test, a flexible, lighted viewing tube (colonoscope) is passed
through the anus, rectum, the full length of the large intestine
(or colon), and sometimes into the lower part of the small
intestine. The colonoscope is equipped with fiberoptic cables
that enable a physician to visually inspect the lining of
these organs for any evidence of disease or abnormality.
In addition, instruments may be passed through the scope to obtain
tissue biopsies or stool samples for microscopic examination.
is primarily performed in people with symptoms of a bowel abnormality
(for example, blood in the stool, recent changes in bowel habits,
or abdominal pain) when the cause is unclear or when the results
of less invasive tests, such as sigmoidoscopy or barium enema,
are negative or inconclusive. It may also be done therapeutically
to perform procedures such as polyp removal.
Purpose of the Test
To detect and
evaluate inflammatory or ulcerative bowel disease, polyps, tumors,
bleeding, and other bowel abnormalities.
evaluate tumors, ulcers, and narrowed passages (strictures) detected
by a barium enema.
To screen for
colon cancer or precancerous polyps in people with a high risk
of developing the disease, such as those with a strong family
history of colorectal cancer or familial polyposis.
patients who have been treated for colorectal cancer for recurrence.
patients with inflammatory bowel disease for the development
of colorectal cancer.
to remove polyps, stop active bleeding, dilate narrowed passages,
or remove an obstruction.
Who Performs It
may provoke some anxiety, the procedure usually causes only minor
discomfort. You will receive a sedative medication before the
You must wait
at least a week after having a barium x-ray procedure before
undergoing colonoscopy, since the presence of barium in the abdomen
interferes with visual inspection of the colon.
should not be performed in people with a suspected colon perforation
or an extremely dilated colon (megacolon), in women who are about
to give birth, or in those who have had a recent heart attack
or abdominal surgery.
may not be possible in people with painful anorectal conditions
such as fissures or hemorrhoids; diverticulitis (inflammation
in the sacs of the colon); active bleeding in the bowel or rectum;
or acute colon inflammation.
may be performed in a hospital or an outpatient setting.
Before the Test
doctor if you regularly take nonsteroidal anti-inflammatory drugs
(such as aspirin, ibuprofen, or naproxen) or anticoagulants such
as warfarin (Coumadin, Panwarfin). These medications must be
discontinued for several days before the test to reduce the risk
intestine before colonoscopy is essential to provide clear visibility
during the procedure. Your doctor will give you specific instructions.
you should consume only clear liquids (such as water, bouillon,
or gelatin) for 24 to 48 hours before the scheduled procedure,
and drink large amounts of water on the day before. Do not eat
or drink anything after midnight on the day before the test.
your doctor will prescribe an oral laxative agent to take on
the day before the procedure. (Sometimes, instead of a laxative,
the bowel cleansing is accomplished by drinking a gallon of nonabsorbable
salty liquidfor example, GoLYTELY, Colyte, or NuLYTELY.)
On the morning
of the procedure, a cleansing enema may be administered at the
o Immediately before the test, an intravenous (IV) needle or catheter is inserted
into a vein in your arm. A mild sedative medication is usually administered,
but you will remain conscious throughout the procedure (so-called conscious
What You Experience
You lie on
your side on a table, with your knees drawn to your chest, and
you are draped to minimize any embarrassment.
begins by inserting a gloved, lubricated finger into your rectum
to perform a manual examination.
Next, the lubricated
scope is gently inserted through the anus and rectum and then
into the colon.
You may experience
some abdominal cramping or feel the urge to defecate as the instrument
is inserted and advanced. Breathe deeply and slowly through your
mouth to relax your abdominal muscles and reduce this discomfort.
In order to
advance the scope through the deepest portion of the colon, the
doctor or a nurse may help you to lie on your back. The doctor
may palpate your abdomen or use fluoroscopy to help guide the
passage of the scope.
As the scope
is slowly withdrawn, the doctor carefully inspects the lining
of your colon, rectum, and anus, looking for any abnormalities.
of air will be instilled through the scope to dilate the intestinal
passage for better viewing. This may cause you to feel bloated
and to pass gas.
the circumstances, a biopsy forceps or other instruments may
be inserted through the scope to obtain tissue or stool specimens.
Polyps may be entirely removed using an electrocautery device.
(These procedures are painless, since the lining of the colon
contains no pain receptors.) Tissue and fluid samples will be
sent to a laboratory for analysis.
time typically ranges from 30 to 60 minutes.
Risks and Complications
include bleeding, impaired respiration due to oversedation, and,
rarely, perforation of the rectum or colon. Perforation requires
surgery to repair the hole in the colon.
After the Test
You will rest
in a recovery room until the sedative wears off (usually about
an hour). During this time, your vital signs will be checked
periodically, and you will be observed for signs of complications.
someone to drive you home.
You may experience
flatulence or gas pains for several hours after the procedure.
If a biopsy
was performed, you may have a small amount of rectal bleeding
for several hours.
Rest in bed
for the remainder of the day and drink only clear liquids and
no alcohol for 24 hours.
After 24 hours,
you may resume your normal activities and any medications withheld
before the test.
Blood may collect
and clot under the skin (hematoma) at the IV insertion site;
this is harmless and will resolve on its own. For a large hematoma
that causes swelling and discomfort, apply ice initially; after
24 hours, use warm, moist compresses to help dissolve the clotted
doctor immediately if you develop fever, chills, excessive rectal
bleeding, or abdominal pain or distention.
visual inspection of the bowel, the doctor will note any abnormalities
such as bleeding, inflammation, abnormal growths, or ulcers.
tests may be necessary to pinpoint a diagnosis. For example,
biopsied tumors and excised polyps are examined under a microscope
by a pathologist for evidence of cancer or another abnormality.
If no abnormality
is found, your doctor will recommend a schedule of periodic follow-up
exams to monitor your health.
If a problem
is diagnosed based on the findings of this test, appropriate
medical or surgical treatment will be recommended.
From The Johns
Hopkins Consumer Guide to Medical Tests. You can order
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