Synopsis
Recognise superficial and occult perianal sepsis, drain abscesses without dangerous delay, and plan sphincter-preserving investigation and treatment of anal fistulae.
- Most anal abscesses arise from infected anal glands, but Crohn disease, hidradenitis, trauma, malignancy, tuberculosis and sexually transmitted infection can produce similar or recurrent disease.
- A superficial abscess causes constant throbbing pain, focal tenderness and swelling; an ischiorectal or supralevator collection may have few external signs despite severe deep pain.
- Antibiotics alone do not replace drainage of a drainable anorectal abscess, even when they transiently reduce fever.
Key red flags
Constant escalating anal pain, focal erythema, warmth, swelling and exquisite tenderness, sometimes with fever or spontaneous pus, usually permit a clinical diagnosis and urgent drainage referral.
Investigation priorities
Identify sepsis, necrosis and a drainable superficial focus rapidly.
Management branches
Focal fluctuant swelling or deep clinical suspicion of a collection.
- Assess physiology, give analgesia, establish intravenous access when unwell and involve the emergency general or colorectal surgical team promptly; keep the patient nil by mouth if theatre is likely.
- Drain the abscess adequately under appropriate anaesthesia, opening loculations while protecting sphincter; send pus for culture in recurrent, unusual, immunocompromised or treatment-resistant infection.
Key medicines
Broad-spectrum antimicrobial therapyUse the current local perineal or intra-abdominal sepsis regimen with organ adjustment.
Non-constipating analgesiaTitrate regular simple analgesia with monitored opioid rescue only when necessary.