Indications for Lateral Internal Sphincterotomy
Lateral internal sphincterotomy is indicated for chronic anal fissures that have failed 6-8 weeks of conservative medical management, including topical calcium channel blockers or nitroglycerin, and represents the gold standard surgical treatment with superior long-term healing rates compared to medical therapy. 1
Primary Indication
Chronic anal fissure unresponsive to medical therapy is the definitive indication for lateral internal sphincterotomy. 1 The procedure should only be considered after documented failure of:
- At least 6-8 weeks of conservative management including fiber supplementation (25-30g daily), adequate fluid intake, warm sitz baths, and topical analgesics 1, 2
- Topical calcium channel blockers (diltiazem or nifedipine with 65-95% healing rates) or glyceryl trinitrate ointment (25-50% healing rates) 1
- Botulinum toxin injection may be attempted before surgery, with 75-95% cure rates 1
Critical Exclusions Before Surgery
Lateral internal sphincterotomy is absolutely contraindicated in acute anal fissures and should never be performed without ruling out atypical pathology. 2
Mandatory Pre-Surgical Evaluation:
- Fissure location must be typical (posterior midline in 90% of cases, or anterior midline in 10% of women vs 1% of men) 3
- Lateral or multiple fissures mandate urgent workup for Crohn's disease, HIV/AIDS, ulcerative colitis, tuberculosis, syphilis, leukemia, or malignancy before any surgical intervention 4, 3
- Atypical fissures require endoscopy, CT scan, MRI, or endoanal ultrasound to exclude underlying serious pathology 3
Surgical Timing and Approach
Surgery should be performed only in the chronic phase, never acutely, with the procedure targeting the length of sphincter division to match the fissure length. 2, 5
Technical Considerations:
- The sphincterotomy length should equal the fissure length to minimize incontinence risk while ensuring adequate sphincter relaxation 5
- Contralateral sphincterotomy is preferred when performing repeat procedures 5
- Minimal sphincterotomy techniques that divide only the fibrotic portion of the internal anal sphincter show excellent outcomes with 98% healing and only 0.4% gas incontinence 6
Expected Outcomes and Complications
Lateral internal sphincterotomy achieves 98-100% healing rates with low recurrence (1.3-4%) but carries a small permanent incontinence risk. 6, 5, 7
Complication Profile:
- Wound-related complications (fistula, bleeding, abscess, non-healing wound) occur in up to 3% of patients 2
- Minor incontinence (gas or seepage) occurs in 0.4-4% of patients with modern minimal techniques 6, 5
- Long-term fecal continence is preserved in the vast majority of patients at 6-year follow-up, with no difference in incontinence scores compared to medical therapy 7
- Patient satisfaction is superior to medical therapy, with 92-100% reporting they would choose the same treatment again 5, 7
Contraindications
Manual anal dilatation is absolutely contraindicated due to unacceptably high permanent incontinence rates of 10-30%. 2, 1 This historical practice has been abandoned in favor of lateral internal sphincterotomy, which demonstrates superior outcomes with controlled sphincter division 2.
Recurrent Fissures After Prior Surgery
Repeat lateral internal sphincterotomy is highly effective for surgically recurrent chronic anal fissures, with 98% healing and minimal incontinence risk when performed contralaterally. 5 This confirms that inadequate initial sphincter division, rather than excessive cutting, is often the cause of surgical failure 5.