Anal fistula

What is an anal fistula?

Anal fistulas are commonly caused through inflammation of the anal glands, which result in the development of a tunnel between the anal canal and perianal skin.

Signs and symptoms of anal fistula

Signs and symptoms of an anal fistula often aren’t noticeable until there is an active inflammation of the area. Very often, the first sign of an anal fistula is an abscess with painful swelling, redness and tenderness near the anus. Another common symptom is discharge, which may include mucus, pus or fecal matter from the tunnel opening, and a foul odour.


Anal fistula are most commonly treated through surgery. This may include:

  • Fistulotomy – where the whole length of the fistula is cut open, so that it heals as a flat scar. The size of the wound will depend on the extent of the anal fistula and can take a few weeks to heal completely. A fistulotomy is considered to be the most effective treatment for simple low fistulas that minimally impact the sphincter muscles, as they present the lowest risk of incontinence.1
  • Seton placement – recommended if the fistula passes through a significant portion of anal sphincter muscle. The process involves the surgical insertion of thread, known as seton, into the anal fistula to keep it open and promote drainage and healing. The seton is left in the fistula for several weeks to months and involves several procedures where a small part of the fistula is opened and the seton is readjusted into a new position. By avoiding cutting a large part of the sphincter muscles during a single procedure, continence is preserved.1
  • Fistula plug – recommended for high or complex (with multiple branches) anal fistula. A fistula plug involves blocking the internal opening of the fistula through the insertion of a collagen scaffold made from animal tissue into the fistula tract, facilitating the growth of tissue and leading to the closure of the fistula. Although studies suggest this technique provides a less invasive option compared to conventional surgery, the result is not consistent.1


For a full list of references, click here.
  1. NHS. (2019). Treatment – Anal fistula. Retrieved on 3 December 2019 from

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