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25 Cards in this Set
- Front
- Back
If you have a patient with intense thirst, polyuria, and inability to concentrate urine, what diagnosis should you think of? |
Diabetes Insipidus
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What are the types of Diabetes Insipidus? Basic issue?
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- Central DI: lack of ADH
- Nephrogenic DI: insensitivity to ADH |
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What are possible causes of Central Diabetes Insipidus?
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- Pituitary tumor
- Auto-immune process - Trauma - Surgery - Ischemic encephalopathy - Idiopathic |
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What are possible causes of Nephrogenic Diabetes Insipidus?
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- Hereditary (ADH receptor mutation)
-2° to hypercalcemia, lithium, demeclocycline (ADH antagonist) |
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If you have a patient with intense thirst, polyuria, and inability to concentrate urine, and you get the following lab results, what diagnosis should you make?
- ↓ ADH - Urine specific gravity <1.006 - Serum osmolarity >290 mOsm/L - Hyperosmotic volume contraction |
Central Diabetes Insipidus
* Only way to distinguish from Nephrogenic is based on ↓ ADH |
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If you have a patient with intense thirst, polyuria, and inability to concentrate urine, and you get the following lab results, what diagnosis should you make?
- Normal ADH - Urine specific gravity <1.006 - Serum osmolarity >290 mOsm/L - Hyperosmotic volume contraction |
Nephrogenic Diabetes Insipidus
* Only way to distinguish from Central is based on normal ADH |
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What are the following values in diabetes insipidus:
- ADH level - Urine specific gravity - Serum osmolarity - Type of volume contraction |
- ADH: ↓ if central or normal if nephrogenic
- Urine specific gravity: < 1.006 (dilute) - Serum osmolarity >290 mOsm/L (concentrated) - Hyperosmotic volume contraction |
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How do you diagnose Central Diabetes Insipidus?
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Water restriction test:
- No water intake for 2-3 hours - Followed by hourly measurements of urine volume / osmolarity and plasma Na+ concentration / osmolarity * Central: >50% ↑ in urine osmolarity * Nephrogenic: no change in urine osmolarity |
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What should you do if after a water restriction test normal values are not clearly reached?
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Give DDAVP (ADH analog) - this will improve central diabetes insipidus
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How do you treat central diabetes insipidus?
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- Intranasal DDAVP (ADH analog)
- Hydration |
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How do you treat nephrogenic diabetes insipidus?
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- HCTZ, indomethacin, amiloride
- Hydration |
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What can cause excessive water retention, hyponatremia, urinary Na+ excretion, and urine osmolarity > serum osmolarity?
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SIADH: Syndrome of Inappropriate Anti-Diuretic Hormone
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What are the findings of SIADH?
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- Excessive water retention
- Hyponatremia w/ continued urinary Na+ exretion - Urine osmolarity > serum osmolarity |
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How does the body normally respond to water retention?
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↓ Aldosterone (hyponatremia) to maintain near-normal volume status
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What are the possible consequences of the hyponatremia in SIADH?
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Can lead to cerebral edema and seizures
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When correcting hyponatremia in SIADH, what do you need to do? Why?
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Correct hyponatremia slowly to prevent central pontine myelinolysis
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What are the possible causes of SIADH?
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- Ectopic ADH (small cell lung cancer)
- CNS disorders / head trauma - Pulmonary disease - Drugs (eg, cyclophosphamide) |
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How do you treat SIADH?
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- Fluid restriction
- IV hypertonic saline - Conivaptan (ADH inhibitor) - Tolvaptan (ADH receptor antagonist) - Demeclocycline (ADH antagonist) |
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What can cause under-secretion of pituitary hormones (hypo-pituitarism)?
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- Non-secreting pituitary adenoma, craniopharyngioma |
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What tumors can cause hypo-pituitarism?
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- Non-secreting pituitary adenoma |
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What is Sheehan syndrome?
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Ischemic infarct of pituitary following post-partum bleeding, usually presents with a failure to lactate (no prolactin being released because of pituitary damage) |
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What causes empty sella syndrome? Effect?
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- Atrophy or compression of pituitary, often idiopathic |
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What kind of brain injury can cause hypo-pituitarism?
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- Hemorrhage (pituitary apoplexy)
- General brain trauma - Radiation |
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How do you treat hypo-pituitarism?
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Hormone replacement therapy:
- Corticosteroids - Thyroxine - Sex steroids - Human growth hormone |
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What cause of hypo-pituitarism is common in obese women?
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Empty Sella Syndrome
- Atrophy or compression of pituitary, often idiopathic |