Anal Abscess/Fistula

What is an anal abscess?

An anal abscess is a collection of pus in a cavity next to the anus.

What causes an anal abscess?

An anal abscess is usually due to blockage of an anal gland just inside the anus. Blockage of the gland leads to infection that can extend to different areas around the anus causing an abscess. The abscess may burst through the skin or be drained by a doctor.

What are the symptoms of an abscess?

An abscess usually causes constant pain around the anus. There may be a swollen tender lump and sometimes a fever or chills. If the abscess has burst, there will be some malodorous discharge (pus).

How is an abscess treated?

An abscess needs to be drained to prevent a more severe infection. Sometimes this can be done under local anaesthetic in the doctors office. A larger abscess may require drainage in an operating room by a surgeon. Antibiotics alone will not cure an abscess.

What is a fistula?

After an abscess has been drained or burst opened, a tunnel or tract between the wound and the anal gland may persist. A fistula usually develops after an abscess but may occur without an abscess.

What are the symptoms of a fistula?

A fistula causes chronic discharge that can lead to irritation around the anus. Symptoms include discharge, pain, itch and difficulty with hygiene.

Does an abscess always become a fistula?

No. A fistula develops in around 50% of patients following an anal abscess.

Is a fistula related to other diseases?

Sometimes. Most fistula are related to a previous abscess. Sometimes, patients with Crohn’s disease develop anal abscess and fistula.

How is a fistula treated?

Usually, the fist step in fistula treatment is to get control of the infection. This usually involves an examination in the operating theatre by a surgeon and insertion of a soft drain (Seton). Sometimes, your surgeon will recommend further tests such as a colonoscopy or an MRI scan. Once there is control of the infection, there are a number of options to treat the fistula including:

• Fistulotomy; laying open the fistula by dividing the tissue between the wound (external opening) and the anal canal/gland (internal opening) to form a groove
• Fistula plug; securing a soft absorbable plug in the fistula tract
• Mucosal advancement flap (MAF); involves closing the internal opening and securing a flap of tissue over the repair
• Ligation intersphincteric fistula tract (LIFT); involves making a cut between the internal and external sphincter muscle and dividing the fistula tract.

The best option for you will depend on your individual fistula anatomy, previous attempts at repair and the risks and benefits of the procedure.

How successful is treatment?

Fistula treatment can be particularly frustrating for patients as it can take multiple attempts at repair before it is fixed. The treatment with the highest success rate is a fistulotomy (90-95%). However, if too much sphincter muscle is cut there is a risk of loss of control of ‘wind’ and rarely faecal leakage/incontinence and is not suitable for all fistulas. The other treatment options have a roughly 50% success rate although a plug is probably even lower than this. You should discuss the options with your colorectal surgeon.

What is a colorectal surgeon?

A colorectal surgeon is an expert in the surgical and non-surgical treatment of colon and rectal conditions. In Australia, a colorectal surgeon has completed general surgical training to be a specialist general surgeon (FRACS). A minimum of 2 years of clinical post-fellowship training is then undertaken in high volume accredited institutions through the Colorectal Surgical Society of Australia and New Zealand (CSSANZ). There is also a research requirement and a written examination on colon and rectal conditions. An equivalent domestic or international experience may qualify a surgeon for CSSANZ accreditation.