LIS is a quick, minimally invasive procedure typically performed as an outpatient surgery:

1. Before Procedure Evaluation:
   
   • Diagnosis is confirmed via:
     
     • Physical examination: Identifies the fissure, sentinel tag, or hypertrophied papillae.
     • Anoscopy: Visualizes the internal anal canal to confirm the fissure’s location and exclude other conditions (e.g., fistulas, hemorrhoids).
     • Anorectal manometry (rarely): Measures sphincter pressure in complex cases.
   • Blood tests ensure surgical fitness, particularly for patients with comorbidities.
   • Bowel preparation (enemas or laxatives) may be advised to reduce contamination.
   • Patients are counseled on post-operative pain, hygiene, and the small risk of incontinence.
2. Surgical Technique:
   
   • Open Lateral Internal Sphincterotomy:
     
     • Performed under general, spinal, or local anesthesia with sedation, lasting 15–30 minutes.
     • The patient is positioned in the lithotomy (legs raised) or prone position.
     • A small incision is made laterally (at the 3 or 9 o’clock position) in the anal canal, away from the fissure (typically posterior at 6 o’clock).
     • The internal anal sphincter is partially divided (up to 1 cm or the fissure’s length) to reduce pressure, leaving the external sphincter intact to preserve continence.
     • The wound is left open to heal naturally, and the fissure may be left untreated or gently curetted.
   • Closed Lateral Internal Sphincterotomy:
     
     • A similar approach but uses a small stab incision, through which a scalpel divides the sphincter under palpation guidance, minimizing tissue trauma.
     • The incision is closed with a suture, reducing bleeding risk.
     • Preferred in some centers for its cosmetic outcome and slightly lower infection risk.
   • Fissure Management:
     
     • The fissure itself is usually left to heal naturally post-sphincterotomy, though some surgeons perform a concurrent fissurectomy (excision of scar tissue) for chronic cases.
   • The procedure is typically outpatient, with same-day discharge unless complications arise.
3. After Procedure:
   
   • Patients are monitored for a few hours to ensure recovery from anesthesia and pain control.
   • Pain medications (e.g., paracetamol, ibuprofen) and stool softeners (e.g., lactulose) ease bowel movements and reduce strain.
   • Sitz baths (warm water soaks) 2–3 times daily promote healing and reduce discomfort.
   • Follow-up visits assess fissure healing and bowel function.