Anal and Rectal Lesions - Anorectal Abscess

Question 1

What is a perianal abscess?

Answer 1

Collection of pus within the subcutaneous tissue of the anus that has tracked from the tissue surrounding the anal sphincter.

Question 2

Epidemiology of perianal abscess (3).

Answer 2

1. Commonest form of anorectal abscess (60%).
2. 2x commoner in men.
3. Average Age : 40.

Question 3

Clinical Features of perianal abscess (4).

Answer 3

1. Pain around anus, exacerbated by sitting.
2. Hardened fluctuant tender swelling in the anal region.
3. Pus-like discharge from the anus.
4. Longstanding abscess : features of systemic absorption.
   * PR Bleeding suggests anal fissure more than Abscess.

Question 4

Aetiology of perianal abscess (2).

Answer 4

1. Generally colonised by gut flora e.g. E. coli.

2. If S. aureus is involved, more likely to be a skin infection.

Question 5

Investigation of perianal abscess.

Answer 5

1. DRE.
2. Colonoscopy and Bloods.
3. MRI - Gold Standard and Transperineal US (preferred in complicated/severe cases).

Question 6

Associations of perianal abscesses (4).

Answer 6

1. Underlying IBD, especially Crohn’s.
2. Diabetes Mellitus - affected wound healing.
3. Malignancy : risk of bowel perforation.
4. Anal Fistulae.

Question 7

Management of perianal abscess.

Answer 7

1. Surgical Incision and Drainage (1st line) with LA and then pack or leave the wound open; it will heal in 3-4 weeks.
2. Antibiotics - only if systemic upset secondary to the abscess.

Question 8

Other Types of anorectal abscesses (4).

Answer 8

1. Ischiorectal Abscess - between Obturator Internus muscle + External Anal Sphincter.
2. Supralevator Abscess - infection tracks superiorly from the peri-sphincteric area to above the levator ani.
3. Intersphincteric abscesses - between internal and external anal sphincters (rare).
4. Horseshoe abscess - between coccyx and anal canal (complication of supralevator abscess).