Perianal Abscess / Fistula

See Pilonidal Sinus & Abscess for the distinct sacrococcygeal condition, which sits nearby anatomically but is a separate disease process.

Perianal (anorectal) abscess

Infection in one of the anal glands that drain the anal canal — generally polymicrobial. Common in Crohn’s disease, though patients with Crohn’s are a minority of those presenting with abscesses (and fistulas).

History: severe, constant, throbbing pain; fever.

Examination: hot, red, tender swelling adjacent to the anal margin; non-fluctuant.

Management: urgent surgical drainage; a drain tube may need to be inserted to enable ongoing drainage. Antibiotics are usually only an adjunct to surgery — Augmentin if mild; IV gentamicin + metronidazole + ampicillin if severe.

Perianal fistula

An abnormal communication between the skin and rectum — a complication of acute or chronic perianal abscess.

Examination: determine the presence of an abscess and the location of the fistula.

Management: refer to gastroenterology or a colorectal surgeon.