I would like a professional opinion on a topic. If you don't need it, why have it done? Colonoscopy???????

If one dr tells you that you need to have it done because you are over 50 is that a logical reason to have it done? I am specifically referring to the famous colonoscopy. There are risks like in anything else. If nothing is wrong why have the test because of the age factor? The general physician says no do not have this test done unless you are haveing problems. I would like an honest opinion. Thank you