This prospective randomized controlled trial compares three lateral internal sphincterotomy (LIS) techniques in patients with chronic anal fissure refractory to medical treatment: (1) Spasm-Controlled LIS (serial small sphincterotomies using an anal calibrator until 30 mm anal caliber is achieved, under local anesthesia plus sedation), (2) LIS up to the Fissure Apex (spinal or general anesthesia), and (3) LIS up to the Dentate Line (spinal or general anesthesia). The primary outcomes are fissure healing rate and fecal incontinence incidence at 12 months, assessed using the Wexner Incontinence Score. Secondary outcomes include postoperative pain (VAS), recurrence rate, patient satisfaction, and complications. A total of 150 patients (50 per group) will be enrolled and followed for 12 months.
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)
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