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Lateral Internal Sphincterotomy

Lateral internal sphincterotomy (LIS) is a surgical procedure used to treat chronic anal fissures by making a small incision in the internal anal sphincter. This reduces muscle tension, allowing the fissure to heal while improving blood flow to the area. LIS has a high success rate, though minor risks such as temporary incontinence may occur.

Lateral internal sphincterotomy showing separation of the skin from the internal anal sphincter muscle

Lateral Sphincterotomy, separating skin from IAS muscle

Image Credit: Surgery E-learning, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons

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