What is a virtual colonoscopy? A virtual colonoscopy is an imaging procedure that uses technology known as computerized tomography (CT) to produce hundreds of cross-sectional images of the rectum and entire colon. A virtual colonoscopy is used to look for the cause of:
- Abdominal pain, changes in bowel movements or weight loss
- Anemia due to low iron
- Blood in the stool or black tarry stools
A virtual colonoscopy can also show irritated and swollen tissue, ulcers and abnormal growths including polyps. In addition this exam looks at the entire abdomen and can show abnormalities outside of the gastrointestinal (GI) tract.
A virtual colonoscopy can also be used to screen for colon cancer. A gastroenterologist (GI) may order a virtual colonoscopy as a colonoscopy alternative if he/she was not able to move the flexible tube, called a colonoscope, all the way through the colon during a traditional colonoscopy. This type of screening does not require sedation or insertion of a scope into the colon.
Preparing for a Virtual Colonoscopy
Similar to a traditional colonoscopy, you will need to empty your colon prior to the exam. Any residue in your colon may obscure the images taken during the exam. Your doctor will provide you with specific instructions in order to accomplish this. Make sure you tell your doctor about all of the medications you are taking. You may need to stop taking certain medications before your exam.
You will be asked to stop eating solid foods a day or two before the exam. To avoid dehydration, you will need to follow a liquid diet that includes clear, fat-free bouillon or broth, gelatin, strained fruit juice, water, plain and unsweetened coffee or tea, or diet soda. You will not be allowed to eat or drink anything after midnight the night before your exam. You may be asked to take a laxative in either pill or liquid form the night before the exam, and you may also need to use a suppository to clear any remaining residue in your colon.
You may be asked to drink a contrast agent before your exam. This medication helps identify stool in your colon and helps the doctor differentiate between colon abnormalities and stool residue.
What Happens during a Virtual Colonoscopy?
You’ll begin the exam lying on your side on the exam table with your knees drawn up towards your chest. The doctor will place a catheter, or a small tube, inside your rectum to fill your colon with air or carbon dioxide. The air or gas, which helps create clear images, may cause a feeling of pressure in your abdomen. Sedation is not necessary for a virtual colonoscopy, but you may be given medicine to reduce the likelihood of stomach cramps during the exam.
For the next part of the exam, you’ll lie on your back, and the exam table will be moved into the CT machine. In order to get accurate, clear images, you will need to remain completely still. You may be asked to turn and hold various positions, and you may be asked to hold your breath at times. If necessary, a contrast agent may be given through an IV in your arm to help create clearer images. The exam usually takes between 10 and 15 minutes.
The computer combines all the images, which are viewed on a video monitor. The images can be viewed as two-dimensional CT scans, which display any possible abnormalities protruding from the lining of the colon. The images can also be combined to generate a three-dimensional view of the colon, allowing doctors to “fly through” the organ looking for any suspicious growths or protrusions.
What Happens After a Virtual Colonoscopy?
Most of the air or gas will be removed from your colon through the catheter in your rectum. You may feel bloated or pass gas for a few hours after the exam as you clear the remaining air or gas from your colon. Walking may help relieve any discomfort. If these symptoms do not improve on their own, contact your doctor. You can return to your usual diet and activities right away.
What Are the Results of a Virtual Colonoscopy?
Your doctor will review the results of the colonoscopy, and then share the results with you. The results of a virtual colonoscopy are considered either negative or positive. A negative result means that the doctor did not find any abnormalities in the colon. If no polyps were found, your doctor may recommend repeating the exams in five years, but it may be sooner depending on your family history and other risk factors.
A positive result means that the doctor found polyps or abnormal tissue in the colon. Depending on the size and number of polyps, your doctor may recommend a traditional colonoscopy to obtain samples of the abnormal tissue or remove the polyps. In some cases a traditional colonoscopy can be performed on the same day as the virtual colonoscopy. You will need someone to take you home afterwards because a traditional colonoscopy typically uses sedation. If your doctor is concerned about the quality of the view obtained with the virtual colonoscopy, a repeat virtual colonoscopy or another screening test may be recommended.