James, I don't know if my experiences with colonoscopies will help you at all but here goes. I was diagonsed with Crohn's Disease when I was 19 and have had this procedure many times over the years. After 3 bowel resections and tons of prednisone and other medications I had a heart attack at age 48 which was largely due to many years of huge doses of prednisone. Since the heart attack I've had 2 colonoscopies with no problems at all. When I was diagnosed with Crohn's, colonoscopy was a new procedure and really was terrible to go thru. Over the years that has greatly improved and I now have no problem with them at all. Also, you may look into a new procedure called Virtual Colonoscopy which is non-invasive. I've just heard about it and am looking for information for myself. No sedation is needed which is probably the reason for the risk to your father. Hope this helps you out.