Anorectal abscess - Disorders of the rectum and anus

Anorectal abscess

Definition

Anorectal abscesses may occur as perianal, ischiorectal or high muscular abscess.

Age

Most common 20–40 years.

Sex

2M : 1F

Aetiology

In the majority of patients there is no apparent cause for abscess formation. Recurrent abscesses occur in inflammatory bowel disease, HIV and rectal carcinoma.

Pathophysiology

Infection of an anal gland may cause a tracking down to form a perianal abscess, or tracking out to form a ischiorectal abscess, or upwards to produce a high inter-muscular abscess.

Clinical features

Perianal abscess is common and presents in well patients with an acute tender swelling at the anal verge.

Ischiorectal abscess present with a diffuse hard painful swelling lateral to the anus, which may extend behind the anal canal to form a horseshoe abscess. Patients have significant systemic upset.

High intermuscular abscesses cause pain exacerbated on defecation, a boggy tender swelling is felt on rectal examination.

Management

Perianal and ischiorectal abscesses are drained under general anaesthetic and de-roofed by making a cruciate incision and excising the resultant 4 triangles of skin. 25% of abscesses recur.