MBBS OSCE · General Surgery
OSCE — Perianal Abscess and Anal Fistula
Eight-minute OSCE station on Perianal Abscess and Anal Fistula: focused history, examination priorities, investigations, emergency and definitive management.
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Brief (to candidate)
You will assess a patient with a presentation consistent with Perianal Abscess and Anal Fistula.
You have 8 minutes to take a focused history, outline examination, investigations, and management including red flags.
Clinical context
Perianal abscess and anal fistula (fistula-in-ano) are two stages of a single cryptoglandular disease process. Obstruction of an anal gland duct at the dentate line produces an acute pus collection (abscess) which, on drainage, may leave a permanent epithelialised tract (fistula) in 30 to 50 percent of patients. Abscess presents with severe throbbing perianal pain, fever, and a tender fluctuant mass; fistula presents with recurrent discharge and recurrent abscesses. Goodsall's rule predicts the internal opening. Park's classification grades fistulas by sphincter involvement. Abscess is treated by incision and drainage; low fistula by fistulotomy; high or complex fistula by a loose seton, LIF
Candidate tasks
- Clarify onset, severity, associated features, and red-flag symptoms.
- State focused examination priorities.
- List first-line investigations and any named score/criteria.
- Give immediate resuscitation steps.
- Outline definitive management with doses/routes where standard.
- Name complications and disposition (ward / HDU / theatre / discharge safety-net).
- Mention one special-population modifier (pregnancy, child, elderly, CKD).
Examiner checklist
| Domain | Pass behaviours |
|---|---|
| Definition | Correct working diagnosis language |
| Assessment | Focused, prioritised, red flags sought |
| Investigations | Appropriate first-line + interpretation |
| Emergency care | ABC / time-critical actions first |
| Definitive care | Specific drugs/procedures, not generic phrases |
| Safety | Severe perianal pain with fever and systemic signs — perianal abscess with sprea |
| Safety | Perianal sepsis with skin necrosis, crepus, or rapidly spreading erythema with s |
| Safety | Diabetic or immunocompromised patient with perianal sepsis — higher risk of necr |
| Communication | Clear plan and safety-netting |
Model outline
Lead with the working diagnosis and life threats. Resuscitate before definitive tests when unstable. Use guideline-standard therapy with named agents and doses. Document escalation criteria and follow-up. A safe candidate is specific, structured, and never delays critical care for non-urgent imaging.