01OverviewDefinition, clinical context and the essential points that orientate the chapter.
An anal fissure is a linear break in the anal lining, usually extending from the dentate line towards the verge. A hard stool can initiate a tear, but diarrhoea and repeated irritation can also do so. Pain during defaecation promotes withholding, which can worsen constipation and perpetuate trauma. In many chronic fissures, increased internal sphincter tone impairs local perfusion and healing. Treatment therefore addresses both stool trauma and sphincter spasm rather than treating every episode as haemorrhoidal bleeding.
The usual pain has a temporal relationship to bowel opening: tearing or cutting pain at passage followed by an ache or spasm that can persist for hours. Small-volume fresh blood on paper is common. A visible sentinel skin tag can be mistaken for a haemorrhoid, but its association with a tear changes the diagnosis. Acute fissures have symptoms for less than six weeks; longer duration and exposed sphincter fibres, a sentinel tag or a hypertrophied proximal papilla support chronicity. Duration is useful alongside appearance, not as a substitute for examination.
Most fissures lie in the posterior midline; an anterior midline lesion is also recognised, particularly in women. Lateral or multiple lesions should prompt evaluation for inflammatory bowel disease, HIV-associated or other infection, syphilis, tuberculosis and malignancy where the presentation supports these possibilities. A fissure-like ulcer with induration or an unexplained anal mass is not adequately managed by another empiric nitrate course. Ask sensitively about gastrointestinal, systemic and relevant sexual-health symptoms and explain why additional investigation may be necessary.
The treatment conversation must separate pain relief, actual healing and preservation of continence. Rectogesic has a UK licence for adult chronic-fissure pain after conservative treatment failure; its product trials did not establish healing as its licensed efficacy claim. Guidelines nevertheless discuss topical nitrates among medical fissure treatments. Topical calcium-channel blockers can have similar efficacy with fewer headaches, but UK topical diltiazem is an unlicensed preparation requiring a specific specialist prescription. Persistent disease may be treated with botulinum toxin, a tailored sphincterotomy or an advancement flap according to anatomy and function.
Key points
- A fissure typically causes sharp defaecatory pain followed by pain lasting minutes to hours, with a small amount of fresh blood.
- A posterior or anterior midline tear is typical; lateral or multiple lesions need a broader inflammatory, infective and malignant differential.
- Correct traumatic stool consistency first; chronic symptoms may need topical sphincter relaxation after an eligibility and medication check.
- Rectogesic 4 mg/g is an adult intra-anal pain treatment: a 2.5 cm strip every twelve hours until pain abates, for no more than eight weeks.
- Do not use Rectogesic with PDE5 inhibitors, other nitrates, hypotension, recurrent migraine or its other contraindications; do not use it during pregnancy.
- Before sphincterotomy, assess continence and previous sphincter injury; a sphincter-preserving strategy may be preferable when function is already compromised.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Stool-related injury
Hard stool, repeated straining or frequent diarrhoea can disrupt the anal lining. Withholding after a painful episode may worsen the initiating stool problem.
Secondary fissure-like disease
Inflammation, infection and neoplasia can produce atypical lesions, particularly when fissures are multiple, lateral or accompanied by other clinical abnormalities.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Spasm and impaired perfusion
In a typical chronic fissure, internal sphincter hypertonicity can impair local blood flow, making the initially small tear persist.
- 2Self-reinforcing painful defaecation
Pain discourages bowel opening, and retained harder stool causes additional trauma. Stool treatment and sphincter relaxation address different parts of this cycle.
- 3Scarred chronic wound
A persistent tear can develop exposed sphincter fibres, a proximal hypertrophied papilla and a distal sentinel tag as the surrounding tissue responds.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Explain the examination and gently separate the buttocks to look for a tear. A typical visible fissure may establish the diagnosis without forcing a painful digital examination or anoscopy. If the cause is uncertain, arrange an appropriate specialist examination rather than repeatedly traumatising the canal.
Ask about stool form, frequency, straining, deliberate withholding and diarrhoea. Review constipating medicines and the patient’s fluid and dietary intake. A stool diary can reveal alternating hard and loose stool that would be worsened by indiscriminate escalation of a laxative.
Document the position, number and chronic features of lesions. Persistent lateral ulceration, unusual tags, fistula drainage, diarrhoea or weight loss supports a broader work-up. The absence of a classic sentinel tag does not exclude a fissure early in its course.
Ask directly about loss of wind, liquid or solid stool, urgency and pad use. Record obstetric tears, earlier anal surgery, inflammatory bowel disease and previous treatment response. Normal reported function after a birth injury does not guarantee an intact sphincter, so selected imaging may be relevant.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Clinical inspection with deferred painful instrumentationFirst step - Why
- Identify a typical tear while limiting avoidable pain and further trauma.
- Interpretation and limitations
- An uncomplicated midline fissure often needs no immediate laboratory or imaging test. Failure to identify an explanation for severe pain should prompt reassessment, including examination under anaesthesia where appropriate, rather than assumption that a tiny tear explains every symptom.
- 02
Targeted inflammatory and infectious assessment - Why
- Investigate lateral or multiple lesions and associated systemic or luminal symptoms.
- Interpretation and limitations
- Select faecal inflammatory testing, luminal endoscopy, biopsy or microbiological testing according to the clinical hypothesis. These tests are not a compulsory panel for every typical acute fissure. An unexplained anal ulcer or mass can require direct suspected cancer referral.
- 03
Continence assessment and selected sphincter imaging - Why
- Estimate the functional risk of an irreversible sphincter intervention.
- Interpretation and limitations
- A structured history is essential. Endoanal ultrasound can identify a suspected structural defect in selected patients; anorectal physiology may contribute to specialist assessment when function is uncertain. A normal pressure measurement alone does not make every sphincterotomy safe.
- 04
Prescribing review before topical nitrate - Why
- Identify systemic and interaction risks before using a locally applied vasodilator.
- Interpretation and limitations
- Measure clinically relevant blood pressure and review postural symptoms, volume depletion, migraine, cardiac obstruction, severe anaemia, glaucoma and current medicines. Topical administration does not remove nitrate interactions with sildenafil, tadalafil, other PDE5 inhibitors or other nitrate/NO-donor products.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Occult anorectal collection
An intersphincteric or deeper abscess may produce severe anal pain without a conspicuous external swelling and needs source assessment rather than topical treatment alone.
Inflammatory or malignant ulcer
A persistent atypical lesion, induration or mass should prompt targeted investigation; a fissure label does not rule out Crohn disease or anal cancer.
External thrombosis
An acute blue tender lump below the dentate line is different from a linear tear, although both can cause pain with bowel opening.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Worked caseComplete a monitored topical courseFirst stepA 37-year-old woman has ten weeks of painful bowel opening despite correction of hard stools.+
- 1Gentle inspection shows a chronic posterior midline fissure without an atypical ulcer or swelling. She has no baseline leakage, obstetric injury, pregnancy or breastfeeding, nitrate/PDE5 use, recurrent headache, hypotension or listed cardiac, cerebral or ocular contraindication. Renal and hepatic history is unremarkable. Her stool is now soft, but pain persists after defaecation.
- 2Following the eligibility check she applies a measured 2.5 cm strip of Rectogesic 4 mg/g, approximately 375 mg ointment containing 1.5 mg GTN, circumferentially inside the anal canal using a covered finger every twelve hours. She is shown the carton measure and told to stop and seek review for significant dizziness, troublesome headache or increased bleeding. Treatment stops when pain resolves and must not exceed eight weeks.
- 3At two weeks she reports a mild short-lived headache after the first applications but no dizziness, hypotension or bleeding increase; technique and dose are checked and the benefit remains acceptable. At six weeks defaecatory pain has resolved. Follow-up inspection shows epithelialisation of the tear and she stops the ointment, retaining the stool routine.
- 4The recorded outcome is both pain resolution and an observed healed surface with unchanged continence. She receives advice to return for recurrence, lateral lesions or new bowel symptoms. The individual healing observation is distinguished from the selected product’s licensed pain indication.
02Initial careInterrupt the pain and stool-trauma cycleA patient has a typical recent midline tear without systemic or atypical features.+
- 1Explain the mechanism and encourage regular comfortable bowel opening, sufficient fluid and gradually adjusted fibre. Warm baths can provide comfort. Avoid repeated straining and prolonged withholding; assess diarrhoea rather than automatically adding a laxative to already loose stool.
- 2If dietary change is insufficient and there is no obstruction, swallowing difficulty, unexplained bleeding or other contraindication, use the selected bulk-forming product with adequate water. Reassess stool form and the response rather than allowing pain-related constipation to continue untreated.
- 3AlternativeFor persistent chronic symptoms, review topical eligibility. NHS Highland’s June 2026 adult pathway uses unlicensed diltiazem 2% cream, a pea-sized amount on the anal verge twice daily for eight weeks after initial measures fail, with GTN as an alternative. This is the selected local regimen; other centres use different quantities and courses. Before prescribing, check diltiazem or excipient allergy, heart disease, blood-pressure medicines, other diltiazem, pregnancy and breastfeeding. Headache, postural dizziness, local soreness or bleeding requires review. There is no validated renal/hepatic adjustment schedule for this unlicensed topical preparation in these sources, so significant organ disease requires an individual pharmacy/prescriber assessment rather than an invented dose reduction.
03Persistent fissureChoose escalation around continence riskEscalationPain or an unhealed fissure persists despite a properly used medical treatment.+
- 1Check adherence, actual stool consistency, application technique and whether the diagnosis remains typical. Reassess a persisting ulcer for another cause before interpreting the episode as pharmacological failure.
- 2Discuss botulinum toxin as a reversible sphincter-relaxing intervention or a tailored lateral internal sphincterotomy in a suitable patient with intact function. Botulinum dosing and injection technique vary; product units are not interchangeable, so a selected formulation and specialist injection prescription are necessary.
- 3AlternativeA patient with baseline incontinence, documented sphincter injury, previous anorectal surgery or relevant obstetric trauma needs a continence-sensitive specialist choice. An advancement flap can provide a sphincter-preserving alternative. If sphincterotomy is selected, tailoring division to fissure length can reduce functional harm compared with division to the dentate line.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Rectogesic glyceryl trinitrate 4 mg/g rectal ointment
For adults aged eighteen or over with chronic fissure pain after conservative failure, apply a 2.5 cm strip, about 375 mg ointment containing 1.5 mg GTN, intra-anally every twelve hours with a covered finger. Apply circumferentially to the canal to the distal finger joint. Continue until pain abates, at most eight weeks.Contraindications include nitrate/excipient allergy; PDE5 inhibitors such as sildenafil, tadalafil or vardenafil; other organic nitrates/NO donors; hypotension, postural hypotension or uncorrected hypovolaemia; raised intracranial pressure or inadequate cerebral circulation; migraine or recurrent headache; aortic/mitral stenosis, hypertrophic obstructive cardiomyopathy, constrictive pericarditis or tamponade; marked anaemia and closed-angle glaucoma. Do not use during pregnancy; breastfeeding use is not recommended. Severe renal/hepatic disease requires caution, with no defined adjustment and limited elderly data. Review alcohol, antihypertensives, diuretics, other vasodilators, tricyclics, acetylcysteine and dihydroergotamine. Stop and reassess excessive hypotension, troublesome headache or increased haemorrhoidal bleeding; persistent pain needs diagnostic review.
Fybogel Orange 3.5 g ispaghula sachets
An eligible adult may take one sachet in the morning and one in the evening, stirred into at least 150 mL liquid and consumed promptly after meals. Keep half to one hour clear of other oral medicines and avoid dosing immediately before bedtime. Review after three days if symptoms persist or stool has not passed.Exclude known allergy to ispaghula husk or any Fybogel excipient, unexplained rectal bleeding, a sudden bowel-habit change lasting over two weeks, failure to pass stool after a laxative, faecal impaction, intestinal narrowing or obstruction, reduced gut motility, oesophageal disease and swallowing or throat problems. Never swallow dry granules. Opioid coadministration requires medical supervision; review thyroid replacement, diabetes treatment and delayed absorption of other medicines. Consider potassium restriction in renal disease and aspartame in phenylketonuria. Pregnancy/breastfeeding use can be considered after inadequate dietary change. Stop for new abdominal pain, allergic symptoms or choking.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Chronic pain and avoidance
Persistent defaecatory pain can impair nutrition, work, sleep and bowel behaviour, even when the amount of bleeding is small.
Treatment-related functional harm
Nitrate headache and hypotension may prevent medical treatment; sphincter division can cause lasting continence problems if functional reserve is inadequate.
Recurrence after initial recovery
A healed tear can recur if hard stool, diarrhoea or straining returns; repeated episodes may require renewed assessment of the underlying mechanism.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Review both pain and stool form early enough to identify continued withholding, excessive laxation or poor treatment technique.
- Check headache, dizziness, postural symptoms and bleeding after starting a nitrate, including whether new medicines introduce a contraindication.
- At the end of treatment document the appearance of the fissure, symptom resolution and continence rather than recording prescription completion alone.
- Reassess recurrent or atypical lesions and any new diarrhoea, weight loss, discharge or mass through the relevant inflammatory, infectious or cancer pathway.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Pain relief and healing
A lower pain score is useful but does not establish an epithelialised fissure; the clinical follow-up should distinguish these endpoints.
Avoid unsupported injection equivalence
Botulinum toxin preparations have product-specific units, and published dose variation does not justify a universal conversion or standard injection dose.
Respect existing sphincter damage
Prior obstetric injury or continence symptoms can make a flap or another sphincter-preserving option more appropriate than a technically straightforward division.
Reconsider low-pressure fissures
The common hypertonic mechanism does not describe every patient; inflammatory disease and pre-existing sphincter injury require a more individual strategy.
11Common pitfallsFrequent interpretation and management errors.
- 01
A sentinel tag is a marker that can sit beside a fissure; removing it without treating the tear and bowel pattern may not relieve pain.
- 02
Locally applied GTN still has important systemic nitrate contraindications, including recurrent migraine and PDE5 interactions.
- 03
Performing sphincterotomy before documenting continence and prior injury can trade fissure healing for avoidable long-term leakage.
- 04
Continuing repeated topical courses for a lateral nonhealing ulcer can delay recognition of Crohn disease, infection or anal cancer.