Anal fissure: the diagnosis is anatomical, and so is the algorithm

Hard stool → tear → internal sphincter hypertonia → posterior midline ischaemia → non-healing. Each treatment targets one limb of this cycle.

Stepwise approach (adapted from Common Anal Conditions, v2.0)

1. Diagnose by gentle buttock separation. DRE/anoscopy is not required and is often intolerable when acute.
2. Atypical (lateral, multiple, painless, indurated, non-healing)? Exclude Crohn's disease, TB, HIV/HSV/CMV, syphilis/LGV and anal SCC. EUA, biopsy, cultures/PCR. No sphincterotomy.
3. Typical, acute (<6 wk): fibre, fluids, stool softener, sitz baths, topical lidocaine.
4. Typical, chronic (sentinel tag, hypertrophied papilla, exposed fibres): 6–8 wk of topical diltiazem 2% or nifedipine 0.2–0.3%. GTN only if no PDE5-inhibitor/riociguat exposure.
5. Failure at 6–8 wk: tailored lateral internal sphincterotomy (LIS) if continence risk is low; botulinum toxin or advancement flap if not (obstetric sphincter injury, multiparity, prior anal surgery, IBD).

Recent evidence

• ASCRS 2023: topical CCBs heal comparably to nitrates with fewer side effects; LIS is the most effective definitive therapy [1].
• Double-blind RCT, n=110 (2026): nifedipine vs diltiazem healed 70.9% vs 67.3% at 6 weeks, no significant difference [2].
• Meta-analysis, 10 trials, n=698 (2026): botulinum toxin outperformed topical GTN for healing (RR 1.18, 95% CI 1.02–1.36) with fewer headaches; recurrence was similar [3].

Topical GTN with PDE5 inhibitors or riociguat risks profound hypotension. Chart "posterior midline", never "6 o'clock".

Free open-access chapter: /books/common-anal-conditions/chapter-04

Educational content for healthcare professionals. Follow local guidelines and the treating team's judgement.