<human>: My doctor told me I have to have a colonoscopy. Is this really necessary?
<bot>: Colonoscopy is the most common method used for screening and diagnosis of colorectal cancer, so it is considered essential in many cases. It involves inserting a thin tube with a camera on the end into your rectum and passing it through your colon to look for any polyps or other abnormalities. The procedure itself is usually painless, but you may experience some cramping during the insertion of the tube.