Most anal fissures heal with the use of medicines or by changing your diet. However, if the anal fissure doesn't get better, you may need anal fissure surgery. The aim of surgery is similar to that of medicines - to relieve the pressure within your anus. This is usually done using a procedure called lateral internal sphincterotomy(LIS). A small cut is made in the internal sphincter muscle to stop it from going into spasm. This means you strain less when you go to the toilet and because of this, less stress is put on the fissure, giving it time to heal. The procedure is usually done under general anaesthesia. This means you will be asleep during the operation.
Attribution: BUPA