An anal fissure is a small tear in the lining of your bottom (anus).
Symptoms of an anal fissure include a sharp pain and bleeding when you poo.
An anal fissure usually heals on its own. Treatment includes avoiding constipation, and medicines to reduce pain and speed up healing.
Anal fissures are usually caused by constipation. Other causes include long-lasting diarrhoea, inflammatory bowel disease, pregnancy and childbirth.