Colon and rectal cancer diagnostic tests
Determining the stage of colorectal cancer.
If you or a loved one start experiencing the signs and symptoms of colon or rectal
cancer, your physician will conduct tests to confirm or rule out the possibility
of colorectal cancer.
A correct diagnosis of colorectal cancer is very important. It will help your healthcare
team determine what stage the colon or rectal cancer is in. And it will
also help determine your prognosis and treatment options. Here are some
of the tests used to determine the stage of colon or rectal cancer:
- Biopsy: During a colonoscopy or sigmoidoscopy, an abnormal growth
may be found from which doctors will want to take a sample of tissue, or a biopsy.
This sample may come from the colon and/or rectal area.
- Blood tests: No blood test can definitively detect colon cancer,
but your doctor may order them to better understand what may be causing your symptoms.
- Chest X-ray: X-rays of the chest can show whether cancer has spread
to the lungs.
- Colonoscopy: A thin, flexible tube with a light and camera attached
is gently inserted through the rectum into the colon so the doctor can view the
entire length of your colon for any other abnormal areas. A colonoscopy
is recommended every 10 years.
- CT scan: An X-ray machine linked to a computer takes a series of
detailed pictures of areas inside the body. The patient may receive an injection
of a contrast dye, which will help outline abnormal areas in the body on the scan.
Tumors in the liver, lungs, or other places in the body show up on the CT scan.
- Digital rectal exam (DRE): A test in which a doctor or nurse will
insert a lubricated, gloved finger into the rectum to check for lumps or abnormal
areas.
- Double-contrast barium enema (DCBE): In this test, a series of
colon and rectum X-rays are taken. The patient is given an enema with a barium solution,
and air is pumped into the rectum. The barium and air outline the colon and rectum
on the X-rays. It detects approximately 30% to 50% of the cancers found with standard
colonoscopy, and may miss small polyps.
- Endorectal ultrasound (EUS): An ultrasound probe is inserted into
the rectum. The probe sends out sound waves (out of range of human hearing) that
bounce off the rectum and nearby tissues. During an endorectal ultrasound exam a
computer-generated picture, created from the echoes, shows how deep a rectal tumor
has grown or if the cancer has spread to lymph nodes or other nearby tissues.
- Fecal occult blood test (FOBT): A stool sample is examined for
blood.
- Sigmoidoscopy: The rectum and lower colon are examined with a lighted
instrument. Precancerous and cancerous growths found can be removed or biopsied
for further investigation.
-
Magnetic resonance imaging (MRI): Your doctor may also use other tests,
such as MRI, to see if the cancer has spread. A contrast material is often injected
into a vein before the scan to make details easier to see.
- Lymph node sampling: The lymphatic system is a network of organs, lymph nodes, lymph ducts,
and lymph vessels. It is a major component of the body’s immune system. Lymph nodes
are small bean-shaped collections of immune system cells clustered at various points
of the body.
Because colon and rectal cancers often spread to nearby lymph nodes, ideally your
doctor will take a biopsy of at least 12 lymph nodes to check for disease. This
helps show how far the cancer has spread.
Sampling at least 12 lymph nodes is important because:
- it can give doctors a more accurate diagnosis of your condition
- it helps your medical team make informed treatment decisions, which may lead to
a better survival rate for you
Learn
about the treatment options for colon and rectal cancer.
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