SPINAL FLUID AND RELATED TESTS

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SPINAL FLUID AND RELATED TESTS

In addition to blood and urine, other fluids can provide important information. To get a sample of these fluids, a needle is inserted to extract the fluid. Although there is little danger from the procedure, it is more uncomfortable than the sampling of blood or urine.

The brain and spinal cord are surrounded by spinal fluid, which acts as a protective cushion for the nervous system. In health the fluid is clear and contains normal amounts of salts, nutrients, and a few white blood cells for protection from infection. During illnesses in which the nervous system is damaged, the spinal fluid may develop abnormalities that make it possible to diagnose the disorder.

To obtain spinal fluid, a thin needle is passed into the spinal canal through the lower back, after a local anesthetic is used to freeze the area to prevent pain or discomfort. This test is called a lumbar puncture (spinal tap). While the needle is in the spinal canal, the pressure of the spinal fluid can also be measured. The fluid is extracted and analyzed for infection or bleeding within the nervous system. Some special tests require that substances be injected into the spinal canal. In certain infections antibiotics are introduced through the needle into the spinal fluid. It is occasionally necessary to repeat the lumbar puncture to follow the effects of treatment.

Sometimes fluid accumulates in the pleural space around the lungs or in the abdomen, and very occasionally around the heart. At times there may be excess fluid within a joint. Whenever there is an abnormal collection of fluid in the body, it may be necessary to extract it for analysis. Obtaining the fluid may also result in an improvement in symptoms, as when it is taken from around the heart or lungs. Usually a small amount of local anesthetic is used to freeze the skin and muscles before the needle is inserted. Although you may feel the pressure of the needle, you should not experience an undue amount of pain.

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