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Colonoscopy
A colonoscopy (koh-luh-NAH-skuh-pee) allows a doctor to look inside the
entire large intestine. The procedure enables the physician to see things
such as inflamed tissue, abnormal growths, and ulcers. It is most often used
to look for early signs of cancer in the colon and rectum. It is also used
to look for causes of unexplained changes in bowel habits and to evaluate
symptoms like abdominal pain, rectal bleeding, and weight loss.
What is the colon?
The colon, or large bowel, is the last
portion of your digestive tract, or gastrointestinal tract. The colon is a
hollow tube that starts at the end of the small intestine and ends at the
rectum and anus. The colon is about 5 feet long, and its main function is to
store unabsorbed food waste and absorb water and other body fluids before
the waste is eliminated as stool.
Preparation
You will be given instructions in advance
that will explain what you need to do to prepare for your colonoscopy. Your
colon must be completely empty for the colonoscopy to be thorough and safe.
To prepare for the procedure you will have to follow a liquid diet for 1 to
3 days beforehand. The liquid diet should be clear and not contain food
colorings, and may include
Thorough cleansing of the bowel is
necessary before a colonoscopy. You will likely be asked to take a laxative
the night before the procedure. In some cases you may be asked to give
yourself an enema. An enema is performed by inserting a bottle with water
and sometimes a mild soap in your anus to clean out the bowels. Be sure to
inform your doctor of any medical conditions you have or medications you
take on a regular basis such as
The medical staff will also want to know if you have heart disease, lung
disease, or any medical condition that may need special attention. You must
also arrange for someone to take you home afterward, because you will not be
allowed to drive after being sedated.
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Procedure
For the colonoscopy, you will lie on your
left side on the examining table. You will be given pain medication and a
moderate sedative to keep you comfortable and help you relax during the
exam. The doctor and a nurse will monitor your vital signs, look for any
signs of discomfort, and make adjustments as needed.
The doctor will then insert a long,
flexible, lighted tube into your rectum and slowly guide it into your colon.
The tube is called a colonoscope (koh-LON-oh-skope). The scope transmits an
image of the inside of the colon onto a video screen so the doctor can
carefully examine the lining of the colon. The scope bends so the doctor can
move it around the curves of your colon.
You may be asked to change positions at
times so the doctor can more easily move the scope to better see the
different parts of your colon. The scope blows air into your colon and
inflates it, which helps give the doctor a better view. Most patients do not
remember the procedure afterwards.
The doctor can remove most abnormal
growths in your colon, like a polyp, which is a growth in the lining of the
bowel. Polyps are removed using tiny tools passed through the scope. Most
polyps are not cancerous, but they could turn into cancer. Just looking at a
polyp is not enough to tell if it is cancerous. The polyps are sent to a lab
for testing. By identifying and removing polyps, a colonoscopy likely
prevents most cancers from forming.
The doctor can also remove tissue samples
to test in the lab for diseases of the colon (biopsy). In addition, if any
bleeding occurs in the colon, the doctor can pass a laser, heater probe,
electrical probe, or special medicines through the scope to stop the
bleeding. The tissue removal and treatments to stop bleeding usually do not
cause pain. In many cases, a colonoscopy allows for accurate diagnosis and
treatment of colon abnormalities without the need for a major operation.
During the procedure you may feel mild
cramping. You can reduce the cramping by taking several slow, deep breaths.
When the doctor has finished, the colonoscope is slowly withdrawn while the
lining of your bowel is carefully examined. Bleeding and puncture of the
colon are possible but uncommon complications of a colonoscopy.
A colonoscopy usually takes 30 to 60
minutes. The sedative and pain medicine should keep you from feeling much
discomfort during the exam. You may feel some cramping or the sensation of
having gas after the procedure is completed, but it usually stops within an
hour. You will need to remain at the colonoscopy facility for 1 to 2 hours
so the sedative can wear off.
Rarely, some people experience severe
abdominal pain, fever, bloody bowel movements, dizziness, or weakness
afterward. If you have any of these side effects, contact your physician
immediately. Read your discharge instructions carefully. Medications such as
blood-thinners may need to be stopped for a short time after having your
colonoscopy, especially if a biopsy was performed or polyps were removed.
Full recovery by the next day is normal and expected and you may return to
your regular activities.
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Publications produced by
the Clearinghouse are carefully reviewed by both NIDDK scientists and
outside experts. This publication was originally reviewed by Michael
Wallace, M.D., Mayo Clinic
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GI Associates of
Delaware P.A.