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276 The ASCRS Manual of Colon and Rectal Surgery
Fig. 13.2. Classifi cation of anorectal abscess. (Reprinted from Vasilevsky CA.
Fistula-in-ano and abscess. In: Beck DE, Wexner SD, eds. Fundamentals of
Anorectal Surgery. London: WB Saunders, copyright 1998, with permission from
Elsevier.)
intersphincteric, and supralevator (Fig. 13.2 ). Perianal abscesses
are the most common type whereas supralevator abscesses are
the rarest.
• Pus can also spread circumferentially through the intersphincteric, supralevator, or ischioanal spaces, the latter via the deep
postanal space, resulting in a horseshoe abscess.
Evaluation and Treatment
Symptoms
• Pain, swelling, and fever are the hallmarks associated with an
abscess.
• Severe rectal pain accompanied by urinary symptoms such as
dysuria, retention, or inability to void may be suggestive of an
intersphincteric or supralevator abscess.
Physical Examination
• Inspection will reveal erythema, swelling, and possible fl uctuation.
• It is crucial to recognize that no visible external manifestations will be present with the intersphincteric or supralevator
abscesses despite the patient’s complaint of excruciating pain.
13. Benign Anorectal: Abscess and Fistula 277
• Although digital examination may not be possible because of
extreme tenderness, palpation, if possible, will demonstrate
tenderness and a mass.
• With a supralevator abscess, a tender mass may be palpated on
rectal or vaginal examination.
• Anoscopy and sigmoidoscopy are inappropriate in the acute
setting.
Treatment
General Principles
• Essentially, the treatment of an anorectal abscess involves incision and drainage.
• Watchful waiting under the cover of antibiotics is ineffective
and may allow the suppurative process to progress resulting in
the creation of a more complicated abscess and thus possible
injury to the sphincter mechanism.
• Rarely, delay in diagnosis and management of anorectal
abscesses may result in life-threatening necrotizing infection
and death.
Operative Management
Incision and Drainage
• Perianal abscesses can be effectively drained under local
anesthesia. After the most tender point has been determined,
the area is infi ltrated with 0.5% lidocaine with 1:200,000 epinephrine. A cruciate or elliptical incision is made and the edges
are trimmed to prevent coaptation which may result in poor
drainage or recurrence (Fig. 13.3 ). No packing is required.
• Most ischioanal abscesses can be incised and drained in a similar
manner with the site of incision shifted close to the anal side of
the abscess, minimizing the complexity of a subsequent fi stula.
• Large ischioanal or horseshoe abscesses often require drainage
with the patient under a regional or general anesthetic and in
the prone jackknife or left lateral (Sim’s) position. The location
of infection is often in the deep postanal space.
– Counter-incisions are made over each ischioanal fossa to
allow drainage of the anterior extensions of the abscess
(Hanley procedure) (Fig. 13.4 ).
• Because the diagnosis of an intersphincteric abscess is entertained when the patient presents with pain out of proportion
278 The ASCRS Manual of Colon and Rectal Surgery
Fig. 13.3. Drainage of abscess. ( a ) Injection of local anesthesia. ( b ) Cruciate
incision. ( c ) Excision of skin. ( d ) Drainage cavity.
to the physical fi ndings, an examination under anesthesia is
mandatory to completely assess the cause of the pain. Once
the diagnosis is established, either by palpation of a protrusion
13. Benign Anorectal: Abscess and Fistula 279
Fig. 13.4. Drainage of horseshoe abscess.
into the anal canal or by needle aspiration in the intersphincteric plane, treatment consists of dividing the internal sphincter
along the length of the abscess cavity. The wound is then marsupialized to allow adequate drainage and quicker healing.
• Before the treatment of a supralevator abscess, it is essential
to determine its origin because it may arise from an upward
extension of an intersphincteric or an ischioanal abscess, or
downward extension of a pelvic abscess (Fig. 13.5 ).
Catheter Drainage
An alternative method of treatment is catheter drainage.
• Using local anesthetic, a stab incision is made over the abscess
cavity near the anus.
• A10–16 French soft latex mushroom catheter is inserted over a
probe into the abscess cavity.
• The shape of the catheter holds it in place and the external end
is trimmed 2–4 cm outside the skin.
• The patient is instructed on wound care and is eeen in follow up
in 7–10 days. The catheter is removed if drainage has stopped
and the cavity has closed down around the catheter.
280 The ASCRS Manual of Colon and Rectal Surgery
Fig. 13.5. Drainage of a supralevator abscess.
Primary Fistulotomy
• A point of controversy is whether primary fi stulotomy should be
performed at the time of initial abscess drainage. A recent metaanalysis which compared incision and drainage alone to primary
fi stulotomy demonstrated that primary fi stulotomy resulted in an
83% reduction in recurrence but higher risk of incontinence to
fl atus, On the other hand, 72% of patients who underwent incision & drainage alone did not develop a recurrence.
• Primary fi stulotomy eliminates the source of infection and
decreases the rate of recurrence, obviating the need for subsequent
surgery with the potential to decrease disability and morbidity.
• Opponents are reluctant to perform primary fi stulotomy in the
presence of acute infl ammation because the search for an internal opening may lead to creation of false passages resulting in
neglect of the main source of infection.
• Failure to identify an internal opening has been reported to
occur in as high as 66% of patients. In addition, 34–50% of
patients who present with an abscess for the fi rst time will not
13. Benign Anorectal: Abscess and Fistula 281
develop a fi stula. Thus, primary fi stulotomy in these patients
would be unnecessary and may result in needless disturbances
of continence.
• Of those patients whose abscesses are drained, 11% may develop
a fi stula whereas 37% may develop a recurrent abscess. This is
most often observed in conjunction with ischioanal abscesses.
• A prospective, randomized trial of drainage alone vs. drainage
and fi stulotomy for acute perianal abscesses with proven internal openings revealed that incision and drainage alone demonstrated no statistical signifi cance in recurrence compared with
concurrent fi stulotomy although there was a tendency to recurrence in the former group.
• If the internal opening of a low transsphincteric fi stula is readily apparent at the time of abscess drainage, primary fi stulotomy is feasible with the following exceptions (1) patients with
Crohn’s disease, (2) patients with acquired immunodefi ciency
syndrome (AIDS), (3) elderly patients, (4) patients with high
transsphincteric fi stulas, and (5) women with anterior fi stulas
and episiotomy scars.
• The decision to perform a primary fi stulotomy should be individualized but should only be attempted by a surgeon with a
sound knowledge of the regional anatomy. Insistence upon
fi nding a fi stula may encourage creation of a false passage and
unnecessary division of sphincter muscle.
• Many of the former proponents of primary fi stulotomy have
abandoned this approach and have instead elected to await the
appearance of a fi stula after drainage only to treat it with fi brin
glue ranal plug so as to avoid cutting any sphincter muscle.
Antibiotics
• There is little if any role for antibiotics in the primary management of anorectal abscesses except as an adjunct in patients
with valvular heart disease or prosthetic valves, extensive soft
tissue cellulitis, prosthetic devices, diabetes, immunosuppression, or systemic sepsis.
Postoperative Care
• Patients are instructed to continue with a regular diet and to
take a bulk-forming agent, non-codeine-containing analgesic,
and sitz baths.
282 The ASCRS Manual of Colon and Rectal Surgery
• Patients are generally seen in follow-up in 2–4 weeks or for intersphincteric or supralevator abscesses, 2 weeks postoperatively.
Complications
Recurrence
• After incision and drainage, ischioanal and intersphincteric
abscesses are associated with the development of recurrent
abscesses or fi stulas in as many as 89% of patients.
• Reasons for recurrence of anorectal infections include missed
infection in adjacent anatomic spaces, the presence of an undiagnosed fi stula or abscess at initial abscess drainage, and failure
to completely drain the abscess.
Extra-Anal Causes
• Extra-anal disease should be considered once the usual causes
of recurrence have been ruled out. Hidradenitis suppurativa
and downward extension of a pilonidal abscess should be considered. A prospective review of recurrent anorectal abscesses
by Chrabot et al. reported hidradenitis in one-third of patients
with recurrent abscesses. In addition, the possibility of Crohn’s
disease should be suspected.
Incontinence
• Incontinence may result after incision and drainage of an
abscess either from iatrogenic damage to the sphincter or inappropriate wound care. Continence may be compromised if the
superfi cial external sphincter is inadvertently divided during
drainage of a perianal or deep postanal abscess in a patient
with preoperative borderline continence.
• Prolonged packing of a drained abscess may impair continence
by preventing the development of granulation tissue and
promoting the formation of excess scar tissue.
• Although advocated to decrease recurrence rates, primary fi stulotomy may result in unnecessary division of sphincter muscle
in acutely infl amed tissue.
Special Considerations
Necrotizing Anorectal Infection
• Rarely, anorectal abscesses may result in necrotizing infection
and death. Factors thought to be responsible include delay in
13. Benign Anorectal: Abscess and Fistula 283
diagnosis and management, virulence of the organism involved,
bacteremia and metastatic infections, or underlying disorders
such as diabetes, blood dyscrasias, heart disease, chronic renal
failure, hemorrhoids, and previous abscess or fi stula.
Symptoms and Signs
• Spreading soft tissue infection of the perineum can be classifi ed into two groups.
– The fi rst group includes anorectal sepsis in which the
infection extends superfi cially around the perineum
resulting in necrosis of skin, subcutaneous tissue,
fascia, or muscle. Perianal crepitation, erythematous,
indurated skin, blistering, or gangrene may be present
(Fig. 13.6 ).
– The second group includes sepsis in which the preperi-
toneal or retroperitoneal spaces have become involved.
Subtle signs may be present which include abdominal
wall induration, tenderness, or a vague mass. It is important to realize that systemic symptoms such as fever,
tachycardia, and vascular volume depletion may precede
the appearance of overt signs of infection.
Treatment
• Treatment consists of vigorous intravenous fl uid hydration, restoration of electrolyte balance, and insertion of a Foley catheter.
• Accompanying coagulopathy, respiratory insuffi ciency, and
renal failure must be aggressively treated.
• Invasive monitoring and ventilatory support may be necessary.
• Pus or necrotic tissue from the infected region must be cultured
for aerobes and anaerobes. A Gram stain can be used to distinguish between the presence of clostridial and nonclostridial
organisms.
• Empiric broad-spectrum antibiotic therapy should be instituted regardless of Gram stain and culture results. The chosen
antibiotic regimen should be effective against Staphylococci
and Streptococci , Gram-negative coliforms , Pseudomonas,
Bacteroides, and Clostridium . For Gram-positive rods seen on
Gram stain, antibiotics administered should include sodium
penicillin G in doses of 24–30 million units per day and an
aminoglycoside. Tetanus toxoid should also be administered.
284 The ASCRS Manual of Colon and Rectal Surgery
Fig. 13.6. Necrotizing anorectal infection.
• Surgical treatment consists of wide radical debridement until
healthy tissue is encountered. The goals of surgical debridement are to remove all nonviable tissue, halt the progression of
infection, and alleviate the systemic toxicity.
• It is crucial to realize that the preoperative skin changes may
be minimal compared with the operative fi ndings which may
include edema, liquefactive necrosis of subcutaneous tissues,
watery pus formation, and extensive necrosis of underlying
fascia. Reexamination under anesthesia is usually necessary
because this is the only manner by which adequate wound
examination can be conducted.
• The need for colostomy is a debatable issue and has been recommended if the sphincter muscle is grossly infected, if there
is colonic or rectal perforation, if the rectal wound is large,
if the patient is immunocompromised, or if incontinence is
present.
• Although antibiotics and adequate surgical drainage are thought
to be suffi cient, the use of hyperbaric oxygen (HBO) has been
advocated as an adjunct to treatment, particularly in patients
with diffuse spreading infections who do not have chronic
obstructive pulmonary disease. It is postulated that HBO has a
direct antibacterial effect on anaerobic bacteria by diminishing
the effect of endotoxins and optimizing leukocyte phagocytic
function. HBO may also promote wound healing by facilitating fi broblast proliferation.
13. Benign Anorectal: Abscess and Fistula 285
• Despite aggressive surgical and multidisciplinary management
of anorectal sepsis, mortality rates ranging from 8 to 67% have
been reported. This high mortality rate is attributable in part
to the aggressive nature of the infection and to the underlying
comorbid diseases that are present in these patients. Mortality
rates are 2–3 times higher in diabetics, in elderly patients, and
in patients in whom treatment is delayed.
Anal Infection and Hematologic Diseases
• Acute anorectal suppuration poses an interesting and often
life-threatening problem in patients with acute hematologic
diseases. In patients with acute leukemia, mortality rates of
45–78% have been reported.
• There is a defi nite relationship between the number of circulating granulocytes and the incidence of perianal infection
in patients with hematologic diseases. In one study, patients
with neutrophil counts below 500 per cubic millimeter had an
incidence of anorectal infections of 11% whereas those with
counts greater than 500 per cubic millimeter had an incidence
of 0.4%.
• The most important prognostic indicator was the number of
days of neutropenia during the infectious episode.
• The most common presenting symptoms include fever which
precedes pain, and urinary retention. Point tenderness and
poorly demarcated induration constitute the earliest signs,
whereas external swelling and fl uctuation often appear late in
the course of infection.
• Controversy surrounds the treatment of acute anorectal infections in patients with hematologic malignancies. Surgery has
generally been avoided because what may seem to be simple
incision and drainage may produce scant or no pus and may
instead cause hemorrhage, poor wound healing, or expanding
soft tissue infection.
• Any patient with perianal pain is assumed to have a perianal
complication and is started on precautionary measures which
consist of no digital rectal examinations, suppositories, or enemas. Sitz baths, stool softeners, bulk agents, and analgesia are
advised.
• On aspiration of most abscesses in this group, the most common
organisms have been found to be Escherichia coli and group
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