Anal Fistulas

Question 1

Definition

Answer 1

Anal fistulae are abnormal communications, hollow tracts lined with granulation tissue connecting the primary opening inside the anal canal to a secondary opening in the perineal skin. They are usually associated with anorectal abscesses (obstruction of ducts leading to infection).

Question 2

Clinical Presentation

Answer 2

• Intermittent purulent discharge ± bleeding
• Pain – which increases till temporary relief occurs with pus discharge

Question 3

Associated conditions

Answer 3

• Crohn’s disease
• Unusual Infection (i.e. TB, Actinomycosis, Chlamydia, HIV)
• Systemic disease (i.e DM)
• Hidradenitis suppurativa
• Malignancy
• Radiation
• History of trauma to anal region

Question 4

PE

Answer 4

• Assess for external opening on perineum seen: may be open, covered in granulation tissue
• Assess for fibrous tract that can be felt underneath skin on DRE

Question 5

What is Goddsall’s Rule

Answer 5

Goddsall’s Rule
- For fistula within 3cm of the anal verge and posterior to line drawn through ischial spines if
▪ Anterior to transverse anal line: straight radially directed tract into anal canal
▪ Posterior to transverse anal line: curve tract open into anal canal midline posteriorly (at level of dentate line)
- Exception: anterior external opening is >3cm from the anal margin – such fistula usually tack to the posterior midline

Question 6

What is the classification

Answer 6

Question 7

What investigations?

Answer 7

• Endoanal U/S (H2O2 aided for hyperechoic effect) – to view course of fistula tract – more accurate than Goodsall’s Rule
• MRI – able to visualise entire pelvis, beyond the sphincter complex (gold standard)
• CT/fistulography (in emergency situation) – for complex fistulas / unusual anatomy

Question 8

What is the management?

Answer 8