Summary

An anal fissure is a longitudinal tear in the squamous epithelium of the anal canal, most commonly occurring in the posterior midline. It is characterised by severe pain during and after defecation, often described as "passing broken glass," accompanied by bright red bleeding. Fissures may be acute (<6 weeks) or chronic (>6 weeks), with the latter developing a chronic wound triad: visible fissure, sentinel pile (skin tag), and hypertrophied anal papilla. The condition is common, affecting all ages, and is largely related to constipation and anal sphincter spasm. Most acute fissures heal with conservative management; chronic fissures require medical therapy (GTN, diltiazem) or surgery.

Key Facts

• Definition: Longitudinal tear in the anal canal lining, typically at posterior midline
• Prevalence: Very common; lifetime prevalence ~10%
• Peak Age: 20-40 years; bimodal incidence (young adults, elderly)
• Classic Symptom: Severe tearing pain during/after defecation + bright red blood on wiping
• Location: Posterior midline (90%); anterior midline (10%, more common in women)
• Key Management: Laxatives + topical GTN/diltiazem for chronic; surgery for refractory
• Critical Finding: Lateral or atypical fissures suggest secondary cause (Crohn's, HIV, malignancy)

Clinical Pearls

"Posterior Midline": 90% of primary fissures occur in the posterior midline due to poor blood supply in this area. A fissure located laterally should raise suspicion of Crohn's disease, anal cancer, HIV, tuberculosis, or syphilis.

The Vicious Cycle: Fissure → pain → sphincter spasm → reduced blood flow → poor healing → chronic fissure. Breaking this cycle (with sphincter relaxation or surgery) is the key to treatment.

"Never miss Crohn's": Multiple fissures, lateral position, painless presentation, associated perianal abscesses or fistulae, or non-healing fissures should prompt investigation for Crohn's disease.

Why This Matters Clinically

Anal fissure causes disproportionate suffering relative to its severity — patients are often in severe pain and may avoid defecation, worsening constipation and the fissure itself. Accurate diagnosis (which can usually be made clinically) and appropriate treatment lead to rapid improvement. Failure to recognise atypical fissures can delay diagnosis of conditions like Crohn's disease or anal cancer.

Structured Approach

General:

• Patient often anxious due to anticipated pain
• May report avoiding defecation

Inspection:

• Positioning: Left lateral (Sims) or genupectoral (knee-chest)
• Parting buttocks gently — fissure often visible in posterior midline
• Sentinel pile — skin tag at external end of chronic fissure
• Perianal skin changes — excoriation, other skin tags, fistula openings

Digital Rectal Examination:

• Often not possible due to severe pain and sphincter spasm
• If tolerable: assess resting tone (usually high), tenderness, masses
• Do not force examination if severe pain — may need examination under anaesthesia (EUA)

Anoscopy/Proctoscopy:

• Usually deferred in acute setting due to pain
• Useful for visualising chronic fissure, ruling out other pathology
• May require EUA if not tolerable

Special Tests

Natural History

Acute anal fissures often heal spontaneously within 4-6 weeks with conservative measures (stool softening, avoidance of constipation). Without treatment, many progress to chronic fissures which rarely heal without intervention due to the self-perpetuating cycle of spasm and ischaemia.

Outcomes with Treatment

Prognostic Factors

Good Prognosis:

• Acute fissure
• Posterior midline location
• First episode
• Addresses constipation/dietary factors
• No underlying inflammatory bowel disease
• Response to medical therapy

Poor Prognosis:

• Chronic fissure
• Lateral location (suggests secondary cause)
• Recurrent fissures
• Crohn's disease
• Risk factors not addressed
• Failed medical therapy

Key Guidelines

1. American Society of Colon and Rectal Surgeons (ASCRS) Clinical Practice Guidelines: Management of Anal Fissure (2017) — Strong recommendation for conservative management in acute; medical therapy before surgery in chronic; LIS as gold-standard surgery. PMID: 27824729
2. Association of Coloproctology of Great Britain and Ireland (ACPGBI) Guideline — Similar stepwise approach; emphasises informed consent regarding incontinence with surgery.
3. NICE CKS: Anal fissure (2020) — UK primary care guidance on diagnosis and initial management.

Landmark Trials

GTN vs Placebo — Multiple RCTs established efficacy of topical GTN for chronic fissure.

• Healing rates 50-70% vs 30% placebo
• Headache major side effect
• Clinical Impact: GTN became first-line medical therapy

Diltiazem vs GTN — Comparative studies showed similar efficacy with better tolerability.

• Diltiazem associated with fewer headaches
• Clinical Impact: Diltiazem preferred by many clinicians

Botox vs Sphincterotomy — RCTs comparing botulinum toxin to surgery.

• Botox: 70-80% healing but higher recurrence
• LIS: 95%+ healing, lower recurrence, but incontinence risk
• Clinical Impact: Botox useful for patients at high risk for incontinence; LIS for definitive treatment

Evidence Strength

What is an Anal Fissure?

An anal fissure is a small tear or crack in the lining of the back passage (anus). It's a very common condition and is usually caused by passing a hard stool. The tear causes intense pain during and after bowel movements, often described as "like passing broken glass," and you may notice bright red blood on the toilet paper.

Why does it happen?

• Passing hard or large stools (usually from constipation)
• Straining during bowel movements
• Chronic diarrhoea
• Childbirth
• Sometimes, underlying conditions like Crohn's disease

The tear causes a spasm in the muscle around the anus, which reduces blood flow and prevents healing — creating a vicious cycle.

How is it treated?

1. For new (acute) fissures:

   • High fibre diet (fruits, vegetables, wholegrain)
   • Plenty of fluids
   • Stool softeners (lactulose, Movicol)
   • Warm baths after bowel movements (sitz baths)
   • Pain relief before opening bowels

2. For older (chronic) fissures (lasting more than 6 weeks):

   • Ointments like GTN (glyceryl trinitrate) or diltiazem, applied twice daily to relax the muscle
   • Botox injections into the muscle (if ointments don't work)
   • Surgery (lateral sphincterotomy) as a last resort — highly effective but small risk of weakening the muscle

What to expect

• Most fissures heal within 4-8 weeks with treatment
• Keeping stools soft is crucial to prevent recurrence
• Surgery has the highest cure rate but is usually only needed if other treatments fail

When to seek help

• If pain is severe and not improving with home treatment
• If bleeding is heavy or persistent
• If you notice a fissure in an unusual location (side rather than back)
• If you have other symptoms like weight loss, fever, or discharge
• If you have Crohn's disease or are immunocompromised