Diabetes insipidus Flashcards
What is diabetes insipidus?
Patient will present as → a 25-year-old male complaining of an unabated thirst that began three weeks ago. He is constantly drinking and goes to the bathroom around five times a night. He has lost five pounds over the last few weeks. The patient is on lithium for bipolar disorder. His BP is 115/70. The patient’s labs are significant for serum Na of 145 mEq/L (normal: 135-145). Urine osmolality is 185 mOsm/kg, and urine specific gravity is 1.004 (normal: 1.012 to 1.030).
What is diabetes insipidus caused by?
A deficiency of or resistance to vasopressin (ADH), which decreases the kidneys’ ability to reabsorb water, resulting in massive polyuria
What are the two different types of diabetes insipidus?
Central diabetes insipidus
Nephrogenic diabetes insipidus
What is central diabetes insipidus?
Deficiency of ADH from posterior pituitary/hypothalamus
What happens with central diabetes insipidus?
No ADH production most common type: idiopathic, autoimmune destruction of posterior pituitary from head trauma, brain tumor, infection, or sarcoidosis
What happens with nephrogenic diabetes insipidus?
Lack of reaction to ADH
caused by drugs (Lithium, Amphoterrible), hypercalcemia and hypokalemia affect the kidney’s ability to concentrate urine, acute tubular necrosis
What is the diagnosis for diabetes insipidus?
Serum osmolality (concentration) is high (unable to stop the secretion of water into the kidneys so blood becomes more concentrated) and urine osmolality is low because it is so dilute
Water deprivation test – simplest/most reliable method - continued production of dilute urine despite water deprivation
Desmopressin stimulation test:
Central: reduction in urine output indicating a response to ADH
Nephrogenic: continued production of dilute urine (no response to ADH) because kidneys can’t respond
What is the treatment for diabetes insipidus?
Central = desmopressin/DDAVP
Nephrogenic = sodium and protein restriction, HCTZ, indomethacin
