34. Diabetes insipidus Flashcards Preview

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Flashcards in 34. Diabetes insipidus Deck (24)

Diabetes innsipidus is charcterized by

1. intense thirst
2. polyuria
3. inability to concentrate urine


Diabetes insipidus (DI) is divided to

1. Central DI
2. Nephrogenic DI


Diabetes insipidus - inability to concentrate urine due to

1. lack of ADH ( central DI)
2. failure of response to circulating ADH ( peripheral DI)


causes of central DI

1. pituitary tumor
2. autoimmune
3. trauma
4. surgery
5. ischemic encephalopathy
6. idiopathic


causes of nephrogenic DI

hereditary ( ADH receptor V2 mutation ) or secondary :
a. hypercalcemia
b. lithium
c. demeclocycline
d. hypokalemia


central diabetes insipidus - lab findings

1. decreased ADH
2. Urine specific gravity less than 1.006
3. serum osmolarity more than 290
( Hyperosmotic volume contraction)


nephrogenic diabetes insipidus - lab findings

1. normal or increased ADH
2. Urine specific gravity less than 1.006
3. serum osmolarity more than 290
( Hyperosmotic volume contraction)


central diabetes insipidus - treatment

1. intranasal desmopressin acetate
2. hydration


nephrogenic diabetes insipidus - treatment

1. Hydroclorothiazide
2. Indomethacin
3. Amiloride
4. Hydration
5. avoidance of offending agents


water deprivation test - process

No water intake for 2–3 hr followed by hourly measurements of urine volume and osmolarity and plasma Na+ concentration
and osmolarity. ADH analog (desmopressin acetate) is administered if serum osmolality > 295–300 mOsm/kg, plasma
Na+ ≥ 145, or urine osmolality does not rise despite a rising plasma osmolality.


Nephrogenic diabetes insipidus - water deprivation test

minimal change in urine osmolarity, even after administration of desmopressin acetate


central diabetes insipidus - water deprivation test

> 50% increased in urine osmolarity only after administration of desmopressin acetate


diabetes insipidus - urine specific gravity

less than 1.006


diabetes insipidus - serum osmolarity

>290 m Osm / kg


• A man has intense thirst, polyuria, and dilute urine. Diabetes mellitus test is negative. What endocrine disorder is on your differential?

Diabetes insipidus


• A man has low ADH and dilute urine. A significant increase in urine osmolality occurs after he takes an ADH analog. List 6 possible causes.

Pituitary tumor, trauma, surgery, ischemic encephalopathy, autoimmune, idiopathic (this is central diabetes insipidus)


• A man has normal ADH, dilute urine, and no change in urine osmolality after taking an ADH analog. List 4 possible causes.

Hereditary (ADH receptor mutation), 2§ to hypercalcemia, lithium, demeclocycline (ADH antagonist) (it's nephrogenic diabetes insipidus)


• In a patient with diabetes insipidus, you expect to see a ____ (low/high) urine-specific gravity and a ____ (low/high) serum osmolality.

Low (often <1.006); high (often >290 mOsm/kg)


A woman presents with increased thirst, polyuria, and dilute urine. What test would confirm diabetes insipidus?

Water deprivation for 2 to 3 hours (in diabetes insipidus, urine osmolality does not increase, even with low fluid intake)


• A woman with polydipsia and polyuria continues to have dilute urine after a water deprivation test. What is the next step in your work-up?

Administering desmopressin (ADH analog)—urine will concentrate if patient has central diabetes insipidus but stay dilute if it's nephrogenic


What lifestyle change can be used to manage both central and nephrogenic diabetes insipidus (DI)? Otherwise, how do treatments differ?

Hydration; central DI is treated with intranasal desmopressin acetate, nephrogenic DI with HCTZ, indomethacin, or amiloride


After a traumatic brain injury from a bike accident, a man cannot concentrate his urine. Is his serum osmolarity 150, 250, or 350 mOsm/kg?

350 mOsm/kg (which is high)—head trauma can cause central diabetes insipidus


A man has diabetes insipidus. What is the underlying defect in this condition? What are the two main categories of causes?

Inability to concentrate urine; central (lack of ADH production) and nephrogenic (inability to respond to ADH)


What are common findings in central and nephrogenic diabetes insipidus?

Urine specific gravity < 1.006, serum osmolality > 290 mOsm/kg, hyperosmotic volume contraction