Colon cancer screening should be started at age 50, assuming there is no family history of colon cancer which may indicate a necessity to begin screening earlier, and assuming there are no symptoms such as rectal bleeding. Although hemorrhoids may occasionally bleed, unless the physician on examination can actually see the site of the bleeding, no assumption should ever be made that the bleeding is only from hemorrhoids. Hemorrhoids are so common that it is possible for the bleeding to be coming from colon cancer or a polyp that may eventually may become cancerous. Colonoscopy is the gold standard test to tell if there is a polyp or cancer in the colon. Early diagnosis and treatment is necessary for cure of the cancer, or to allow removal of the polyp to prevent cancer.
Do not settle for tests which are not as sensitive. Hemoccult test (yearly checking the stool for blood) is good only to detect bleeding for the times checked...colon cancer or polyps don't bleed every day.
Colon cancer can occur anywhere in the colon, and sigmoidoscopy only looks at about a third of the colon. Many cancers are found throughout the colon.
Colon cancer is one of the most preventable cancers...please discuss screening with your primary care doctor.