Colonoscopy can detect colon and rectal cancers. By conducting a colonoscopy, it can be determined whether a space-occupying lesion is in the colon or the rectum. In the workplace, it can also confirm the distance from the anus in centimeters, to guide the next steps of surgical treatment. If a colon or rectal tumor is found during colonoscopy, a pathological biopsy may be needed. Combined with the pathological biopsy, a diagnosis can be made whether the patient has colon cancer or rectal cancer. At the same time, colonoscopy can also detect other diseases, such as colon polyps, ulcerative colitis, Crohn's disease of the colon, and so on.