An anal fissure is a small tear or cut in the lining of the anus, often caused by passing hard or large stools. It can lead to pain, discomfort, and bleeding during or after bowel movements. Although fissures are usually small, they can cause significant discomfort if not treated properly.

In some cases, fissures may become chronic, leading to repeated pain and difficulty in healing due to muscle spasm in the anal region.