Diabetes insipidus Flashcards

1
Q

define diabetes insipidus?

A

a disorder of inadequate secretion of antidiuretic hormone or an insensitivity to antidiuretic hormone

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2
Q

what are the two types of DI?

A
  • Cranial DI: failure of ADH secretion by the posterior pituitary
  • Nephrogenic DI: insensitivity of the collecting duct to ADH
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3
Q

what are the causes of cranial DI?

A
  • Idiopathic
  • Tumours (e.g. pituitary tumour)
  • Infiltrative (e.g. sarcoidosis)
  • Infection (e.g. meningitis)
  • Vascular (e.g. aneurysms, Sheehan syndrome)
  • Trauma (e.g. head injury, neurosurgery)
  • Haemochromatosis
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4
Q

what are causes of nephrogenic DI?

A
  • Idiopathic
  • Drugs (e.g. lithium)
  • Post-obstructive uropathy
  • Pyelonephritis
  • Pregnancy
  • Osmotic diuresis (e.g. diabetes mellitus)
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5
Q

what is the epidemiology of DI?

A

• Median onset is 24 years

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6
Q

what are the presenting symptoms of DI?

A
  • Polyuria
  • Polydipsia
  • Nocturia
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7
Q

what are the signs of DI?

A
•	If fluid intake < fluid output, signs of dehydration will be present 
o	tachycardia
o	reduced tissue turgor
o	postural hypotension
o	dry mucous membranes
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8
Q

what might the blood results show for DI?

A

o U&Es and Ca2+
o Increased plasma osmolality
o Decreased urine osmolality

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9
Q

how does a water deprivation test work?

A

o Water is restricted for 8 hrs
o Plasma and urine osmolality are measured every hour for 8 hrs
o STOP the test if the fall in body weight is > 3%
o Desmopressin is given after 8 hrs and urine osmolality is measured

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10
Q

how to treat cranial DI?

A

o Give desmopressin

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11
Q

how to treat nephrogenic DI?

A

o Thiazide diuretics (chlorothiazide)

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12
Q

complications of DI?

A
  • Hypernatraemic dehydration

* Excess desmopressin –> hyponatraemia

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13
Q

what is the prognosis for patients with DI?

A
  • Cranial DI may be transient following head trauma

* It may be cured by removing the cause

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