Colonoscopy: Choosing CT or Conventional

If you're over 50, check your health insurance policy to see whether you have a choice of CT colonography or conventional colonoscopy to screen for colorectal cancer. Two gastroenterologists from Walter Reed Army Medical Center and the National Naval Medical Center reported in a recent review that both screening methods are reasonable options to be considered on an individual basis.

CT (computed tomographic) colonography is also called “virtual colonoscopy”. It uses x-rays with computer technology to produce three-dimensional images of the colon. The advantages over conventional optical colonoscopy are:

1. The CT method is less invasive, with no risk of perforation of the colon or bleeding.
2. Sedation is not required, so the patient can drive home and return to ordinary activities immediately. After a conventional colonoscopy, the patient is legally under the influence of drugs for the rest of the day. When I had it done, I turned into a couch potato watching TV and taking naps for the afternoon.

The disadvantages of the CT method are:
1. If polyps are found, the patient still needs a conventional colonoscopy to have them removed. Reference 1 reports that 12 percent of patients screened by the CT method require a follow-up colonoscopy.
2. It is not completely painless. The bowel must be inflated with carbon dioxide to produce a good quality image. Some patients are not happy getting this done without sedation.

The American College of Gastroenterology recommends the same bowel preparation procedure for both methods. Most of us call this getting “cleaned out”. The day before the colonoscopy, the patient consumes only liquids and takes a high dose of laxatives. On a personal note, I found it was not as bad as it sounds. Diarrhea caused by infection or food poisoning is accompanied by nausea, cramps, and a general feeling of yuckiness. The clean out procedure just requires a lot of trips to the bathroom. Still, this is the most objectionable part for the average patient.

I found two studies of patient preference for the two methods. A Korean study reported that most preferred conventional colonoscopy. A European study reported that most preferred CT colonography, but this study used a more limited bowel preparation with the use of x-ray contrast agents.

Ask your doctor about the options available for you.

References:

1. Veerappan GR et al, “Should computed tomographic colonography replace optical colonoscopy in screening for colorectal cancer?”, Pol Arch Med Wewn. 2009 Apr; 119(4): 236-41.

2. Jung HS et al, “A comparison of patient acceptance and preferences between CT colonography and conventional colonoscopy in colorectal cancer screening”, Korean J Intern Med. 2009 Mar; 24(1): 43-7.

3. Bipat JS et al, “CT colonography with limited bowel preparation: prospective assessment of patient experience and preference in comparison to optical colonoscopy with cathartic bowel preparation”, Eur Radiol. 2010 Jan; 20(1): 146-56.

4. American College of Gastroenterology FAQ:
http://www.acg.gi.org/patients/ccrk/VCFAQ.pdf

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

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