Fissure-in-Ano: A Comprehensive Surgical Account

1. Definition

"An anal fissure is an elliptical or oval-shaped tear in the anal canal starting at the anal verge and extending proximally for a varying length toward the dentate line." - Sabiston Textbook of Surgery

2. Aetiology and Pathophysiology

1. Initiating trauma - passage of hard stool (constipation), prolonged diarrhea, anal receptive intercourse, or childbirth tears the anoderm.
2. IAS hypertonia - the pain from the tear causes reflex spasm of the internal anal sphincter, which is involuntary smooth muscle.
3. Ischaemia - the hypertonic IAS decreases blood supply to the posterior midline anoderm, creating relative tissue ischaemia.
4. Non-healing - ischaemia prevents wound healing; further defecation re-tears the fissure, perpetuating the cycle.

• 75% of fissures occur here. The posterior midline has a relatively less robust blood supply compared to other quadrants.
• Shearing forces during defecation are maximal at the posterior midline.
• The anoderm here is less elastic and has an increased density of longitudinal muscle extensions.
• Anterior fissures (10-15%) are more common in women, often following vaginal delivery.
• Less than 1% occur off the midline - these must raise suspicion of a secondary cause.

3. Classification

4. Clinical Features

• Severe anal pain during defecation - classically described as "passing pieces of glass" or "razor blades" or "a knife cutting." The pain typically resolves then recurs with the next bowel movement.
• Throbbing and anal spasm - can persist for minutes to hours after defecation.
• Bright-red bleeding - usually a trace on toilet paper; rarely more than that.
• Pruritus ani - from irritation by the sentinel tag or discharge.
• Mucus discharge - from the ulcer or an associated intersphincteric fistula.
• In severe chronic cases, patients may avoid oral intake (and lose weight) due to dread of defecation.

• The fissure is often visible by gently separating the buttocks - examine in this gentle manner first.
• Chronic fissure triad:
  1. Sentinel skin tag/pile externally (at the anal verge)
  2. Indurated ulcer with visible IAS fibers at the base
  3. Hypertrophied anal papilla proximally (at dentate line)
• Digital rectal examination, anoscopy, and proctoscopy are often deferred because even gentle palpation reproduces intolerable pain.
• If the fissure is not clearly visible, focal pressure with a fingertip or cotton-tip applicator at the posterior or anterior anal canal reproduces pain.

5. Atypical / Secondary Fissures

• Crohn's disease
• Tuberculosis
• HIV-related ulcers
• Syphilis, Chlamydia, chancroid, lymphogranuloma venereum (LGV)
• Herpes simplex virus (HSV), Cytomegalovirus (CMV)
• Kaposi's sarcoma, B-cell lymphoma
• Squamous cell carcinoma (SCC)
• Leukaemia

6. Treatment

6.1 Conservative (First-Line for All Fissures)

• Increased fibre and fluid intake - bulk-forming agents to produce soft, formed stools.
• Stool softeners - to minimise anal trauma.
• Warm sitz baths - demonstrated to provide significant pain relief in >90% of patients with acute fissures.
• Topical local anaesthetics (e.g., 2% lidocaine jelly) - additional symptomatic relief.
• Anorectal biofeedback - for patients with normal bowel habits but excessive straining.

These conservative measures heal almost all acute fissures and the majority of chronic fissures.

6.2 Chemical Sphincterotomy (Pharmacological Relaxation of IAS)

• A nitric oxide donor that causes smooth muscle relaxation and vasodilation.
• 0.2% ointment, applied 2-3 times per day to the anal margin.
• Healing rate: approximately 50% of chronic fissures.
• Major side effect: severe headaches - limits acceptability; patients stop therapy in up to 20%.

• Diltiazem 2% (applied twice daily) or nifedipine - relax the IAS and promote vasodilation.
• Healing rates similar to GTN for chronic fissures.
• Significantly better side-effect profile - fewer headaches - making these the preferred first-line topical agents (Sabiston).
• Note: No readily available commercial formulation in some countries; must be obtained from compounding pharmacies.

• Causes temporary muscle paralysis by preventing acetylcholine release from presynaptic nerve terminals.
• Dose: 20-100 IU (10-100 units) injected into the IAS in a single or divided dose.
• Produces IAS relaxation lasting approximately 3 months.
• Can be done in-office or as an outpatient procedure with sedation.
• Healing rate: ~50% (similar to topical therapies as first-line; modest improvement as second-line after failed topical therapy).
• Side effects: temporary incontinence to flatus (up to 10%); rarely - increased urinary residual volume, heart block.
• Used as an alternative to surgical sphincterotomy at some centres.

6.3 Surgical Treatment (For Chronic Fissures Failing Medical Therapy)

A. Lateral Internal Sphincterotomy (LIS) - Procedure of Choice

• A radial incision is made in the anoderm at the lateral position (3 or 9 o'clock), exposing the distal IAS muscle fibers.
• The distal segment of the IAS is divided sharply for a length corresponding to the length of the fissure.
• The wound can be left open or closed primarily with absorbable sutures.

• The distal IAS is palpated with a bivalved speculum at the intersphincteric groove.
• A small no. 11 blade scalpel is inserted directly into the intersphincteric groove, advanced parallel to the sphincter.
• The blade is then rotated so its sharp edge faces the IAS, dividing the distal third laterally.
• Alternatively, dissecting scissors open the intersphincteric space and divide the IAS:

• Pressure is applied to the wound for a few minutes to prevent haematoma formation.
• Wound is closed with absorbable sutures.

• Baseline incontinence
• Females with prior obstetric injuries
• Previous anorectal operations
• Documented anal sphincter injury

B. Anal Sphincter Dilatation (Lord's Procedure)

• Forcible dilatation of the anal canal (manually) to reduce sphincter tone.
• Largely abandoned - disrupts the anal sphincters at multiple unpredictable sites with an unacceptably high risk of incontinence.
• Rarely indicated in current practice.

C. Fissurectomy

• Surgical excision of the fibrotic edges of the fissure, curettage of the base, and excision of the sentinel tag and/or anal papilla.
• Used as an alternative to LIS when there are contraindications to sphincterotomy.
• Frequently combined with an anal advancement flap anoplasty.

D. Anal Advancement Flap Anoplasty

• Should be considered in patients with increased risk of altered continence after LIS - especially postpartum women and those with normal or low resting anal pressures.
• After fissurectomy, an inverted house-shaped flap of perianal skin is carefully mobilised on its blood supply and advanced to cover the fissure.
• VY advancement flaps with or without sphincterotomy have also been reported to successfully treat chronic fissures (Schwartz's).

7. Management Algorithm Summary

Anal Fissure Diagnosed
        |
   Acute (<6-8 wks)                    Chronic (>6-8 wks)
        |                                      |
Conservative Rx                      Conservative + Chemical
(Fibre, sitz baths,                  Sphincterotomy
stool softeners)                     (GTN/CCB topically → 
        |                             Botox if fails)
   Healed ✓                                    |
                                     Fails (~50%)
                                               |
                                  Off-midline? → EUA + Biopsy
                                  Midline → Lateral Internal
                                            Sphincterotomy
                                  High incontinence risk →
                                  Advancement Flap

8. Key Points to Remember (Surgical Summary)

• Location: 75% posterior midline; 10-15% anterior (more common in women); <1% lateral (always secondary cause).
• Pathophysiology: Tear → IAS spasm → ischaemia → non-healing (vicious cycle).
• Triad of chronic fissure: Sentinel tag + ulcer with IAS fibers exposed + hypertrophied anal papilla.
• First-line medical: Topical CCBs (diltiazem) preferred over GTN due to fewer headaches.
• Botox: Office procedure, 3-month effect, 50% healing, 10% temporary incontinence.
• Surgery of choice: Lateral internal sphincterotomy - divides distal 1/3 of IAS laterally.
• Open vs Closed LIS: Equivalent results; both heal 85-95%.
• Risk of LIS: Flatus incontinence 5-15%; warn all patients preoperatively.
• Advancement flap: Alternative for patients at high incontinence risk.

Fissure-in-Ano

Definition

• A longitudinal ulcer (tear) in the anoderm of the distal anal canal
• Extends from the anal verge proximally toward (but not beyond) the dentate line
• Synonym: fissure-in-ano
• Acute: present < 6-8 weeks | Chronic: present > 6-8 weeks

Aetiology

• Passage of hard stool (most common)
• Prolonged diarrhea
• Anal trauma or anal receptive intercourse
• Vaginal delivery (anterior fissures in women)
• Underlying cause if off-midline: Crohn's, TB, HIV, syphilis, HSV, SCC, leukaemia

Sites

• Posterior midline - 75% (less blood supply + maximum shearing force)
• Anterior midline - 10-15% (more common in women post-delivery)
• Off-midline - <1% (always secondary; investigate)

Pathophysiology (Vicious Cycle)

• Tear in anoderm → pain
• Pain → IAS (internal anal sphincter) spasm / hypertonia
• Spasm → reduced blood supply (ischaemia) to anoderm
• Ischaemia → poor healing → repeated trauma → chronic fissure
• Local pain reinforces spasm → cycle continues

Clinical Features

Symptoms

• Severe anal pain during defecation - "passing broken glass" or "razor blades"
• Pain settles, then recurs with next bowel movement
• Throbbing / anal spasm lasting minutes to hours after defecation
• Bright-red bleeding - trace on toilet paper, streaking on stool
• Pruritus ani - from sentinel tag irritation
• Mucus discharge - from ulcer or associated intersphincteric fistula
• Severe cases: patients avoid eating (fear of defecation) → weight loss

Signs

• Acute: Shallow, fresh tear visible on gentle buttock separation
• Chronic triad:
  1. Sentinel skin tag - externally at anal verge
  2. Indurated ulcer - with exposed IAS fibres at base
  3. Hypertrophied anal papilla - internally at dentate line
• DRE, anoscopy, proctoscopy often deferred due to intolerable pain
• If diagnosis unclear → EUA (examination under anaesthesia) + biopsy

Treatment

Step 1 - Conservative (All fissures, first line)

• High-fibre diet + increased fluid intake
• Stool softeners / bulk-forming agents
• Warm sitz baths (pain relief in >90% of acute fissures)
• Topical local anaesthetic (e.g., 2% lidocaine jelly)
• Anorectal biofeedback - if excessive straining with normal bowel habit
• Heals almost all acute fissures and majority of chronic fissures

Step 2 - Chemical Sphincterotomy (If conservative fails)

a) Topical GTN (Glyceryl Trinitrate / Nitroglycerin)

• Nitric oxide donor → smooth muscle relaxation + vasodilation
• 0.2% ointment, 2-3 times/day to anal margin
• Healing: ~50% of chronic fissures
• Side effect: severe headaches (therapy stopped in up to 20%)

b) Topical Calcium Channel Blockers (Preferred first-line topical)

• Diltiazem 2% (twice daily) or nifedipine
• Relaxes IAS + promotes vasodilation
• Healing: similar to GTN (~50%)
• Fewer side effects (fewer headaches) - preferred over GTN

c) Botulinum Toxin (Botox) Injection

• Blocks acetylcholine release at neuromuscular junction → temporary IAS paralysis
• Dose: 20-100 IU into IAS; effect lasts ~3 months
• Healing: ~50% (similar to topical; modest improvement as 2nd-line)
• Can be done in-office or outpatient under sedation
• Side effects: temporary flatus incontinence (up to 10%), rarely urinary retention

Step 3 - Surgical Treatment (Chronic fissure failing medical therapy)

A. Lateral Internal Sphincterotomy (LIS) - GOLD STANDARD

• Procedure of choice for chronic anal fissure
• Divides distal 1/3 of IAS at the lateral position (3 or 9 o'clock) - away from the fissure
• Aim: reduce IAS spasm → improve blood flow → allow healing

• Healing rate: 85-95%
• Recurrence: <10%
• Flatus incontinence: 5-15% (warn all patients)
• Soiling: ~6%
• Solid stool incontinence: <1%

• Baseline incontinence
• Women with prior obstetric sphincter injuries
• Previous anorectal surgery
• Documented sphincter defect on imaging

B. Lord's Dilatation (Anal Sphincter Dilatation)

• Forcible manual dilatation of anal canal to reduce sphincter tone
• Largely abandoned - uncontrolled sphincter disruption at multiple sites
• High risk of permanent incontinence - rarely used today

C. Fissurectomy

• Excision of fibrotic fissure edges + curettage of base
• Excision of sentinel tag and/or anal papilla
• Used when LIS is contraindicated
• Usually combined with advancement flap anoplasty

D. Advancement Flap Anoplasty

• For patients with high incontinence risk (low/normal resting anal pressures, postpartum women)
• After fissurectomy, a house-shaped perianal skin flap is mobilised on its blood supply and advanced to cover the defect
• VY advancement flap with or without sphincterotomy

Summary Box (Quick Revision)

Types of Fissure-in-Ano

By Duration

By Aetiology

• Primary (Idiopathic) - no underlying disease; occurs in midline (posterior or anterior)
• Secondary (Specific) - off-midline; caused by Crohn's, TB, HIV, syphilis, HSV, SCC, leukaemia

By Position

• Posterior midline - 75% (most common; less blood supply + maximum shearing force)
• Anterior midline - 10-15% (commoner in women, post-delivery)
• Off-midline / Lateral - <1% (always secondary - investigate with EUA + biopsy)

Pathogenesis - Vicious Cycle

INITIATING FACTOR
(Hard stool / Diarrhoea / Trauma / Childbirth)
              ↓
     TEAR IN ANODERM
(Disruption of distal anal canal epithelium)
              ↓
          ACUTE PAIN
              ↓
   REFLEX IAS SPASM / HYPERTONIA
  (Involuntary smooth muscle tightens)
              ↓
  REDUCED BLOOD SUPPLY TO ANODERM
        (Relative ischaemia)
              ↓
     IMPAIRED WOUND HEALING
              ↓
  RE-TEARING AT NEXT DEFECATION
              ↓
    ← VICIOUS CYCLE PERPETUATED ←
    (Pain → Spasm → Ischaemia → Non-healing)
              ↓
    (if cycle not broken)
              ↓
       CHRONIC FISSURE
  (Fibrosis + Sentinel tag +
Hypertrophied papilla + Exposed IAS fibres)