Sometimes it is necessary for the doctor to introduce air into the colon to improve visibility. Before having a colonoscopy the colon must be clear of stool so that the doctor has good visibility. The patient must undergo a preparation that may include a liquid diet, enema, and laxatives to clear stool from the colon. The technique for bowel preparation may differ by health facility. A sedative is given before a person undergoes colonoscopy.
Many people sleep through the whole procedure and feel little or no discomfort.
Occasionally, the insertion of air during the procedure may cause the same kind of discomfort as gas pain. If a polyp is found, removal through the colonoscope may be sufficient, although surgery may be recommended for some patients. If cancer is found at examination, the doctor will recommend colorectal surgery. Removing the entire colon is the only way to completely prevent the development of another colon cancer. Proctocolectomy and colectomy, demonstrated below, show the difference between having both colon and rectum removed and having just colon removed, while the rectum remains intact.