Colonoscopy
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What is the
test?
In colonoscopy, an endoscope is passed through
the anus and all the way up through the entire
colon (also called the large intestine) so that
the doctor can see any abnormalities. This screening
test is used to find early cancers and potentially
cancerous polyps (growths on the colon lining).
With colonoscopy, the doctor can immediately
remove polyps and take biopsies of suspicious
tissue. You should have regular screening for
colon cancer starting at age 50, using either
colonoscopy or sigmoidoscopy . Many people wonder
which test is right for them.
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How
do I prepare for the test?
For the doctor to get a clear look at the lining
of your large intestine, it's important that
you drink only clear liquids, such as juice or
broth, the night before the procedure. During
the afternoon and evening before the procedure,
you need to clear your bowels by drinking a fluid
that will help flush them out. Because this fluid
will cause you to go to the bathroom frequently,
it's best to stay home after you take it. Some
doctors recommend a laxative instead of this
liquid, or they recommend using both. Your doctor
may recommend an enema 30-60 minutes before the
colonoscopy, so you have one last bowel movement.
For many people who undergo a colonoscopy, the "clean-out
procedures" before the test are more unpleasant
than the test itself.
Avoid taking aspirin or other NSAIDs for several
days before the test to reduce the risk of bleeding
in case a biopsy must be taken or a polyp removed.
Also, let your doctor know if you're taking a
blood-thinning medicine. In addition, tell your
doctor if you've had any abdominal surgery and
if you're taking insulin. Since you must limit
what you eat on the day before the colonoscopy,
if you take your usual dose of insulin, your
blood sugar might become dangerously low.
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What
happens when the test is performed?
You may receive a sedative through an IV (see "Sedatives
and anesthesia,"
page 8). You wear a hospital gown for the test
and lie on your side on a table.After putting
on a glove and applying some clear jelly to the
outside of it, the doctor feels the inside of
your rectum with a finger. He or she gently inserts
one end of the colonoscope into your rectum.
The colonoscope is a type of endoscope that is
about half an inch wide and a little more than
5 feet long so it can reach the entire length
of your large intestine (see "Endoscopes," page
27).
The doctor fills your intestine with air so
that the camera at the end of the colonoscope
gets a good view. If you didn't receive a sedative,
you might feel a cramplike pain - similar to
the cramping you might get when you have gas-when
air is pumped into your colon. Images of the
interior of your colon appear on a video screen.
If your doctor sees a suspicious place on the
bowel lining, he or she might use some small
clippers on the end of the scope to take a biopsy.
If your doctor sees a polyp, he or she removes
it with a loop of wire pushed through the colonoscope.
The doctor tightens the loop around the polyp's
stem and sends a brief electric current through
the wire to burn the stem and separate it from
your intestine. This process isn't painful because
there are few nerve endings in the stem of the
polyp. The polyp can be removed using vacuum
pressure on the colonoscope or another tool on
the end of the scope.When the doctor is finished,
he or she sucks the extra air out of your intestine
and gently pulls the colonoscope out. The test
usually takes 20-90 minutes, depending on whether
any polyps are removed.
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What
risks are there from the test?
The risks are small, although they are greater
for this test than with sigmoidoscopy. If you
had a biopsy, you might have a small amount of
bleeding after the procedure. Some bleeding complications
require another colonoscopy or surgery. It's
also possible to have an adverse reaction to
the sedative- for example, an allergic reaction
or even heart or breathing complications. You
may also feel some bloating or pain for a few
days after the procedure.
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Must
I do anything special after the test is over?
Because you have been given a sedative, arrange
for a friend or family member to drive you home
afterward. Call your doctor if you have more
than half a cup of bleeding from the rectum or
if you have severe abdominal pain, fever, or
chills.
In rare cases, polyps that are separated from
the colon wall cannot be pulled out of the colon
with the scope. If this happens, your doctor
might ask you to take a laxative and use a strainer
to catch the polyp when you have a bowel movement,
so it can be examined in the laboratory.
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How
long is it before the result of the test is
known?
Your doctor can tell you the results of the
exam immediately afterward. If biopsy samples
or polyps were removed, they are examined in
a laboratory for cancer and other diseases. It
may take a few days for your doctor to get the
lab report.
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