How anal fissures are caused
Extreme constipation or diarrhea, usually combined with nervous tension over a prolonged period of time, can cause abrasions of the anus, which are simple fissures such a tear or ulcers on the anal verge.
In the case of constipation, it is usually caused by the passage of hard and dry stools that tear the inside of the anus during defecation. While in case of diarrhea, it is usually caused by overuse and excessive wiping of an irritated anal canal.
In some patients, the anal fissure does not heal and becomes a painful sore that is constantly re-injured or torn with each defecation. The anal fissure usually develops a white fibrous base over time. In addition, an outer skin pocket on the anus called a thymus may develop, and an enlarged nipple on the upper border of the anus.
Fragments of undigested material (e.g., pebbles, small pieces of corn and sunflower seed shells) may pass through the anus in a patient, tearing the skin of the anus and causing an anal fissure. Anal stretch marks can also be secondary symptoms from an orthopedic surgery, proctitis, tuberculosis or anal cancer.