Lateral Internal Sphincterotomy

Alexandra W. Elias, MD, Matthew R. Albert, MD

Video Summary

The patient has a chronic anal fissure refractory to medical management. A perianal block is performed. The anal canal is inspected. The intersphincteric groove is identified and incised. The internal sphincter muscle is sharply cut to the level of the dentate line. The incision is closed.


Teaching Points

  1. Patient preparation: enemas
  2. Patient position: lithotomy
  3. Critical steps:
    1. Perform a perianal block.
    2. Inspect the anal canal.
    3. Place a Pratt retractor.
    4. Palpate and use a hemostat to help identify the left intersphincteric groove.
    5. Make an incision in the left intersphincteric groove with electrocautery.
    6. Use a hemostat to isolate the internal sphincter muscle.
    7. Sharply cut the internal sphincter muscle to the level of the dentate line.
    8. Close the wound.
  4. Technical pearls/tips:
    1. When you sharply cut the internal sphincter muscle to the level of the dentate line, slide scissors into the space medial to the muscle, slightly open the scissors, pull back, and slide forward such that the muscle is between the blades of the scissors. Cut. Using your finger to palpate the distal aspect of the muscle, repeat the move with the scissors until you feel the muscle release to the level of the dentate line.
  5. Potential areas for injury/complication:
    1. Do not cut the external sphincter.
    2. End your cut of the internal sphincter at the dentate line.
Last updated: July 22, 2022