Synopsis
Recognise a typical anal fissure, identify atypical secondary causes, and sequence bowel regulation, topical sphincter relaxation and continence-preserving specialist intervention.
- The classic symptom is sharp tearing pain during defaecation followed by burning or spasm lasting minutes to hours, often with a small amount of bright blood.
- Most primary fissures are posterior midline; an anterior fissure can occur, particularly after childbirth, but lateral or multiple fissures require investigation for secondary disease.
- Chronic fissures show exposed sphincter fibres, a sentinel skin tag or hypertrophied anal papilla and persist despite basic bowel measures.
- Constipation and hard stool are common triggers, but recurrent diarrhoea, postpartum injury, Crohn disease, sexually transmitted infection, tuberculosis and malignancy also matter.
- A gentle visual diagnosis is often enough; forcing digital rectal examination or proctoscopy through severe acute pain adds little and can worsen spasm.
- First make stool soft and easy to pass, optimise fibre and fluid, avoid straining and use warm bathing and simple analgesia for comfort.
- Topical glyceryl trinitrate is licensed for chronic fissure; topical diltiazem is used off-label in UK practice and requires explicit counselling and local-formulary confirmation.
- Botulinum toxin or lateral internal sphincterotomy may help refractory hypertonic fissure, but baseline continence, obstetric injury and a hypotensive sphincter change the safest procedure.
Key red flags
Lateral, multiple, painless, irregular or broad ulcers raise Crohn disease, HIV-related or sexually transmitted infection, tuberculosis, haematological disease, trauma or anal cancer and warrant specialist assessment.
Constant throbbing pain, fever, swelling, fluctuance or systemic illness is not explained by a simple fissure and requires urgent search for occult perianal sepsis.
Investigation priorities
Confirm site, chronic features and competing visible pathology.
Management branches
A concordant painful midline tear without secondary-disease features.
- Explain the pain–spasm–constipation cycle, provide gentle hygiene advice and offer warm shallow bathing and non-constipating analgesia for symptom relief.
- Make stool consistently soft using gradual dietary fibre, adequate fluids and a formulary laxative; address diarrhoea as actively as constipation when it is the trigger.
- Avoid repeated traumatic examinations and review within an agreed interval to confirm pain and bleeding are settling and the patient is passing stool without fear.
- Escalate earlier for atypical site, persistent bleeding, systemic symptoms, immune compromise, inflammatory bowel symptoms or a suspicious indurated edge.
Key medicines
Macrogol or another suitable laxativeTitrate the locally preferred product until stool is soft and easily passed.Avoid indiscriminate escalation in diarrhoea, obstruction or impaction; counsel about fluid intake, bloating and dose adjustment, and use age-specific prescribing for children.
Glyceryl trinitrate rectal ointmentApply the licensed preparation according to current BNF instructions for the full course.Headache and dizziness are common; assess hypotension and nitrate interactions, avoid phosphodiesterase-5 combinations, and check pregnancy or breastfeeding advice before prescribing.