Anorectal Abscess lecture note written by Gboneme Sandra, Useful for USMLE

1. G B O N E M E S . E
ANORECTAL ABSCESS

2. OUTLINE
• Introduction
• Epidemiology
• Relevant Anatomy
• Etiology
• Classification and Pathogenesis
• Clinical Features
• Management

3. INTRODUCTION AND DEFINITION
• Anorectal Abscess can simply be defined as infection of
the soft tissues surrounding the anal canal and the
rectum with formation of an abscess cavity.
• It is of importance as it may lead to complications which
includes fistula in ano.

4. EPIDEMIOLOGY
• Age: 3rd and 4th decade
• Sex: Affects more males than females
• Race: No racial predilection
• Commonly found amongst the immunosuppressed.

5. RELEVANT ANATOMY

6. RELEVANT ANATOMY CONTD
• Anal Columns (longitudinal)are attached by Anal
Valves(Horizontal) to form Anal Sinuses which drain into
the Anal glands located in the intersphincteric zone.
• At the area of the Anal Sinuses lies the pectinate/dentate
line.
• Dentate line acts as a boundary for the rectum and the
anal canal

8. ISCHIORECTAL FOSSA
• Pyramidal structure
• Apex- towards the Pubis symphysis
• Roof- Levator Ani Muscle
• Lateral Wall: Obturator internus muscle and fascia
• Medial: Medial part of ischial tuberosity

9. ETIOLOGY AND RISK FACTOR
• Etiology: Common organisms include Staph Aureus,
Streps, Bacteroides.
• Other causes include: Crohn’s disease, ulcerative colitis,
Tuberculosis, STD’s, appendicitis.
• Risk Factor: Immunosuppression, Malignancy, Trauma,
Radiation therapy.

10. CLASSIFICATION
• Classified into 5
• 1. Intersphicteric Abscess
• 2. Perianal Abscess
• 3. Ischiorectal Abscess
• 4. Pelvirectal Abscess
• 5. Submucous Abscess

11. CRYPTOGLANDULAR THEORY
• Anal Sinuses drain into the crypts around the dentate
line, these crypts drain into the anal glands at the
intersphincteric zone, hence the intersphincteric abscess
is usually the starting point.
• Suppuration of the Anal Pile – Perianal Abscess

12. CONTD
• Suppuration of the Ischiorectal fossa – Ischiorectal
abscess. (usually due to the presence of poorly
vascularized fat)
• Intersphincteric abscess extends laterally through the
anal sphincter.
• It may communicate posteriorly to form a HORSE SHOE
abscess.

13. CONTD
• Submucous Abscess: Suppuration above the dentate
line. Responsible for 5%
• Pelvirectal: Suppuration above the Levator Ani muscle.
Can occur due to intersphincteric abscess or a pathology
in the pelvis or abdomen e.g Appendicitis.

14. CLINICAL FEATURES
• Patient presents with:
• Pain which may be in the perianal region or in the
anorectum (seen in submucosa abscess)
• Fever
• Swelling which may be discharging or is ulcerated.

15. CONTD
• Signs Include:
• Tender, Smooth swelling
• Soft if Perianal, Hard if ischiorectal
• Patient is febrile and generally unwell.

16. MANAGMENT
• Investigations:
• DRE
• USS : Shows and abnormal collection
• CT
• MRI
• CT and MRI used to identify the cause in Pelvirectal
• PUS culture – M/C/S

17. MANAGMENT
• Treatment:
• Analgesics for the pain
• Incision and drainage of the Abscess, followed by
appropriate ANTIBIOTICS based on selectivity.
• Incised area should be packed with sterile gauze and
dressed twice daily.
• Stool softeners should be given to avoid constipation
which may worsen the problem.

18. COMPLICATION AND CONCLUSION
• Complications include: Fistula in ano, Founier’s
gangrene, Anal fissure and Overwhelming sepsis.
• In conclusion, abscess must be drained before
antibiotics is administered.