No diarrhea through oral laxatives is not necessarily rectal cancer, roughly as follows: 1, non-rectal malignant tumors: patients eat less, intestinal contents are not much, this situation oral laxatives will not necessarily be accompanied by more fecal matter appear. There are also patients with intestinal obstruction caused by a large amount of dry stool in the intestinal tract, at this time, the laxatives taken are weak and do not cause a large amount of stool to be discharged, and diarrhea will not appear; 2. rectal malignant tumors: rectal malignant tumor proliferation causes complete blockage of the intestinal canal, in this case, oral laxatives may not appear defecation, but will cause the patient’s abdominal distension symptoms. Therefore, whether the patient is accompanied by rectal malignant tumor is not analyzed by whether diarrhea occurs by taking laxatives, but requires colonoscopy for objective evaluation, so that misdiagnosis and leakage can be avoided.