[6] Anal Fistula

Question 1

What is an anal fistula?

Answer 1

An abnormal connection (a channel) between the anal canal and the perianal skin

Question 2

What are anal fistulas associated with?

Answer 2

Anorectal abscess formation

Question 3

Who are anal fissures more common in?

Answer 3

Males

Question 4

What does the formation of an anal fistula typically occur as a consequence of?

Answer 4

Anal abscesses

Question 5

What % of individuals with an anal abscess will develop an anal fistula?

Answer 5

Between 25-50%

Question 6

Is it common for anorectal cancers to present with an anal fistula?

Answer 6

No, it is rare

Question 7

What are the risk factors for anal fistulas?

Answer 7

Inflammatory bowel disease
Systemic diseases
History of trauma to anal region
Previous radiation therapy to anal region

Question 8

What systemic diseases increases the risk of anal fistulas?

Answer 8

Tuberculosis
Diabetes
HIV

Question 9

What do anal fistulae commonly occur in cases of?

Answer 9

Chronic anal infection

Question 10

How do anal fistuale often present?

Answer 10

With an intermittent or continuous discharge onto the perineum
They may also cause severe pain, swelling, change in bowel habit, and systemic features of infection

Question 11

What may the discharge be in anal fistulae?

Answer 11

Mucus, blood, pus, or faeces

Question 12

What will be found on examination with anal fistulae?

Answer 12

An external opening on the perineum, which can be fully open or covered in granulation tissue
A fibrous tract may be felt underneath the skin on DRE

Question 13

What can the Goodsall rule be used for?

Answer 13

To clinically predict the trajectory of a fistula tract, depending on the location of the external opening

Question 14

What does the Goodsall rule say about external openings posterior to the transverse anal line?

Answer 14

The fistula tract will follow a curved course to the posterior midline

Question 15

What does the Goodsall rule say about external openings anterior to the transverse anal line?

Answer 15

The fistula tract will follow a straight radial course to the dentate line

Question 16

What imaging can be used in the investigation of an anal fistula?

Answer 16

Rigid sigmoidoscopy
Fistulography
Endo-anal ultrasound
MRI imaging

Question 17

What can a rigid sigmoidoscopy be used for in anal fistulas?

Answer 17

To visualise the opening of the tract in the anal canal

Question 18

What are fistulography, endo-anal ultrasound, or MRI imaging used for in anal fistulas?

Answer 18

May be used to visualise the remaining part of the tract

Question 19

What is used for the classification of anal fistulae?

Answer 19

Park’s classification system

Question 20

What are the types in Park’s classification system?

Answer 20

Inter-sphincteric fistula
Trans-sphincteric fistula
Supra-sphincteric fistula
Extra-sphincteric fistula

Question 21

What is the most common type of anal fistula?

Answer 21

Inter-sphincteric fistula

Question 22

What is the least common type of anal fistula?

Answer 22

Supra-sphincteric fistula

Question 23

What does the definitive management of an anal fistula depend on?

Answer 23

Depends largely on the case

Question 24

When may a conservative approach be used in the management of anal fistulae?

Answer 24

If the patient has no symptoms

Question 25

What are the surgical options for an anal fistula?

Answer 25

Fistulotomy | Placement of a seton and/or opening the perianal skin adjacent to the external opening

Question 26

What does a fistulotomy involve?

Answer 26

Laying the tract open and allowing it to heal by secondary intention

Question 27

How is the tract opened in a fistulotomy?

Answer 27

A probe is passed into the tract, and the skin, subcutaneous tissue, and internal sphincter are divided in turn, thus opening the tract

Question 28

Is there an impairment in continence following a fistulotomy?

Answer 28

If the fistula has a low tract course, continence is rarely impaired post-operatively. If the fistula has a high tract course, then there is a higher chance of impairment in continence

Question 29

What is meant by a low tract course in anal fistulae?

Answer 29

The tract travels through less subcutaneous tissue and muscle

Question 30

What is the purpose of the placement of a seton and/or opening the perianal skin adjacent to the external opening?

Answer 30

It promotes healing before external closure, and prevents recurrence of an abscess

Question 31

When should surgery for an anal fissure not be performed?

Answer 31

In the setting of an acute anorectal abcess