I’d be very surprised to learn that colonoscopies themselves are useless considering that we know polyps lead to cancer and are cancerous and we are visually identifying and removing them with the good ole rectal camera device.

Also colonoscopies aren’t just used for cancer prevention and are used on IBD to determine the condition of the disease. Basically any time you have a problem with your lower intestine or rectum, they’re a cheap and effective way to find out what’s going on.