Traditional Colonoscopy vs. No Laxative CT Colon Exam

Research radiologists at the Massachusetts General Hospital in Boston evaluated the accuracy and detail of imaging the colon (a virtual colonoscopy or colonography) with no laxatives as preparation and comparing it with traditional colonoscopy.  There are clear evidence based guidelines suggesting that all low-risk men and women have a screening for colon cancer with a colonoscopy at age 50.  If that study is normal they are directed to repeat it every 10 years.  Routine screening colonoscopies are discontinued after age 80 years old.  There is no question that screening colonoscopies save lives from colon cancer.  There is no question that the laxative taken the day before to clean you out, plus the actual procedure, are reasons that individuals avoid going for colon cancer screening.

The study directors fed their patients a low fiber diet before the scan. The patients drank an oral contrast material that marked stool feces and allowed the radiologists to distinguish colon abnormalities from retained feces and stool.  This virtual colonography was excellent at detecting larger colon adenomas of 10 mm or larger picking up 91% of the existing lesions as compared to 95% with traditional preparation and colonoscopy. The difference between the 91% on virtual colonography and 95% on traditional prep and colonoscopy was not felt to be statistically significant.   The virtual colonography didn’t do as well at detecting the smaller growths.  Researchers pointed out that “the vast majority of polyps that impact cancer and survival outcomes are 10 mm or larger.”  They went on to say that the “the laxative free method would likely be worthwhile as a way to reach the many adults whose strong aversion to laxative bowel preparations stops them from getting screened.”

Clearly getting screened is always preferable to no screening.   The laxative free virtual colonoscopy was not as good as the traditional colonoscopy at finding smaller lesions.

The data in this research study were based on the skill and experience of three radiologists only. Previous studies have emphasized the need to have an experienced radiologist interpret these studies.  The researchers did not discuss the radiation exposure, which is significant, with the virtual colonoscopy.   They additionally did not mention the cost which many health insurance companies will not pay for at this time.

Despite these issues it is wonderful to have another tool in the fight against colon cancer especially to offer to those patients who have said they will “never” have a colonoscopy.

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