“It’s like passing glass — sharp pain when I go, then it throbs for ages, and there’s bright blood on the paper”

ANAL FISSURE presents with SEVERE SHARP PAIN on defecation (classically "passing glass/razor blades") with a lingering throb/sphincter spasm afterwards and BRIGHT RED blood on the paper or stool surface, usually from a tear in the POSTERIOR MIDLINE precipitated by hard stool/CONSTIPATION or occurring POSTPARTUM — with the painful defecation and fear of going being characteristic; examine gently, face to face with a chaperone offered (full PR is often too painful and should not be forced, but inspection may reveal the fissure/sentinel tag; arrange review if the examination is incomplete). Acute fissures are under 6 weeks; chronic 6 weeks or more. Distinguish it from HAEMORRHOIDS, which usually cause painless bright bleeding. Importantly, ATYPICAL fissures (lateral position, multiple, non-healing, or with other features) should prompt consideration of underlying disease — inflammatory bowel disease/Crohn’s (perianal disease), infection (HIV, syphilis, TB), trauma and rarely malignancy — so screen GI/systemic symptoms and consider referral/further assessment for atypical or non-healing fissures. The cornerstone of management is treating CONSTIPATION/optimising stool: adequate fluids, fibre increased gradually where appropriate (fibre without enough fluid can make things worse) and an osmotic laxative titrated to soft stools if they stay hard (dose per BNF), continued after healing, to keep stool soft and avoid straining (breaking the pain–constipation–spasm cycle), with analgesia, a short course of topical lidocaine and sitz baths for relief — most acute fissures heal with stool softening. For persistent or chronic fissures, consider a topical sphincter relaxant: Rectogesic (GTN 0.4%) is licensed for pain in chronic anal fissure (every 12 hours for up to 8 weeks; the SPC reports no statistically significant healing benefit over placebo; headache very common; not with PDE-5 inhibitors or other nitrates; do not use in pregnancy; not recommended when breastfeeding, MHRA SPC), and diltiazem 2% is an unlicensed alternative twice daily for about 6–8 weeks (local formulary). Review at 6–8 weeks and refer to colorectal surgery for chronic/non-healing or recurrent fissures (the specialist chooses between botulinum toxin and sphincter surgery) or red flags/atypical features. Reassure that most heal, address the fear of defecation, ask about postnatal mood (NICE CG192), and safety-net. A fissure does not exclude other pathology: blood mixed with stool, a persistent change in bowel habit, weight loss, iron-deficiency anaemia or a mass need assessment under NICE NG12, with FIT where indicated (NICE HTG690); a rectal or anal mass or unexplained anal ulceration → consider a suspected cancer pathway referral.