Colon and rectum are part of the large intestine which absorb nutrients from the digested food and store the solid waste till it is expelled from the body.
Colorectal cancer almost always develops from precancerous polyps (abnormal growths) in the colon or rectum. Screening tests can find precancerous polyps, so that they can be removed before they turn into cancer. Screening tests can also find colorectal cancer early, when treatment works best.
The people at high risk of colon cancer are:
People should talk to their doctor for when to go for the screening and what tests to have. One or more of the following test may be used for colon cancer screening:
Flexible Sigmoidoscopy: Sigmoidoscope is used to view the inside of the rectum and lower colon. A finger size thick tube with a camera at the end is inserted from the rectum and images of the inner wall of rectum and part of colon can be seen on the monitor. It can be used for taking biopsy of the polyp or tumor and for removing some polyps. But colonoscopy needs to be done to view the whole colon and remove all polyps or tumors. It is fairly safe but has small risk of bowel tear, bleeding and infection.
Colonoscopy: Colonoscope is similar to sigmoidoscope but is longer than it and is used to examine the inner wall of whole of colon. It is inserted from the rectum and doctor can see the images of entire colon on the monitor. Special surgical tools can be passed through the colonoscope to take biopsy and remove polyps. Sedation is required. There is a small risk of bowel tear, bleeding or infection after the procedure.
Virtual Colonoscopy: It is the computed tomography scan of the colon. The person is made to lie on a table of the CT scanner which takes cross-sectional images of the colon. It is a non- invasive technique and does not require sedation. If any abnormalities are found, colonoscopy needs to be done to remove the polyps or tumors.
Double Contrast Barium Enema: A small tube is inserted in the rectum and barium sulfate, a white chalky liquid and then air is pumped into the colon. The barium suspension lines the outer walls of colon. X-ray images of colon are then taken to reveal abnormalities on the inner wall of the colon. If abnormalities are found, colonoscopy is done to remove the polyps or tumors.
Fecal Test: They are done with the fecal sample and are totally safe. These may not give confirmatory results but may suggest the abnormalities in gastrointestinal tract warranting for further tests. Colonoscopy need to be repeated if results are positive indicating presence of cancerous growth in colon. They are of three types: