‘Virtual colonoscopy’

Dear Dr. Roach: I had a Cologuard test and was told that there is blood in my stool. My doctor tried to do a colonoscopy, but told me he was unable to complete it due to my colon being very twisted. He sent me to the hospital for a “virtual colonoscopy.” He assured me that it was not invasive and that I would only get dye in my vein. The hospital he sent me to does not perform this test, and also told me that there is no test on the colon that is not invasive. Is this really true? If so, what was my doctor talking about? — C.L.

Answer: Cologuard is a test that looks for both blood and abnormal DNA in the stool. A positive result should be followed up with a definitive test.

There certainly is such a thing as a virtual colonoscopy. It is more properly termed “CT colonography,” as it uses the CT scanner to take high-resolution pictures of the colon. It is not invasive in the sense that no instrument is inserted; however, the test still might be unpleasant. That is because, at the current time, the preparation for both virtual and traditional colonoscopies is still the same, and most people find that the preparation is the worst part of the experience; the colonoscopy itself usually is done under sedation, and people really don’t recall much or any of the experience.

However, people usually are not sedated for CT colonography. That’s good because it eliminates potential side effects from sedation, but it’s bad because the colon still needs to be distended with air, and this is uncomfortable for some people. (Sometimes more than just uncomfortable: I have had more than one patient tell me that they would never get this procedure again.) On the other hand, it is quick — normally, less than 15 minutes. The radiation itself has potential for risk, although that risk probably is very small, but I want to identify all the risk from the procedure.

If an abnormality is found by CT colonography, the next step sometimes would be a biopsy, which typically would be done via a colonoscopy. Given the difficulty your doctor had doing a colonoscopy, that might prove challenging. Sometimes a different doctor or just a different day can make the procedure possible.