A colonoscopy is a diagnostic modality that examines the large intestine and the interior of the colon for lesions, allowing for the examination of structures and changes throughout the interior of the intestines. During a colonoscopy the rectum, sigmoid colon, descending colon, transverse colon, ascending colon and terminal ileum are accessed through the anus. The colonoscopy examines the interior of the large intestine and the terminal small intestine, and can visually detect intestinal bleeding, inflammation, ulcers, polyps, tumors, etc. A biopsy or removal of colorectal polyps can be taken if needed. It should be noted that, the anorectal stenosis when the colonoscope can not be inserted or peritoneal irritation, contraindicated for colonoscopy. If discomfort occurs, it is recommended to consult a doctor in a timely manner, under the guidance of the doctor for targeted treatment.