Fast Five Quiz: What Do You Know About Hyponatremia?

Romesh Khardori, MD, PhD


April 19, 2016

Urine osmolality helps to differentiate between conditions associated with impaired free water excretion and primary polydipsia, in which water excretion should be normal (provided intact kidney function). With primary polydipsia, as with malnutrition (severe decreased solids intake) and a reset osmostat, the urine osmolality is maximally dilute, generally < 100 mOsm/kg. A urine osmolality > 100 mOsm/kg indicates impaired ability of the kidneys to dilute the urine. This is usually secondary to elevated vasopressin (antidiuretic hormone; ADH levels), appropriate or inappropriate.

For more on the workup of hyponatremia, read here.


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