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Old 05-11-2011
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Help SIADH versus DI

Can anyone please explain in very simple words the difference between SIADH and DI...and the how to diagnose each
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Old 05-11-2011
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SIADH is too much ADH
DI is too less ADH
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lookingup (05-11-2011)
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Lol Jajeek I love your reply. Very kool and simple

Diabetes inspidus - Lack of ADH - Can be central diabetes insipidus due to head trauma for e.g. or nephrogenic secondary to hypercalcemia or lithium etc. or hereditary. In order to diagnose it:
Do a fluid restriction test - this is supposed to increase the plasma osmolality and thus promote the release of ADH - then check the urine osmolality. Under normal circumstances, urine osmolality should be high. If there is diabetes insipidus, it will be low. Then u must diff. between central and nephrogenic so administer vasopressin - if urine osmolality increases, then it is central. If it doesn't, it is nephrogenic.

SIADH - too much ADH secondary to let's say small cell carcinoma of the lung, as Jajeek said. Produces normovolemic hyponatremia. You must demonstrate normal plasma volume, and increased urinary sodium concentration etc.
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Future Radiolog (05-11-2011), TomMeritt (05-13-2011)


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