URINE AND STOOL TESTS
Urine, which is produced by the kidneys, contains a large amount of water, within which the body’s waste products are dissolved. Infections that occur in the urinary system can lead to abnormalities in the urine. If the kidneys are damaged, the normal amounts of elements in the urine are altered. During illnesses such as diabetes mellitus, sugar may “leak” into the urine. Its measurement can be useful in controlling the degree of blood sugar elevation.
Some urine tests require only a small sample of urine. Other tests require a whole day’s urine, sometimes collected in a special container that contains a preservative to keep it from decomposing. It is sometimes necessary to bring the first urine passed in the morning.
When the physician checks your urine for signs of infection, it must be collected in a way that keeps the bacteria in the urine from being contaminated by the bacteria on your skin. Urine collected in this way is called a midstream urine (MSU) or clean-catch specimen. Such a sample requires a sterile container so that only the germs in the urine are examined.
In men it is usually easier to collect a clean-catch specimen. As the man urinates into the toilet, and while the stream is flowing, he can place the sterile container under it without interrupting the flow.
In women, bacteria normally inhabit the area around the urethra. If these enter the container with the urine, the test results may wrongly suggest an infection. It is therefore necessary for women to clean the area around the urethra and vagina with sterile water before collecting the urine. Then, as the urine flows, while standing over a toilet, the specimen is collected in a sterile container without interrupting the stream. In older women with physical disabilities or who are unsteady, it may be necessary for a technician or nurse to help obtain a clean-catch specimen.
The stools may be tested for bacteria or parasites if there is a suspicion of infection, for example, if you experience severe or prolonged periods of diarrhea. Sometimes the stools contain bright red blood if bleeding from the colon or rectum has occurred. If there is significant bleeding from the stomach, the stools may become black and look like tar (tnelena). Small amounts of blood in the stool may not be visible to the naked eye; this is called occult bleeding. Such bleeding may cause anemia. Special tests are used to check stool samples for occult blood. In order to diagnose bowel malignancies at an early stage, some physicians recommend that older individuals take stool samples at home and apply them to home testing kits which can then be brought to the physician for analysis.
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