Blood in stool for 6 years is an abnormal manifestation, most likely caused by internal hemorrhoids, anal fissure and colorectal cancer. 1. Internal hemorrhoids: clinical manifestations are bleeding and prolapse. Often manifested as intermittent fresh blood after stool. The most common sites are truncus 3, 7, 11 bells and whistles. 2. Anal fissure: clinical manifestations are pain, constipation and bleeding. The pain is severe, including pain during defecation and sphincter contracture pain after defecation. A small amount of blood is often found during defecation. 3. Colon and rectal cancer: colon cancer mainly manifests as change of bowel habit, including constipation, diarrhea, blood in stool, etc. Rectal cancer mainly manifests as symptoms of rectal irritation, including urgency and heaviness, change of bowel habit, etc. When the cancer breaks down, blood in stool may appear. Blood in stool for 6 years may also be caused by other causes such as colorectal polyps or vascular diseases. If there is blood in stool, one should be admitted to hospital in time to clarify the cause of the blood and be treated under the guidance of doctor.