Colon Cancer Screening
Colon and rectum together make up the large intestine. The large intestine is the last part of the digestive tract. The main function of the large intestine is to reabsorb water from the contents of the intestine and store the solid waste till it is expelled from the body.
Colon cancer screening is the process of looking for polyps and cancerous outgrowths on the inner wall of the colon and rectum when no gastrointestinal symptoms are present for the disease. Polyp is a noncancerous outgrowth that may become cancerous later. Early detection and removal of the noncancerous polyp and malignant tumors can thus prevent further complications and death due to colon cancer.
The people at high risk of colon cancer are:
- People above 45 years
- People whose close family members such as parents, sibling or children have or had colon cancer
- People who had colon cancer earlier
- People with ulcerative colitis and Crohn's disease
- People with an inherited familial adenomatous polyposis, a condition where individuals develop numbers of polyps in colon and rectum
- Women with a previous history of breast, ovarian or uterine cancer
- People with sedentary lifestyle, unhealthy eating habits and who smoke
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:
Colonoscopy: Colonoscopy is the gold standard for examining colon. This procedure is diagnostic as well as therapeutic. Polyps seen during this procedure can also be removed at the same session. The procedure is performed using a video endoscope called colonoscope. This is a finger size thick long flexible tube with a camera at the end. This video endoscope is used to view the inside of the rectum and entire colon. The colonscope is inserted from the rectum and images of the inner wall of rectum and entire colon can be seen on the monitor. Special surgical tools can be passed through the colonoscope to take biopsy and remove polyps. Sedation is required. The procedure is quite safe but carries a small risk of bowel tear, bleeding or sedation related complications.
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.
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:
- Fecal occult blood test detects blood in the feces not visible to normal eyes through chemical reaction
- Fecal Immunochemical test detects blood through 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 test.
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