Anorectal abscess

Question 1

What is an anorectal abscess?

Answer 1

• Collection of pus in the anal/rectal region
• More common in men
• High rates of recurrence
• 1/3 patients have associated perianal fistula

Question 2

Pathophys of anorectal abscess

Answer 2

• Caused by plugging of anal ducts
• These usually drain the anal glands in the anal wall - these normally help the passage of faecal matter using mucus
• Blockage = stasis of fluid in ducts –> infection

Question 3

Common causative organisms ano-rectal abscess

Answer 3

• Escherichia coli
• Bacteriodes species
• Enterococcus species

Question 4

Where are the anal glands located?

Answer 4

• Intersphincteric space
• Between internal and external anal sphincters
• Infection then spreads to adjacent areas

Question 5

Categorisation of anorectal abscess

Answer 5

Based on area:
* Perianal - most common
* Ischiorectal
* Intersphincteric
* Supralevator

Question 6

Symptoms of perianal abscess

Answer 6

• Severe pain perianal region
• Worse with direct pressure eg sitting down
• Perianal discharge or bleeding
• Severe may have systemic features of infection/sepsis

Question 7

Examination of ano-rectal abscess

Answer 7

• Erythematous, fluctuant tender peri-anal mass
• May be discharging pus or have surrounding erythema and induration (hardened and thickened)
• If deeper - may not have any external signs but severe tenderness on PR exam

Question 8

Investigations - bedside and bloods for anorectal abscess

Answer 8

• Clinical diagnosis BUT may need bloods for surgical intervention
• FBC, U&E, clotting, group and save

Question 9

Anorectal abscess without fistula in ano - what to check

Answer 9

Check HbA1C for underlying diabetes

Question 10

Investigations for atypical presentations

Answer 10

• If atypical OR if supralevator, complex perianal fistula or perianal Crohns
• May need MRI pelvis (CT if unavailable)

Question 11

Management anorectal abscess

Answer 11

• Antibiotics
• Sufficient analgesia
• Examination undeer anaesthesia and incision and drainage - under GA wherever possible
• Leave to heal via secondary intention - +/- packing

Question 12

What should be performed during EUA?

Answer 12

• Intra-operative protoscopy to check for fistula in ano
• If identified - insertion of seton can be considered (lay open fistula)

Question 13

Can you treat anorectal abscess with just abx?

Answer 13

• If very small perianal abscess and no signs of systemic sepsis - can trial

Question 14

Post-op management anorectal abscess

Answer 14

• Some data shows abx post op may lower risk of fistula formation