Perianal abscess

Notes

Overview

Perianal abscesses are one of the most common complaints on the general surgery take.

Perianal abscess present with an acute and tender perianal swelling. Systemic upset - with fevers and malaise - may be present.

Management is typically with incision and drainage, though conservative management with antibiotics may be trialed. 

Risk factors

There are a number of risk factors associated with perianal abscesses.

  • Fistula-in-ano
  • Inflammatory bowel disease
  • Diabetes mellitus  
  • Immunosuppression

Clinical features

Symptoms are typically pain and swelling in the peri-anal region.

Most patients are systemically well at presentation, but a significant minority may present with features of systemic infection or sepsis.

Symptoms

  • Perianal swelling
  • Perianal pain
  • Malaise

Signs

  • Fluctuant, tender perianal swelling
  • Pus discharge
  • Erythema
  • Fever

Investigations

Blood tests give an indication as to the severity of the infection.

Bedside

  • Vital signs
  • BM

Bloods

  • FBC
  • UE
  • CRP
  • HbA1c
  • Blood borne virus screen

Imaging

MRI anal sphincter: May be ordered following I+D (after several weeks for inflammation to settle) in patients with suspected fistula-in-ano. Rarely imaging will be indicated pre-operatively, in patients with complex, extensive or suspected occult disease.

Management

Incision and drainage is the definitive management for a peri-anal abscess.

Patients who are systemically unwell, have markedly raised inflammatory markers, are elderly or co-morbid should be admitted until definitive management. Consider commencing IV antibiotics.

Patients with significant cellulitis, diabetes, immunosuppression or sepsis should have an I+D urgently.

Young patients who are systemically well without co-morbidities can be discharged and brought in the following morning (NBM from 2am) for a daycase procedure.

I+D

Patients should be consented for a examination under anaesthesia (EUA) and incision and drainage of peri-anal abscess. It is a relatively quick operation. The EUA allows evaluation of the anorectum for obvious signs of fistulas. 

The I+D itself involves a cut into the abscess, allowing drainage of pus. This is then packed with a gauze like material. This prevents the cavity closing over and pus re-accumulating. Typically further antibiotics are not needed but may be given if evidence of overlying cellulitis or other concerns exist. Pack changes are continued by the GP practice nurse until it heals via secondary intention.

Follow-up

The majority of patients do not need any follow-up following their first peri-anal abscess.

Routine general surgery follow-up is not required. Patients should continue dressing pack with the GP practice nurse until it heals via secondary intention.

Patients with recurrent abscesses, inflammatory bowel disease or evidence of fistula-in-ano should be seen in colorectal clinic and MRI anal sphincter ordered.

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