Patient Information
Virtual colonoscopy is a new method that allows doctors
to look at the large bowel (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
(Barium Enema). Research has shown that Virtual
Colonoscopy is better able to see polyps than Barium
Enema and is nearly as accurate as Conventional
Colonoscopy. In addition, most patients report that the
Virtual Colonoscopy technique is more comfortable than
either Barium Enema or Conventional Colonoscopy.
Why is it important?
Colorectal cancer (CRC) is a leading cause of
cancer-related death in the United States. In 1999,
approximately 140,000 cases of colon cancer will be
diagnosed in the United States, and 60,000 patients will
die of the disease. Colon cancer can be prevented if
polyps are discovered and removed early. Tumors, masses
of abnormal cells, take years to develop. Initially, a
cell from the colon starts to multiply abnormally and
forms a benign (non-cancerous) polyp, which can remain
harmless for a long time before becoming an aggressive
cancer. Polyps, when detected, can be removed
preventively. Nevertheless, individuals at greatest risk
of developing colorectal cancer remain largely
underscreened. This is due, in part, to poor public
awareness and acceptance of current screening
techniques.
What are the current methods used to detect polyps?
There are several tests that are used to try and detect
polyps. Several government agencies as well as the
American Cancer Society recommend that patients undergo
a test that allows the doctor to see the entire colon at
age 50 and then every three to five years. Currently
there are two accepted methods for seeing the entire
colon; Conventional Colonoscopy and the Barium Enema.
Other tests like the Flexible Sigmoidoscope or which can
only see a small portion of the large bowel (colon) are
considered inferior tests. Conventional Colonoscopy is
associated with increased risk and cost. Conventional
Colonoscopy is unable to see the entire colon in 1 out
of ten people. In addition, Conventional Colonoscopy may
cause an injury of the colon (tear or perforation) in
one of 1500 patients. Medication given into the vein
(intravenous sedation) is usually required to make the
exam bearable and therefore patients cannot resume
normal activities immediately after the test. The
introduction of a safe, noninvasive, and effective
method of detecting colorectal polyps and cancers has
obvious appeal.
How is Virtual Colonoscopy done?
Virtual colonoscopy uses a standard computed tomography
(CT or CAT scan) of the abdomen, which allows
radiologists (special physicians with advanced training
in x-ray imaging) to create 3-D pictures on a
sophisticated computer workstations that look similar to
those seen by Conventional Colonoscopy. Patients need a
cleansing preparation of their bowel prior to the test.
The day of the test, they come to the radiology
department for a CT scan. The actual virtual colonoscopy
procedure will begin by having a small flexible rubber
tube placed in the rectum, so that air can be
introduced. A CAT scan is then performed while patients
lie comfortably on their back and then on their
stomach. The total time required for the study is
approximately 10-20 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. Doctors (radiologists) analyze
the CT data to detect colon polyps or cancers.
Is it painful?
When air is introduced in the colon some patients
experience minimal temporary abdominal cramping or "gas
pains". An intravenous injection of a widely used
medicine to relax the bowel can also be given to help
reduce gas pains, but this is usually not necessary.
