Colonoscopy and Colon Cancer Screening
Screening means looking for a health problem before you have symptoms. During screening for colorectal cancer, your healthcare provider may ask about your health history, examine you, or do testing.
Types of Colon Screening
Fecal occult blood test (FOBT) or fecal immunochemical test (FIT)
These tests check for blood in stool that you can’t see (hidden or occult blood). Hidden blood may be a sign of colon polyps or cancer. A small sample of stool is tested for blood in a laboratory. Most often, you collect this sample at home using a kit your healthcare provider gives you. Follow the instructions carefully for using this kit. You might need to not eat certain foods and not take certain medicines before the test, as directed.
Stool DNA test
This test looks for DNA changes in cells in the stool. These DNA changes might be signs of cancer. It also looks for hidden blood in stool. For this test, you collect an entire bowel movement. This is done using a special container put in the toilet. The sample is then sent to a lab for testing.
Barium enema with contrast (double-contrast barium enema)
This test uses X-rays to create images of the entire colon and rectum. The day before this test, you will need to do a bowel prep to clean out the colon and rectum. A bowel prep is a liquid diet plus strong laxatives or enemas. You will be awake for the test, but you may be given medicine to help you relax. At the start of the test, a healthcare provider who specializes in imaging tests (radiologist) places a soft tube into the rectum. The tube is used to fill the colon with a contrast liquid (barium) and air. This can be uncomfortable for some people. The liquid helps the colon show up clearly on the X-rays. Because the test uses X-rays, it exposes you to a small amount of radiation.
This test can be used to find and remove polyps anywhere in the colon or rectum. The day before the test, you will do a bowel prep. This is a liquid diet plus a strong laxative solution or an enema. The bowel prep will cleanse your colon. You will be given instructions for this. Just before the test, you are given a medicine to make you sleepy. Then, a long, flexible, lighted tube called a colonoscope is gently inserted into the rectum and guided through the entire colon. Images of the colon are viewed on a video screen. Any polyps that are found are removed and sent to a lab for testing. If a polyp can’t be removed, a sample of tissue is taken and the polyp might be removed later during surgery. You will need to bring someone with you to drive you home after this test. Colonoscopy is the only screening test that lets your healthcare provider see the entire colon and rectum. This test also lets your healthcare provider remove any pieces of tissue that need to be looked at by a lab. If something suspicious is found using any other tests, you will likely need a colonoscopy.
This exam is also called a CT colonography. It uses a series of X-ray photographs to create a 3-D view of the colon and rectum. The day before the test, you will need to do a bowel prep to clean out your colon. Your healthcare provider will give you instructions on how to do this. During the procedure, you will lie on a table that is part of a special X-ray machine called a CT scanner. A small tube will be placed into your rectum to fill the colon and rectum with air. This can be uncomfortable for some people. Then, the table will move into the machine and pictures will be taken of your colon and rectum. A computer will combine these photos to create a 3-D picture. Because the test uses X-rays, it exposes you to a small amount of radiation.
This test is similar to colonoscopy, but focuses only on the sigmoid colon and rectum. As with colonoscopy, bowel prep must be done the day before this test. It might not need to be as complete as the bowel prep for a colonoscopy. You are awake during the procedure, but you may be given medicine to help you relax. During the test, the healthcare provider guides a thin, flexible, lighted tube called a sigmoidoscope through your rectum and lower colon. The images are displayed on a video screen. Polyps are removed, if possible, and sent to a lab for testing.