Causes and Treatment of Anal Fissures
Primary Cause
Anal fissures result from internal anal sphincter hypertonia with decreased anodermal blood flow, creating an ischemic environment that prevents healing. 1
The typical mechanism involves local trauma to the anal canal (often from hard stools), which triggers sphincter spasm and perpetuates the ischemic cycle. 2
Critical Diagnostic Consideration: Location Matters
If the fissure occurs off the midline (lateral position), you must immediately evaluate for serious underlying conditions before initiating any treatment. 3, 4
Lateral fissures mandate urgent workup for:
- Crohn's disease (most common cause of atypical fissures) 4
- HIV/AIDS and associated infections 3, 4
- Ulcerative colitis 3, 4
- Tuberculosis and syphilis 3, 4
- Malignancy (leukemia, anal cancer) 3, 4
Typical fissures occur in the posterior midline in 90% of cases and can be treated conservatively, whereas lateral fissures are red flags requiring complete evaluation before treatment. 4
Treatment Algorithm
Step 1: Conservative Management (First-Line for All Typical Fissures)
Begin with conservative care for 10-14 days, which heals approximately 50% of acute fissures. 3, 1, 5
Conservative management includes:
- Fiber supplementation (25-30g daily) to soften stools and minimize anal trauma 1
- Adequate fluid intake to prevent constipation 3, 1
- Warm sitz baths to promote sphincter relaxation 3, 1
- Topical analgesics (lidocaine) for pain control 3, 1
Acute fissures respond significantly better than chronic fissures (80% vs 40% healing rates with conservative treatment). 6 Healing rates decrease dramatically from 100% in patients with symptoms <1 month to 33.3% in those with symptoms >6 months. 6
Step 2: Pharmacologic Therapy (If No Improvement After 2 Weeks)
Use topical calcium channel blockers as the preferred second-line treatment, achieving 65-95% healing rates. 4, 1
Preferred option:
- Compounded 0.3% nifedipine with 1.5% lidocaine applied three times daily achieves 95% healing after 6 weeks by reducing internal anal sphincter tone and increasing local blood flow 1
Alternative options:
- Topical nitroglycerin (GTN) 0.2% shows 25-50% healing rates but causes headaches in many patients 3, 1, 6
- Botulinum toxin injection demonstrates 75-95% cure rates with low morbidity and is nearly as effective as surgery 1, 7, 8
Step 3: Surgical Intervention (After 6-8 Weeks of Failed Medical Therapy)
Lateral internal sphincterotomy (LIS) remains the gold standard for chronic fissures unresponsive to medical therapy, with >95% cure rates and 1-3% recurrence. 3, 1, 7
LIS offers technical simplicity, minimal morbidity, rapid symptom relief, and high cure rates, though it carries a small risk of minor permanent incontinence defects. 3, 7
Critical Pitfalls to Avoid
- Never use manual dilatation due to high risk of permanent incontinence 4, 5
- Do not use hydrocortisone beyond 7 days as it causes perianal skin thinning and atrophy, worsening the fissure 1
- Do not perform surgery for acute fissures 4
- Avoid instrumentation of the anal canal in the setting of marked pain or tenderness, as it is traumatic and rarely yields diagnostic information 3
Special Population Considerations
In patients with inflammatory bowel disease (particularly Crohn's disease), fissures may be atypical in location and require more conservative surgical approaches due to impaired healing. 4 These patients need comprehensive evaluation before any intervention. 3, 4