Differential diagnosis of polyuria

The Bottom Line: Differential diagnosis of polyuria includes the intake of diuretic drugs, hyperglycemia, fluid overload, and fluid mobilization.

Fink: Textbook of Critical Care, 5th ed.
Copyright © 2005 Saunders, An Imprint of Elsevier

In all these conditions, however, urine remains close to isotonic (osmolality about 300 mOsm/kg). Abundant intake of hypotonic fluid can cause polyuria and urine hypotonicity, but does not result in hypernatremia if renal function is normal. The observation of decreased urine output after ADH administration is not diagnostic of diabetes insipidus because ADH is able to reduce urine output and to increase urine osmolality in all conditions except nephrogenic diabetes insipidus.

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