An anal fissure is a tear in the lining of your anus or anal canal, the lowest part of your intestinal tract. It can make bowel movements very painful, and can even cause pain that lasts for hours after you've gone to the bathroom. You may even try to avoid the bathroom to prevent the pain.
An anal fissure is usually a short-term (or acute) problem, with symptoms that last 6 weeks or less. It's considered chronic when symptoms last for more than 6 weeks. Chronic anal fissures may be harder to treat and may be a symptom of another condition, such as Crohn's disease or ulcerative colitis.