Colon cancer (colorectal cancer) is the second most common tumor causing death in the United States, after lung cancer. Colon cancer is treatable and can be cured if it is in its early stages. Because deaths from colon cancer are preventable, doctors want to catch colon cancer before it grows too large or spreads to other organs. Screening for people who do not have signs or symptoms related to colon cancer (such as checking for blood in the stool or low blood counts) is called “screening. Screening for colon cancer is recommended for all people 50 years of age or older. Screening methods 1. Fecal occult blood test Colon cancer may cause a small amount of invisible bleeding (not visible to the naked eye). The way to check for invisible bleeding is to put a small amount of stool on a card and add a chemical solution. If the result shows invisible bleeding, then further tests are needed to find the source of the bleeding. This test is simple, but it is not always able to detect colon cancer. 2.Sigmoidoscopy The sigmoid colon is the most terminal part of the colon, near the rectum (the last section of the large intestine). Sigmoidoscopy is to cleanse the last section of the large intestine by enema, then stick the tube with light source into the rectum, and then gently enter the sigmoid colon forward to see if there is something abnormal growing in the intestinal wall of the sigmoid colon. 3. Colonoscopy If your doctor recommends a colonoscopy (for screening or sigmoidoscopy to find abnormal growths), you will need to take a liquid and a laxative to cleanse the small intestine before the test. The colonoscopy is not really painful, but it can be uncomfortable and sedative medication may be used during the procedure. The doctor will insert a colonoscope (a tube with a light source and a camera on one end) into your rectum while you are lying on your side. The pictures taken by the camera will be seen on an external monitor. The colonoscope is gently advanced as far into the deepest part of the colon as possible and continuously. If the doctor finds any suspicious abnormalities, a biopsy (tissue sample) may be performed. Colon polyps can also be removed by colonoscopy. 4. Barium enema It is an X-ray test, prepared in a similar way to a colonoscopy.