Colorectal Cancer

Colorectal cancer (CRC) is the second leading cause of cancer mortality in North America, next to lung cancer. An estimated 6% of Canadians will develop CRC, half of whom will be asymptomatic until advanced stages of the disease emerge. CRC generally develops from benign adenomas, called polyps, which physicians can easily detect and remove during colonoscopy. It could take a polyp ten to fifteen years to develop into cancer. Screening for polyps and removing them during a colonoscopy can dramatically improve patient health outcomes, because when detected in its early stages, colorectal cancer is easily treated. Physicians diagnose close to 19,200 patients with CRC each year in Canada, and 8,400 will die from the disease.

Unfortunately, only 1 in 5 Canadians undergo the important screening process. The prospect of colonoscopy may be daunting to patients who recall ‘horror stories’ of painful colonoscopies from a previous era, when equipment was larger and less flexible, and some are simply too embarrassed to think or talk about bowel related issues. Thankfully, modern technology has made colonoscopy a vastly more comfortable procedure to undergo, and it is now more socially acceptable to discuss medical issues such as bowel habits than in the past.

How is CRC detected?

Screening is a term that describes when doctors perform regular tests or examinations in people who do not have any signs of a disease. These individuals may be more likely to develop a disease because they have high risk factors. There is much debate over the extent to which screening of the general population for polyps or CRC needs to take place, and by what means.

In Canada, there are a number of screening tools available for your doctor to use to determine if you are progressing toward CRC. Researchers continue to find ways of detecting and predicting CRC that include studying a patient’s DNA for known genetic markers that place them at a higher risk of developing CRC. Some of the more common current tests are shown below along with the recommended interval for these tests to occur (shown in brackets) for all individuals over age 50 with no family history of CRC. Those with higher risk factors require screening that is more frequent.

Fecal Occult Blood Test

For this test, the patient provides three consecutive stool samples that are examined for hidden blood. If blood is found, then your doctor will order further tests. (Every two years), and

Flexible Sigmoidoscopy

During this procedure, a doctor inserts a flexible tube with a tiny camera into the lower portion of the colon through the rectum. While viewing the surface of the lower colon lining, the physician may take a small amount of tissue (biopsy) of specific areas that will later be examined in a laboratory or entire polyps may be removed on the spot. The patient does not need sedation. However, because this test reaches only the lower portion of the colon, all possible sites for abnormalities may not be ruled out. (Every five years), or

Fecal Occult Blood Test and Flexible Sigmoidoscopy

See descriptions above. (In combination, every five years), and

Double Contrast Barium Enema

This is a series of x-rays of the rectum and lower portion of the intestine, called the colon, taken after the patient is given an enema with a white, chalky solution that contains barium. The contrast of the solution on X-ray allows doctors to see if any polyps or abnormalities are present in the colon. Instilling air into the colon along with the barium contrast medium further defines structures of the colon and rectum, thus providing a double contrast. Your doctor may request further tests, depending on the barium X-ray results. (Every five years)


During this procedure, a doctor inserts a thin flexible tube with a tiny camera into the colon through the rectum. The procedure usually takes place in an outpatient clinic, often located within a hospital. As with the sigmoidoscopy, while viewing the surface of the lining of the entire colon, the physician may take a small amount of tissue (biopsy) of specific areas that will later be examined in a laboratory or they may remove entire polyps on the spot. Light sedation makes the procedure more comfortable for the patient. (Every ten years)

Which Test Is For Me?

Of these common tests, colonoscopy is the most accurate means of detecting polyps or CRC and allows for the immediate removal of most polyps. Patients may choose to watch on a video screen. The procedure usually takes ten to twenty minutes. Recovery is quick and usually pain-free.

For IBD patients and others at high risk, a colonoscopy provides the greatest reassurance that his or her colon is free of cancer. Other tests to screen for CRC are less reliable but may be acceptable for those not considered to be at high risk. The intervals for the screening tests mentioned above are more frequent when there is greater risk. Your doctor will determine the appropriate interval for you.

Our American neighbours are encouraged by health policy makers to undergo colonoscopy regardless of their individual likelihood of developing CRC, but Canadian policy toward average risk patients is ambivalent, probably because we lack the capacity to perform the requisite number of colonoscopies. However, for individuals who have an above average risk of developing CRC, doctors recommend colonoscopy screening. Of course, individuals who notice blood in their stools or who have other bowel related symptoms should immediately report these to their physician.

Who Should Be Screened?

The Canadian Association of Gastroenterology and the Canadian Digestive Health Foundation Guidelines on Colon Cancer Screening recommend that:

  • People with chronic IBD (colonic Crohn’s disease or ulcerative colitis) should be screened every 1 to 2 years, once they have had the disease for 8 to 10 years.
  • Those with a first-degree relative with CRC (parent or sibling) diagnosed before age 60, or with multiple affected relatives, should be screened once every 5 years. The first screening should take place 10 years before the relative’s age of diagnosis or at age 40, whichever comes first.
  • Individuals with three or more affected relatives, or with a first degree relative affected before age 40, should be considered for genetic counseling and possibly genetic testing for specific hereditary diseases which dramatically increase the CRC risk and which may require much more intensive screening.
  • People with no risk factors should be considered for some form of screening beginning at age 50; this may be colonoscopy every 10 years, fecal occult blood testing every 1-2 years, or other options that may be discussed with their physician.
  • Remember, colonoscopy in expert hands is generally not painful. In fact, most patients report that the most unpleasant part of the procedure is the preparation. However, while it is true that the side effects of some preparation medications can be unpleasant, a newer product available might suit your tastes better.

Preparing for Colonoscopy

Knowing what to expect can help eliminate fears and ease discomfort.

Preparation for a colonoscopy means having a clean colon. A doctor’s ability to see inside your colon depends on how thoroughly it is cleared of stool (feces). If your bowel is not completely clean, test results may not be accurate. The exact requirements for preparing for your colonoscopy may vary from the descriptions below as some hospitals or clinics performing colonoscopies have very specific requirements. Be sure to follow the precise instructions given to you by your physician.

To clean the colon, your doctor will send you to your pharmacy to purchase a purgative (a drug that causes evacuation of the bowels) to be taken the day before your colonoscopy. In addition to taking the purgative, you must restrict yourself to a clear liquid diet, and generally stay close to the bathroom. Your doctor may also advise you to modify the way you take some of your other medications in the days leading up to the procedure.

There are several types of purgatives. All are osmotic agents, which work by pulling water from the body into the bowel. They are safe and effective when used for appropriate patients according to the directions, but they vary from patient to patient in tolerability. If a patient does not tolerate a purgative very well, its effect may not be complete, and the colon may not be sufficiently clean to allow a thorough examination.

A commonly used purgative is polyethylene glycol (PEG). Although it comes in four flavoured varieties to disguise the salty taste (Colyte®, PegLyte®, Golytely®, Klean-Prep®), the main disadvantage is having to drink four litres of the solution, which often is too much for a patient to manage.

With the purgative, phospho-soda (Fleet®, PMS phosphate solution®), patients must drink two bottles of the solution, diluted in three glasses of fluid (each), 24 hours apart. Although effective, not everybody likes the taste or side effects, which may include sudden diarrhea, abdominal cramping, nausea, and vomiting. Sometimes doctors advise their patients to consume an electrolyte replacement drink (e.g. Gatorade®) to combat possible dehydration, electrolyte loss, and kidney impairment.

Nearly one-third of patients who could not tolerate their bowel preparation the first time do not go through with their next colonoscopy. This discouraging situation may change with the availability of a new purgative called Pico-Salax® (magnesium oxide, citric acid, sodium picosulphate), which is already receiving positive feedback from patients. Pico-Salax® is the only dual action purgative, which means it works in two ways (osmotic and stimulant) and it is easier on the body. The stimulant further helps the bowel eliminate fecal matter. Clinical studies show that patients tolerate it better than the other preparations, and experience fewer side effects. It has a pleasant taste that, according to some, is similar to Tang® or tart lemonade, and is a manageable volume to drink (one 5-oz glass, twice during the day). It is important, however, for people to drink at least 4 to 6 large glasses of water or clear liquid following each 5-oz glass dose. Pico-Salax® is also the only purgative that children over the age of one can safely use.

During bowel preparation, drink plenty of clear liquids (if you can see through it you can drink it) to avoid dehydration and to help completely clean out your colon; do not eat any solid foods. Stop drinking clear liquids three hours before the colonoscopy. And remember, stay within close access to a toilet. You will be likely be given a sedative before the colonoscopy, so arrange to have someone take you home afterward.

The key to preventing colorectal cancer is to get screened at the right time and with the right test. It might be the smartest thing you’ve ever done!

Risk Factors for CRC

The following place an individual at increased risk for developing CRC:

  • Prior diagnosis of polyps or early stage CRC
  • A family history of CRC or polyps
  • Longstanding inflammatory bowel disease (IBD)
  • A family history of uterine or ovarian cancer in young or multiple relatives
  • Age 50 years or greater

Early Warning Signs of CRC

  • Blood in or on the stool (either bright red or very dark in colour)
  • A persistent change in normal bowel habits such as diarrhea, constipation or both, for no apparent reason
  • Frequent or constant cramps if they last for more than a few days
  • Stools that are narrower than usual
  • Persistent or recurrent abdominal discomfort, bloating, fullness, or cramps
  • A frequent or continual feeling of need to empty the bowels, but with passage of little stool
  • A feeling that the bowel does not empty completely
  • Weight loss for no known reason
  • Constant tiredness

Note: Many people diagnosed with CRC never had any symptoms or early warning signs.

Image: aslysun |