Comparison of Lateral Internal Sphincterotomy Techniques for Chronic Anal Fissure

Chronic anal fissure (CAF) is a longitudinal tear in the anoderm persisting for more than 8 weeks. Lateral internal sphincterotomy (LIS) is the gold-standard surgical treatment for CAF refractory to medical management, achieving healing rates of 90-98%. However, postoperative fecal incontinence remains its most significant complication, with rates ranging from 1-15% for permanent incontinence.

To reduce incontinence risk, various techniques limiting the extent of sphincterotomy have been proposed. Mentes et al. (2005) demonstrated that LIS up to the dentate line provided faster healing but caused significant continence disturbance, while LIS limited to the fissure apex was associated with lower incontinence but a higher treatment failure rate. Mentes et al. (2008) subsequently showed that spasm-controlled LIS using anal calibrators achieved faster pain relief with lower early incontinence rates compared to fissure apex sphincterotomy. However, no randomized trial has compared all three techniques simultaneously.

This single-center, prospective, three-arm RCT will enroll 150 adult patients with CAF refractory to at least 6 weeks of medical treatment. Patients will be randomized (1:1:1) to one of three groups: Group 1 (Spasm-Controlled LIS): serial small sphincterotomies under local anesthesia plus sedation until anal caliber reaches 30 mm using an anal calibrator. Group 2 (LIS up to Fissure Apex): open sphincterotomy extended to the proximal end of the fissure under spinal or general anesthesia. Group 3 (LIS up to Dentate Line): open sphincterotomy extended to the dentate line under spinal or general anesthesia.

All procedures will use the open technique with patients in lithotomy position. Randomization will be performed using computer-generated block randomization (block size 6), stratified by sex and fissure location. Outcome assessors will be blinded to group allocation.

Patients will be evaluated preoperatively and at postoperative day 1, week 1, week 2, month 1, month 2, month 6, and month 12. The Wexner (Cleveland Clinic) Incontinence Score will be used to assess continence at each visit. Fissure healing will be defined as complete epithelialization with no symptoms. Statistical analysis will follow the intention-to-treat principle, with Bonferroni correction applied for multiple comparisons.

• Spasm-Controlled Lateral Internal Sphincterotomy (Procedure), also known as Calibrated LIS: Serial small open sphincterotomies under local anesthesia plus IV sedation using an anal calibrator until anal caliber of 30 mm is achieved.
• Lateral Internal Sphincterotomy up to Fissure Apex (Procedure), also known as Tailored LIS: Open LIS extended to the proximal end of the fissure under spinal or general anesthesia.
• Lateral Internal Sphincterotomy up to Dentate Line (Procedure), also known as Traditional LIS / Classical LIS: Open LIS extended to the level of the dentate line under spinal or general anesthesia.

Primary outcomes

• Fissure Healing Rate [12 months]: Complete epithelialization of the anal fissure with no symptoms at 12 months postoperatively, assessed by clinical examination.
• Fecal Incontinence Incidence [12 months]: Incidence of de novo fecal incontinence assessed using the Wexner (Cleveland Clinic) Incontinence Score. A score increase of ≥1 point from preoperative baseline is defined as de novo incontinence.

Secondary outcomes

• Postoperative Pain Score [Day 1, Week 1, Week 2, Month 1, Month 2, Month 6, Month 12]: Pain assessed using the Visual Analog Scale (VAS, 0-10) at each follow-up visit.
• Recurrence Rate [Month 6 and Month 12]: Proportion of patients with recurrence of anal fissure after an initial healing period.
• Patient Satisfaction [Month 2, Month 6, Month 12]: Patient satisfaction assessed on a numeric scale (0-10) at follow-up visits.
• Postoperative Complications [12 months]: Rate of surgical complications including bleeding, hematoma, infection, abscess, and fistula.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Age 18 years or older
* Diagnosis of chronic anal fissure (duration ≥8 weeks)
* Failure to heal after at least 6 weeks of appropriate medical treatment (topical agents, fiber supplementation, sitz baths)
* Complete preoperative fecal continence (Wexner Incontinence Score = 0)
* Primary anal fissure (posterior or anterior midline location)
* Written informed consent

Exclusion Criteria:

* Any degree of preoperative fecal incontinence
* Secondary anal fissure (associated with Crohn's disease, tuberculosis, HIV, syphilis, or other systemic conditions)
* Previous anal sphincter surgery
* History of obstetric sphincter injury
* Active anorectal infection (abscess or fistula)
* Pregnancy or breastfeeding
* Uncorrectable coagulopathy or current anticoagulant use
* Inability to cooperate with study procedures or attend follow-up visits

• Results publication: Elsebae MM. A study of fecal incontinence in patients with chronic anal fissure: prospective, randomized, controlled trial of the extent of internal anal sphincter division during lateral sphincterotomy. World J Surg. 2007 Oct;31(10):2052-7. doi: 10.1007/s00268-007-9177-1. PMID 17665247
• Results publication: Mentes BB, Guner MK, Leventoglu S, Akyurek N. Fine-tuning of the extent of lateral internal sphincterotomy: spasm-controlled vs. up to the fissure apex. Dis Colon Rectum. 2008 Jan;51(1):128-33. doi: 10.1007/s10350-007-9121-3. Epub 2007 Dec 18. PMID 18085337
• Results publication: Mentes BB, Ege B, Leventoglu S, Oguz M, Karadag A. Extent of lateral internal sphincterotomy: up to the dentate line or up to the fissure apex? Dis Colon Rectum. 2005 Feb;48(2):365-70. doi: 10.1007/s10350-004-0812-8. PMID 15711861