ASCRS · 2023

Anal Fissure — Acute vs. Chronic, Medical vs. Surgical Management

Source: The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Anal Fissures, Diseases of the Colon & Rectum, 2023

Guideline: Strong Guideline: Conditional Guideline: Not recommended ClinicoQ pathway suggestion (not from the cited guideline)

Diagnosis

Diagnostic criteria A linear tear or crack in the distal anal canal, most often in the posterior midline (90%) or anterior midline (10%). Acute fissure: present less than 6-8 weeks, involving only the epithelium. Chronic fissure: present more than 6-8 weeks, with exposed internal sphincter fibers at the base, a hypertrophied anal papilla proximally, and often a sentinel skin tag distally. Diagnosis is typically made by inspection; digital exam and anoscopy may be deferred if too painful.

⚠ Alarm features (investigate before diagnosing)

Fissure in an atypical location (lateral position) — raises suspicion for Crohn's disease, tuberculosis, HIV, syphilis, or malignancy rather than a typical fissure
Multiple fissures
Non-healing fissure despite adequate treatment

Initial workup

Test	When to order
Visual inspection	Sufficient for diagnosis in typical midline fissures; usually no further workup needed.
Further evaluation (colonoscopy, biopsy, etc.)	Atypical location, multiple fissures, or fissures resistant to treatment — to rule out an underlying cause.

Decision Points

❓ Is the fissure acute (<6-8 weeks) or chronic?

Acute (<6-8 weeks) → Acute fissure — conservative management

Chronic (>6-8 weeks), or with sentinel tag/exposed sphincter fibers → Chronic fissure — medical therapy

❓ For chronic fissure: has the patient failed an adequate trial of topical medical therapy (CCB and/or nitrates, +/- botulinum toxin)?

No — not yet tried, or still within treatment course → Chronic fissure — medical therapy

Yes — failed adequate medical therapy (see baseline_continence question below for LIS vs. anocutaneous flap) → Lateral internal sphincterotomy (LIS)

❓ For chronic fissure needing surgery: does the patient have baseline fecal incontinence or other risk factors that make LIS less suitable?

No — no baseline incontinence, standard-risk patient → Lateral internal sphincterotomy (LIS)

Yes — baseline fecal incontinence or elevated incontinence risk → Anocutaneous flap

Treatment

Acute fissure — conservative management

1 Fiber supplementation, sitz baths, stool softeners, adequate hydration Strong (Guideline recommendation) — nonoperative treatment is safe and typically first-line for acute fissures

Dose: Standard fiber/stool-softening regimen
Duration: Ongoing until healed
Evidence level: Moderate
Avoid if: -
If no response ClinicoQ pathway: If not healed, treat as chronic fissure with topical medical therapy

Chronic fissure — medical therapy

1 Topical calcium channel blocker (2% diltiazem) Strong (Guideline recommendation) — comparably effective to nitrates with fewer side effects (less headache); can be first-line

Dose: Pea-sized amount applied topically to the anal verge/canal twice daily
Duration: 6-8 weeks
Evidence level: Moderate-High
Avoid if: Known hypersensitivity to diltiazem
If no response ClinicoQ pathway: Trial topical nitroglycerin, or move to botulinum toxin injection

2 Topical nitroglycerin (0.2-0.4%) Strong (Guideline recommendation) — effective, but headache (in up to ~30-50% of patients in trials) may limit use/adherence

Dose: Applied to the anal canal twice daily (0.4% formulation applied rectally with a finger cot/glove)
Duration: 6-8 weeks
Evidence level: High
Avoid if: Concurrent use of PDE5 inhibitors (sildenafil, etc.) — risk of severe hypotension; significant hypotension or headache disorder
If no response ClinicoQ pathway: Move to botulinum toxin injection

3 Botulinum toxin A injection into the internal anal sphincter Strong (Guideline recommendation) — comparable to topical therapy as first-line, improved healing as second-line after failed topical treatment; can cause transient fecal incontinence in about 5% of patients

Dose: 20 units total (e.g., 0.4 mL of 50 U/mL solution), injected as two 0.2 mL aliquots on either side of the anterior midline
Duration: Single procedure; reassess healing at follow-up (weeks)
Evidence level: High
Avoid if: Known hypersensitivity to botulinum toxin; neuromuscular disorders (e.g., myasthenia gravis)
If no response ClinicoQ pathway: Proceed to surgical therapy if pharmacologically naive/failed options — LIS if no baseline incontinence, anocutaneous flap if baseline incontinence or elevated risk

Lateral internal sphincterotomy (LIS)

1 Lateral internal sphincterotomy (LIS) Strong (Guideline recommendation) — treatment of choice for chronic fissure in selected patients without baseline fecal incontinence; healing rates >=88% at up to 6 years, but fecal incontinence can occur in up to 30% of patients depending on technique/series

Dose: - surgical procedure; open or closed technique (similar outcomes); tailoring sphincterotomy length to fissure length reduces incontinence risk vs. extending to the dentate line
Duration: Single procedure
Evidence level: High
Avoid if: Baseline fecal incontinence (relative contraindication) — see Anocutaneous flap instead
If no response: Short-term outcomes of repeat LIS or botulinum injection for recurrent fissure show good healing with low FI risk, though data are limited

Anocutaneous flap

1 Anocutaneous advancement flap Guideline recommendation (2023 ASCRS update) — a safe surgical alternative for chronic anal fissure, with healing rates comparable to LIS and a lower risk of fecal incontinence; can be added to botulinum toxin injection or LIS to decrease postoperative pain and allow primary wound healing

Dose: - surgical procedure; a flap of perianal skin is advanced to cover the fissure defect, without dividing the internal sphincter
Duration: Single procedure
Evidence level: Moderate
Avoid if: -
If no response: -

✕ Treatments the guideline advises against

Lateral internal sphincterotomy as first-line therapy before a medical treatment trial: Guideline reserves LIS for fissures refractory to nonsurgical measures, not as an initial approach, given the risk of fecal incontinence.

⚠️ Update note: added the anocutaneous flap as its own surgical option (2023 ASCRS guideline) — previously only mentioned as an alternative inside the LIS entry. This is an educational summary of current international clinical practice guidelines and does not replace individualized clinical judgment. Final treatment decisions remain the responsibility of the treating physician.