Sodium, Urine
Urinary sodium determinations are usually performed to detect or confirm the presence of conditions that affect body fluids (e.g., dehydration, vomiting, and diarrhea) or disorders of the kidneys or adrenal glands.
Normal range:
Twenty-four " hour urine:
Male:
Less than 10 years: 41 " 115 mmol/day
10 " 14 years: 63 " 177 mmol/day
Greater than 14 years: 40 " 120 mmol/day
Female:
Less than 10 years: 20 " 69 mmol/day
10 " 14 years: 48 " 168 mmol/day
Greater than 14 years: 27 " 287 mmol/day
Random urine
Male: 23 " 229 mmol/g creatinine
Female: 26 " 297 mmol/g creatinine
Use
Volume depletion: to determine the route of sodium loss. Low urinary sodium indicates extrarenal loss, and high value indicates renal salt wasting or adrenal insufficiency.
Differential diagnosis of acute renal failure: high values are consistent with acute tubular necrosis.
In hyponatremia, low urinary sodium indicates avid renal sodium retention, which may be attributable to either severe volume depletion or sodium-retaining states seen in cirrhosis, the nephrotic syndrome, and CHF. When hyponatremia is associated with urinary sodium excretion that equals or exceeds the dietary sodium intake, it is likely that SIADH is present.
Interpretation
Increased In
Dehydration
Salicylate intoxication
Adrenocortical insufficiency
Diabetic acidosis
Mercurial and thiazide diuretic administration
Ammonium chloride administration
Renal tubular acidosis (<15 mmol/L are seen in prerenal acidosis)
Chronic renal failure
SIADH of different etiology
Any form of alkalosis and alkaline urine
Decreased In
Acute renal failure
Pulmonary emphysema
CHF
Excessive sweating
Diarrhea
Pyloric obstruction
Malabsorption
Primary aldosteronism
Premenstrual sodium and water retention
Acute oliguria and prerenal azotemia
Limitations
Large diurnal variations exist in urine sodium levels. The rate of excretion during night is one fifth of the peak rate during the day.
Levels are highly dependent on dietary intake and state of hydration.