Blood in the stool is one of the most common symptoms of the digestive system. If there is blood at the head of the stool then the site of bleeding is considered to be in the rectum. If there is blood on the surface of the stool with groove-like changes, the site of bleeding is considered to be the rectum and sigmoid colon. If there is blood at the end of the stool or if there is blood on the stool paper, consider bleeding from the anal canal and hemorrhoids, most commonly fissures and hemorrhoids. If the blood is mixed with stool, then the bleeding is considered to be above the sigmoid colon, and organic lesions in the descending, transverse, or ascending colon, such as polyps and tumors, can cause blood in the stool. To make a definite diagnosis, colonoscopy is needed to find out whether there are organic lesions in the intestine, and to observe whether there are hemorrhoids and anal fissures in the anus and rectum.