Causes of hyponatremia? Diarrhea how?

[BlondeCookie]

Hyponatremia is decreased plasma sodium concentration due to excessive loss of sodium or gain of fluid. Some causes include diarrhea, vomitting, and drinking way too much water.

My question is about diarrhea. What is the mechanism of diarrhea causing hyponatremia? I thought that in diarrhea you are losing too much water and becoming dehydrated, but hyponatremia is a "low sodium/high fluid" abnormality. Any ideas?

---

Members don't see this ad.

 

[Miami_med]

In a secretory diarrhea, water follows electrolytes. Usually, atleast according to my understanding, sodium is the major electrolyte lost, though not the only one. As sodium losses mount, other electrolytes begin to exert a larger impact on the remaining free water. Thus, sodium can be low. Remember that the remaining free water can move freely between compartments.

Also, the loss of volume will stimulate release of ADH, which will disproportionately bring water back from the collecting tubules without directly increasing sodium reabsorption. If sodium loss is severe, there may be incomplete compensation on sodium re-uptake. The body is desperately trying to maintain volume in this state, so electrolyte balance will take a back seat to water reabsorption.

I'm actually not 100% sure, but this is how I understand it. Anyone who knows better feel free to chime in.

 

[blz]

The increased ADH willl cause increased thirst. Usually what happens is people drink their way to hyponatremia (eventhough it's an isotonic loss of fluid). This is how I believed one of my professors explained it.

 

[WhoisJohnGalt]

The increased ADH willl cause increased thirst. Usually what happens is people drink their way to hyponatremia (eventhough it's an isotonic loss of fluid). This is how I believed one of my professors explained it.

I think you're exactly right; Goljan mentioned this as well in his fluid balance lectures. People get thirsty, so they drink water instead of gatorade, leading to hyponatremia.

 

[Miami_med]

The increased ADH willl cause increased thirst. Usually what happens is people drink their way to hyponatremia (eventhough it's an isotonic loss of fluid). This is how I believed one of my professors explained it.

Good point, and that completes the picture.