A colonoscopy allows doctors to examine the inner lining of the colon and rectum. It is performed using a colonoscope. Health professionals can view images of the colon on a display monitor to check for abnormalities or signs of disease. Colonoscopies are used mainly for screening for colon cancer and are recommended for adults starting at age 45 to 50 and then periodically after that, depending on individual risk factors and findings. This procedure can also help diagnose causes of unexplained bowel habit changes, abdominal pain, rectal bleeding, and weight loss. During a colonoscopy, doctors can also remove polyps or other types of abnormal tissue for further analysis and take biopsies if needed. Preparing for a colonoscopy typically involves following a special diet and taking laxatives to ensure the colon is empty.