Colon Cancer Screenings

There are two main preventative screenings that are used to detect and deter the incidence of colon cancer: a flexible sigmoidoscopy and a colonoscopy. Screening is the process of looking for cancer in people who have no symptoms of the disease. These tests as well as others can also be used when people have symptoms of colon cancer and other digestive diseases.



For this test, the doctor looks at the entire length of the colon and rectum with a colonoscope, which is basically a longer version of a sigmoidoscope. It is inserted through the rectum into the colon. The colonoscope has a video camera on the end that is connected to a display monitor so the doctor can see and closely examine the inside of the colon. Special instruments can be passed through the colonoscope to biopsy (sample) or remove any suspicious-looking areas such as polyps, if needed.

Colonoscopy may be done in a hospital outpatient department, in a clinic, or in a doctor’s office. Before the test, be sure your doctor knows about any medicines you are taking, as you might need to change how you take them before the test. The colon and rectum must be empty and clean so your doctor can see their inner linings during the test. You will need to take laxatives (usually a large volume of a liquid, but sometimes pills, as well) the day before the test and possibly an enema that morning.

Your doctor will give you specific instructions. It is important to read these carefully a few days ahead of time, since you may need to shop for special supplies and get laxatives from a pharmacy. If you are not sure about any of the instructions, call the doctor’s office and go over them step by step with the nurse. Many people consider the bowel preparation the worst part of the test, as it usually requires you to be in the bathroom much of the night before the exam. This discomfort, however, is insignificant compared to the possibility of undetected colon cancer.

You will probably also be told not to eat or drink anything after midnight the night before your test. If you normally take prescription medicines in the mornings, talk with your doctor or nurse about how to manage them for the day.

You usually need to arrange for someone to drive you home from the test because a sedative is used during the test that can leave you groggy and affect your ability to drive. Most doctors require that someone you know drive you home (not a taxi).

During the test: The test itself usually takes about 30 minutes, but it may take longer if a polyp is found and removed. Before the colonoscopy begins, you will be given a sedating medicine (usually through your vein) to make you feel comfortable and sleepy during the procedure. You will probably be awake, but not be aware of what is going on and probably won’t remember the procedure afterward. Most people will be fully awake by the time they get home from the test.

The doctor will look at the inner walls of the colon as he or she slowly withdraws the colonoscope. If a small polyp is found, the doctor may remove it. Some small polyps may eventually become colon cancer. For this reason, they are usually removed. This is usually done by passing a wire loop through the colonoscope to cut the polyp from the wall of the colon with an electrical current. The polyp can then be sent to a lab to be checked under a microscope to see if it has any areas that have changed into colon cancer. If your doctor sees a larger polyp or tumor or anything else abnormal, a biopsy may be done. For this procedure, a small piece of tissue is taken out through the colonoscope. The tissue is looked at under a microscope to determine if it is colon cancer, a benign (non-cancerous) growth, or a result of inflammation.

Last Updated: March 07, 2016