What is a lateral internal sphincterotomy?

Lateral Internal Sphincterotomy (LIS)

A lateral internal sphincterotomy is a surgical procedure that involves cutting a portion of the internal anal sphincter muscle to reduce anal canal pressure and treat chronic anal fissures. This procedure is considered the gold standard surgical treatment for chronic anal fissures that have not responded to conservative management, with healing rates exceeding 90% and rapid symptom relief. 1

Procedure Details

The procedure involves:

• Making an incision at the intersphincteric groove (between internal and external sphincters)
• Dividing a portion of the internal anal sphincter muscle laterally (usually on the left side)
• The division is typically performed to the level of the dentate line or to match the length of the fissure

Two main techniques are used:

1. Open technique: Direct visualization of the sphincter with an incision at the anal verge
2. Closed technique: Performed through a small stab incision without direct visualization

Indications

LIS is primarily indicated for:

• Chronic anal fissures (persisting >8 weeks) that have failed conservative management 1
• Fissures associated with severe, intractable pain
• Fissures with internal anal sphincter hypertonia

Efficacy and Outcomes

The procedure is highly effective:

• Healing rates of 93-96% 2, 3
• Rapid pain relief, often within days
• Low recurrence rates (7-8%) 3, 4
• High patient satisfaction (98% in long-term follow-up) 4

Contraindications and Cautions

LIS should be avoided in:

• Acute anal fissures (conservative management is recommended first) 1
• Patients with pre-existing fecal incontinence
• Patients with inflammatory bowel disease, particularly Crohn's disease 1
• Patients with compromised sphincter function

Potential Complications

The most significant complications include:

• Fecal incontinence: Reported in up to 45% of patients at some point post-procedure, though most cases are minor and transient 4
  • Higher risk in women (53.4% vs. 33.3% in men) 4
  • Permanent significant incontinence is rare (1-3%) 4
• Bleeding (2.5-3%) 3
• Hematoma/ecchymosis (2.5%) 3
• Wound infection or abscess (rare)
• Fistula formation (rare)
• Recurrence (0.3-8%) 5, 4

Surgical Variations and Considerations

Some technical considerations that may improve outcomes:

• Marginal suturing of the incision may reduce early complications like bleeding and abscess formation 2
• Open technique under local anesthesia is considered effective and safe 3
• For recurrent fissures after failed sphincterotomy, a contralateral repeat procedure can be performed with good results and minimal risk of incontinence 6

Post-Procedure Care

After LIS, patients typically require:

• Pain management with topical anesthetics and oral analgesics
• Stool softeners and increased fiber intake
• Sitz baths
• Follow-up to assess healing and continence

Comparison to Alternative Treatments

While LIS is the most effective treatment, less invasive options are recommended as first-line therapy:

• Conservative management (fiber, fluids, sitz baths)
• Topical medications (calcium channel blockers, nitrates)
• Botulinum toxin injections

These alternatives have lower healing rates (25-80%) but avoid the risk of incontinence 1.

Treatment Algorithm

1. First line: Conservative management for 6-8 weeks (fiber, fluids, sitz baths)
2. Second line: Topical therapy (calcium channel blockers preferred over nitrates due to fewer side effects) 1
3. Third line: Consider botulinum toxin injection
4. Fourth line: Lateral internal sphincterotomy if non-operative management fails after 8 weeks 1

LIS should not be performed for acute anal fissures, as these often heal with conservative measures alone 1.