drainage across the ischiorectal fossa would create a suprasphincteric fistula. Supralevator abscesses also may be addressed via computed
tomography–guided percutaneous drainage (alone or in combination with
transrectal/transgluteal approaches), particularly when they are caused by
downward extension of an intraabdominal process such as diverticulitis.
(From Yeo CJ, et al.Shackelford’s Surgery of the Alimentary Tract.ed 7.
Philadelphia: Saunders; 2007.)
necessary. Patients will require supportive management in the intensive care setting and empiric coverage with broad-spectrum antibiotics. Transfer to a tertiary center with hyperbaric oxygen capability
should be considered if infection persists after initial debridement.
By limiting the growth of anaerobic and other forms of bacteria
and by boosting the effects of antibiotics and the immune system,
hyperbaric oxygen is emerging as a powerful adjunct in treating this
disease process and promoting healing. The need for fecal diversion
is debatable and should only be considered in the subacute setting
after hemodynamic stability is well established.
FISTULA-IN-ANO
Etiology and Classification
The cryptoglandular theory suggests that the acute suppurative
process of anorectal sepsis originates at one of 8 to 10 anal glands
located at the dentate line. These glands originate in the intersphincteric space and penetrate the internal sphincter with their ducts.
They can become blocked and allow bacteria to cause infections
which propagate along the path of least resistance until the growing
pressure is released by surgical or spontaneous drainage. A fistula
is the chronic sequelae of this process if the tract fails to heal and
Presentation and Diagnosis
Patients will frequently, although not always, have a history of a previous perianal abscess that spontaneously drained or required surgical intervention; patients may experience initial healing and have a
recurrent abscess or other symptoms weeks, months, or even years
after the index infection. Some patients will experience continual
drainage and intermittent swelling months after recovering from an
acute abscess, indicating a persistent tract from the internal opening
to an either open or closed external opening.
Patients describe intermittent anal pain, pruritis, drainage that
is mucoid, bloody, or feculent, or occasionally blood per rectum
caused by friable granulation tissue at the internal opening. Cyclic
discomfort and swelling that is relieved after spontaneous drainage
is a common feature. Patients should be queried regarding gastrointestinal symptoms suggestive of inflammatory bowel disease and
their current level of fecal continence. A history of anal surgery, anal
infections, radiation, trauma, obstetric trauma, and systemic disease
including inflammatory bowel disease, hematologic malignancy, or
immunosuppression should be elicited, given these factors may affect
continence and healing with many types of surgical interventions.
On examination, the external opening is easily identifiable as an
inflamed pyogenic granuloma; a palpable cord may be present and
suggest the path of the tract. When less active, the external opening
may be more subtle and appear more like a subtle dimple or scar. The
internal opening can occasionally be palpated on digital rectal examination as a nodule or pit and is usually at the dentate line. Anoscopy,
when tolerated, can assist in visualizing the internal opening as well
as assess whether a distal proctitis is present. Further endoscopy can
be considered in a patient with symptoms suggestive of inflammatory bowel disease.
Routine diagnostic imaging is typically unnecessary for patients
with anal fistula, however imaging may be helpful in patients with
a suspected occult anorectal abscess, recurrent or complex fistula,
an unrevealing EUA, or suspected or confirmed anal Crohn’s disease. Preoperative endoanal ultrasound (EAUS) may help preserve
anorectal function by measuring sphincter involvement; EAUS can
successfully predict the amount of sphincter that would be divided
if primary fistulotomy is performed as well as identify undrained
sepsis, complex anatomy, and high blind tracts (Fig. 5). MRI appears
to have higher sensitivity in evaluating secondary extensions, suprasphincteric tracts, and extrasphincteric tracts in complex fistulas
when compared to EAUS and has been shown to alter surgical
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FIG. 4 Classification of anal fistulas.
(A) Intersphincteric: the tract remains in the
intersphincteric plane. (B) Transsphincteric: the
fistula tract passes from the intersphincteric
plane through the external sphincter muscle. 1,
uncomplicated. (C) Suprasphincteric: there is
an upward extension of the fistula tract in the
intersphincteric plane. The tract then passes
above the level of the puborectalis muscle and
continues downward through the ischiorectal
fossa to the perianal area. (D) Extrasphincteric:
there is a tract that passes from the skin of
the perineum through the ischiorectal fossa
and the levator muscles before entering the
rectal wall. This fistula may be a consequence
of an extension of a transsphincteric fistula
or secondary to trauma, anorectal disease,
or pelvic inflammation. (Modified from Yeo CJ,
D
et al.Shackelford’s Surgery of the Alimentary
Tract.ed 7. Philadelphia: Saunders; 2007.)
TABLE 1 Features of Complex Fistulas
Anatomy Comorbid Conditions
Multiple fistulas Compromised fecal continence
Suprasphincteric fistulas Inflammatory bowel disease
Extrasphincteric fistulas Refractory diarrhea
Associated high blind
Anterior fistulas in women
tract(s)
High transsphincteric
fistulas (>30% of anal
Immunodeficiency or compromised
wound healing
sphincter length)
History of regional radiation
History of obstetric trauma
Elderly patients
Prior anorectal surgery
approach and decrease recurrence rates. Transperineal ultrasound
may be a lower-cost, less-invasive imaging option with similar
diagnostic accuracy compared to EAUS and MRI, although it is less
widely available. CT lacks adequate resolution to identify tracts and
their relationship to the sphincters and levators with comparable
accuracy. When imaging is indicated, the best option may be based
on local radiologic expertise.
Surgical Treatment
There are four tenets of fistula surgery: (1) define the fistula anatomy, (2) ensure the resolution of sepsis, (3) assess and preserve anal
sphincter function, and (4) minimize recurrence risk. Maintaining
these principles are critical at each step of treatment.
Define Fistula Anatomy
The anatomy of a fistula includes the internal and external openings,
the course of the intervening tract(s), and the presence of any blind
tracts or sinuses. The internal opening is described by its location
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1
1
142°
FIG. 5 Ultrasound scan of right posterior transsphincteric fistula. (A) Coronal view revealing a 142-degree internal sphincter defect on the left
side from a previous hemorrhoidectomy. The hypoechoic internal opening of a right transsphincteric fistula is noted by the arrow. Giventhe edge of the
internal sphincter defect abuts the fistula tract, ligation of the intersphincteric fistula tract procedure may not be feasible. (B) Angled sagittal view showing
the hypoechoic transsphincteric fistula. Note the internal opening(arrows)nears half the length of the hyperechoic external sphincter; therefore, a fistulotomy would not be appropriate. (Courtesy Amy Thorsen, MD.)
and relationship to the dentate line, whereas tracts are delineated by
their relationship with the sphincter complex and levators. Fistula
anatomy can be estimated by office examination but is most definitively assessed in the operating room with an EUA. The patient may
usually be consented for a definitive procedure, with the caveat that
if a more complex fistula or unexpected findings are discovered
during operative evaluation, a staged procedure may be required
to preserve sphincter function and ensure successful surgical treatment. The patient is placed in the prone jack-knife position with the
buttocks taped widely apart; some surgeons prefer high lithotomy or
left lateral positioning. The perianal region is inspected, identifying
evident external openings, suspicious lesions, or scars, which can be
probed. Goodsall’s rule predicts that an external opening posterior to
a transverse line across the anus drains to a posterior midline internal
opening, while those that open anterior to the line have short, radial
courses to the internal opening. Although Goodsall’s rule is accurate
for a majority of the posterior external openings, it has been shown
to be less accurate in women with anterior openings.
Digital rectal examination is performed to assess for undrained
sepsis and location of the internal opening. Anoscopy is used to
identify the internal opening and to note any signs of proctitis or
malignancy. A fistula probe is inserted into the external opening
and gently advanced toward the anticipated internal opening with
subtle redirection as resistance dictates. The fistula tract should
easily accept the probe without the sensation of tissue destruction; a
false tract must not be created as it will only serve to complicate the
disease and neglect the primary tract. The internal opening may also
be identified by injecting dilute hydrogen peroxide into the external
opening with an angiocatheter. If the internal opening is not easily
identified, the surgeon should not persist to find or create one. Once
the internal and external openings are identified, the tract can be
cannulated with the fistula probe; if the tract is not cannulated fully,
the tract may be curved. Curving the fistula probe or straightening
the tract with a Kocher clamp may facilitate cannulation. Once
cannulated, the type of fistula is established by determining its relationship to the internal and external sphincter complex, the levators,
and presence of multiple fistulas or blind tracts. The percentage of
sphincter complex caudal to the tract is determined by palpating
the apex of the sphincter complex in relationship to the probe. Low
transsphincteric fistulas are defined as those that involve less than
30% of the external sphincter complex.
If the tract cannot be fully cannulated, the external opening is
enlarged toward the anal verge, a curette is used to debride the tract,
and the operation is terminated. This approach may be associated
with a higher risk of recurrence but avoids creating an iatrogenic
false internal opening at a false location. Adjunctive imaging with
ultrasound or MRI to better identify fistula anatomy is performed
after 3 to 6 weeks to allow for inflammation related to surgery to
subside.
Ensure the Resolution of Sepsis
For many patients with complex fistulas or an obvious fistula at the
time of operative treatment of anorectal sepsis, a conservative, staged
approach with the initial placement of a seton is most appropriate.
This allows the possibility of multiple options to treat the fistula in
the future without compromising sphincter integrity.
For a patient treated initially with a seton, a second-stage procedure can be considered when the internal opening is less than 5
mm and the tract is simple, narrow, and without an associated cavity.
Ongoing sepsis, as evidenced by pus, cellulitis, induration, or a persistent cavity, prevents healing and closure of the tract; any efforts to
close the fistula definitively will likely fail. In the setting of persistent
infection, a fistulotomy can be performed only in a simple intersphincteric or low transsphincteric fistula to simultaneously address
the sepsis and the fistula. Complex fistulas with persistent sepsis
should be considered to have an undrained source of infection. They
can be addressed with debridement of the tract around the seton,
widening of the external opening, and a search for a high blind or
circular tract. If additional treatable sources of the persistent sepsis
cannot be identified or sepsis continues despite these approaches,
imaging is pursued.
Assess and Preserve Anal Sphincter Function
Although a controlled anal fistula with or without a seton can cause
significant discomfort and problems with personal hygiene, fecal
incontinence is far more disruptive to a patient’s quality of life. For
that reason, preservation of continence is always a priority when
choosing the proper management strategy. Division of the internal
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TABLE 2 Management Strategy by Fistula Classification
Advancement
Type of Fistula Fistulotomy Seton* LIFT
Flap Fibrin Glue Collagen Plug
Superficial/intersphincteric X
Low transsphincteric X X X X X X
High transsphincteric X X X X X
Suprasphincteric X X X X
Extrasphincteric X X
LIFT,Ligation of intersphincteric fistula tract.
*Seton placement can be a first stage or definitive treatment option.
Address Intraabdominal
or Pelvic Source
sphincter is usually well tolerated without much effect on continence, especially in men. Division of the distal third of the external
sphincter is considered “safe” in healthy male individuals; this can be
considered in the posterior external sphincter in women without preexisting sphincter dysfunction. The degree of sphincterotomy tolerated without affecting continence is undoubtedly patient-dependent.
Careful analysis of a patient’s risk for incontinence includes an
assessment of their current degree of continence, prior anorectal
surgery, trauma, and obstetric history as well as associated conditions
that may cause diarrhea or inhibit healing. Women in particular are
vulnerable to incontinence as a result of a shorter sphincter complex,
anatomic and neurologic injury to the pelvic floor sustained during
childbirth, and loss of elasticity and muscle attenuation associated
with aging and menopause. Patients with active inflammatory bowel
disease involving the anorectum and immunodeficiencies often heal
poorly and suffer recurrent or metachronous fistula disease. Sphincter-preserving techniques are preferred in these patient populations.
Table 2 provides a guide to choosing the proper surgical technique,
although it does not take into account relevant patient factors.
Minimize Recurrence Risk
Complex fistulas are a frustrating disease process because they are
prone to recurrence despite meticulous surgical technique. Although
primary fistulotomy has the lowest recurrence risk, it also is associated with the highest risk of incontinence because of inherent
disruption in the sphincter complex. All other sphincter surgical
procedures, although they preserve the muscular anatomy, are associated with much higher recurrence risk. This must be considered in
an informed consent discussion with patients. Reported outcomes in
many of these described procedures vary widely; a surgeon’s personal
experience with a procedure may be the most important factor in
reducing recurrence.
Fistulotomy
Fistulotomy can be done at the time of abscess presentation, at the
time of initial fistula presentation, or as a second-stage procedure in
appropriately selected patients. Regardless of timing, a fistulotomy is
only appropriate in low-risk patients with a superficial, intersphincteric, or low transsphincteric fistula. Once the anatomy of the fistula
is determined, the tract is cannulated and the tissue overlying the
probe is divided with electrocautery. The tract is debrided with a
curette to remove debris and granulation tissue. The deepithelialized
wound, now effectively a ditch instead of a tunnel, is allowed to heal
by secondary intention.
For larger wounds, wound healing can be accelerated and bleeding avoided by marsupialization of the wound; this is performed by
sewing the wound edges to the base of the wound with a continuous
locking absorbable suture. Marsupialization can prevent both the
premature epithelization of the wound edges before the deeper base
heals and the subsequent formation of a subcutaneous fistula.
Sphincter-sacrificing procedures have the highest success rates,
generally over 90%, but are also associated with some degree of fecal
incontinence in up to 40% of patients in some series. Hence fistulotomy is usually not appropriate for high or complex fistulas. Factors
related to recurrence after fistulotomy include branching of fistulas,
failure to accurately identify the internal opening, and fistulas associated with Crohn’s disease.
Seton
A noncutting seton allows for ongoing drainage of sepsis and promotes fibrosis and maturation of the fistula tract as well as resolution
of any abscess cavity, often in preparation for a second-stage procedure. After the fistula tract has been defined and debrided, the external opening is opened slightly toward the anal verge. Circular, high
blind tracts, and long subcutaneous tracts are appropriately laid open
or drained and curetted. A thin silastic band, vessel loop, or nonabsorbable suture is threaded through the tract and secured in a loop or
omega shape with several interrupted silk sutures. The seton should
not be tight; a hemostat should easily fit between the skin and loop
without tension. The second-stage procedure, either fistulotomy or a
sphincter-preserving operation, is usually performed 6 to 10 weeks
later, although a waiting period of 3 to 4 months is advised for more
complex fistulas and abscess cavities. Setons used in this fashion for
complex fistulas have success rates of 62% to 100%, depending on
patient factors and the choice of the secondary procedure. For some
Crohn’s or other high-risk patients, seton placement can be the definitive operation; it is left in place for prolonged periods (years) to prevent recurrent sepsis without the intention to perform a second-stage
procedure due to the likelihood of failure or iatrogenic incontinence.
In rare situations, a seton can be used to perform a slow, controlled fistulotomy in complex fistulas. Historically, a cutting seton
was used when the risk of incontinence from a traditional fistulotomy was considered to be too high. The cutting seton is tightened
at interval office visits to gradually divide the fistula and involved
sphincter muscle. Cutting setons have high success rates in resolving
anal fistulas, however some studies report some level of impaired
continence in up to 67% of treated patients. Hence cutting setons
should be used very selectively.
LIFT
Ligation of the intersphincteric fistula tract (LIFT) is a relatively
new sphincter-preserving technique first described in 2007. This
procedure is most often performed as a second-stage procedure for a
transsphincteric fistula after a mature tract has developed. A draining seton may be used before the LIFT procedure to allow for fibrosis
of the tract, but this has not been clearly shown to affect the success
rate of the LIFT procedure.
With the patient in the prone jack-knife position with the buttocks taped widely apart, the fistula tract is cannulated with a probe.
The external opening is widened to allow for drainage (Fig. 6). A
1- to 2-cm curvilinear incision is made with electrocautery over
the palpated intersphincteric groove superficial/distal to the fistula
tract. A Lonestar retractor (CooperSurgical) deployed along the
anoderm edges provides excellent exposure. The intersphincteric
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EF
FIG. 6 (A) The fistula tract is cannulated. (B) A curvilinear incision is made overlying or slightly distal to the intersphincteric groove. A Lone Star retractor
(Cooper Surgical) is helpful for exposure. (C) The intersphincteric plane is developed on either side of the tract(arrows).(D) Dissection continues around
the tract until it is isolated. The probe is removed. (E) Division and ligation of the fistula tract. The tract is encircled with a Vicryl (Ethicon) tie, and the tract
is ligated at the border of the internal anal sphincter(right arrow).If a long tract is present, it can be excised, and the tract near the external anal sphincter
is either ligated or imbricated with Vicryl suture(left arrow). (F) The repair is tested by injecting hydrogen peroxide into the internal and external openings.
The ligated ends can also be probed to ensure closure. If there is a leak, the fistula opening is further imbricated. (G) The external opening(arrow)is slightly
enlarged, and the distal aspect of the tract is debrided with a curette. (Courtesy Jeffery J. Morken, MD.)
plane is bluntly developed with a fine-tipped hemostat. The fistula
tract is circumferentially isolated with care to avoid disrupting it.
The probe is removed, and both distal and proximal ends of the
intersphincteric tract are suture-ligated with 3-0 absorbable suture.
The tract is sharply divided with a scalpel. The external opening is
injected with hydrogen peroxide; if there is a persistent leak, the
intersphincteric opening of the external sphincter is oversewn until
there is no longer a leak. Some authors test the internal opening with
peroxide as well to ensure proper closure of the proximal portion of
the tract. The anoderm is reapproximated with a running absorbable
suture. Very high fistula tracts or those that track long distances
within the intersphincteric space may be difficult to properly isolate in the intersphincteric plane and not good candidates for this
approach.
A meta-analysis of 1378 LIFT procedures from 26 studies demonstrated an overall success rate of 76%, an overall complication rate
of 14%, and a low rate of fecal incontinence of 1.4%. Horseshoe
anatomy, Crohn’s disease, and prior fistula surgery were risk factors
for failure. Some failures result in resolution of the external sphincter involvement, converting the fistula to a simple intersphincteric
fistula that is more amenable to fistulotomy. Because of this, secondary healing after surgical reintervention can be as high as 77%
to 86%.
Endorectal Advancement Flap
The endorectal advancement flap is a sphincter-preserving operation
used as a second-stage procedure for high fistula tracts, suprasphincteric tracts, and low tracts in high-risk patients with healthy rectal
mucosa (see Table 1). For lesions below the dentate line, fistulotomy
or a dermal advancement flap is preferred to prevent the creation of a
mucosal ectropion that can form if the rectal mucosa is brought down
to near the anal verge. Patients may undergo a preoperative bowel
preparation. Performed under general anesthesia, the prone jackknife position is preferred for most fistulas, although the lithotomy
position is often used to address posterior midline internal openings.
The seton is removed, and the internal opening serves to mark the
apex of the flap (Fig. 7). Beginning at the internal opening, a flap is
created by distal-to-proximal dissection with electrocautery including mucosa, submucosa, and a few fibers of the internal sphincter
(partial thickness). To ensure adequate perfusion, it is crucial that
G
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