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Stool Examination for Presence of Blood

Men and women over age 40 should have their stools examined each year for blood, an important step in detecting bowel cancer.

Bowel cancer is one of the most frequently occurring cancers in the United States. Unfortunately, we do not know the cause of most bowel cancers other than the presence of polyps (benign growths) and some gene abnormalities. At present, there is no adequately documented method of preventing bowel cancer, though eating plenty of fruits and vegetables does help to reduce the risk, as may reasonably vigorous exercise. The most effective way to prevent invasive cancer is finding tumors very early or find and remove polyps before they turn cancerous. Polyps, especially those that turn cancerous, and early cancers tend to bleed. Testing the stools for blood every year, in addition to regular bowel examination with a sigmoidoscopy or colonoscopy, is a good preventive step.

The best way to detect silent intestinal bleeding is the Hemoccult slide. This is a chemically treated slide to which a tiny amount of bowel movement is added by use of an applicator. The material on the slide is air-dried and then a drop of color developer is placed on the slide. If blood is present, a blue color is seen within one minute. Home tests may also be useful.

It is also important to realize that, if the test is positive, it does not necessarily mean cancer. In at least 80% (and probably in over 90%) of positive tests, the patient has hemorrhoids or some other minor disease. If the test is positive, further investigation is necessary to distinguish between the non-malignant and the malignant (cancerous) causes of the positive result. If the positive test is from a bleeding polyp, that polyp needs to be removed.

One problem with the test for blood in the stools is the false negative tests that result from improper techniques. One reason for this is the failure to study three consecutive specimens. If you collect a specimen on Monday, Wednesday, and Friday, but have bowel movements also on Tuesday and Thursday, then the collection technique is incorrect because the bleeding can be intermittent and missed unless three specimens are submitted from consecutive bowel movements. If a person has two movements a day, then both bowel movements from one day and the first bowel movement from the next day must be examined.

The other major reason for failure to get a positive in the presence of a cancer is an incorrect diet. It is important that 72 hours before the day you collect specimens, you place yourself on a special diet that contains roughage that will cause the tumor to bleed. It is not a very onerous diet. It consists of white fish, ham, poultry, fruits (prunes, apples, grapes), certain vegetables (lettuce, spinach, corn), peanuts, whole grain bread, and bran cereals. Red meats are not permitted because they contain blood and give false positive tests.

The final point relates to speed of processing the slides. If you use Hemoccult slides, you should get them to the physician or laboratory within two days. The slides must then be processed immediately (it takes only one minute to test each slide).

Healthful Life recommends that every man and woman over age 40 have their stools (bowel movements) examined each year for blood. Doing this test every two years instead of yearly is not nearly as effective. As with other types of cancer, it makes a great deal of difference if the tumor is found early. Examining three stool specimens every year may mean the difference between detecting bowel cancer at an early, curable stage or waiting until the malignancy has spread.