When is a lateral internal sphincterotomy indicated for a chronic anal fissure?

When to Perform Lateral Internal Sphincterotomy

Lateral internal sphincterotomy is indicated for chronic anal fissures (symptoms >8 weeks) that have failed 6-8 weeks of comprehensive medical therapy, including fiber supplementation (25-30g daily), adequate hydration, warm sitz baths, and topical calcium channel blockers. 1, 2

Absolute Contraindications

• Never perform sphincterotomy for acute anal fissures (symptoms <8 weeks), as approximately 50% heal with conservative management alone within 10-14 days 1, 2
• Never operate on atypical fissures (lateral or off-midline location, multiple fissures) without first ruling out Crohn's disease, HIV/AIDS, ulcerative colitis, tuberculosis, syphilis, or malignancy 2, 3
• Manual anal dilatation is absolutely contraindicated due to permanent incontinence rates of 10-30% 1, 2

Required Pre-Operative Medical Therapy Trial

Before considering sphincterotomy, patients must complete the following for 6-8 weeks 1, 2:

• Fiber supplementation: 25-30g daily via diet or supplements 1, 2
• Adequate fluid intake to soften stools 1, 2
• Warm sitz baths 2-3 times daily to promote sphincter relaxation 1, 2
• Topical calcium channel blocker therapy: Either compounded 0.3% nifedipine with 1.5% lidocaine applied three times daily (95% healing rate) or 2% diltiazem cream twice daily (48-75% healing rate) 1, 2

Exception: Acute Fissures with Intractable Pain

Sphincterotomy may be appropriate for acute fissures when severe, intractable pain makes conservative care impossible to tolerate, though this represents a rare exception to the standard algorithm 2

Expected Surgical Outcomes

• Healing rate: >95% with recurrence in only 1-3% of cases 1, 2, 4
• Minor incontinence risk: 3-8% experience minor soiling or flatus incontinence, with only 1-3% reporting permanent solid stool incontinence 5, 6, 7
• Wound complications: Fistula, bleeding, abscess, or non-healing wound occur in up to 3% of patients 1
• Patient satisfaction: 91-98% report satisfaction with the procedure 4, 6, 7

Critical Pitfalls to Avoid

• Do not rush to surgery in acute fissures: 50% heal with conservative care alone, and premature surgery exposes patients to unnecessary incontinence risk 1, 2
• Verify adequate medical therapy duration: Many "failed" medical therapies were actually inadequate trials of <6 weeks or improper dosing of topical agents 8, 5
• Always confirm typical posterior midline location: Lateral fissures (occurring in <10% of women, <1% of men) mandate urgent evaluation for systemic disease before any surgical intervention 2, 3
• Avoid superficial or incomplete sphincterotomy: The length of sphincter division should match the length of the fissure to prevent recurrence from inadequate sphincter release 4

Open vs. Closed Technique

Both open and closed lateral internal sphincterotomy achieve similar healing rates, though open technique is associated with higher postoperative pain and delayed wound healing at 1 year, making closed technique preferable 1

Special Populations

• Pregnancy: Prioritize conservative measures and topical calcium channel blockers after obstetric consultation; defer surgery until postpartum unless absolutely necessary 2
• Children: Reserve surgery only for truly refractory cases after prolonged medical therapy to minimize lifelong incontinence risk 2

Algorithmic Decision Tree

1. Confirm typical posterior midline location → If lateral/atypical, stop and evaluate for IBD, infection, malignancy 2, 3
2. Initiate 2-week conservative trial (fiber, fluids, sitz baths, topical lidocaine) 2
3. If no improvement at 2 weeks, add topical calcium channel blocker (nifedipine 0.3% + lidocaine 1.5% TID or diltiazem 2% BID) 2
4. Continue pharmacologic therapy for total 6-8 weeks 1, 2
5. If fissure remains unhealed after 6-8 weeks of comprehensive medical therapy, refer for lateral internal sphincterotomy 1, 2