Anal Fissure

Definition

Classification

Pathophysiology

Location

• Posterior midline: ~75–90% of cases (relatively poor blood supply)
• Anterior midline: ~10%, more common in females
• Off midline (<1%): atypical — must exclude secondary causes

Atypical (off-midline) fissures raise concern for: Crohn's disease, anal cancer, tuberculosis, HIV, syphilis, herpes, leukemia.

Clinical Features

• Severe, sharp anal pain with defecation — classically described as "passing razor blades" or "pieces of glass"
• Post-defecation throbbing and anal spasm lasting minutes to hours
• Bright-red rectal bleeding — typically mild, on toilet paper or streaking stool
• Chronic fissure: unrelenting pain; in severe cases, patients avoid eating to avoid defecation

• Diagnosis is often made on history alone
• Gentle buttock separation may reveal the fissure or sentinel tag
• Focal pressure with a cotton-tip applicator at the posterior/anterior anal canal reproduces pain
• DRE and anoscopy are often deferred (too painful); markedly elevated sphincter tone is typical
• Examination under anesthesia (EUA) if diagnosis unclear or malignancy suspected

Management

Step 1 — Conservative (all fissures)

• High-fiber diet (≥30 g/day) + 6–8 glasses of water + fiber supplements (3–6 g/day)
• Warm sitz baths — pain relief in >90% of acute fissures
• 5% lidocaine ointment applied to the fissure (not via rectal tube or suppository)
• Stool softeners / bulk agents
• Commercially available anorectal creams: minimal benefit; steroids not for long-term use
• Avoid: rectal tube applicators, suppositories, anal dilators, silver nitrate, electrocautery

Step 2 — Pharmacological sphincter relaxants (for persistent/chronic fissures)

Topical diltiazem/nifedipine have no commercial US formulation — must be compounded.

Step 3 — Botulinum Toxin (BTX) injection

• Mechanism: blocks ACh release from presynaptic terminals → temporary IAS paralysis (~3 months)
• Dose: 20–100 IU
• Efficacy: similar to topical agents as first-line; modest improvement as second-line after failed topicals
• Side effects: transient flatus incontinence, rarely urinary retention, heart block, allergic reaction
• Can be done in-office or under sedation

Step 4 — Surgery: Lateral Internal Sphincterotomy (LIS)

• Goal: divide ~30% of internal sphincter fibers laterally → reduce tone → promote healing
• Healing rate: 88–100% (superior to all medical therapies)
• Technique: open (radial incision exposing IAS) or closed (narrow-bladed scalpel via intersphincteric groove) — both have equivalent results
• Fecal incontinence risk: 8–30%, usually minor (flatus); most in first 30 days
• Avoid LIS in: baseline incontinence, females with obstetrical sphincter injuries, prior anorectal surgery, documented sphincter defects

Differential Diagnosis

• Hemorrhoids (distinguish by history; hemorrhoids rarely cause pain like fissures)
• Perianal abscess / fistula
• Crohn's disease perianal involvement
• Anal cancer / squamous cell carcinoma
• STIs: syphilis, herpes, gonorrhea, HIV-related ulcers
• Tuberculosis, leukemic infiltrates

Summary Algorithm

Anal fissure
│
├── Acute (<6–8 wk)
│   └── Conservative: fiber, sitz baths, topical lidocaine
│       ├── Heals → done
│       └── Fails → move to chronic protocol
│
└── Chronic (>6–8 wk)
    ├── Topical CCB (diltiazem/nifedipine) ← preferred first-line
    ├── Topical NTG (if CCB unavailable/failed)
    ├── BTX injection (second-line or office alternative)
    └── LIS (gold standard if all else fails)