What are colonoscopies and virtual colonoscopies?

Cancers diagnosed: Cancers of the large intestine and rectum, precancerous adenomas, polyps

Why performed: These procedures are intended for the prevention and early detection of colon cancer for people over the age of fifty, or earlier when indicated. They are also a necessary component in the management of inflammatory bowel diseases (Crohn's disease and ulcerative colitis) or for individuals who have a family history of polyps or diseases of the large intestine. As of 2014, the American Cancer Society advises everyone at average risk of colorectal cancer to have a traditional colonoscopy procedure performed every ten years; a virtual colonoscopy should be performed every five years.

Many patients resist the procedure as a result of embarrassment and/or concern over the bowel preparation, which is the same for both traditional and virtual colonoscopy. Neither procedure replaces the need for yearly testing for blood in the feces with a fecal occult blood test (FOBT) or a fecal immunochemical test (FIT). There are several considerations in deciding on the appropriate procedure. Patients should discuss family history of any bowel disease, increasing age, existing medical problems, and other personal issues with a physician when deciding the most appropriate procedure. Both forms of colonoscopy are considered the most thorough and accurate in examining the entire large intestine, but there are differences in how they are performed and what happens if a test is abnormal.

Patient preparation: Patients should not stop taking any medications (such as insulin, aspirin, or blood thinners) to prepare for a colonoscopy unless approved by their physicians. Three days before either procedure, the patient should stop eating a high-fiber diet or taking fiber supplements and iron-containing vitamins or iron tablets. The day before the procedure, all three meals should consist only of clear liquids, such as tea, broth, gelatin, clear juices, tea, or coffee.

The doctor will provide bowel preparation information and laxatives, either tablets or liquid, to take the day before the procedure and possibly again four hours before the procedure. The large intestine must be completely empty and free of all fecal matter in order to clearly see any abnormal growths or changes in the wall of the intestine. The patient may not eat or drink anything after midnight before the procedure unless it is water to take approved medication.

Steps of the procedure: Traditional colonoscopy is usually performed in an outpatient surgery suite. Patients are moderately sedated and given pain medication through an intravenous catheter. It is common for patients to sleep through the procedure, which can take thirty to sixty minutes.

The patient lies on the left side, and a colonoscope is inserted through the anus and rectum. The doctor watches a video screen as the tube is guided through the large intestine. Examination includes visualization during slow withdrawal of the tube, as some growths can be hidden in folds in the intestine. The gastroenterologist is looking at the actual lining of the intestine, not a computerized image.

The following can be done during this procedure: removal of polyps, sampling of abnormal tissue (biopsy), removal of small growths, stopping of small areas of bleeding, laser treatment of abnormal tissue or growths, and the introduction of certain medicines.

Virtual colonoscopy is performed by a radiologist in a radiology suite. No sedation is necessary. The patient is asked to lie on the back on a table. A thin tube is inserted into the rectum introducing air to inflate the large intestine for better visualization. The table passes through the scanner as three-dimensional computerized images of the large intestine are made and immediately viewed on a video screen. The patient is instructed to periodically hold the breath to be sure that the images taken are clear. The procedure is repeated with the patient lying on the stomach and is completed in ten to fifteen minutes.

Identification of anything abnormal might require traditional colonoscopy. Repeat bowel preparation will be necessary if the procedure cannot be performed the same day.

After the procedure: The patient will need to be driven home after traditional colonoscopy, as the sedation used during the procedure makes it unsafe to drive. It can take one to two hours after traditional colonoscopy for the patient to be alert enough to be driven home. There can be some abdominal cramping and feelings of gas. Normal activities can be resumed the following day.

Virtual colonoscopy does not require medication, and patients are free to leave immediately after the procedure. Some cramping might occur following virtual colonoscopy because of the introduction of air during the procedure.

Risks: Perforation and/or infection of the large intestine, while very uncommon, is a possible complication from traditional colonoscopy. The doctor will provide an information sheet that describes what is normal and not normal following colonoscopy. Symptoms that should indicate calling the doctor include bloody diarrhea, blood coming from the rectum, dizziness, fever, severe abdominal pain, and weakness. There is radiation exposure with virtual colonoscopy.

Results: Both procedures are considered the most thorough in examining the entire large intestine. Traditional colonoscopy is better at finding growths smaller than 10 mm and has the advantage of permitting biopsies of abnormal growths, removal of polyps, treatment of inflammation or disease, and laser treatment during the examination. Virtual colonoscopy is a much newer procedure and has been widely embraced by those who are fearful of traditional colonoscopy. Traditional colonoscopy is required following virtual colonoscopy if any abnormalities are found. Some studies have found that certain abnormalities on virtual colonoscopy were normal when traditional colonoscopy followed. Studies continue comparing the benefits and drawbacks of each procedure.

"American Cancer Society Recommendations for Colorectal Cancer Early Detection." American Cancer Society. Amer. Cancer Soc., 31 Jan. 2014. Web. 11 Sept. 2014.

Cotterchio, Michelle, et al. “Colorectal Screening Is Associated with Reduced Colorectal Cancer Risk: A Case-Control Study Within the Population-Based Ontario Familial Colorectal Cancer Registry.” Cancer Causes & Control 16.7 (2005): 865–75. Print.

Kahi, Charles J., ed. Gastroenterology Clinics of North America: Colonoscopy and Polypectomy 42.3 (2013): 429–700. Print.

Waye, Jerome D., et al, eds. Colonoscopy: Principles and Practice. 2nd ed. Malden: Wiley, 2009. Print.

Waye, Jerome D., et al. Practical Colonoscopy. Malden: Wiley, 2013. Print.

Yee, Judy. Virtual Colonoscopy. Philadelphia: Lippincott, 2008. Print.

Zauber, Ann G., et al. "Colonoscopic Polypectomy and Long-Term Prevention of Colorectal-Cancer Deaths." New England Journal of Medicine 366.8 (2012): 687–96. Print.