[6] Anal Fistula Flashcards
What is an anal fistula?
An abnormal connection (a channel) between the anal canal and the perianal skin
What are anal fistulas associated with?
Anorectal abscess formation
Who are anal fissures more common in?
Males
What does the formation of an anal fistula typically occur as a consequence of?
Anal abscesses
What % of individuals with an anal abscess will develop an anal fistula?
Between 25-50%
Is it common for anorectal cancers to present with an anal fistula?
No, it is rare
What are the risk factors for anal fistulas?
Inflammatory bowel disease
Systemic diseases
History of trauma to anal region
Previous radiation therapy to anal region
What systemic diseases increases the risk of anal fistulas?
Tuberculosis
Diabetes
HIV
What do anal fistulae commonly occur in cases of?
Chronic anal infection
How do anal fistuale often present?
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
What may the discharge be in anal fistulae?
Mucus, blood, pus, or faeces
What will be found on examination with anal fistulae?
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
What can the Goodsall rule be used for?
To clinically predict the trajectory of a fistula tract, depending on the location of the external opening
What does the Goodsall rule say about external openings posterior to the transverse anal line?
The fistula tract will follow a curved course to the posterior midline
What does the Goodsall rule say about external openings anterior to the transverse anal line?
The fistula tract will follow a straight radial course to the dentate line
What imaging can be used in the investigation of an anal fistula?
Rigid sigmoidoscopy
Fistulography
Endo-anal ultrasound
MRI imaging
What can a rigid sigmoidoscopy be used for in anal fistulas?
To visualise the opening of the tract in the anal canal
What are fistulography, endo-anal ultrasound, or MRI imaging used for in anal fistulas?
May be used to visualise the remaining part of the tract
What is used for the classification of anal fistulae?
Park’s classification system
What are the types in Park’s classification system?
Inter-sphincteric fistula
Trans-sphincteric fistula
Supra-sphincteric fistula
Extra-sphincteric fistula
What is the most common type of anal fistula?
Inter-sphincteric fistula
What is the least common type of anal fistula?
Supra-sphincteric fistula
What does the definitive management of an anal fistula depend on?
Depends largely on the case
When may a conservative approach be used in the management of anal fistulae?
If the patient has no symptoms
What are the surgical options for an anal fistula?
Fistulotomy
Placement of a seton and/or opening the perianal skin adjacent to the external opening
What does a fistulotomy involve?
Laying the tract open and allowing it to heal by secondary intention
How is the tract opened in a fistulotomy?
A probe is passed into the tract, and the skin, subcutaneous tissue, and internal sphincter are divided in turn, thus opening the tract
Is there an impairment in continence following a fistulotomy?
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
What is meant by a low tract course in anal fistulae?
The tract travels through less subcutaneous tissue and muscle
What is the purpose of the placement of a seton and/or opening the perianal skin adjacent to the external opening?
It promotes healing before external closure, and prevents recurrence of an abscess
When should surgery for an anal fissure not be performed?
In the setting of an acute anorectal abcess
