Heredity plays a role in what diseases we "may" get, but knowing your grandfather died of colon cancer puts you one step ahead of the game. If you haven't started getting your colonoscopies at age 50...it's time to start. We all need to start at age 50 and this is to catch everything very early so that we don't end up with cancer. Just stay on top of this just like you are with your ovarian cancer. See a Gastroenterolgist so you can schedule a colonoscopy and if nothing is found, you won't need another one for 5 years...just like all the rest of us. Normally after 50 when we have a colonoscopy they may find some polyps (very common) which they remove during the procedure, but this means they are catching things very early. A colonoscopy allows the specialist to actually view the colon and see if there are any abnormalities in the lining, and if so they can prevent it from going and further. Constipation doesn't cause cancer, but be careful you're not eating too much fiber as this will cause constipation as well. When they do the CT of your abdomen, if there is a big abnormality in your colon they will see it, but you don't want to wait until something is big enough to be seen on a CT scan. I hope this helps and take care.