The causes of bright red blood in the stool are usually seen in rectal and anal canal diseases, which can be benign or malignant, including hemorrhoids and tumor diseases, as follows: 1. 2. Neoplastic diseases: Especially, you need to be alert to neoplastic diseases, such as polyps or villous tubular adenomas, or even intestinal cancer in severe cases, which usually require timely surgical removal and pathological examination to exclude the possibility of malignancy. If malignancy is confirmed, it is usually necessary to add radical treatment of intestinal cancer with postoperative comprehensive treatment. If the gastrointestinal bleeding is in the upper gastrointestinal tract or colon cavity, the blood stays in the intestinal cavity because it is far from the anus, and when it is oxidized and discharged, it is usually black stool or dark red blood stool.