Urinary osmolality (osmolality) measures the number of osmotically active particles in the urine, or otherwise the concentration of urine. This, in turn, reflects the ability of the kidneys to condense urine. The test is useful for assessing fluid and electrolyte balance as well as determining fluid requirements for the body. The test is also particularly useful in the evaluation of hyponatraemia and hypernatraemia and to distinguish renal azotemia from acute ischemic tubular necrosis. After overnight fasting, the osmolality of the urine should be at least three times greater than the osmolality of the blood.
Medications affecting the measurement: antibiotics, antidepressants, antipsychotics, bromocriptine, chemotherapy, dextran, diuretics, glucose, mannitol and silicone preparations.
Possible Interpretation of Pathological Values
- Increase: Addison's disease, azotemia, congestive heart failure, dehydration, diabetes mellitus, diarrhea, edema, glucosuria, hepatic cirrhosis, protein-rich diet, hyperglycemia, hyperthyroidism, ketatriemia antidiuretic hormone (SIADH), urea
- Decrease: Acute kidney failure, aldosteronism, diabetes mellitus, edema, fever, glomerulonephritis, hypercalcaemia, hypokalaemia, hyponatraemia, multiple myeloma, fluid overload, sickle cell anemia, pleural effusion, anemia
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.