While preparations for VC vary, the 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. A suppository is also used to cleanse the
rectum of any remaining fecal matter. The patient may
also given a solution designed to coat any residual
faeces which may not have been cleared by the laxative.
This is called 'faecal tagging'. This allows the user
(usually a consultant radiologist), viewing the 3D
images to effectively subtract the left over faeces,
which may otherwise give false positive results.
VC takes place in the radiology department of a hospital
or medical center. The examination takes about 10
minutes and does not require sedatives.
* The patient is placed in a
supine position on the examination table * A thin
tube is inserted into the rectum, so that air can be
pumped through the tube in order to inflate the colon
for better viewing. * 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. * The 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.
After the examination,
the images produced by the scanner must be processed
into a 3D image, +/- a fly through (a cine program which
allows the user move through the bowel as if performing
a normal colonoscopy). A radiologist evaluates the
results to identify any abnormalities.
patient may resume normal activity after the procedure,
but if abnormalities are found and the patient needs
conventional colonoscopy, it may be performed the same