Di

[sweetieann]

Quick question about diabetes insipidus. I understand that in this condition, the person urinates alot, and thus loses alot of fluid relative to amount of sodium electrolyte in the body (and thus ends upwith hypernatremia). However, why wouldn't, when the person is urinating so much, the Na just leave in the urine, resulting in hyponatremia?

Thanks!

[hollya5334, LPN]

From what I understand about this disease is that when the person is losing all that fluid, the NA+ stays in the body, while the K+ leaves. Hope this helps!!

[sirI, MSN, APRN, NP]

quick question about diabetes insipidus. i understand that in this condition, the person urinates alot, and thus loses alot of fluid relative to amount of sodium electrolyte in the body (and thus ends upwith hypernatremia). however, why wouldn't, when the person is urinating so much, the na just leave in the urine, resulting in hyponatremia?

thanks!

hello, sweetie715,

check out this link from emedicine regarding diabetes insipidus:

http://www.emedicine.com/med/topic543.htm

here are some good links regarding the rationale behind hypernatremia and hyponatremia:

http://www.emedicine.com/emerg/topic275.htm

http://www.emedicine.com/emerg/topic263.htm

[VickyRN, MSN, DNP, RN]

When you think ADH, think water - pure water. With ADH, only pure water will be retained by the kidney. ADH makes the walls of distal tubules and collecting ducts more permeable to water, enhancing free water reabsorption, and thus the urine becomes more concentrated. Causes more water to be reabsorbed and returned to the circulation, making the blood more dilute (reduced osmolarity of the blood).

Don't confuse ADH with aldosterone. Aldosterone enhances sodium reabsorption in the distal tubules. Since water follows sodium, both sodium and water will be reabsorbed into the bloodstream in isotonic proportions.

However, when you don't have enough ADH on board (as in the case of diabetes insipidus), just the opposite occurs - not enough free water in the bloodstream. The distal tubules and collecting ducts will not reabsorb the free water. You will retain salt in the bloodstream, but water will be excreted, resulting in hypernatremia and a large hypo-osmolar urinary output (low urine SG). Hope this helps :)

http://www.pituitary.org.uk/gp-factfile/8-di.htm