Anal Fissure

An anal fissure is a longitudinal tear in the anoderm distal to the dentate line.^[1] Fissures are classified by duration: acute fissures have been present for less than about 6 weeks, while chronic fissures persist beyond about 6-8 weeks and, by that point, typically show secondary signs of chronicity — indurated (raised, fibrotic) fissure margins, a sentinel skin tag at the distal end, a hypertrophied anal papilla at the proximal end, and sometimes the pale horizontal fibers of the internal anal sphincter visible at the base of the tear.^[1][2]

The pathophysiology explains both the disease and why the first-line drug classes work: hypertonicity and spasm of the internal anal sphincter (IAS) reduce local anodermal blood flow, and perfusion within the anal canal inversely correlates with sphincter pressure — the tighter the spasm, the less blood flow reaches the healing tissue.^[1] This creates a self-sustaining pain-spasm-ischemia cycle: pain triggers reflex sphincter spasm, spasm further reduces perfusion, and the resulting ischemia both perpetuates the pain and prevents the tear from healing. The posterior midline is the area of lowest baseline perfusion in the anal canal, which is why roughly 90% of primary (typical) fissures occur there.^[1] Every first-line topical pharmacotherapy for fissure — a topical calcium channel blocker or topical nitroglycerin — works by relaxing the internal anal sphincter and restoring blood flow, not by acting on the tear itself; understanding that mechanism is what makes the dosing and counseling points below make sense rather than feel arbitrary.

Anal fissure is a common, genuinely painful condition, and most typical, posterior-midline presentations — acute or chronic — respond to conservative measures and topical pharmacotherapy without ever needing a procedure.^[2][3] The pharmacist's highest-value contribution is not selecting between diltiazem and nitroglycerin — it is recognizing the minority of fissures that are off-midline, multiple, or otherwise atypical, which point toward a different underlying cause and a different workup entirely.^[2]

Typical (primary) vs. atypical (secondary) fissure

A typical (primary) fissure is solitary and located at the posterior midline (or, less commonly, the anterior midline) — about 90% of primary fissures occur posteriorly, reflecting the anal canal's area of lowest baseline blood flow.^[1] An atypical (secondary) fissure is off the midline, multiple, unusually large or deep, or otherwise abnormal-appearing, and should prompt investigation for an underlying cause — Crohn disease, tuberculosis, HIV or another sexually transmitted infection, or malignancy — rather than being treated as routine idiopathic fissure disease.^[2][1]

Presentation

The hallmark symptom is sharp, tearing anal pain that begins with defecation and can persist for minutes to several hours afterward — often described as passing "glass" or a "razor blade." Bright red blood, typically a small amount on the toilet tissue or streaked on the surface of the stool rather than mixed into it, is common. Pruritus, a visible tear or skin tag, and — in longstanding chronic disease — mild fecal soiling can also occur.^[1]

• Constipation and passage of large or hard stools, with associated straining — the most common precipitant of the initial tear.^[1]
• Chronic diarrhea — repeated mechanical and chemical trauma to the anoderm is a recognized cause alongside constipation.^[1]
• Low dietary fiber intake and inadequate fluid intake, which drive the constipation above.
• Vaginal childbirth — obstetric perineal/anal trauma is a well-recognized cause, particularly of anterior fissures in postpartum patients.^[1]
• Prior anal surgery or instrumentation, which can alter local anatomy and healing.
• Receptive anal intercourse or other anal trauma — also raises the differential for an atypical-location or infection-related fissure and should prompt STI risk-factor screening when relevant.
• Inflammatory bowel disease, particularly Crohn disease — a major cause of atypical (multiple, off-midline, or non-healing) secondary fissures.^[2][1]
• Elevated resting internal anal sphincter tone — an intrinsic physiologic risk factor independent of bowel habit, and the direct pharmacologic target of first-line topical therapy.^[1]

History

• Characterize the pain specifically: sharp/tearing quality, onset with defecation, and duration afterward (minutes vs. hours) — pain that persists well after defecation is classic for fissure and helps distinguish it from other anorectal pain.
• Ask about bleeding: amount (usually small), color (bright red), and pattern (on the tissue or stool surface, not mixed in) — a pattern that differs meaningfully should prompt broader investigation.
• Establish duration to classify acute vs. chronic (about 6-8 weeks), and ask whether this is a first episode or a recurrence.
• Screen bowel habits: stool consistency and frequency, straining, and any recent change (new constipation or diarrhea) that may have precipitated the tear.
• Ask about prior anal fissures, prior anorectal surgery, obstetric history (recent vaginal delivery), inflammatory bowel disease, immunosuppression, and — when clinically relevant — sexual history and STI risk factors.
• Screen every red flag explicitly, since anorectal symptoms are frequently under-reported due to embarrassment.

Examination

Gentle visual inspection of the perianal area with careful buttock/labial retraction under good lighting is usually sufficient to see a typical fissure, sentinel tag, or hypertrophied papilla.^[1] Digital rectal examination and anoscopy are often too painful to tolerate in an acute fissure and are not required to make the diagnosis when a typical, midline fissure is clearly visualized on inspection alone; if internal examination is genuinely needed, consider a topical anesthetic first or defer to a specialist.^[1] When a fissure is atypical in location or appearance, does not heal with adequate therapy, or the exam cannot be tolerated in the office, refer for examination under anesthesia, which allows a full assessment and biopsy if needed.^[1]

Differential diagnosis

• Break the pain-spasm-ischemia cycle by pharmacologically lowering internal anal sphincter tone, restoring local blood flow, and allowing the tear to heal.^[1]
• Normalize stool consistency and defecation habits so the anoderm is not re-traumatized during healing and after resolution.
• Relieve pain promptly enough to support adherence to a therapy that typically needs 6-8 weeks to show its full effect.^[5]
• Minimize class-specific harms — headache and hypotension with nitrates, transient incontinence with botulinum toxin or sphincterotomy — by choosing the option with the best benefit-to-harm ratio first.^[5][3]
• Correctly identify the minority of fissures that are atypical or secondary to another condition, which need a different workup rather than a longer trial of standard fissure therapy.^[2]

• Increase dietary fiber gradually toward a total intake of roughly 25-30 g/day, pairing the increase with about 2 L of fluid daily to limit bloating and keep stool soft.
• Use a commercial fiber supplement (e.g., psyllium) when dietary sources alone are not enough to reach target intake.
• Add a stool softener when straining persists despite adequate fiber, since re-trauma from a hard stool is what perpetuates the tear.
• Take a warm sitz bath — water covering the hips and buttocks — for about 10-20 minutes after bowel movements and 2-3 times daily; warmth helps relax the spastic internal anal sphincter and improve comfort, though the comparative trial evidence for sitz baths specifically improving healing rates is more limited than for topical pharmacotherapy.
• Avoid straining and limit prolonged time spent on the toilet.
• Respond promptly to the urge to defecate rather than deferring it, which allows stool to harden further.
• Practice gentle anal hygiene — pat rather than wipe vigorously — to avoid further mechanical trauma to the fissure.
• Treat the underlying driver directly: constipation or chronic diarrhea, whichever applies, rather than only treating the fissure it produced.^[1]

Pregnancy and postpartum

Anal fissures are common postpartum, related to obstetric perineal/anal trauma and to constipation; anterior fissures in particular are more common in this group than in the general fissure population.^[1]

Pediatrics

Anal fissures are a common cause of painful defecation and stool-withholding behaviour in infants and toddlers, usually from a hard, large stool. Most respond to conservative measures alone — adequate fiber and fluid intake, and a stool softener (e.g., polyethylene glycol) when needed. Topical pharmacotherapy is used more cautiously in children, at lower concentrations and under prescriber direction; an atypical-appearing fissure, one that does not respond to simple conservative measures, or any presentation raising concern for another cause warrants prompt medical assessment rather than an extended self-care trial.

Older adults

Age itself does not change first-line topical therapy, but it does change the surgical risk-benefit calculation — older patients carry a higher baseline risk of impaired continence, which favours a sphincter-preserving option (advancement flap, or a tailored/limited sphincterotomy) over an extended sphincterotomy if surgery becomes necessary.^[3]

Inflammatory bowel disease (Crohn disease)

A fissure in a patient with known or suspected Crohn disease should be treated as a secondary fissure: manage it alongside optimizing the underlying Crohn therapy, and avoid sphincterotomy given baseline sphincter dysfunction and a higher risk of impaired healing and complications in this group.^[3][2]

Immunosuppression

Immunosuppressed patients (HIV, chemotherapy, transplant) have a higher likelihood of an atypical, infection-related, or malignant cause for an anorectal lesion that looks like a fissure, and warrant a lower threshold for specialist assessment and biopsy rather than routine fissure therapy.^[1]

Set a specific follow-up point at about 6-8 weeks — the duration used in the trials behind both topical calcium channel blockers and topical nitroglycerin — rather than judging success or failure earlier.^[5][3]

1. Confirm the diagnosis and location again — reconsider whether this was ever a typical, midline fissure, and arrange examination under anesthesia or specialist referral if the diagnosis or location was never clearly confirmed.^[2][1]
2. Confirm adherence to conservative measures specifically — actual daily fiber and fluid intake, and correct topical application technique and frequency — since under-dosing either is the most common reason a genuinely appropriate therapy appears to fail.
3. Confirm the topical course ran its full 6-8 weeks before being judged a failure; an early switch can miss a therapy that was actually working.^[5][3]
4. If a first topical agent (calcium channel blocker or nitroglycerin) was not tolerated or did not work, try the other class before moving to a procedure, unless red flags or a clearly atypical fissure make that inappropriate.
5. Re-screen every red flag — a fissure that looked typical initially can reveal atypical features (or new bleeding, weight loss, or bowel-habit change) that shift management from continued topical therapy to investigation.^[2]
6. If diagnosis, adherence, and duration are all confirmed adequate but the fissure has not healed, proceed to botulinum toxin injection if not already tried, or refer for surgical evaluation (lateral internal sphincterotomy, or an advancement flap in patients at higher incontinence risk).^[3]

• Treating every anal fissure as a typical primary fissure without checking whether it is off-midline, multiple, or otherwise atypical — a distinction that changes the whole workup.^[2][1]
• Performing a digital rectal exam or anoscopy on an acutely painful fissure when the diagnosis is already clear on visual inspection — usually unnecessary and often not tolerated.^[1]
• Starting topical nitroglycerin without counseling on headache and orthostatic symptoms, or without checking for concurrent PDE5-inhibitor use — a combination that risks severe hypotension.
• Judging a topical therapy a failure before it has run its full 6-8 week course.^[5][3]
• Assuming a visible fissure fully explains rectal bleeding in a patient who otherwise has risk factors for colorectal pathology, and skipping further investigation as a result.^[2]
• Referring a Crohn disease patient for sphincterotomy without first considering that surgery is generally avoided in this group given baseline sphincter dysfunction and impaired healing.^[3]
• Leaving the underlying constipation or diarrhea untreated while only managing the fissure it produced.^[1]
• Not setting a specific follow-up point — an open-ended self-care or topical-therapy trial delays recognizing that escalation (botulinum toxin or surgical referral) is needed.

How to use this table: Doses are adult doses unless a separate line is given, and require patient-specific confirmation. Select any drug name to open its complete Pharmasist Drug Database page.

Bulk-forming fiber supplements

First-line for every patient, acute or chronic — about half of acute fissures heal with fiber and adequate fluid intake alone.

Stool softeners and short-term laxative adjuncts

Added when straining persists despite adequate fiber, since re-trauma from a hard stool is what perpetuates the tear.

Topical calcium channel blockers

Now the preferred first-line topical class for chronic or persistent fissure — comparable healing to topical nitroglycerin with a far lower headache incidence (about 7% vs 56% in trial data). Relax the internal anal sphincter to restore local blood flow.

Topical nitrates

A reasonable alternative when a calcium channel blocker is not tolerated or available; heals roughly 60% of chronic fissures vs ~40% with placebo, but headache is the dominant limiting side effect.

Topical anesthetics

Symptom relief only — do not promote healing and should not replace a healing-directed therapy.

Botulinum toxin (chemical sphincterotomy)

Specialist-administered injection for an inadequate response to topical therapy, or as an alternative first-line option per the 2023 ASCRS guideline — not a self-care or routine pharmacist-initiated option.