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Break or tear in anal canal skin
An anal fissure is a break or tear in the skin of the . Anal fissures may be noticed by bright red on toilet paper and undergarments, or sometimes in the toilet. If acute they are painful after , but with chronic fissures, pain intensity often reduces and becomes cyclical.
Most anal fissures are caused by stretching of the anal 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 of the muscle which results in impaired blood supply to the anal mucosa. The result is a non-healing ulcer, which may become infected by .
In adults, fissures may be caused by , 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, , occult abscesses, leukemic infiltrates, , acquired immunodeficiency syndrome () or should be considered as possible causes. Some can promote the breakdown of tissue resulting in a fissure: , , and .
