How Does an Anal Fissure Develop?
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Injury to the Anal Canal
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Anal fissures are tears in the rectal lining, or anal canal, that cause pain and bleeding during bowel movements. Generally, anal fissures are a result of some type of trauma to the anal canal. Trauma to the anal canal may be caused by a number of things, including passing hard stools during a bout of constipation, anal irritation resulting from frequent diarrhea, the insertion of objects or digits into the anus, anal intercourse and childbirth. These events may cause a tear, or small cut, in the sensitive lining of the lower rectum. If this tear bleeds, a small amount of blood may be expelled during a bowel movement. Future bowel movements may cause increasing pain or make the tear worse.
Excessive Sphincter Tension
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The sphincters are the two muscular rings that control the anus. Some experts theorize that excessive tension in these rings may result in the development of anal fissures. Although the external sphincter is under conscious control, the internal ring remains under constant pressure at all times. If the resting pressure of this sphincter becomes too high, spasms may result and blood flow to the area may be inhibited. This can cause irritation and swelling, and may sometimes lead to small tears in the anal canal.
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Secondary to Another Condition
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Anal fissures may develop secondary to a number of other disorders, including proctitis, cancer of the anus and tuberculosis. They are also more common following anorectal surgery, and often result from the chronic rectal irritation experienced by those with Crohn's and other inflammatory bowel diseases.
Any condition that causes a prolonged change in bowel habits may lead to the development of anal fissures, and the tearing may become cyclic. The passing of hard stools during constipation, for example, may cause a cut in the lining of the anal canal. If the constipation is treated or clears up, the anal fissure will typically heal on its own. However, if hard stools become a chronic problem, the anal lining may remain irritated, and each subsequent bowel movement can potentially cause a new tear or prevent the initial tear from healing. To prevent this cycle from occurring, the underlying medical disorder needs to be treated promptly.
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