The pain in the small of the stomach, accompanied by blood in the stool, may be caused by ulcerative colitis. Because of the patient’s prolonged colitis, resulting in local mucosal ulceration, caused by blood in the stool, as well as the symptoms of abdominal pain. Detailed examinations, such as colonoscopy or ultrasound examination of the abdomen, should be conducted to clarify the diagnosis, and after the diagnosis is clear, symptomatic treatment should be given in a timely manner. Secondly, it may be caused by colon cancer, which is a symptom of blood in stool and abdominal pain caused by cancer cells infiltrating the inner wall of the colon and bleeding. The diagnosis can be clarified through colonoscopy, and if necessary, a small amount of lesion tissue can be cut for pathological examination. There may also be infectious diseases of the intestinal tract such as bacterial dysentery and amoebic enteropathy.