Practice Clinical updates

Perianal abscess

BMJ 2017; 356 doi: https://doi.org/10.1136/bmj.j475 (Published 21 February 2017) Cite this as: BMJ 2017;356:j475
  1. Kapil Sahnan, specialist registrar in colorectal surgery1,
  2. Samuel O Adegbola, specialist registrar in colorectal surgery1,
  3. Phillip J Tozer, specialist registrar in colorectal surgery1,
  4. Josef Watfah, consultant emergency surgeon2,
  5. Robin KS Phillips, professor of colorectal surgery, consultant surgeon and clinical director of St Mark’s Hospital1
  1. 1Imperial College Faculty of Medicine, St Marks Hospital, London SW7 2AZ, UK
  2. 2Northwick Park Hospital, London, UK
  1. Correspondence to: K Sahnan ks303{at}doctors.org.uk

What you need to know

  • Perianal abscesses almost always require surgical drainage, even if they have spontaneously discharged

  • Patients with diabetes, immunosuppression, evidence of systemic sepsis, or substantial local cellulitis require urgent drainage

  • In uncomplicated cases, offer incision and drainage within 24 hours

  • Drainage leads to an open cavity that typically takes 3-4 weeks to heal

  • Persistent failure to heal may indicate an underlying fistula

The annual incidence of perianal abscess is estimated between 14 000 and 20 000 people in the UK, resulting in about 12 500 operations in the NHS each year.1 A recent Swedish cohort study estimated the incidence at 16.1 per 100 000.2 The true incidence may be higher, since many patients are treated with antibiotics in the community and some abscesses spontaneously regress or discharge.23 Patients usually present with an erythematous swelling near the anus and may be embarrassed or reluctant to seek treatment. They may present to a non-specialist in the first instance. This article provides information on the causes and different types of perianal abscess and an update on how they are best managed.

What are perianal abscesses?

An abscess is a localised collection of infected fluid. Although there are strict anatomical definitions for the different anorectal abscesses, initial management is the same in most cases and the term “perianal abscess” is generally used as a result (fig 1).

Fig 1 Possible sites of anorectal (“perianal”) abscesses

About 90% of idiopathic perianal abscesses occur because of infection of the cryptoglobular glands.45 Most occur posteriorly and in the intersphincteric space, where the anal glands are located.6 Abscesses are classified as superficial or deep in relation to the anal sphincter. If the infection bursts through the external sphincter, it will form an ischiorectal abscess. If it spreads laterally on both sides it can form a collection of sepsis, which …

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