Do I Really Need a Colonoscopy?

In addition to treating chronic conditions like diabetes and hypertension and acute illnesses like infections, primary care physicians are responsible for providing preventive care. In general, I find this aspect of my work satisfying. I enjoy knowing that by keeping my patients current on recommended screening tests, I am helping them live longer and remain healthier. Patients are usually willing to comply with my suggestions, even when tests are uncomfortable or unpleasant.

The women’s health movement has been particularly effective in educating women about our ability to prevent breast and cervical cancer. I can’t think of a single patient who enjoys reporting for her annual mammogram or Pap smear, but of women over 40, 71 percent have had a mammogram and 80 percent have had a Pap smear within the past two years. My job is tougher when recommending colorectal cancer screening. I am not alone–less than 30 percent of people over 50 have undergone screening for colorectal cancer.

Colorectal cancer begins in the colon (or large intestine) or rectum. It is the second leading cause of cancer-related deaths in the United States. Sometimes, colorectal cancer presents with symptoms including bleeding from the rectum, blood in the stool, change in the shape of the stool, pain in the abdomen or other changes in bowel movements. These symptoms can be caused by conditions other than cancer and should be evaluated by a physician.

Colorectal cancer usually begins as a polyp–a small, harmless growth in the wall of the colon that can become cancerous. Screening allows these polyps to be detected and removed before cancer or its symptoms develop. There are several tests available for screening and you should talk with your doctor to select the most appropriate one.

The American Cancer Society recommends that all people over 50 should follow one of the following screening options:

• Yearly fecal occult blood testing (FOBT)

• Flexible sigmoidoscopy every five years

• Yearly FOBT plus sigmoidoscopy every five years

• Double-contrast barium enema every five years

• Colonoscopy every 10 years

In FOBT, three stool samples are taken with a home testing kit and returned to your doctor. If one of the samples contains microscopic blood, you will need to undergo colonoscopy. This test is easy to perform, inexpensive and has a simple preparation. FOBT, however, only identifies about 40 percent of cancers.

Flexible sigmoidoscopy involves inserting a thin flexible tube with a camera on the end into your rectum. Your doctor can view your rectum and the lower portion of the colon and can identify small polyps. Around 25 percent of patients who have sigmoidoscopy will have at least one polyp which will need to be removed by colonoscopy. This method can find about 90 percent of cancers in the rectum and lower colon, but misses most cancer in the upper colon. Preparation involves using an enema or oral laxative and the test is performed without sedation.

Colonoscopy is similar to sigmoidoscopy except that it allows your doctor to view your entire colon, take biopsies of suspicious areas and remove polyps. Greater than 90 percent of cancers can be identified by colonoscopy which is performed under sedation and requires preparation with a liquid diet for 24 hours and taking an oral laxative. Compared to sigmoidoscopy, this test has a higher risk of perforating the colon, involves the risk of taking sedatives and is more expensive. Barium enema has been recommended in the past, but identifies fewer than 50 percent of polyps larger than one centimeter and has fallen out of favor as an approach to screening.