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McKesson Clinical Reference Systems: Women's Health Advisor 2002.2
Spanish version
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Colorectal Cancer Screening
What is colorectal cancer screening?
Colorectal cancer screening involves several tests or exams
used to check for cancer of the rectum and colon (large
intestine).
Why is colorectal cancer screening important?
Colorectal cancer is the second leading cause of cancer
deaths in the U.S. It is often found too late for a cure.
This does not always have to be the case. When found in the
early stages, colorectal cancer can usually be cured by
surgery. It is important for you to know the symptoms of
colorectal cancer and to have the screening tests that can
detect this cancer in its early stages before it causes
symptoms.
If you have a parent or a sibling who has had colonic polyps
or cancer, you may be at an increased risk for a colonic
polyp or cancer. (Colonic polyps are growths on the lining
of the bowel.) With this family history, your health care
provider may want to screen you for colorectal cancer
earlier and more often than people with no family history of
these problems.
What are the signs of colorectal cancer?
Call your health care provider right away if you notice any
of these signs of possible colorectal cancer:
- rectal bleeding
- blood in your stool
- a change in your bowel movements, especially if you have
bouts of constipation that alternate with bouts of
diarrhea
- pain in your lower abdomen that doesn't go away or that
comes back often
- a feeling of discomfort or the urge to move your bowels
when there is no stool present.
What are the screening tests?
Four ways to screen for colorectal cancer are:
- A digital rectal exam, in which your health care provider
feels the inside of your rectum with a gloved finger to
look for growths. This exam has limited value because
your provider can check only the rectum with it and not
the colon. Most colorectal cancers are in the colon.
- A lab test of a sample of bowel movement (stool) for
traces of blood. This test is relatively easy and
inexpensive. However, many factors can interfere with
its accuracy. Also, blood can be present for reasons
other than colorectal cancer. Tests that show traces of
blood need to be followed by more tests.
Eating certain substances before this test may lead to
inaccurate results. For 2 days before having your stool
tested, avoid eating turnips, horseradish, and red meat.
Don't take vitamin C and iron supplements or medicines
that irritate the stomach, such as aspirin.
- Flexible sigmoidoscopy. After giving you a sedative
to relax you, the doctor inserts a slim, flexible,
lighted tool called a sigmoidoscope into your rectum.
The doctor looks at the lower part of your colon with the
scope. He or she can also use this tool to get samples
of tissue for lab tests. About half of all colorectal
cancers or polyps can be seen with this exam.
- Colonoscopy. After giving you a sedative to relax you,
the doctor inserts a slim, flexible, lighted tool called
a colonoscope into your rectum. This tool is longer than
the sigmoidoscope. With it the doctor can see most of
the colon and check for polyps and cancer.
If a sigmoidoscopy or colonoscopy finds an abnormal area in
the rectum or colon, the doctor can use the scope to remove
a sample of tissue from the area for lab tests (a biopsy).
Sometimes the entire abnormal area can be removed with the
scope.
When should I have screening tests for colorectal cancer?
Doctors don't all agree on the best timing for colorectal
screening. There is also controversy over which procedures
are best. Ask your health care provider what tests are best
for you and when you should have them.
If you are age 40 or over, ask your health care provider if
you should have the digital rectal exam and how often.
If you are over age 50, ask your health care provider how
often you should have a stool sample tested for blood and a
sigmoidoscopy or colonoscopy. If you are at risk for
developing colorectal cancer (for example, you have a family
history of colonic polyps or cancer), your provider may
recommend these exams at an earlier age.
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