What is a CT Virtual Colonoscopy?

• Computed tomography is an imaging test that uses X-rays and a computer to make detailed images of the body. A CT scan shows details of the bones, muscles, fat, and organs. CT scans are more detailed than standard X-rays.
• In a CT scan, an X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure. The X-ray information is sent to a computer that interprets the X-ray data and displays it in a 2-D form on a monitor.
• CT scans may be done with or without "contrast." Contrast refers to a substance taken by mouth or injected into an IV (intravenous) line that causes the particular organ or tissue under study to show up more clearly on the scan.
• CT colonography, also known as virtual colonoscopy, uses low dose radiation CT scanning to obtain an interior view of the colon (the large intestine).
• Virtual colonoscopy is a minimally invasive exam to screen for cancer of the large intestine (colon cancer).
• Unlike traditional colonoscopy, which requires a scope to be inserted into your rectum and advanced through your colon, virtual colonoscopy uses a CT scan to produce hundreds of cross-sectional images of your abdominal organs. The images are combined and digitally manipulated to provide a detailed view of the inside of the colon and rectum.

What are the advantages of CT virtual colonoscopy rather than invasive colonoscopy?

• This minimally invasive test provides both 2-D and 3-D images that can depict many polyps and other lesions as clearly as when they are directly seen by conventional colonoscopy.
• CT colonography has a much lower risk of perforating the colon than conventional colonoscopy.
• CT colonography is an excellent alternative for patients who have clinical factors that increase the risk of complications from colonoscopy.
• Elderly patients, especially those who are frail or ill, will tolerate CT colonography better than conventional colonoscopy.
• CT colonography can be helpful when colonoscopy cannot be completed because the bowel is narrowed or obstructed for any reason, such as by a large tumor.
• If conventional colonoscopy cannot reach the full length of the colon.
• CT colonography can detect abnormalities outside of the colon.
• CT colonography is well tolerated. Sedation and pain relievers are not needed.
• CT colonography is less costly than colonoscopy.

Why do I need a CT virtual colonoscopy?

• The major reason for performing CT colonography is to screen for polyps or cancers in the large intestine. Polyps are growths that arise from the inner lining of the intestine. A very small number of polyps may grow and turn into cancers.

How to prepare for a CT virtual colonoscopy?

This exam require some special preparations (As bowel cleaning) The bowel-cleansing regimen for CT colonography consist of :
• Smaller volume of cleansing liquid.
• Your diet will be restricted to clear liquids the day before the examination.
• It is very important to clean out your colon the night before your CT colonography examination.
• You will be asked to take either a set of pills and/or a liquid laxative.
• Additional agents may also be taken the day before the exam. These may include small quantities of barium and iodinated liquids. These agents help the radiologist better distinguish stool from polyps by "tagging" the remaining stool and fluid.

Other common preparations for CT exam :
• You should wear comfortable, loose-fitting clothing to your exam.
• Metal objects, including jewelry, eyeglasses, dentures and hairpins should be left at home or removed prior to your exam. You may also be asked to remove hearing aids and removable dental work. Women will be asked to remove underwire containing metal.
• Women should always inform their physician and the CT technologist if there is any possibility that they may be pregnant.
• You should inform your doctor of all medications you are taking and if you have any allergies.
• Inform your doctor of any recent illnesses or other medical conditions and whether you have a history of heart disease, asthma and diabetes or kidney diseases.

In case of contrast examinations :
• You should not to eat or drink anything (fasting) for a few hours (4 to 6 h) before the exam, and do renal function test, inform your doctor or radiology technician if you have any allergies or kidney diseases.