It is complete examination of rectal by which different problems occurring in rectal system can be determined. It is recommended that all individuals over the age of forty have yearly digital examinations of the rectum and their stool tested for hidden or “occult” blood. During digital examination of the rectum, the doctor inserts a gloved finger into the rectum to feel for abnormal growths. Stool samples can be obtained to test for occult blood (see below). The prostate gland can be examined at the same time.

An important screening test for colorectal cancers and polyps is the stool occult blood test. Tumors of the colon and rectum tend to bleed slowly into the stool. The small amount of blood mixed into the stool is usually not visible to the naked eye. The commonly used stool occult blood tests rely on chemical color conversions to detect microscopic amounts of blood. These tests are both convenient and inexpensive. A small amount of stool sample is smeared on a special card for occult blood testing. Usually, three consecutive stool cards are collected. A person who tests positive for stool occult blood has a thirty to forty-five percent chance of having a colon polyp, and a three to five percent chance of having a colon cancer.

Colon cancers found under these circumstances tend to be early and have a better long term prognosis.

It is important to remember that having stool tested positive for occult blood does not necessarily mean the person has colon cancer. Many other conditions can cause occult blood in the stool. However, patients with a positive stool occult blood should undergo further evaluations involving barium enema x-rays, colonoscopies, and other tests to exclude colon cancer, and to explain the source of the bleeding. It is also important to realize that stool which has tested negative for occult blood does not mean the absence of colorectal cancer or polyps. Even under ideal testing conditions, at least twenty percent of colon cancers can be missed by stool occult blood screening. Many patients with colon polyps are tested negative for stool occult blood. In patients suspected of having colon tumors, and in those with high risk factors for developing colorectal polyps and cancer, flexible sigmoidoscopies or screening colonoscopies are performed even if the stool occult blood tests are negative.

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