Patient with recent brain surgery who has developed hypernatremia with dilute urine and polyuria, consistent with diabetes insipidus (most likely central due to brain surgery)
Causes of central diabetes insipidus (decreased ADH release): Pituitary tumor, trauma, surgery, autoimmune disease, ischemic event
Causes of Nephrogenic diabetes insipidus (decreased responsiveness of kidney to ADH): Inherited, hypocalcemia, hypokalemia, lithium, demeclocycline
Note: Excessive ADH production and renal salt wasting would lead to hyponatremia, 0.9% is isotonic (so wouldnโt lead to significant electrolyte changes), and hyperaldosteronism leads to normal Na+ levels due to aldosterone escape
submitted by โstep_prep5(246)
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