Never had one, yet. Every five years my GP has me drop a deuce in a box and ship it to a lab. So far, the results did not warrant a colonoscopy.
Makes me laugh when I do it. Reminds me of when I was a kid. We'd schiet in a box or bag, put on someones porch, light it on fire, then ring the bell and run.
If you are 50 and over, I would find a new doctor