All of the body’s cells normally grow, divide, and then die in order

to keep the body healthy and functioning properly. Sometimes this process gets out of control: cells keep growing and dividing even when they are supposed to die. When the cells lining the colon and rectum multiply uncontrolled, colorectal cancer may ultimately develop.

Fortunately, most colorectal cancers begin as small precancerous (adenomatous) polyps. These polyps usually grow slowly and do not cause symptoms until they become large or cancerous. Colorectal cancer can be prevented by removing these precancerous polyps. Also, if detected early, colorectal cancer is potentially curable. That is why it is important to screen for colorectal polyps and cancer before symptoms develop.​

Screening for colorectal cancer should begin at the age of 40, when the risk for developing colorectal polyps and cancer starts to increase. However, if you have a personal or a family history of colorectal polyps or cancer, screening should begin at age 40 or even younger in some circumstances. Men and women should undergo screening since colorectal polyps and cancer affect both genders.

Several tests are used to screen for colorectal cancer. The following is a list of the most common screening tests as well as how often they should be done. Although colonoscopy - the gold standard - is recommended, other options are available.

• Fecal occult blood test (FOBT) - This is the least accurate colorectal cancer screening test. The exam - done at home - checks for blood in the stool, which may be caused by large polyps or cancer. If this test is the one chosen, it should be done yearly. If blood is detected on any specimen, a colonoscopy is needed.
• Flexible sigmoidoscopy - This is a brief outpatient procedure, usually without sedation, in which the inside of the lower large intestine (the sigmoid colon and rectum) is examined using a short, flexible scope. This test should be done every 5 years with a yearly FOBT. If polyps are detected in the sigmoid colon or rectum, then a full colonoscopy should be performed to look for polyps in the remaining colon.
• 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 X-ray. Barium enema is not the most accurate method and should not be the procedure of choice for colorectal cancer screening. It does require a bowel preparation. The study should be repeated every 5 years if no polyps are seen.
• CT colonography - In this newer method for screening, also known as CT colonoscopy or virtual colonoscopy, a CT scan of the abdomen and pelvis is performed after drinking a contrast dye and inflating air into the rectum. Like colonoscopy and barium enema, the colon must be cleaned out prior to the examination. If no polyps are seen on the CT scan, then the study may be repeated in 5 years. In the case that a polyp is found, then a colonoscopy must be performed.
• Colonoscopy - Colonoscopy is the best procedure to check for colorectal polyps and cancer. It allows for polyps to be removed during the exam. Colonoscopy is an outpatient procedure in which a physician uses a long, flexible scope to view the rectum and entire colon. This exam, performed with a light sedative, requires a bowel preparation to clean out the colon. It is usually repeated once every 10 years, unless polyps are found or there is a family history of colorectal polyps or cancer.