A colonoscopy is a test in which a thin, flexible tube with a light and a video camera on its tip is placed in your colon to search for polyps. It’s the most effective way to detect them. Your treatment team will prescribe a clear-liquid diet and medication to clear out your bowel during the 24 hours before the procedure. You’ll also be sedated during the exam. Your doctor can usually remove any polyps that are detected, which then go to a pathologist (a doctor who specializes in diagnosing disease) for examination and analysis.
There are other screening tests for colon cancer in addition to colonoscopy, listed below. You should note that these tests are not as thorough as a colonoscopy. If polyps or tumors are suspected based on these tests, you will still need to have a colonoscopy.
Flexible sigmoidoscopy is much like colonoscopy, but looks at only part of the colon and rectum. If polyps are found, they may be removed during the test, or you may need to have a colonoscopy later. Bowel prep may be required, but is not as extensive as the one used for colonoscopy. Most people do not need to be sedated during this test. If polyps or suspicious areas are seen, a colonoscopy will be needed to look at the rest of the colon. Flexible sigmoidoscopy must be done every five years.
Fecal Immunochemical Test
A fecal immunochemical test (FIT) also screens for colon cancer by detecting blood in the stool. Unlike more traditional fecal occult blood testing, you don’t have to follow a special diet before the test. FIT reacts to a part of the hemoglobin molecule (a protein found in red blood cells). If an abnormality is detected, you may need to undergo a colonoscopy for further management. This test is also called immunochemical fecal occult blood test.
Fecal Occult Blood Test
Because colon or rectal bleeding can be a possible sign of colon cancer, a fecal (stool) occult blood test may detect small amounts of blood in your stool that are not otherwise visible. The test works like this: For three consecutive days, you’ll place small stool samples on chemically treated cards. You’ll send those cards to a lab for testing. During this time, you’ll have to follow a special diet to ensure accurate test results. If an abnormality is detected, you may need to undergo a colonoscopy for further management.
Stool DNA Test
A stool DNA test also screens for cancer by looking for gene changes and blood in your stool sample. Like FIT, you do not need to follow a specific diet prior to submitting a sample. And like the other stool tests, if an abnormality is detected, you may need to undergo a colonoscopy for further management.
Double-contrast Barium Enema
Double-contrast barium enema is a type of x-ray test. It involves putting a liquid called barium into the rectum, which spreads through the colon. Air is then pumped in to spread the barium in a thin, smooth layer to show better detail. Then x-rays are taken. It requires bowel prep, but no sedation. If polyps or suspicious areas are seen on the test, a follow-up colonoscopy will be needed. Barium enemas also need to be repeated every five years.
Virtual Colonoscopy is a scan of the colon and rectum that produces detailed cross-sectional images so the doctor can look for polyps or cancer. It requires bowel prep, but no sedation. Air is pumped into the rectum and colon, and then a CT scanner is used to take images of the colon. If something is seen that may need to be biopsied, a follow-up colonoscopy will be needed. CT colonography must be done every five years.