A perianal abscess is an acute collection of pus in the tissues around the anus, usually starting from an infected anal gland. It presents with severe pain, swelling and redness next to the anus. The definitive treatment is prompt incision and drainage — not antibiotics alone — which relieves the pain immediately.
What is a perianal abscess?
A perianal abscess is an acute, localised collection of pus in the tissues surrounding the anus and rectum. In the great majority of cases it starts from infection of a small anal gland (the cryptoglandular theory): the gland becomes blocked, infected, and pus accumulates to form the abscess.
Depending on the space it extends into, an abscess is described as perianal, ischiorectal, intersphincteric or supralevator. The abscess and the anal fistula are essentially two phases of the same disease: the abscess is the acute phase, the fistula the chronic one.
How common is it?
A perianal abscess is one of the most common emergencies in proctology. It occurs at all ages, with a peak between 20 and 40, and is about twice as common in men as in women.
It is estimated that in one third to one half of patients an anal fistula will follow after drainage. This is why follow-up after the acute episode is important.
How does it present?
The main symptoms of a perianal abscess are:
- Intense, throbbing pain next to or around the anus, worse on sitting and defecation.
- Swelling, redness and warmth in the area — often a palpable, tender lump.
- Fever, chills and a feeling of being unwell when the infection spreads.
- Discharge of pus, if the abscess "bursts" and drains spontaneously.
- Difficulty and pain on defecation or urination in deep abscesses.
How is it diagnosed?
The diagnosis is usually clinical and is based on the history and examination of the area:
- Clinical inspection and palpation of the perianal region — often enough for the diagnosis.
- Digital rectal examination, when tolerated, for deep abscesses.
- Examination under anaesthesia (EUA) in painful or complex cases.
- Endoanal ultrasound or pelvic MRI for deep, recurrent or complex abscesses (e.g. horseshoe) and to assess for a fistula.
What increases the risk?
Most abscesses are cryptoglandular in origin, but certain factors increase the risk or complicate the course:
- A previous perianal abscess or fistula.
- Inflammatory bowel disease, especially Crohn's disease.
- Diabetes and immunosuppression.
- Smoking and obesity.
- Chronic diarrhoea or constipation and local trauma.
Modern treatment options
The treatment of an established abscess is surgical: prompt incision and drainage of the pus. Antibiotics have only an adjunctive role in selected cases and do not replace drainage.
For details of the techniques, see the Surgical Services page.
Incision & Drainage
The treatment of choice. Through a small incision over the abscess the pus is drained and the pain is relieved immediately. It is done under local anaesthesia or sedation, often as a day case, depending on the size and location.
Drainage under Anaesthesia
For deep, extensive or complex abscesses (ischiorectal, supralevator, horseshoe). The procedure is done under full anaesthesia, with complete drainage and simultaneous assessment for any underlying fistula.
Fistula Treatment
If an anal fistula develops after drainage, it is treated at a second, planned stage with sphincter-preserving techniques. See the Anal Fistula page for details.
Frequently asked questions
Are antibiotics enough for a perianal abscess?
No. The definitive treatment of an established abscess is incision and drainage of the pus. Antibiotics alone do not 'dissolve' an abscess and are used only as an adjunct in selected cases (extensive cellulitis, diabetes, immunosuppression or systemic signs of infection).
Is it urgent? Can I wait?
It is urgent. A perianal abscess should be drained promptly, because delay can allow the infection to spread into the surrounding tissues. If you have severe pain and swelling next to the anus, especially with fever, see a surgeon without delay.
Will a fistula form after drainage?
In a significant proportion (about one third to one half) of perianal abscesses, an anal fistula subsequently develops — a persistent connection between the bowel and the skin. This may require a second, planned operation for definitive treatment.
Does it hurt a lot? How will I get relief?
An abscess causes intense, throbbing pain that worsens on sitting and defecation. Drainage relieves the pain immediately and dramatically. Do not try to 'burst' it yourself: you risk spreading the infection and causing more damage.
Will it come back?
Correct, complete drainage cures the acute episode. Recurrence or persistent discharge usually indicates an underlying fistula, which must be treated definitively. Managing factors such as diabetes or Crohn's disease reduces the risk of recurrence.