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I was reading about diabetic ketoacidosis(DKA), where it was mentioned about osmotic diuresis caused by glucose within the renal tubules.

Okay, I understand about the fluid loss due to osmotic potential of glucose leading to polyuria.

However, why it is also mentioned about the hypokalemia or sodium loss and chloride as well,

I understand about the insulin decrement and how insulin maintains intracellular potassium concentration, but I can't understand how -

osmotic diuresis will cause loss potassium?

Source :https://en.wikipedia.org/wiki/Osmotic_diuretic

I tried searching for the same, however all mention same line as above, perhaps is there something to do with (my thoughts and hypothesis)

  1. sodium glucose cotransporter causes more sodium loss along with glucose
  2. increased sodium causes its reabsorbtion at collecting tubule and loss of potassium

But can't think about chloride, moreover I'm also worried about apparent hyponatremia because of hypovolemic hypernatremia causes increased sodium excretion.

Or is hypovolemia the main cause that leads to apparent increase in concentration of these ions which causes their increased excretion.

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As another answer has noted, increased tonicity of the blood increases the tonicity of the extracellular fluid causing water to flow out of cells into the extracellular space and subsequently the intravascular space. This is the mechanism of action for hypertonic mannitol infusion. 1

However this is not the end of the story. Increased intravascular volume subsequently causes increased renal blood flow. This has two consequences. Firstly, the glomerular filtration rate is increased, this means that the total amount of fluid filtered by the glomerulus into the nephron is increased. Second there is increased perfusion of the renal medulla. This collapses the normal concentration gradients of electrolytes which impairs the ability of the nephron to concentrate urine. There is a net loss of electrolytes as a result with the production of increased volumes of urine. Total body potassium is decreased (although because it is being removed from a large intracellular reservoir perhaps the serum potassium will not fall). 2

In fact it is relatively common for serum potassium to be normal and there are case reports of hyperkalaemia associated with DKA.

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Loss of intracellular free water because of increased plasma osmolality, this causes water to move out of cell.

After this, potassium concentration has increased inside cell, so this causes extracellular movement of potassium (secondary to increased intracellular potassium concentration)

Similar mechanism happens at level of kidney tubules and interstitium.

Source: Uworld step 1 qbank( Q Id 985) (may not be accessible)

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