Colorectal Cancer is the second most common cause of cancer death among men and women combined. Yet the American Cancer Society states that 90% of all colorectal cancer cases and deaths are thought to be preventable through lifestyle improvements and timely screening. The American Cancer Society recommends that patients undergo a screening colonoscopy beginning at age 50, earlier if there are risk factors present.
Virtual Colonoscopy is a promising new method that allows doctors to look at the colon to detect polyps and cancers. Polyps are small growths in the colon that may become cancerous if they are not removed. Virtual colonoscopy is a recently developed technique that uses a CT scanner and computer virtual reality software to look inside the body without having to insert a long tube (Conventional Colonoscopy) into the colon or without having to fill the colon with liquid barium as in Barium Studies.
What are some common uses of the procedure?
Indications for virtual colonoscopy include screening for polyps, incomplete or failed colonoscopy, preoperative assessment of the colon proximal to an occlusive cancer, frail, elderly patients, and patients who cannot otherwise tolerate traditional colonoscopy.
- Polyp detection
Recent studies have shown that CT virtual colonoscopy with fecal tagging has demonstrated a high degree of sensitivity and specificity in the detection of clinically significant polyps (>5mm).
Such polyps have significant malignant potential.
- Incomplete or failed colonoscopy
Traditional Colonoscopy fails to visualize the cecum in a significant number of patients. This means an entire section of the colon goes unexplored. This is not an issue with Virtual Colonoscopy. Virtual Colonoscopy has the additional ability to view structures outside the wall of the colon, allowing the physician the potential of identifying abdominal abnormalities.
- Occlusive Cancer
Another application of virtual colonoscopy is the assessment of the colon prior to surgery involving a tumor that may be blocking the colon. Using traditional colonoscopy, a scope would not advance without causing trauma to the patient, but Virtual Colonoscopy could help the surgeon in planning his surgical procedure and identify if there were other tumors present.
- Frail, Elderly Patients
Aged, infirmed patients who require examination of colon are more easily examined by Virtual Colonoscopy than by traditional colonoscopy with high diagnostic accuracy for pathology that would be relevant in this age group.
Other patients who would be excellent candidates for Virtual Colonoscopy would be those who cannot tolerate traditional colonoscopy for other reasons, i.e. bleeding disorders or taking blood thinners, perforated bowel, inability to be sedated, severe hemorrhoids, anatomically difficult bowel, etc.
How should I prepare for the procedure?
You should inform the x-ray technologist about any recent illnesses or other medical conditions, as well as any allergies you might have to medications. Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.
The quality of your virtual colonoscopy examination is dependent in part on your bowel preparation. Without a preparation, the normal debris and residue within the colon can be confused as polyps which might cause an unnecessary colonoscopy. Alternatively, large amounts of residual colonic content may hide small polyps and make the test much less useful. Because of this, it is imperative that you follow the instructions that we provide. We will provide you with a prep kit and detailed instructions on how to use it. The prep consists of 1.5 oz of liquid, 4 tablets, and a suppository to cleanse your digestive tract and 4 bottles of Tagitol to mark any remaining stool, for differentiation from polyps. The day prior to the exam, you will eat light meals, drink clear liquids, and perform your prep. After 9PM that evening, you should take nothing by mouth.
Once you arrive at a Methodist Diagnostic Center, you will be asked to change into a gown before your examination. You will also be asked to remove jewelry, eyeglasses, or any metal objects that could obscure the images.
What does the equipment look like?
The CT scanner is a large, square machine with a hole in the center, something like a doughnut. The patient lies still on a table that can move up or down, and slide into and out from the center of the hole. Within the machine, an x-ray tube on a rotating gantry moves around the patient's body to produce the images, making clicking and whirring noises as the arm moves. Though the technologist will be able to see and speak to you, you will be alone in the room during the actual exam..
How does the procedure work?
During a traditional colonoscopy, a long, flexible tube is passed from the rectum through the entire length of the colon while the physician views the lining. The procedure is usually performed in a surgical suite and requires sedation or occasionally anesthesia. Penetration of the colon wall is also a problem. Virtual Colonoscopy is safer and less invasive than traditional colonoscopy, and requires no sedation. The colon is gently inflated with air rather than an invasive tube. Thereafter, a special high-speed CT scanner captures a few hundred thin-slice images through the abdomen. The scan takes about 30 seconds with the patient lying on his/her back and then once more lying on his/her stomach. Then a powerful computer reconstructs a 3-D semi-transparent image of the colon that is reviewed from all angles. In addition to the inside of the colon, wall thickening and abnormalities outside the colon may be detected.
How is the procedure performed?
You will be positioned on the CT table lying on your back first.
The actual Virtual Colonoscopy procedure will begin by having a small flexible rubber tube placed in the rectum, so that CO2 (Carbon Dioxide) can be introduced into the colon. The colon is gently inflated with the CO2 and a CT scan is performed while the patient lies comfortably on his /her back and then on his/her stomach. The total time required for the study is approximately 20-30 minutes. Because sedation is not required, patients are free to leave the CT suite immediately without the need for observation or recovery. Patients can resume normal activities immediately after the procedure and can eat, work or drive without a delay.
You will be alone in the room during the scan; however, the technologist can see, hear, and speak with you at all times.
What will I experience during the procedure?
CT scanning causes no pain, and with spiral CT the need to lie still for any length of time is reduced.
Some centers use room air to insufflate the colon, but at Methodist Diagnostic Centers, we use CO2, because it is much more patient friendly. You may feel the CO2 as it is filling the colon, but it is readily absorbed by the body and usually does not cause discomfort or bloating like room air.
Who interprets the results and how do I get them?
Dr. Lynn Carvel, Board Certified Radiologist, who received her Virtual Colonoscopy training under Dr. Michael Macari, Medical Director at NYU, will be interpreting your exam. Dr. Macari is the physician who performed Katie Couric’s Virtual Colonoscopy live on the Today Show. You will be mailed a written report along with a burned CD of your Virtual Colonoscopy within 7-10 days of your exam. We will be happy to provide a copy of the report to your physician as well.
What are the benefits of Virtual Colonoscopy?
- Virtual Colonoscopy is safer and less invasive than traditional colonoscopy, and it requires no sedation.
- Virtual Colonoscopy requires a much gentler, less intimidating bowel preparation than some of those often prescribed for traditional colonoscopy.
- Patients can resume normal activities immediately after the procedure and can eat, work or drive without a delay.
- Virtual Colonoscopy has the additional ability to view structures outside the wall of the colon, allowing the physician the potential of identifying abdominal abnormalities.
There is a remote risk of causing perforation within the rectum upon insertion of the enema tip.
What are the limitations of Virtual Colonoscopy?
This procedure is not recommended for individuals who have a history of colorectal cancer, Crohn's disease, rectal bleeding, history of diverticulitis, ulcerative colitis, or those who have had had a recent colonoscopy with positive findings.
As with any procedure, including traditional colonoscopy, there are no guarantees that all clinically significant growths will be detected. It should be remembered that between 10 and 20% of all polyps, and up to 5% of colon cancers are missed, even on traditional colonoscopy. VC (like the Barium Enema) is a diagnostic, not therapeutic technique. All patients in whom polyps are identified would need to undergo traditional colonoscopy for removal.