Perianal and perirectal abscess: symptoms, drainage and recovery

An abscess is a painful, swollen area with pus inside, and pus is a yellow or green liquid made by infected tissue, according to Guy's and St Thomas' NHS Foundation Trust. A perianal abscess is one near the opening of your bottom. Doctors also use the terms perirectal or anorectal abscess for infections in or beside the lower rectum and anus, depending on exactly where the pus collects.

The Trust explains that often a small gland just inside the bottom becomes infected and an abscess forms. Crohn's disease, a lifelong condition in which parts of the digestive system become inflamed, can make these infections more likely, but most people with a perianal abscess do not have Crohn's disease.

The Trust lists the symptoms of a perianal abscess as pain, irritation around the bottom, swelling, a pus discharge, a high temperature and feeling generally unwell. The NHS page on anal fistula, which commonly follows an abscess, describes swelling and redness around the anus and a high temperature if you also have an abscess, and says symptoms of a fistula can include skin irritation, a constant throbbing pain that may be worse when you sit, move, poo or cough, smelly discharge and passing pus or blood when you poo.

Because the symptoms overlap with other conditions, it is worth getting them examined. The NHS advises seeing a GP if you have persistent symptoms around the anus. A GP will ask about your symptoms, whether you have any bowel conditions, and may examine the area. The Trust lists a high temperature and feeling generally unwell among the symptoms, and if you feel feverish and unwell with a painful swelling near the anus, it is sensible to seek same-day advice from your GP or NHS 111.

Guy's and St Thomas' says surgery is often the only way to treat an abscess and remove all the infected tissue. You will be reviewed by the surgical team and assessed by an anaesthetist before surgery, and the operation, which does not take long, is often done as a day case so you can leave on the same day. You usually have a general anaesthetic in an operating theatre. The surgeon examines where the abscess is, drains the pus and cleans the area.

The Trust also says that, sometimes, an abscess can drain by itself without treatment or be very small and not need any surgery, and that the surgeon will talk through your treatment options.

The Trust says most people recover well after drainage with no complications, but for a small number of people the abscess returns, which is more common if a fistula is present. Other complications include bleeding, problems with the wound such as delayed healing and wound infection, and scars.

If the abscess or a fistula involves the anal sphincter muscles, there can be a temporary change in how you control bowel movements, including holding in wind. The Trust says this is almost always temporary and that draining the abscess is the best way to reduce any chance of it.

The NHS explains that an anal fistula is a small tunnel between the end of the bowel and the skin near the anus, usually caused by an infection near the anus, that will not usually get better on its own and for which surgery is recommended in most cases. Less common causes include Crohn's disease, diverticulitis, hidradenitis suppurativa, TB or HIV infection and surgery near the anus.

The sources read for this page do not detail wound packing or dressing routines, and practice differs between hospitals, so follow the instructions you are given on discharge. If you notice increasing pain, fever, spreading redness or discharge after surgery, contact your surgical team or NHS 111.

Seek help promptly if you are unwell with a fever, because infection near the anus can spread. NHS Lothian's guidance for clinicians refers to sepsis and to suspected Fournier's gangrene as situations that need different, urgent management, so a rapidly worsening, very painful or very swollen area, or feeling seriously unwell, should be treated as an emergency.

On the NHS the usual route is a GP or emergency department assessment followed by referral to a general or colorectal surgical team for drainage, and a colorectal surgeon can later review any fistula.

Private colorectal surgeons also drain abscesses and treat fistulas. Whichever route you choose, ask who will check that the wound has healed and who will assess for a fistula.