How does Virtual CT Colonoscopy work?
Virtual (CT) Colonoscopy is the latest technological advance in CT scanning and allows excellent images of the colon without the risks and inconvenience of anesthesia. After a one-day bowel cleansing prep using a 24 hour clear liquid diet and magnesium citrate plus bisacodyl the evening before, the colon is slowly and gently filled with carbon dioxide (one of the components of air) by way of an enema tip. Numerous images are obtained in one or two breath holds while the patient is supine, and the scan is repeated with the patient turned over to the prone position. Multiplanar reconstruction is also utilized. The total procedure time is less than 30 minutes and the patient can return to usual activity.
Our Board Certified Radiologist reviews the images after which the findings are relayed to the referring doctor within 24 hours. In some cases the Virtual Colonoscopy will demonstrate parts of the colon that the conventional colonoscopy cannot reach. The possible findings on colonoscopy are polyps, diverticula and tumors.
The advantages of virtual CT colonoscopy over conventional colonoscopy are as follows:
- No anesthesia, sedation or pain medication is required.
- There is high patient acceptance and compliance for the procedure.
- Patient can return to normal activities immediately afterward.
- There are virtually no complications.
- The test is almost as sensitive as conventional colonoscopy, and it allows visualization of the junction between the small intestine and the large intestine (right colon), an area that is not completely visualized 10 to 15% of cases with conventional colonoscopy.
- A CT scan of all the other organs of the abdomen and pelvis is included.
- The total cash price is much less than the charges for conventional colonoscopy. In Kentucky all commercial insurance companies are required to reimburse for Screening Virtual Colonoscopy.
- There are many patients who refuse conventional colonoscopy who will have a virtual CT colonoscopy.
- Virtual colonoscopy is an excellent option for patients who cannot be taken off anticoagulants for conventional colonoscopy.
The disadvantages of virtual CT colonoscopy over conventional colonoscopy are as follows:
- The ability to differentiate stool from artifact and polyp may not be as good.
- If a biopsy is needed, conventional colonoscopy will still be required.
- There is exposure to significant radiation.
- CT of the abdominal and pelvic organs may reveal benign findings that require additional testing and costs.
Virtual CT colonoscopy is performed at Lexington Diagnostic Center in the following manner:
- The patient is asked to be on a clear liquid diet for 24 hours.
- A colon bowel cleansing prep is used the evening before, (a magnesium citrate and biscolyl prep with the recommended oral fluids.)
- The patient is placed on their back on the CT table, a small rectal tube is inserted and the colon is filled with CO2 gas. This causes a feeling of fullness and usually only mild discomfort, although occasionally there is moderate cramping.
- During one breath hold, totaling 15 to 20 seconds, a fast CT scan is obtained through the abdomen and pelvis, covering the entire colon. The patient is then asked to turn to the prone position (on the stomach) and the procedure is repeated.
- The patient is then discharged to return to normal activities. The gas is expelled and/or absorbed. The total time in our office should be 1 hour or less.
- The CT scan images are then processed by a special computer viewer and the axial images and 3d surface (Virtual) rendering is prepared for the radiologist to interpret. A report is ready in about 24 hours.
Contraindications to virtual CT colonoscopy includes a history of the following:
- Total hip replacement (metal in hips causes CT scan artifact).
- Active Crohn's disease, ulcerative colitis, inflammatory bowel disease or diverticulitis (increased risk of perforation).
- History of previous bowel perforation.
- Severe pain or cramps on day of examination.
- Special dietary considerations may be needed for diabetics.
- Alternate low sodium bowel prep is recommended for cardiac and renal patients on low sodium diets.
What are the indications for virtual CT colonoscopy?
The indications are the same as for conventional screening colonoscopy, which are:
- Patients over 50 years of age
- Patient over 40 with history of colon cancer
- Patients with family history of colon cancer
- Repeat scan every 5 years, or more frequently at doctors discretion.
Kentucky Commercial insurance companies are now required to reimburse for Screening Virtual Colonoscopy just as it would for any colon cancer screening test recommended by the American Cancer Society. Medicare and Medicaid do not yet cover for these screening tests. If your doctor orders these tests because of symptoms and you have been unable to complete a traditional colonoscopy, or if your Gastroenterologists feels that you are not a candidate for traditional optical colonoscopy, then Medicare and most commercial insurance companies will pay for them. If the test is ordered and done only for screening purposes, a few will pay, but most will not.
Yes, a cleansing bowel prep is necessary. Any solid material remaining in the colon would make it impossible to identify small polyps. We recommend a Magnesium Citrate and Bisacodyl preparation protocolwith a liquid diet the day before. These items can be purchased over the counter at most pharmacies and drug stores. We do not recommend Golytely or other similar liquid preparations for routine cases.
If a polyp or tumor is found, another test such as flexible colonoscopy or surgery will be required for removal. This is the same for any noninvasive screening test. If we do find significant polyps (and if patient desires), we have made arrangements with gastroenterologists and colorectal surgeons to have our patients seen the same day for traditional optical colonoscopy in order to avoid returning another day and having another bowel prep.
We perform a CT Abdomen and Pelvis with the patient on their back and then again on their stomach, so there would be more radiation than a conventional CT scan. However, the amount of radiation involved is still within a safe range.
We require payment of $751 at the time of the test.
This test requires the insertion of a small tube into the rectum and inflating the colon with air or carbon dioxide. This is much like having an enema. There are no needles or injections required and therefore it is noninvasive.
No. Since Virtual Colonoscopy is noninvasive, blood thinners are not a problem, as they are with conventional flexible colonoscopy.
Virtual Colonoscopy is very safe. There is virtually no risk of colon perforation such as there is in a small percentage of cases with conventional flexible colonoscopy.
No. Virtual Colonoscopy does not require any sedation, pain medications, oral or IV medications.
Patients describe Virtual Colonoscopy as uncomfortable with mild cramping (but not painful) when the colon is being filled with air. The CT scan can be completed in one or two breath holds and then the rectal tip is removed and the air is expelled or absorbed.
Virtual Colonoscopy has been shown to be as good as conventional flexible colonoscopy in detecting clinically significant polyps and cancers. Virtual Colonoscopy will visualize the entire colon in most cases. Conventional colonoscopy will fail to visualize the entire colon in 10 to 15% of cases.