Osmolality Urine Test
|See Also||Lab Tests|
Urine osmolality is a measurement of the number of dissolved particles in the urine. It is considered to be a more accurate measurement of urine concentration than specific gravity is as specific granvity is dependent on the weight and density of particles in the urine. Osmolality can also be measured over a wider range than specific gravity., 
- Osmolality is used to evalutate the concentrating ability of the kidney.
- This test can also be used to monitor fluid and electrolyte balance.
- Osmolality plays a vital role in the workup of patients with renal disease, inappropriate Antidiuretic Hormone (ADH) secretion, and diabetes insipidus.
- Urine osmolality is more easily interpreted when the serum osmolality is simultaneously measured.
- preparation for a fasting urine specimen may require ingestion of a high-protein diet for 3 days before the test.
High levels indicate:
- Syndrome of inappropriate Antidiuretic Hormone (ADH) (SIADH)
- Paraneoplastic syndromes
- Hepatic cirrhosis
- Congestive heart failure
Low levels indicate:
- Diabetes insipidus
- Excess fluid intake
- Renal tubular necrosis
- Severe pyelonephritis
- Pagana Kathleen D, Pagana Timothy J (1998) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby, Inc
- Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain