Hyponatremia can be broadly divided into two fundamental categories: “true hyponatremia” (in which the serum sodium concentration is truly less than normal), or “pseudohyponatremia,” in which the serum sodium concentration is actually normal but erroneously reported as low…
Changes in the regulation of serum osmolarity is just one of the many chances that occurs during the normal physiologic response to pregnancy. Beginning with the first trimester, the plasma osmolarity level, serum Na, and osmolarity thresholds for…
We all know that if you are stranded on a lifeboat in the middle of the ocean, you are not supposed to drink the salt water. Why is this the case–shouldn’t the kidney be smart enough to retain…
The water deprivation test is useful in the workup of patients with polyuria under certain situations. The differential diagnosis of polyuria often comes down to the following: does the patient have diabetes insipidus (either central or nephrogenic), psychogenic…
It is important to realize the difference between HYPOVOLEMIA and DEHYDRATION, two terms which are often used interchangeably but in fact reflect different things. Read the Up-To-Date entry « Dehydration is not synonymous with hypovolemia » by Burton…
I recently learned the “Survival Rule of Threes”–which gives a rough estimate of how long a person can live in various extreme survival conditions. For example…. …you can expect to live for 3 minutes without air. …you can…
In central diabetes insipidus induced by cerebral trauma or following neurosurgery, there is a “triphasic” presentation which may occur. Briefly, the patient begins with a tendency towards hypernatremia, then develops a tendency towards hyponatremia, and finally ends with…
It has been long recognized that IVIG–given for a variety of immune-mediated diseases and infections–has been associated with hyponatremia. In the recent “Electrolytes” edition of Neph-Sap, their explanation is a multifactorial one: 1. pseudohyponatremia: there is a massive…
One of the admittedly rare causes of hyponatremia is beer potomania–the excessive consumption of beer in the absence of much food. How does beer potomania work? Beer has a very low content of sodium and protein–and if an…
Did you know that the inventor of the popular sports drink “Gatorade” was a Nephrologist? The 2007 NY Times obituary of J. Robert Cade, the University of Florida nephrologist who concocted Gatorade, describes the story of the beginning…
