The need for colonoscopy is based on the patient’s symptoms, age and family history. For example, patients with prolonged increase in the number of stools, stools with pus or blood, stools with pus, or abdominal pain, pain and refusal to press, weight loss and family history of colorectal cancer need to undergo colonoscopy. Through colonoscopy, we can observe whether the intestinal mucosa is congested, edematous and erosion, whether there are occupying lesions, such as polyps, and whether there is a possibility of cancer. The colonoscopy is a good way to make an assessment to guide the next specific treatment. If the patient cannot tolerate a normal colonoscopy, painless colonoscopy is also an option, but there is a risk of anesthesia.