There are some symptoms that could indicate the presence of colon cancer, such as change in bowel frequency, change in stool size (thin caliber), bleeding per rectum, unexplained weight loss, and others. Unfortunately, these symptoms are neither “sensitive” (they don’t always occur even when colon cancer is present) nor “specific” (these symptoms can be associated with conditions other than colon cancer). If you have any of the above symptoms, or others that you are concerned about, ask your doctor if you need a colonoscopy or other diagnostic test. Paul Limburg MD