Young people need to undergo colonoscopy. Colonoscopy can determine various diseases of the intestinal tract, especially for the diagnosis of intestinal tumors. Intestinal tumor is a malignant disease, which has become younger in recent years, and even some young people may suffer from intestinal tumor due to various reasons. Once young people have recurrent abdominal pain, blood in stool, and difficulty in defecation, they can be considered for colonoscopy. Colonoscopy can observe the condition of intestinal mucosa and surgical removal can be performed at the same time when polyp phenomenon is found during the examination. When different substances are found, biopsies can also be extracted for pathological examination. However, some young people have abdominal symptoms due to acute enteritis, hemorrhoids and other diseases. In this case, there is no need to perform colonoscopy to confirm the diagnosis, as routine stool and perianal examination can help diagnose the disease.