Definition of Anal fissure:

An anal fissure is a small split or tear in the thin moist tissue (mucosa) lining the lower rectum (anus).

Causes, incidence, and risk factors:

Anal fissures are extremely common in young infants but may occur at any age. Studies suggest 80% of infants will have had an anal fissure by the end of the first year. The rate of anal fissures decreases rapidly with age. Fissures are much less common among school-aged children than infants.

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.

Anal fissures are also common in women after childbirth and persons with Crohn's disease.