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During my residency in family practice, we learned how to become
proficient performing flexible sigmoidscopies. Patients hated the
procedure, from drinking the laxative preparation ("Go Lytely" is
such an oxymoron) to the obvious discomfort it would impose. After
a difficult procedure on a quite uncomfortable procedure, my attending
physician would often remark "I cant wait until they get virtual
colonoscopy running& so I dont have they go through this when Im
50!"
What
is it, and when will it become a reality? Millions of Americans
endure sigmoidoscopies as a regular screening test, and rightfully
so, as colon cancer is one of our greatest killers. However, flexible
sigmodoscopies can have complications, although rare, among the
least of which is patient discomfort.
Regular
colonoscopy , which looks at the entire colon also requires sedation
and along with flexible sigmoidoscopy can carry the risks of bleeding,
infection, and perforation. A development in the gastrointestinal
field known as virtual colonoscopy, also known as CT colography,
is a quicker and easier alternative to colonoscopy, and now appears
as an accurate technique in colon screening According to the latest
reports from the American Society for Gastrointestinal Endoscopy,
virtual colonscopy has emerged as a viable alternative to colonoscopy.
Colon cancer often manifests itself as colon polyps, which can appear
as stalks on the intestinal wall. By utilizing similar software
such as in use with a spiral CT scan, the computer can take and
reproduce images of the colon and reconstruct it into a three-dimensional
model. Much like playing a video game, the virtual colonoscopist
can then view the colon using a joystick controlled camera.
Spiral
CT scans, which are in use today, are faster and produce much higher
resolution than compared with older conventional CT scans. Total
scan time of the colon should take no longer than one to two minutes.
Cost of the test appears virtual colonscopy quite reasonable.
A
colography exam is estimated to cost between $400-500 in comparison
with a colonscopy that is close to $1000. And unlike a flexible
sigmoidscopy, a colonscopy will be able to view the entire colon.
Sedation is not used in virtual colonoscopy, eliminating a substantial
anesthesia risk. Unfortunately, a bowel cleansing preparation may
still need to be a part of virtual colonoscopy to obtain the most
accurate views. Researchers are currently reviewing whether subtraction
of fecal residue via computer modeling can be developed. Also, the
colon will also need to be insufflated with air before procedure.
A protocol for biopsy of a suspicious lesion has also yet to be
instituted.
With
virtual colonscopy however determining the site of the lesion will
be more accurate than ever before in pinpointing the location. Making
it a routine colon screening technique still appears years away.
The procedure is still investigatonal and more clincal trials have
to be conducted before its use can become widespread. There is simply
not enough studies done to assess its cost-effectiveness and comparisons
with conventional colonscopy and sigmoidoscopy.
Many medical centers as yet do not have a spiral CT scan as yet,
due to the cost of each machine costing about a million dollars.
Software for this also ranges in the hundreds of thousands as well.
Development of virtual colonscopy using a MRI (magnetic resonance
imaging) which offers accuracy without radiation risk is also being
developed. Another significant barrier is who will perform the virtual
colonoscopy.
Radiologists
are the most obvious choice as they are trained in reading spiral
CT scans and MRIs. However, advanced colon screening is the area
of expertise of the gastroenterologist, who may not be as forthcoming
in handing over these lucrative procedures. However, there is no
question there is a demand for a safer and non-invasive procedure
to colon screening.
With
time, a once feared procedure may as soon be as routine as getting
a chest x-ray. I know my 45 year old attending physician sure hopes
so.
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