Colonoscopy: Key to Heading Off Colorectal Cancer

A colonoscopy is one of the most effective screening tests for colorectal cancer. Early detection can make a major difference in curability.

colorectal cancer

If polyps—small growths of precancerous tissue on the inside of the colon—turn up during a colonoscopy, the physician can remove them on the spot.

© Sebastian Kaulitzki |

A recent report from the American Cancer Society (ACS) indicates that colorectal cancer rates, and the rate of death from the disease, have fallen in people age 50 and older. ACS experts conclude that the declines are probably due to increased screening for the disease.

Several screening methods are available, with colonoscopy considered the gold standard—it can detect colorectal cancer in its early stage, when the disease is highly curable, and also can help prevent the disease by locating polyps (precancerous tissue) or growths before they can become cancer.
“A colonoscopy is preventive medicine at its best,” confirms Felice H. Schnoll-Sussman, MD, associate professor of clinical medicine at Weill Cornell Medicine. “It can save you from developing colon cancer.”

Even though the evidence is clear, many avoid having a colonoscopy. Dr. Schnoll-Sussman says that anxiety or fear about the preparation for the test, as well as the test itself, can keep people from getting screened.

How Colonoscopy Works

During a colonoscopy procedure, a thin, flexible tube with an attached video camera is inserted into the rectum. The camera enables your doctor to examine the entire length of the colon (large intestine) for abnormal growths and areas of inflammation or bleeding. (Sigmoidoscopy, which is a similar test, examines only the last third of the colon.) Tissue samples may be collected for analysis, and any abnormal growths can be removed.



See your gastroenterologist about a possible colonoscopy if you have any of these signs or symptoms:

  • Rectal bleeding (ranging from bright to dark red) with bowel movements.
  • A change in the consistency of your stools, including diarrhea or constipation.
  • Feeling that your bowel does not empty completely.
  • Persistent abdominal discomfort (cramps, gas, bloating, and pain).
  • A change in bowel habits.
  • Losing weight without dietary changes or increased exercise.

A colonoscopy takes about 30 minutes, and patients are given a sedative to put them to sleep.

“Because of the sedation, most people do not even know the procedure happened, and many experience no pain and minimal discomfort,” says Dr. Schnoll-Sussman.

The Preparation Hurdle

One mental barrier to a colonoscopy is the preparation for the procedure, which requires that you clean out your colon so the camera can get the best possible view of the walls of your colon.

The process involves following a clear liquid diet the day before the exam and taking laxatives. The prep may be unpleasant, since all contents of the intestines need to be expelled, but it is safe, short-term, and has no side effects.

“The laxative effect typically lasts only during this brief period, and patients return to normal eating and bowel movements after the exam,” says Dr. Schnoll-Sussman.

Making the Prep Easier

Before you start your prep, stock up on clear broths, fruit juice, Jell-O, ice pops, and/or soft drinks to consume while you’re fasting; just be sure to avoid anything that is red or purple in color. Also consider purchasing wet wipes and a soothing ointment for use after taking the laxative.

If your doctor has prescribed a liquid laxative, it may have an unpleasant taste that’s difficult to get down; ask your doctor what can be mixed with the laxative to improve the taste. Drinking the solution through a straw placed on the back of your tongue can help make it easier.

If you’re concerned that you won’t be able to drink all the laxative, ask your doctor if you can take the laxative in pill form instead. And make sure your schedule is clear and you can stay at home once you’ve ingested the laxative; if possible, declare one bathroom “yours” until you leave for the procedure the next day.

Screening Schedule

Routine colonoscopies are recommended beginning at age 50 and continuing up until at least age 75. “Begin exams earlier if you have a family history of colon cancer or a personal history of inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease,” Dr. Schnoll-Sussman advises.

If the results are normal and no polyps are detected, retesting is recommended every 10 years. If one or two small polyps are found, your doctor may screen every five years. If three or more small polyps or a large polyp is detected, screening is recommended every three years.

If you’re age 76 or older, the U.S. Preventive Services Task Force advises that the benefits of colorectal screening may be smaller and the potential for harm greater. Be guided by a realistic assessment of your life expectancy and the fact it takes about 10 years for a new polyp to develop into cancer.

Other Available Options

If you’re still unwilling to undergo a colonoscopy, there are other options. Research suggests that a fecal immunochemical test (FIT), which can detect hidden blood in the stool, may be effective for detecting colorectal cancer among people with a family history of the disease. However, colonoscopy remains superior to FIT in locating non-advanced tumors.



Follow these tips to reduce your risk of colon cancer:

  • Include plenty of fiber in your diet; good sources include whole grains, vegetables, fruits, beans, and nuts.
  • Limit your intake of red meat (beef, pork, veal) and processed meat (cold cuts, sausage, bacon).
  • Drink alcohol in moderation.

Another stool-based test is Cologuard. This at-home test detects hidden blood, as with FIT, but it also looks for abnormal DNA that may be shed into your stool from cancer or polyps. (To learn more, visit

Finally, you may be a candidate for a “virtual colonoscopy,” in which a computed tomography (CT) scan takes two- and three-dimensional images of the colon. While a colon cleanse is still required, a CT colonography is not as invasive as a colonoscopy and often requires no sedation. “This test is best for low-risk patients who cannot undergo, or who have failed, a conventional colonoscopy,” says Dr. Schnoll-Sussman.

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Dawn Bialy

Dawn Bialy has been executive editor of Weill Cornell Medicine’s Women’s Health Advisor newsletter since 2007. Bialy also has served as managing editor for a variety of special health reports, … Read More

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