Fissure is a crack around the anal region. It typically causes severe pain and bleeding during bowel movements. The reason for fissure is trauma inside the inner lining of the anus. A hard bowel is responsible for fissure but chronic diarrhea can also be the cause. Do not leave it untreated. Delay in diagnosis may lead to an acute fissure becoming a chronic one and become more difficult to treat. If anal fissure is not diagnosed, it may also allow other conditions to go undetected and untreated, such as serious infections or even cancer.