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Perianal abscess and fistula

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What is a perianal abscess?

A perianal abscess is an infected cavity filled with pus found near the anus and rectum.  An abscess develops from an acute infection within a small gland that lies just inside the anus.  These glands are situated between the two mucles of the anal sphincter.  They drain into the anus through a small duct that passes through the internal anal sphincter.  If the gland or its duct gets blocked and bacteria or foreign matter enters, an infection can develop.  The infection then tends to spread either up and down or travel around between the two muscle layers.  Occasionaly it can cross through one of the sphincters into the fat of the buttock.

.....and a fistula?

An anal fistula is a connection or tract between the skin on the outside and the anus on the inside (see below).

There are many types ranging from relatively simple to very complex branching or networks of tracks. Some involve the muscles (see above) responsible for bowel control. Each one is individual to the patient.  Fistulas tend to develop in less than 50 percent of perianal abscesses.

What are the symptoms and how is an abscess treated?

Abscesses cause constant throbbing pain as the pus collects under pressure.  The skin can become red and inflamed, often accompanied by a swelling.  If not drained, a fever can develoe and in some cases (diabetics, the elderly and immunocompromised) the patient can become ill.  The tratment is incision under a general anaesthetic and drainage of the underlying pus.  

.......and for a fistula?

In a word - Surgery. 

Fistula surgery involves cutting a small portion of the anal sphincter muscle to open the connection between the external and internal openings.  Over a 6-8 week period this heals from within to out.  There are many different surgical approaches and these will be taylored to an individual.   Discuss this with your surgeon.

In some individuals, further treatments, with a return visits to the operating theatre, may be required.  Sometimes we use a stitch (called a seton) - looks and feals like an elastic band, inserted through the tract/connecting tunnel and then out through the anus and tied on the outside.  This is used when it would be inadvisible to divide the muscle.

Post-operative treatments

A dressing will have been used to control bleeding. This can feel strange and uncomfortable so much so that it may make you feel that you want to open your bowels.  Whilst some discomfort is to be expected, it is nothing at all like the pain associated with an abscess. Painkillers will be prescribed, usually a combination of regular paracteamol and an anti-inflammatory.  You will be encouraged to have a bath the next day and soak the dressing (it may need a gentle pull).  Expect some blood loss in the bath.

Dressing your wound

This will depend on the type and extent of the operation performed but in general once a day will sufice and usually following a warm bath or shower.  Wash with aqueous cream (dont worry if you see some blood) and dry with a hair dryer.  You may feal a little silly but it works!  It is sensible to wear a small pad inside your pants to absorb any discharge and protect your clothes.

How long should I stay off work?

The time taken to get back to normal activities varies from person to person and with the extent of the surgery performed as well as your occupation.

Do as much as you feel comfortable. If you are using painkillers which make you drowsy do not drive or operate machinery.  If lifting causes discomfort, avoid it.  Most people need a week or two off work.  You will not do any harm by returning to work early.

At first, avoid sitting still or vigerous activity.   Start with gentle walking and build up your activity level gradually.  Resume sexual activity as soon as you feel comfortable and confident.

Are there any long-term effects of the operation?

In a few cases, patients with a weak anal sphincter and a pre-exisating tendency to urgency, soiling or leakage, symptoms may get worse after the operation.  If this becomes problematic you should consult your specialist again as it may be possible to do something eg physiotherapy.  In general, this will require evaluation with an endo-anal ultrasound  and some physiology testing of sphincter function.



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