last authored: October 2009, David LaPierre
Diabetes insipidus (DI) results from an inability of the kidneys to concentrate urine.
a simple case introducing clincial presentation and calling for a differential diagnosis. To get students thinking.
Central DI results from decreased ADH production in the brain. Causes include:
Nephrogenic DI results from:
Central DI is caused by a loss of ADH-secreting cells from the posterior pituitary.
Central DI presents with polyuria, polydipsia, and enuresis
Nephrogenic DI leads to polyuria, failure to thrive, vomiting, and dehydration leading to hypernatremia.
Fasting serum osmolality above 650 excludes DI, and if 24-h urine volume is below 2.5L and serum Na is normal, DI is unlikely.
Urinalysis shows a dilute urine (SG <1.010) and low urine osmolality.
Increased serum osmolality and hypernatremia are also present.
ADH administration test leading to >50% change in urine osmolality suggests central cause.
Central DI is managed with DDAVP, given intranasally, SC, or PO.
Nephrogenic DI is managed with a low solute diet or with thiazide diuretics (????)
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