What are the causes of Anal Fissure?

Anal fissure is caused by anything which would cause injury to the anal canal. These could be either extreme constipation or diarrhea, usually combined with nervous tension over a prolonged period of time, may produce anal abrasions, simple slit-like fissures, or acute ulcers at the anal verge. With constipation, this condition is usually caused by the passage of a hard dry stool that tears the anal lining upon defecation. With diarrhea, this condition is usually caused by an over use and over-wiping of an inflamed anal canal.

In some patients, the anal fissure doesn’t heal and becomes a painful sore that is constantly re-injured or torn with each bowel movement. The fissure usually develops a white fibrous base over time. Additionally, an external anal skin tag called a sentinel pile, and an enlarged papillae at the superior anal margin may develop.

Human body has a spontaneous reflex in which any pain in the sensitive lower part of anus causes reflex contraction (spasm) of the sphincter muscle. So the tear caused in the lower anal canal leads to sphincter muscle spasm. The resultant sphincter muscle spasm makes passage of even normal stools difficult and painful which further increases the spasm of sphincter muscle thereby starting a vicious cycle in which pain and sphincter muscle spasm increasing each other.