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An anal fissure or rectal fissure is a break or tear in the skin of the anal canal. Anal fissures may be noticed by bright red anal bleeding on toilet paper, sometimes in the toilet. If acute they may cause pain after defecation but with chronic fissures pain intensity is often less. Anal fissures usually extend from the anal opening and are usually located posteriorly in the midline, probably because of the relatively unsupported nature and poor perfusion of the anal wall in that location. Fissure depth may be superficial or sometimes down to the underlying sphincter muscle. == Causes == Most anal fissures are caused by stretching of the anal mucosa beyond its capability. Superficial or shallow anal fissures look much like a paper cut, and may be hard to detect upon visual inspection, they will generally self-heal within a couple of weeks. However, some anal fissures become chronic and deep and will not heal. The most common cause of non-healing is spasming of the internal anal sphincter muscle which results in impaired blood supply to the anal mucosa. The result is a non-healing ulcer, which may become infected by fecal bacteria. In adults, fissures may be caused by constipation, the passing of large, hard stools, or by prolonged diarrhea. In older adults, anal fissures may be caused by decreased blood flow to the area. When fissures are found laterally, tuberculosis, occult abscesses, leukemic infiltrates, carcinoma, acquired immunodeficiency syndrome (AIDS) or inflammatory bowel disease should be considered as causes.〔(【引用サイトリンク】 url = http://www.aafp.org/afp/2001/0701/p77.html )〕 Some sexually transmitted infections can promote the breakdown of tissue resulting in a fissure. Examples of sexually transmitted infections that may affect the anorectal area are syphilis, herpes, chlamydia and human papilloma virus.〔(【引用サイトリンク】 url = http://www.nhs.uk/Conditions/Anal-fissure/Pages/Causes.aspx )〕 Other common causes of anal fissures include: * childbirth trauma in women * Sexual Activities * Crohn's disease 〔 * ulcerative colitis〔http://my.clevelandclinic.org/disorders/anal_fissures/hic_anal_fissures.aspx〕 * poor toileting in young children. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Anal fissure」の詳細全文を読む スポンサード リンク
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