Urine specific gravity (SG) shows the concentration of urine and represents the hydration status of the patient. Normal specific gravity varies from 1.001 to 1.035
increased SG
causes include:
conditions causing dehydration
usefulness of SG in identifying dehydration in infants has been brought into question (2)
glycosuria
renal artery stenosis
heart failure (secondary to decreased blood flow to the kidneys)
inappropriate antidiuretic hormone secretion
proteinuria
some dipsticks give falsely high readings in the presence of dextran solutions and IV radiopaque dyes
however this false positive varies with different dipsticks so check the manufacturer's leaflet
decreased SG
causes include:
excessive fluid intake
renal failure
pyelonephritis
diabetes insipidus
alkaline urine (eg, a high-citrate diet) may cause false low readings for SG
Steiner MJ, Nager AL, Wang VJ; Urine specific gravity and other urinary indices: inaccurate tests for dehydration. Pediatr Emerg Care. 2007 May;23(5):298-303.
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