Colorectal cancer is one of the most common preventable cancers. The colon and rectum make up the large intestine, which absorbs water and some nutrients from digested food, and stores the solid waste until it is expelled from the body.
A colon cancer screening is the process of looking for polyps and cancerous growths on the inner wall of the colon and rectum when no gastrointestinal symptoms of disease are present.
A polyp is a noncancerous growth in the colon. Some of these may become cancerous later. Early detection and removal of colorectal polyps and malignant tumors can prevent complications and death due to colon cancer.
The people at high risk of colon cancer are:
- People above 45 years
- People with an inherited familial adenomatous polyposis, a condition where individuals develop numbers of polyps in colon and rectum
- People who had colon cancer earlier
- Women with a previous history of breast, ovarian or uterine cancer
- People whose close family members such as parents, sibling or children have or had colon cancer
- People with ulcerative colitis and Crohn’s disease
- People with a sedentary lifestyle, unhealthy eating habits and who smoke
People should talk to their doctor about when to go for the screening and what tests to have. One or more of the following tests 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 the colon can be seen on the monitor. It can be used for taking a 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 a small risk of bowel tear, bleeding, and infection.
- Colonoscopy: Colonoscope is similar to sigmoidoscope, but is longer and is used to examine the inner wall of the whole colon. It is inserted from the rectum and the doctor can see the images of the entire colon on the monitor. Special surgical tools can be passed through the colonoscope to take a 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, a 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 air is pumped into the colon. The barium suspension lines the outer walls of the colon. X-ray images of the colon are then taken to reveal abnormalities on the inner wall of the colon. “IF” any abnormalities are found, a colonoscopy needs to be 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 further tests. A colonoscopy needs to be repeated if results are positive, indicating the presence of cancerous growth in the colon. They are of three types:
- Fecal occult blood test detects blood in the feces not visible to normal eyes through a chemical reaction.
- Fecal immunochemical test detects blood through a specific immunochemical reaction of a protein in the blood and can detect hidden blood.
- Stool DNA test looks for certain abnormal DNA genes in the cells shed from cancerous outgrowth or polyps in the stool sample. It is expensive as compared to the other stool tests.