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A 38-year-old man presents with severe throbbing perianal pain for 3 days, fever (38.5C), and a tender fluctuant swelling at the anal verge. He is otherwise fit and well.
Questions
a) What is the diagnosis and immediate management? (2 marks)
Diagnosis: Perianal abscess (acute cryptoglandular infection). Management: Incision and drainage under general anaesthesia — cruciate incision, evacuation of pus, curettage, and packing. Send pus for culture.
b) State Goodsall's rule and explain its clinical significance. (3 marks)
Goodsall's rule predicts the internal opening of an anal fistula based on the external opening position:
- Anterior to an imaginary transverse line through the anus: the tract runs straight (radially) to the nearest anal crypt.
- Posterior to the line: the tract curves to the posterior midline (6 o'clock) at the dentate line.
- Exception: anterior external openings more than 3 cm from the anal verge may have a curved (posterior) tract.
Significance: helps the surgeon plan the surgical approach and locate the internal opening during EUA.
c) Describe Park's classification of anal fistulas. (2 marks)
By relationship to the anal sphincters:
- Intersphincteric (70%) — between internal and external sphincter.
- Transsphincteric (25%) — crosses both sphincters.
- Suprasphincteric (5%) — above puborectalis.
- Extrasphincteric (1%) — from rectum to skin, outside sphincters.
d) How would you manage a high transsphincteric fistula involving significant external sphincter? (3 marks)
Loose seton drainage — a non-absorbable suture/vessel loop through the tract, tied loosely. Maintains drainage, prevents abscess recurrence, allows fibrosis, and does NOT divide the sphincter (avoiding incontinence). Alternatives: LIFT procedure (ligation of intersphincteric tract, 70-80% success). Never perform fistulotomy (lay-open) on a high fistula — risk of significant incontinence.