Often patients ask whether they need to do colonoscopy, do it, most of them are chronic colitis, do not do it, patients always feel uneasy in their hearts, therefore, doctors are sometimes difficult to make a decision, so the doctor’s judgment criteria to everyone, the following cases are sure to do colonoscopy, other cases by the patients themselves to decide it. 1, where the doctor suspects that there is a disease of the colon, the symptoms do not improve or even aggravated by active treatment. 2.Age over 60 years old and accompanied by diarrhea, constipation, abdominal pain and other intestinal symptoms. 3.Patients who are suspected by doctors to have intestinal tumors based on clinical manifestations. 4.Patients with lower gastrointestinal bleeding (blood in stool). 5.Patients with unexplained wasting (persistent weight loss) and loss of appetite. 6.Patients with family history of intestinal cancer who have long-term abdominal discomfort and poor therapeutic effect with long duration of disease. 7.Review of bowel cancer after surgery. 8.Patients who have not undergone colonoscopy due to changes in stool characteristics (thinning and deformation). 9.Other cases considered by the doctor to be in need of colonoscopy.