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First symptoms
Some people do not have any symptoms of colon cancer. Others have changes in their bowel habits or bleeding from the bowel. Diarrhea, constipation, abdominal pain and gas are other symptoms of colon cancer. Blood in the stool can range from bright red to maroon to black. Sometimes your stool will get narrower (smaller in caliber) if the cancer is rectal or near the anus.
Often bleeding is not visible, so your doctor may have you do a simple test on your stool for occult (hidden) blood. He or she may want to test several samples, because early colon cancers may bleed only off and on. You can do these tests at home.
If you have bleeding hemorrhoids, wait to take the test until any bleeding has stopped. It's especially important to screen if you have hemorrhoids, because they share some of the same symptoms with colon cancer.
Diagnosis
During a physical exam, your doctor checks for abdominal masses or an enlarged liver and enlarged lymph nodes in the groin. Your doctor may also do a rectal exam. For this test, he or she will insert a finger in to your rectum to feel for lumps.
When there is blood in the stool or a suspicious lump felt, doctors usually recommend either a sigmoidoscopy or colonoscopy. These tests use a flexible tube with a light and a viewing lens or camera to see inside your bowel. A sigmoidoscope can see the lower part of the large bowel. If a polyp or cancer is found, this test is usually followed with a colonoscopy. A sigmoidoscopy usually takes about 15 minutes. You may be given a mild sedative.
A colonoscopy can examine the entire colon. If any polyps or suspicious areas are found, they are removed or a tissue sample is taken. These biopsied tissues are then checked under a microscope for cancer. This procedure is usually done when you are sedated.
Preparing for either test usually involves drinking clear liquids and taking laxatives or an enema to help clear the bowel.
Another method to look in the colon is to fill the large bowel with x-ray contrast material and take a series of x-rays. The procedure is called a barium enema and is less commonly used. Barium is non-toxic and opaque to x-rays. It is given as an enema to fill the large bowel. Often, air is also pumped in. The three separate densities (air, tissue and barium) make it easy to see the outline of the large bowel and most anything inside that is not normal, such as a tumor.
If there is an abnormality seen on the barium enema, a colonoscopy with a biopsy should be done.
This article was reviewed and updated June 2007.
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