Colonoscopy

A colonoscopy is the test in which a flexible tube with a camera at the tip is passed inside to look at the rectum, the last stretch of the intestine, and the colon, which is the large intestine. The camera shows the inner lining, the layer that coats that wall from the inside, a lot like running a camera down a pipe and working along it section by section to see how it looks in there.

While the tube is inside, more can be done than just looking: tiny pieces of tissue can be snipped out, which are called biopsies, or polyps can be removed. And the same colonoscopy gets ordered for two reasons that are not the same thing. Sometimes it is done in someone who feels nothing at all, and then it is screening; other times it is done because there is a specific reason that prompted it, and then it is a diagnostic test. The procedure is the same. What changes is why it was ordered.