Anal fissures may be caused by an injury from a hard or large bowel movement or from frequent loose bowel movements. Uncommonly, they may also be caused by penetration of the anus during anal sex. Fissures cause the anal sphincter (the muscular ring that keeps the anus closed) to go into spasm, which worsens pain and prevents healing.
Anal fissures can occur in people of any age but are most common among infants.
(See also Overview of the Anus and Rectum Overview of the Anus and Rectum The anus is the opening at the end of the digestive tract where stool leaves the body. The rectum is the section of the digestive tract above the anus where stool is held before it passes out... read more .)
A stool softener or psyllium or increased dietary fiber may reduce the possibility of injury by hard or large bowel movements. Healing is sometimes aided by using zinc oxide ointments or glycerin suppositories that lubricate the lower rectum and soften stool.
Applying topical anesthetics (such as benzocaine or lidocaine) to the anus or soaking in a warm (not hot) sitz bath for 10 to 15 minutes after each bowel movement eases discomfort and helps increase blood flow, which promotes healing. The soaking is accomplished by squatting or sitting in a partially filled tub or using a container filled with warm water placed on the toilet bowl or commode.
To reduce anal sphincter spasms and promote healing of fissures, doctors may inject the anal sphincter with botulinum toxin or have the person apply nitroglycerin ointment or calcium channel blockers (such as nifedipine cream or diltiazem gel) to the area of the fissure.
If these measures do not work, surgery may be needed. To relieve sphincter spasms, doctors cut a portion of the internal sphincter (called internal anal sphincterotomy).