Perianal abscess and fistulae

Question 1

Perianal abscess

Answer 1

Collection of pus within the subcutaenous tissue of anus that has tracked from tissue surrounding anal sphincter

Question 2

Features

Answer 2

Pain around the anus worse on sitting

Hardened tissue in anal region

Pus-like discharge from the anus

May have features systemic infection

Question 3

Causes

Answer 3

Colonised by gut flora such as E.coli

Question 4

Investigations

Answer 4

Inspection of anus and PR exam

Colonoscopy and blood tests to query underlying cause

MRI and transperineal US (gold standard)

Question 5

Associated conditions

Answer 5

Inflammatory bowel disease (especially Crohn’s)

Diabetes mellitis is risk factor due to affected wound healing

Underlying malignancy

Question 6

Treatment

Answer 6

Incision and drainage under local anaesthetic

Wound can be packed or left open

Antibiotics if systemic upset

Question 7

Perianal fistula

Answer 7

Inflammatory tract between anal canal and perianal skin

MRI is investigation of choice

If symptomatic give metronidazole

Inflixumab effective in closing and maintaining closure

Draining seton used for complex fistula