This document provides information about perianal abscesses including their etiology, pathogenesis, classification, clinical presentation, investigations, and management. Anorectal abscesses are infections of the soft tissues around the anus that form abscess cavities. They commonly originate from infections of anal glands. Abscesses are usually drained surgically with antibiotics added for immunosuppressed individuals. The type of drainage depends on the abscess classification. While some advocate primary fistulotomy, others prefer delayed fistulotomy after initial incision and drainage to avoid unnecessary procedures.

1. Perianal Abscess
Dr. Shalu Gupta
MS (Surgery), FMAS, FAIS, FIAGES
SMS Medical College, Jaipur

2. Anorectal Abscess
•Infection of the soft tissues surrounding the anal canal
and the rectum with formation of an abscess cavity.
•Anorectal abscess and fistula-in-ano represent different
stages of the same disease
 acute - Anal sepsis (abscess)
 chronic - Anal fistula
•A fistula and abscess may coexist.

3. EPIDEMIOLOGY
• May resolve itself
• Quite common in infants too
• Age: 3rd and 4th decade
• Sex: Affects more males than females ( M:F::2:1 – 3:1)
• Race: No racial predilection
• Commonly found amongst the immunosuppressed individuals.
• Relation between the formation of ano-rectal abscesses and
bowel habits
• 30% recurrence rate*
*Shrum RC. Dis Colon Rectum 1959; 2:469–472, **Shouler PJ et al . Int J Colorect Did 1986,1:113-5

4. RELEVANT ANATOMY

5. RELEVANT ANATOMY
• Dentate line transition from endo to ecto.
• Rectum has inner – circular.
outer – longitudinal.
• Anal canal – 4cm, pelvic diaphragm to anal verge.
External Sphincter-
- continuation of levator ani
- striated muscle
- voluntary control
- 3 components - sub mucous, superficial and deep.

6. RELEVANT ANATOMY
• Internal sphincter-
- smooth muscle
- autonomic control
- extension of circular muscles of rectum.
- contracted at rest.
• 4-8 anal glands drained by respective crypts, at dentate line.
• Gland body lies in intersphincteric plane.
• Anal gland function is lubrication.
• Columns of Morgagni - 8-14 long mucosal fold.

7. Anorectal Spaces

8. Classification of Anorectal Abscess
• Perianal 60%
• Ischiorectal 20%
• Intersphincteric 5%
• Supralevator 4%
• Submucosal 1%

9. Horseshoe abscess

10. Etiology
• Non specific :Cryptoglandular in origin - most common cause
• Specific :
 IBD- Crohn’s disease, ulcerative colitis
 Infection : E.coli , Staph. , strep. , Bacteroids
 TB
 STDs
 Trauma
 FB
 Surgery – Episiotomy, Haemorrhoidectomy, Prostatectomy
 Malignancy
 DM
 AIDS
 Radiation therapy

11. PATHOPHYSIOLOGY
Originates from an infection arising in the
crypto glandular epithelium lining the anal
canal
The internal anal sphincter normally serves
as a barrier to infection passing from the gut
lumen to the deep perirectal tissues.
This barrier can be breached through the
crypts of Morgagni, which can penetrate
through the internal sphincter into the
intersphincteric space

12. PATHOPHYSIOLOGY
Once infection gains access to the
intersphincteric space, it has easy
access to the adjacent perirectal
spaces
Extension of the infection can
involve the intersphincteric
space 2–5%, ischiorectal space
20-25% , or even the
supralevator space 2.5%.

13. Parks cryptoglandular theory - Obstruction of
anal glands leads to stasis and infection

14. Clinical features
Symptoms-
•Pain Perianal movement ↑
pressure ↑
•Pruritis
•Generally unwell.
•Fever
•Chill and rigor.
Signs-
•Swelling
•Cellulitis
•induration
•Fluctuation
•Subcutaneous mass, near
Perianal orifice.
•DRE- fluctuation at times
in ischorectal.

15. Workup/Investigations :
 No specific test required
 Patients with diabetes , immunosuppresed will need
lab evaluation.
 Imaging – role in only deep seated, Supralevator or
intersphincteric abscesses. CT Scan , MRI or Anal
ultrasonography.
 CBC with differential : may show leukocytosis
 Pus cultures

16. Likely Diagnosis of Anorectal Pain
Pain Alone Pain and swelling Pain and Bleeding Pain with
swelling and
Bleeding
• Anal Fissure • Perianal Hematoma • Anal Fissure • Hemorrhoids
• Anusitis • Strangulated • Proctitis • Ulcerated
• Ulcerative Proctitis Internal Hemorrhoid Perianal
• Proctalgia Fugax • Abscess Hematoma
• Pilonidal Sinus
Pain, bleeding,
with/without Pus
Draining
Pain with swelling,
Pus Draining,
with/without
Bleeding
Pain with swelling, Pus
Draining, and Bleeding
Pain with
swelling, Pus
Draining,
Bleeding, and
Necrotic
Tissue
Perianal Crohn’s
Disease
Hidradenitis
Suppurativa
Fistula-in-Ano
Perianal Tumors
Fournier’s
Gangrene
Differential diagnosis

17. Management
•Mainly surgical
•Antibiotics in diabetics & immunocompromised
individuals.
•Early drainage is indicated as delay can cause-
* prolong infection
* tissue destruction ↑
* chances of sphincter dysfunction ↑
* Promote fistula formation.

18. Drainage of perianal or superficial abscesses
The gauze is removed after 24 hours, and the patient is instructed
to take sitz baths 3 times a day and after bowel movements.
Pus is collected and sent for culture. Hemostasis is achieved with
manual pressure, and the wound is packed with iodophor gauze.
A small cruciate incision is made over the area of fluctuancy in
close proximity to the anal verge.

19. Perianal Abscess

20. Perianal Abscess
• Continued drainage of large cavities may be achieved with the use
of a catheter left in situ until drainage subsides. This technique
may be used in a number of different abscesses but is not suitable
for use in cases of submucous or intersphincteric abscess.

21. Ischiorectal Abscess
• After horseshoe extension is excluded by ensuring that the
deep postanal space is not involved.
• Unilateral ischiorectal abscesses may be drained through a
single incision or several counterincisions over the area of
maximal swelling, pain, and fluctuance
• Incision as close to the anal verge as possible.
• Here a catheter may also be used to enhance the drainage of
large cavities.

22. Intersphincteric Abscess
•An intersphincteric abscess is drained by laying open
the internal sphincter (sphincterotomy) overlying the
cavity.
•For hemostasis, adequate drainage, and faster healing,
the edges of the wound may be marsupialized.

23. Submucosal Abscess
•Submucosal abscesses are drained internally by
incising the mucosa over the abscess. The edges of
the wound may be marsupialized.
•No packing or drainage catheter is indicated.

24. Supralevator Abscess
• Anatomic localization of the septic
origin - paramount importance
• Supralevator collections that result
from an upward extension of an
intersphincteric abscess should be
drained transrectally. Transperineal
drainage through the ischiorectal
fossae could result in a
suprasphincteric fistula.
• Supralevator collections that result
from the cephalad extension of a
transsphincteric fistula or an
ischiorectal collection should be
drained transperineally through the
ischioanal fossae.
• If erroneously drained
transrectally, the result will
be an extrasphincteric
fistula. Transperineal
drainage of this type of
collection will likely result
in a transsphincteric fistula
that is relatively easy to
manage

25. Postanal Abscess and Horseshoe Extension
Hanley’s technique-
• The abscess in the postanal space is drained by a
deep posterior midline incision.
• All of the muscles attached to the coccyx, the
superficial external sphincter, and the lower edge
of the internal sphincter are divided.
• When the suppurative process extends to the
ischiorectal spaces as a horseshoe, one or multiple
secondary incisions are placed in the skin
overlying the ischiorectal space.
• These may be connected to each other with soft
drains to allow for continuous drainage.

26. Postanal Abscess and Horseshoe Extension
Modification of Hanley’s technique-
• Posterior midline incision consists of only a
partial distal internal sphincterotomy to
include a fistulotomy with destruction of the
anal gland at the dentate line.
• The external sphincter fibers are usually
splayed out thin as a result of tension from the
abscess.
• This condition allows efficient drainage of the
postanal space via a posterior sphincterotomy
while maintaining the muscular attachments of
the coccyx in place.
• Counter incisions and drains are used for
horseshoe extensions as previously described.

27. Catheter drainage
•A stab incision over the abscess
•A 10-16 F catheter inserted into the abscess cavity
•Shape of catheter- holds in its place
•Removed if drainage has stopped

28. Primary Versus Delayed Fistulotomy
• Primary fistulotomy when draining an abscess remains controversial.
• Controversy include 1. ability to localize an internal opening, 2. effect of primary
fistulotomy on recurrence and continence.
• Type of abscess affect the risk of recurrent fistula?
• Cost effective - one-stage procedure OR second procedure for a fistula
• A one-stage procedure theoretically destroys the cryptoglandular source of sepsis,
decreasing the incidence of fistula formation.
• However, internal openings may not always be found.
• Attempts to define a primary opening may be a hazardous.
• Not all abscesses lead to fistulas; thus some patients would undergo an unnecessary
procedure that puts them at risk for incontinence.
• Scoma et al. found that 66% of 232 patients developed a fistula or recurrent abscess
after incision and drainage alone.
• Vasilevsky and Gordon found that 11% of 83 patients developed recurrent abscess and
37% developed a fistula after incision and drainage. Greatest risk of recurrence was in
ischiorectal abscesses. Patients with no previous episode of anorectal suppuration had a
lower incidence of recurrence.
• Both authors advocated incision and drainage alone for acute abscesses, reserving
fistulotomy as a secondary procedure in patients with recurrence.

29. Primary Versus Delayed Fistulotomy
• In contrast, several authors favor a policy of immediate fistulotomy in the treatment of
anorectal abscesses.
• In a series of almost 800 cases, Eisenhammer described a nearly 100% cure rate
obtained with a single operation. McElwain et al. reported on the outcome of 1000 cases
of primary fistulotomy that the recurrence rate was 3.6%, and the disturbance of
continence rate was 3.2%.
• This approach is further supported by Oliver et al. and demonstrated that drainage with
fistulotomy was safe (incontinence, 6% at 1 year) and effective (recurrence, 5% at 1
year) when compared with drainage alone (0% incontinence and 29% recurrence).
• Ultimately this approach requires the consistent finding of an internal opening to
perform fistulotomy. In general, internal openings can be identified in 34% to 88% of
acute abscesses.
• In summary, primary fistulotomy may decrease recurrence and fistula risk but at the
expense of a small increase in the risk for disturbance of continence.
• Primary fistulotomy - who have a history of previous anorectal sepsis or ischiorectal
abscess with readily apparent internal opening.
• This controversy has no impact in dealing with postanal abscesses with horseshoe
extensions or intersphincteric abscesses. In these cases a fistulotomy is performed when
the sphincterotomy is the primary drainage technique.

30. Post operative
• Analgesics and stool softeners are prescribed to
relieve pain and prevent constipation.
• Antibiotic therapy when indicated– to cover aerobes
and anaerobes e.g. ciprofloxacin 500 mg PO 2x
daily for 5 days
• Follow up: 2-3 weeks for wound evaluation and
inspection for possible fistula-in-ano.

31. COMPLICATIONS
Recurrence and Fistula-in-Ano – Reasons
•Missed infections OR
•Undiagnosed fistula OR
•Failure to complete drainage
Fecal Incontinence – due to
•Iatrogenic damage to sphincter
•Prolonged packing
•Primary fistulotomy

32. COMPLICATIONS
Necrotising anorectal infections –
•Spreading soft tissue infection of perineum
•Pus C &S
•Broad spectrum antibiotics
•Wide redical debridement
•Colostomy- debatable
•Hyperbaric oxygen
•Mortality- 8 to 67%
Fournier’s Gangrene
Carcinoma
Death

33. PROGNOSIS
• Drainage alone results in cure for 50%.
• 50% will have recurrences and develop an anal fistula.

34. Take home message
• Anorectal abscess usually produce throbbing pain, swelling in
the anal region.
• Anatomically classified as perianal, ischiorectal, submucous
and pelvirectal abscess.
• Primary modality of treatment is drainage of pus with
analgesics and appropriate antibiotics.
• Underlying problem should be looked for and adequately
treated