What is virtual colonoscopy?
Medical imaging procedure.
Also known as CT colonography.
Non invasive procedure.
uses x rays and computers.
2D and 3D images of rectum and entire colon.
display them on a screen.
can provide 3D reconstructed endoluminal
views of the bowel.
The colon is also called the large intestine
Final straight portion of the large intestine.
Why the Test is Performed
Follow-up on colon cancer or polyps
Look for the cause of:
• Abdominal pain, changes in bowel movements, or
• anemia due to low iron
• Blood in the stool
• Screen for cancer of the colon
An abnormal growth of tissue projecting from
a mucous membrane
How to Prepare for the Test
Patient need to empty bowels before the exam
patient will usually be asked to take laxatives or other
oral agents at home the day before the procedure to
clear stool from the colon.
How the Test is Performed
Patient is asked to lie on his/her left side on a
narrow table that is connected to an MRI or CT
knees will be up towards the chest.
A small, flexible tube will be inserted into rectum.
Air is pumped through the tube to make the colon
bigger and easier to see.
After this is done, patient will be asked to lie in
The table moves through the scanner to produce
a series of two-dimensional cross-sections along
the length of the colon.
A computer program puts these images together
to create a three-dimensional picture that can be
viewed on the video screen .
patient is asked to hold his/her breath during the
scan to avoid distortion on the images.
The scan is then repeated with the patient lying
in a prone position .
Direction of rotation
Rotating x ray
Virtual colonoscopy is less invasive, safer, and
takes less time than a regular colonoscopy.
A thin tube to insert air into the colon is placed
in the rectum rather than a long flexible tube
that is moved up your colon.
Patients do not require anesthesia or sedation
and can return home on their own or get back to
work immediately after the test.
VC provides clearer, more detailed images
a radiologist cannot take tissue samples (biopsy) or
remove polyps during VC, so a
conventional colonoscopy must be performed if
abnormalities are found.
may not show polyps smaller than 10 mm
There is a slight risk that the CT scan can interfere
with implanted or external medical devices.
The risks of virtual colonoscopy include
exposure to radiation and
perforation—a hole or tear in the
lining of the colon.