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A 35-year-old man presents with a 6-month history of severe pain on defecation, bright red blood on toilet paper, and constipation. On gentle examination, a linear tear is visible in the posterior midline with a sentinel tag. He has been using lactulose and fibre supplements for 2 months with no improvement.
Questions
a) What is the diagnosis? (1 mark)
Chronic anal fissure (posterior midline tear with sentinel tag = chronic; over 6 weeks duration; failed conservative management).
b) What is the underlying pathophysiology that prevents spontaneous healing? (2 marks)
The fissure exposes the internal anal sphincter, causing spasm (increased resting pressure). This reduces blood flow to the posterior midline (a relative watershed area with poorest blood supply). The resulting ischaemia prevents healing. This is a vicious cycle: fissure → spasm → ischaemia → non-healing → worse spasm.
c) Describe four treatment options, starting with the least invasive. (4 marks)
- Conservative: stool softeners (lactulose, ispaghula), high-fibre diet, sitz baths (relax sphincter).
- Topical pharmacological: GTN 0.2% or diltiazem 2% ointment (relax internal sphincter → improve blood flow → 50-70% heal).
- Botulinum toxin injection: into internal sphincter (chemical sphincterotomy, temporary).
- Surgical: lateral internal sphincterotomy (division of lower 1/3 internal sphincter — gold standard for chronic fissure, 90-95% heal).
d) What are two features that should prompt investigation for an underlying cause other than simple fissure? (2 marks)
- Multiple or atypical fissures (not posterior midline) → Crohn disease, HIV, STI.
- Non-healing despite adequate treatment → biopsy to exclude anal cancer, Crohn, TB.
Also: chronic diarrhoea/weight loss with complex fistulas (Crohn).
e) What is Goodsall's rule and when is it used? (1 mark)
Goodsall's rule predicts the course of fistula-in-ano tracks: ANTERIOR external openings have a straight (radial) track. POSTERIOR external openings curve to open in the POSTERIOR MIDLINE of the anal canal. Used to plan fistula surgery.