Perianal Fistula Flashcards
What is a perianal fistula?
A perianal fistula (fistula-in-ano) refers to an abnormal connection between the anal canal and the perianal skin.
Which other anal pathology is commonly linked with perianal fistulas?
The majority are associated with anorectal abscess formation, with one third of patients with an anorectal abscess having an associated perianal fistula at the time of presentation.
What are the risk factors for a perianal fistula?
The formation of an perianal fistula typically occurs as a consequence of an perianal abscess. However, other risk factors for their formation include:
- Inflammatory bowel disease
- Crohn’s disease or ulcerative colitis
- Systemic diseases
- Tuberculosis, diabetes, HIV
- History of trauma to the anal region
- Previous radiation therapy to the anal region
What are the clinical freatures of a perianal fistula?
Anal fistulae usually present with either:
- Recurrent perianal abcesses
- Intermittent or continuous discharge onto the perineum, including mucus, blood, pus or faeces
On examination, an external opening on the perineum may be seen; these can be fully open or covered in granulation tissue. A fibrous tract may be felt underneath the skin on digital rectal examination.
Briefly describe The Goodsall Rule
The Goodsall rule can be used clinically to predict the trajectory of a fistula tract, depending on the location of the external opening:
- External opening posterior to the transverse anal line-fistula tract will follow a curved course to the posterior midline
- External opening anterior to the transverse anal line- fistula tract will follow a straight radial course to the dentate line
What investigations should be ordered for a perianal fistula?
Proctoscopy can be used to visualise the opening of the tract in the anal canal. For complex fistula, MRI imaging is often required to visualise the anatomy of the tract.
Briefly describe Park’s Classification of perianal fistulas
Park’s classification system divides anal fistulae into four distinct types:
- Inter-sphincteric fistula (most common)
- Trans-sphincteric fistula
- Supra-sphincteric fistula (least common)
- Extra-sphincteric fistula
What are the 2 most common surgical options for a perianal fissure?
The most common surgical methods employed are:
- A fistulotomy
- Placement of a seton
What is a fistulotomy?
A fistulotomy (suitable for superficial disease) involves laying the tract open by cutting through skin and subcutaneous tissue, allowing it to heal by secondary intention.
What is the placement of a seton?
The placement of a seton (suitable for high tract disease) though the fistula attempts to bring together and close the tract, passing out at opening of the perianal skin adjacent to the external opening.
