Anal Fissure
Clinical Snapshot
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]
Recognize the Condition
Acute vs. chronic fissure
Acute fissure
Present for less than about 6 weeks. Appears as a simple, fresh linear tear with soft, non-indurated edges — usually superficial, without a sentinel tag or hypertrophied papilla. About half resolve with conservative measures alone.[1][4]
Chronic fissure
Persists beyond about 6-8 weeks. Develops the secondary triad of chronicity: indurated, raised fissure margins; a sentinel skin tag at the distal (anal verge) end; and a hypertrophied anal papilla at the proximal (dentate line) end. Horizontal white fibers of the internal anal sphincter may be visible at the fissure base.[1] Chronic fissures are less likely to heal with conservative measures alone and are the population studied in most topical- and procedural-therapy trials.[5]
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]
Risk Factors
- 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]
Red Flags & Refer
Location and healing pattern — not just the presence of pain — determine whether a fissure needs a different workup. Escalate to medical assessment rather than proceeding with a routine self-care or topical-therapy plan for any of the following:
- Fissure that is off the midline, multiple, or unusually large/deep/irregular — investigate for Crohn disease, tuberculosis, HIV or another sexually transmitted infection (e.g., syphilis, herpes), or anal malignancy rather than treating as typical idiopathic fissure disease.[2][1]
- No healing despite an adequate trial (about 6-8 weeks) of correctly used first-line topical therapy — reconsider the diagnosis and refer for examination under anesthesia, biopsy, or specialist assessment rather than simply repeating or extending the same topical course.[3][1]
- The presence of a fissure should never be assumed to fully explain rectal bleeding in a patient who otherwise has risk factors for colorectal pathology — continue to investigate bleeding on its own merits (age, family history, anemia, altered bowel habit) rather than attributing it entirely to the visible fissure.[2]
- Known or suspected inflammatory bowel disease, especially Crohn disease — changes both the workup and the treatment approach (see Special Populations), and sphincterotomy is generally avoided in this group.[3]
- Fever, or a tender, fluctuant, or spreading perianal swelling — suggests a perianal or perirectal abscess, a surgical emergency rather than a fissure.
- Immunosuppression (HIV, chemotherapy, transplant) — raises the likelihood of an atypical, infection-related, or malignant cause and needs a lower threshold for specialist assessment.[1]
- Unintentional weight loss, a persistent change in bowel habit or stool caliber, or a personal/family history of colorectal cancer — evaluate independently rather than assuming the fissure is the sole cause.
- A child with a perianal tear or bleeding that does not resolve with simple conservative measures, or any atypical features — the pediatric differential (including possible abuse) differs from the adult differential and warrants assessment rather than a self-care trial.
Assessment & Diagnosis
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
| Condition | Features that point away from a typical anal fissure |
|---|---|
| Hemorrhoids | Usually painless bleeding (internal) or a palpable, non-linear, often reducible lump; pain, when present, is typically from thrombosis rather than sharp tearing pain with defecation. |
| Perianal or perirectal abscess | Constant throbbing pain not specifically tied to defecation, fever, and a tender, fluctuant, sometimes spreading swelling — a surgical emergency. |
| Anal fistula | Intermittent or persistent purulent/serosanguinous drainage from an opening near the anus, often with a history of a prior abscess. |
| Crohn perianal disease | Often multiple, off-midline, deep, or indolent fissures/ulcers, sometimes with associated fistulas or skin tags that look different from a typical sentinel tag; diarrhea or other GI symptoms may coexist.[2] |
| Anal or genital ulcer from an STI | Herpes (multiple painful vesicles/ulcers), primary syphilis (typically a single painless indurated chancre), or another STI-related ulcer — location and morphology differ from a linear posterior-midline tear; consider when the fissure is atypical and the history supports it. |
| Anal cancer | A non-healing, irregular, or indurated lesion, especially in an older patient or one with risk factors (HPV, immunosuppression); biopsy any lesion that does not follow the expected course. |
| Pruritus ani | Itching without the sharp defecation-associated pain or visible linear tear of a fissure; often driven by hygiene practices or irritant/contact dermatitis. |
| Levator ani syndrome / proctalgia fugax | Anorectal pain without a visible anodermal lesion on inspection — a functional pelvic floor pain syndrome rather than a structural tear. |
Treatment Targets
- 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]
Choose Initial Treatment
Step 1 — confirm this is a typical fissure and screen for red flags
Confirm the fissure is solitary and midline (posterior or, less commonly, anterior) before proceeding with routine fissure therapy. An off-midline, multiple, or non-healing fissure needs investigation for Crohn disease, malignancy, tuberculosis, HIV, or another STI, not a longer trial of the same topical.[2][1]
Step 2 — conservative measures are first-line for every patient, acute or chronic
1st line, all patients adequate fiber and fluid intake, a stool softener if needed, and warm sitz baths form the foundation of therapy at every stage. About half of acute fissures heal with conservative measures alone; continuing them is also what allows any added pharmacotherapy to work and what prevents recurrence after healing.[1][3]
Step 3 — topical calcium channel blocker is the preferred first-line pharmacotherapy for chronic or persistent fissure
1st-line topical, chronic or persistent fissure topical diltiazem 2% or topical nifedipine 0.2-0.5%, applied twice daily for 6-8 weeks, is now preferred over topical nitroglycerin as the initial topical choice — comparable healing rates with a substantially lower headache incidence (about 7% with a calcium channel blocker vs. about 56% with nitroglycerin in trial data).[5][2]
Step 4 — topical nitroglycerin is a reasonable alternative, with real counseling needs
Alternative topical, 1st or 2nd choice topical nitroglycerin 0.2-0.4%, applied 2-3 times daily for 6-8 weeks, heals roughly 60% of chronic fissures versus about 40% with placebo — a real effect, but headache is common enough (reported in roughly a third to over half of patients depending on concentration) that up to 1 in 5 patients stop treatment because of it.[5][3] Starting at the lower end of the concentration range, titrating gradually, and pretreating with an analgesic reduces this burden without giving up the option entirely.[3]
Step 5 — botulinum toxin for an inadequate response to topical therapy
Special situation / procedural botulinum toxin injected into the internal anal sphincter produces a temporary chemical sphincterotomy lasting about 3 months. The 2023 ASCRS guideline found it comparable to topical therapy when used as a first-line option, and it offers a modest improvement in healing when used as a second-line option after topical therapy has failed — with a lower-dose, similar-efficacy approach favoured specifically to reduce the incidence of transient incontinence.[3][1]
Step 6 — surgical referral for medically refractory chronic fissure
Surgical referral lateral internal sphincterotomy (LIS) is the treatment of choice for chronic fissure that has failed medical therapy in patients without baseline fecal incontinence risk, and is generally tailored to the length of the fissure — this yields similar healing with a lower incontinence rate than a traditional sphincterotomy extended to the dentate line.[3] An anal (anocutaneous) advancement flap, alone or combined with sphincterotomy or botulinum toxin, is a sphincter-preserving alternative for patients at higher baseline risk of incontinence — for example, older patients, those with prior obstetric sphincter injury, or women in general, who carry a higher baseline incontinence risk after sphincterotomy than men.[3][1]
Step 7 — a secondary (atypical) fissure is managed by treating the underlying cause
Special situation for a fissure secondary to Crohn disease, malignancy, infection, or another identified cause, direct treatment at that underlying condition. Sphincterotomy is generally avoided in Crohn disease given baseline sphincter dysfunction and impaired healing, so medical (topical or botulinum toxin) therapy alongside optimizing the underlying disease is the preferred approach.[3][2]
Non-Pharmacologic Treatment
- 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]
Special Populations
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]
Conservative measures — fiber, fluids, stool softeners, and sitz baths — are the mainstay and are well tolerated throughout pregnancy and lactation. Topical calcium channel blockers and topical nitroglycerin both have minimal systemic absorption at the doses used for fissure, but treat the choice of any topical prescription therapy in pregnancy or lactation as a prescriber decision rather than a self-care default, and continue to screen the same red flags (off-midline or non-healing fissure) rather than assuming pregnancy or delivery fully explains the presentation.
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]
Monitoring & Follow-Up
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]
Common Errors to Avoid
- 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.
Clinical Decision Algorithm
Drug Tables
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.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Psyllium | Dosing: Titrate to a total dietary + supplemental fiber intake of ~25-30 g/day | Bloating, gas, especially with rapid dose escalation or inadequate fluid | May reduce absorption of some oral medications taken at the same time — separate dosing by 1-2 hours | Continue indefinitely alongside adequate fluid intake, not just until pain resolves — this is what prevents recurrence. |
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.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Docusate sodium | Adults: 100-200 mg PO once or twice daily | Mild abdominal cramping (uncommon) | None clinically significant | Softens stool but does not add bulk — pair with, not substitute for, fiber. |
| Polyethylene glycol 3350 | Adults: 17 g powder dissolved in liquid, PO once daily | Bloating, cramping, diarrhea if overdosed | None clinically significant | Osmotic laxative alternative, including for pediatric use, when a softener alone is not enough. |
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.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Diltiazem 2% (topical) | Dosing: Apply a pea-sized amount twice daily for 6-8 weeks | Mild local irritation, pruritus, or perianal dermatitis; headache is uncommon | None clinically significant given topical use | Preferred first choice; a compounded 2% cream or ointment is applied directly to the anal verge, not inserted rectally. |
| Nifedipine 0.2-0.5% (topical) | Dosing: Apply externally twice daily for 6-8 weeks | Local irritation; headache and flushing less common than with nitrates | None clinically significant given topical use | Reasonable substitute for diltiazem when compounding availability or patient preference favours it. |
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.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Nitroglycerin 0.2-0.4% (topical) | Dosing: Apply externally 2-3 times daily for 6-8 weeks | Headache (common — roughly a third to over half of patients depending on concentration); up to 1 in 5 discontinue because of it; hypotension, dizziness | Additive hypotension with phosphodiesterase-5 inhibitors (e.g., sildenafil) — do not combine | Start at the lower end of the concentration range and titrate; counsel to pretreat headache with an analgesic and to rise slowly to limit orthostatic symptoms. |
Topical anesthetics
Symptom relief only — do not promote healing and should not replace a healing-directed therapy.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Lidocaine | Dosing: Apply externally up to 3-4 times daily as needed | Local irritation; rare contact sensitization with prolonged use | None clinically significant given minimal systemic absorption with topical use | Reasonable adjunct for breakthrough pain alongside, not instead of, fiber and a topical calcium channel blocker or nitrate. |
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.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Botulinum toxin, injection | Use: Typically 20-100 units, commonly divided into 2 injection sites — specialist-administered only | Transient flatal or fecal incontinence in a minority of patients (more common at higher doses); local injection-site pain | None clinically significant with local injection | Injected into the internal anal sphincter; a temporary chemical sphincterotomy lasting about 3 months. Lower-dose regimens are favoured for similar efficacy with less transient incontinence. |
References
- Anal Fissures — StatPearls (Gerbasi L, Ashurst JV). StatPearls Publishing, updated September 15, 2025
- Anal fissures — CMAJ (Dykstra MA, Buie WD). CMAJ 2019;191(26):E737
- The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Anal Fissures — Diseases of the Colon & Rectum (Davids JS, Hawkins AT, Bhama AR, Feinberg AE, Grieco MJ, Lightner AL, Feingold DL, Paquette IM; ASCRS Clinical Practice Guidelines Committee). Dis Colon Rectum 2023;66(2):190-199
- Management of Anal Fissures: Guidelines From the American Society of Colon and Rectal Surgeons — American Family Physician (Arnold MJ). Am Fam Physician 2024;109(2):188-189
- Topical treatments for anal fissure — Canadian Family Physician (Fagan C, Kolber MR, Lindblad AJ). Can Fam Physician 2023;69(1):33
Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.