An anal fissure is a tear or ulcer in the lining of the anus.
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 to go into spasm, which worsens pain and prevents healing.
Fissures cause pain and bleeding, usually during or shortly after a bowel movement. The pain lasts for several minutes to several hours and then subsides until the next bowel movement. A doctor diagnoses a fissure by gently inspecting the anus.
A stool softener or psyllium or increased dietary fiber may reduce the possibility of reinjury by hard or large bowel movements. Healing is sometimes aided by use of protective zinc oxide ointments or bland suppositories (such as glycerin) that lubricate the lower rectum and soften stool. Anesthetics applied to the anus (such as benzocaine or lidocaine) and a warm sitz bath for 10 to 15 minutes after each bowel movement eases discomfort and helps increase blood flow, which promotes healing.
Treatments to reduce sphincter spasm and promote healing of fissures include injecting the sphincter with botulinum toxin and applying nitroglycerin ointment or calcium channel blockers to the area of the fissure.
If these measures do not work, surgery may be needed. Sphincter spasm can be relieved by cutting a portion of the internal sphincter (internal anal sphincterotomy). The anal canal can also be stretched (controlled anal dilation).
Last full review/revision May 2012 by Parswa Ansari, MD