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Anal Fistulas


An anal fistula is an abnormal communication that develops between the skin around the anus and the anal canal.


The vast majority of anal fistulas develop after a perianal abscess (boil). They occur less commonly in other bowel diseases such as Crohns disease. In very rare cases, they are secondary to other conditions like TB, HIV, radiation and cancer.



Anal fistulas can be superficial (involving no muscle), can involve the internal anal sphincter (intersphincteric) or can involve both internal and external sphincters (transphincteric,suprasphincteric).

Simple Fistulas

These are anal fistulas not involving a large amount of the sphincters (< 30 – 50% of muscle length).

Complex Fistulas

These are anal fistula involving a large amount of the sphincters (>30 – 50 % of muscle length) , anterior fistulas in women, recurrent fistulas and fistulas associated with Crohns disease or radiation.


Anal fistulas can cause intermittent symptoms of pain, swelling and a pus-like discharge.


The diagnosis can usually be made clinically (ie history and examination). Occasionally, an examination under anaesthetic (EUA) is required. In recurrent and complex fistulas an MRI can be useful to plan surgery.


Anal fistulas almost never resolve without surgery. Abscesses must be drained before definitive repair if present.

Simple fistulas are treated by:

Fistulotomy – laying the fistula open (success rate > 95%)

Complex fistulas usually require insertion of a seton (a rubber band drain) to allow infection and inflammation to settle. A seton usually stays in a minimum of 6 weeks. The options of management subsequently are:

  • Rectal mucosa advancement flap (RMAF) (success rate 60 – 80%)
  • Ligation of intersphincteric fistula tract (LIFT procedure) (success rate 60 – 80%)
  • Fistula Collagen Plug (success rate 30 – 50 %)
  • Long term seton
  • Prince of Wales Private Hospital
  • The Royal Hospital For Women Foundation
  • Colorectal Surgical Society of Australia and New Zealand
Randwick Rooms

Prince of Wales Private
Suite 17, Level 7
Barker Street
Randwick NSW 2031

Phone: (02) 9099 4400
Fax: (02) 9650 4924

Double Bay

Level 1
451 New South Head Rd
Double Bay NSW 2028
(Opposite Woollahra Library Double Bay)

Phone: (02) 9096 3133
Fax: (02) 9096 3199

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