A fissure is a tear in the skin of the anus, usually caused when a large, hard stool overstretches the anal opening and damages the fragile skin. It is often associated with constipation, and less frequently, with chronic diarrhea, inflammatory bowel disease or sexually transmitted diseases (STDs) that involve the anus and rectum. Sometimes, the cause is unknown.
Anal fissures can be acute or chronic. An acute fissure is a superficial tear and a short-term condition. A chronic fissure is deeper and may expose underlying muscle. When lifestyle and diet changes and medication fail, and the condition becomes chronic, surgery is recommended. A lateral anal sphincterotomy is the surgical procedure most commonly used to repair a fissure.
Anal sphincterotomy is a treatment for people who suffer from anal fissures. A sphincterotomy is used as a last resort for this condition, and people who experience anal fissures are usually encouraged to try a high-fiber diet, stool softeners, or Botox first. If symptoms are severe or don’t respond to these treatments, a sphincterotomy may be offered.
During the procedure, the surgeon makes a small incision in the internal anal sphincter. The aim of this incision is to release the tension of the sphincter. When the pressure is too high, anal fissures are unable to heal. A sphincterotomy can be performed under local anesthesia which involves injecting the immediate area with a numbing agent or spinal anesthesia, which numbs the entire lower body. In some cases, general anesthesia may be used, which renders the patient unconscious. The choice of anesthesia depends on patient and physician preference, the patient's health, and the standard practice of the particular facility.
REFERENCES
https://www.healthline.com/health/sphincterotomy
https://www.webmd.com/digestive-disorders/anal-fissure-treatment#1