Anal fissures are caused by injury (trauma) to the anal canal. Injury can happen if:
You pass a large stool that stretches the anal canal.
You are constipated and try to pass a hard stool.
You have repeated diarrhea.
Childbirth can also cause trauma to the anal canal.
An anal fissure causes a sharp, stinging, or burning pain during a bowel movement. The pain, which can be severe, may last for a few hours.
Fissures may itch. They often bleed lightly or cause a yellowish discharge. You may see a small spot of bright red blood on toilet tissue or a few drops in the toilet bowl. The blood is separate from the stool. Very dark, tarry stools or dark red blood mixed with stool indicates some other condition, possibly inflammatory bowel disease (IBD) or colon cancer. You should contact a doctor if you have any bleeding with bowel movements.
Non-surgical treatments are recommended initially for acute and chronic anal fissures.These include topical nitroglycerin or calcium channel blockers, or injection of botulinum toxin into the anal sphincter. Other measures include warm sitz baths, topical anesthetics, high-fiber diet and stool softeners.
Surgery may be necessary if medicine fails to heal a tear (fissure) in the anus. The preferred procedure is lateral internal sphincterotomy. A doctor makes a small incision in the internal anal sphincter, one of two muscles that control the anus. This can be done as outpatient surgery under local anesthesia or general anesthesia.