Perianal abscesses and fistulae

Question 1

Define

Answer 1

Perineal Abscess: a pus collection in the perineal region

Perineal Fistula: an abnormal chronically infected tract communicating between the perineal skin and either the anal canal or the rectum

Question 2

Causes

Answer 2

Bacterial infection

Fistulae develop as a complication of an abscess

Fistulae can develop as a complications of Crohn’s disease

• The development of multiple perineal fistulae in Crohn’s disease is called pepper pot perineum

Question 3

Risk factors

Answer 3

IBD

Diabetes mellitus

Malignancy

Question 4

Epidemiology

Answer 4

Peak incidence 20-30 years
Men more frequently affected than women

Question 5

Symptoms

Answer 5

• Constant throbbing pain in the perineum
•  Intermittent discharge (music or faecal)
•  ±Localised tender perineal mass or small skin lesion corresponding to the opening of a fistula
• Pain, swelling and redness
•  ±Fevers, general weakness

Question 6

Signs

Answer 6

PR may allow palpation of abscess or fistula

Question 7

Investigations

Answer 7

Bloods

• FBC
• CRP
• ESR
• Blood culture

Imaging

• MRI
• Endoanal Ultrasound

Less useful than MRI

Question 8

Management

Answer 8

Requires SURGICAL treatment

Open Drainage of Abscess

Laying Open of Fistula

• A probe is inserted to explore the fistula
• A dye can be inserted into the external opening to allow you to find the internal opening

Low Fistula

• Fistulotomy
• Care must be taken to prevent damage to the anal sphincter

High Fistula

• Fistulotomy would cause INCONTINENCE so is NOT performed
• Seton - a non-absorbable suture that is threaded through the fistula and allows drainage

Antibiotics

Question 9

Complications

Answer 9

Recurrence

Damage to internal anal sphincter

Incontinence

Persisting pain

Question 10

Prognosis

Answer 10

High recurrence rate without complete excision