What is involved in screening for colorectal cancer?

What is involved in screening for colorectal cancer?

Several tests are used to screen for colorectal cancer. Although colonoscopy is most recommended, other options are available. These are the most common screening tests:

• Fecal immunochemical test (FIT): This test looks for blood in the stool that is not easily seen visually. This test can be done at home by collecting stool in tubes. The collected stool will be tested at a lab for any blood.
• Guaiac-based fecal occult blood test (gFOBT): Similar to the FIT test, the guaiac-based fecal occult blood test also looks for hidden blood in the stool. The specimen (stool) for this test is also collected at home and sent to a lab. In this test, a chemical reaction is used to screen for any hidden blood. However, the gFOBT is unable to determine where in the digestive tract the blood is coming from. Additional testing will be needed to determine the exact location of the blood.
• Fecal DNA test: The fecal DNA test works by detecting genetic mutations and blood products in the stool. Genetic material, called DNA, is present in every cell of the body, including the cells lining the colon. Normal colon cells and their genetic material are passed with the stool every day. When a colorectal cancer or a large polyp develops, abnormalities (or mutations) occur in the genetic material of the cells. Some mutations present in the polyp or cancer can be detected by laboratory analysis of the stool.
• Flexible sigmoidoscopy: A flexible sigmoidoscopy uses a device called a sigmoidoscope to see inside the rectum and lower colon. Unlike the tool used during a colonoscopy, this device is not as long, limiting how much of the colon can be seen. During this procedure, the sigmoidoscope is inserted into the anus and up through the rectum and sigmoid colon (s-shaped part). Gas is pumped in during the procedure to allow the caregiver the best possible view. This is a brief outpatient procedure, often performed without sedation. The bowel must be empty for this procedure—typically done with the help of a laxative and or enema beforethe test. Small polyps found during the procedure can be removed and tested for cancer. If these tests come back positive, a colonoscopy will be done.
• Colonoscopy: Colonoscopy is the best procedure to check for colorectal polyps and cancer. Colonoscopy is an outpatient procedure in which a physician uses a long, flexible scope (called a colonoscope) to view the rectum and entire colon. During the procedure, polyps can be removed and tested for signs of cancer. The bowel must be cleaned-out—done with the help of a laxative (“bowel preparation”)—before the procedure begins. The patient is usually given a sedative for this procedure and will need help getting home afterwards as the sedative wears off. A colonoscopy is considered a safe procedure with few risks.
• Double contrast barium enema: This is an X-ray examination of the colon and rectum in which barium is given as an enema (through the rectum). Air is then blown into the rectum to expand the colon, producing an outline of the colon on an X-ray. Barium enema is not the most accurate method and should not be the procedure of choice for colorectal cancer screening. It also requires a bowel preparation.
• CT colonography (virtual colonoscopy): In this procedure, also known as CT colonoscopy or virtual colonoscopy, a CT scan (imaging created with the use of X-rays) of the abdomen and pelvis is performed after drinking a contrast dye and inflating contrast and air into the rectum. No sedation is needed for this test. Like colonoscopy and barium enema, the colon must be cleaned out before the examination. In the case that a polyp is found, then a colonoscopy must be performed.