Doctor's Diagnosis: Virtual colonoscopy

How much inconvenience would you put up with in order to avoid dying from colon cancer? Millions of Americans confront this problem and many give a surprising answer: “Not very much.”

This year about 50,000 Americans are expected to die from cancer of the colon (the large intestine). Routine screening colonoscopy could considerably decrease the number of deaths if more widely used. After passing a colonoscope through the rectum, the colon is visually examined, biopsies are taken of any masses that are found and polyps, if present, are removed. Most colon cancers are detected in their early stages while the prognosis is still excellent. 

The procedure can last up to an hour and requires sedation. Additional time after the procedure is needed to recover from the sedation. Patients should not drive and need to have someone accompany them home. A bowel prep the day before, plus this large investment of time and the “bring a friend” factor are major inconveniences for most people.

Virtual colonoscopy avoids these problems. It is actually a high-resolution CT scan and only takes 10 or 15 minutes. Some air is injected into the rectum, but there is no colonoscope used and sedation is not needed. Although there may be some bloating or cramping, as soon as the procedure is completed the patient is free to leave and carry on his or her normal activities. Certainly more convenient, but there are issues.

The procedure requires a bowel prep very similar to that used for regular colonoscopy. This involves fasting and taking laxatives to cleanse the bowel. This is actually the part of the process most people find objectionable and having a virtual colonoscopy does not eliminate the need for it. 

Certain polyps that could have been detected with a colonoscope will be missed on virtual colonoscopy and the significance of this is not clear. Also, virtual colonoscopy can only detect problems, not treat them. If a mass or polyp is found a regular colonoscopy is still needed. 

Virtual colonoscopy results in radiation exposure. Also, while scanning the colon the adjacent structures are visualized and a significant number of exams will detect abnormalities outside the colon. This will lead to anxiety and further testing, which may or may not benefit the patient, depending on what is ultimately found. 
The role that virtual colonoscopy should play in screening for colon cancer is still controversial. 

Dr. Stephen Picca of Massapequa is Board Certified in both Internal Medicine and Anesthesiology. He is retired from practice. Questions and comments can be sent to Dr. Picca at health@newsday.com.