There are many reasons for pain in the stomach and blood in the stool, the first one may be colitis, especially ulcerative colitis, which can lead to pain in the lower abdomen, the pain is not severe, sometimes the stool will be pus and blood, this situation should be promptly checked, if necessary, anoscopy or proctoscopy to clarify the cause. The second, there may be intestinal spasm, after eating unclean food, will lead to inflammation of the gastrointestinal tract, accompanied by spasm, which will cause pain in the small stomach, and sometimes there is blood in the stool. Third, there may be other diseases such as rectal malignancy or rectal adenoma, because adenomas or tumors invade the mucosa and submucosal blood vessels causing bleeding, which sometimes also causes pain in the small stomach. Therefore, there are many causes, and a colonoscopy or abdominal CT examination should be performed in time to clarify the diagnosis.