In clinical pathology, urine specific gravity is a measure or urinalysis parameter that is often used to evaluate kidney function and can help in the identification of a variety of renal diseases. The urine specific gravity test is also commonly referred to as a urine density test. Like the osmolality test, which is a lot more specific, this test identifies urine concentration, but it is a lot easier and more convenient to use.
The kidneys play a vital role in humans as in all other mammals, to aid in the elimination of various water soluble molecules that could include toxins and other metabolic waste. A significant amount of these waste molecules are excreted through urination, and the kidneys play the important role here of concentrating the urine with these molecules so that they can be excreted with the least wastage or loss of water and other nutrients. The specific gravity of urine refers to the measure of the concentration of these excreted waste molecules in the urine. This result is generally described in grams per milliliter. The normal results for a urine specific gravity test would range from 1.002 to 1.028 g/ml. These value ranges may however vary mildly among different laboratories.
It would also be wise to keep in mind that there are certain factors that can influence the outcome or findings of the test. There are certain drugs that can interfere with the test results, increasing gravity measurements, which is why it is important to inform your health care provider about any medications you may be on before going for the test. You may be advised to discontinue such medications if necessary. Intravenous dyes that are used in certain cases for x-ray exams could also interfere with the results for a period spanning up three days.
Under normal circumstance however increases in specific gravity results, or a high concentration of solutes in the urine could be indicative of dehydration, emesis, diarrhea, glucosuria, renal artery stenosis, excessive sweating, and hepatorenal syndrome. It could also indicate a reduced blood flow to the kidneys possibly caused from heart failure. On the other hand, test results that show decreased specific gravity or a lower concentration of solutes in the urine can be related to pyelonephritis, diabetes insipidus, renal failure, interstitial nephritis, acute tubular necrosis, and excessive fluid intake. If the values from the test are found to be abnormal it may also help to do tests for the ph value and protein.
Submitted by M T on January 6, 2010 at 08:58