Diabetes insipidus Flashcards

1
Q

Diabetes insipidus

A

Lack of ADH or lack of response to ADH

Prevents kidneys from being able to concentrate the urine leading to polyuria and polydipsia

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2
Q

Types of diabetes insipidus

A

Nephrogenic or cranial

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3
Q

Causes of cranial

A

Idiopathic

Post head injury

Pituitary surgery

Craniopharyngiomas

Infiltrative (histiocytes, sarcoidosis)

Wolfram’s syndrome

Haemochromatosis

Brain infections

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4
Q

Wolfram’s syndrome

A

Diabetes insipidus

Diabetes mellitus

Optic atrophy

Deafness

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5
Q

Causes of nephrogenic

A

Genetic (more common affects the ADH receptor, less common gene encodes aquaporin 2 channel)

Hypercalcaemia

Hypokalaemia

Lithium

Democlocyline

Tubulo-interstial disease (obstruction, sickle-cell, pyelonephritis)

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6
Q

Presentation

A

Polyuria

Polydipsia

Dehydration

Postural hypotension

Hypernatreamia

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7
Q

Investigations

A

Low urine osmolality

High serum osmolality

Water deprivation test

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8
Q

Water deprivation test method

A

Patients avoid taking any fluids for 8 hours

Urine osmolality measured and synthetic ADH administered

8 hours later urine osmolality measured again

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9
Q

Water deprivation test nephrogenic diabetes results

A

Patient unable to respond to ADH

Diluting their urine with excessive water secretion by the kidneys

Urine osmolality will be low initially and remain low even after synthetic ADH given

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10
Q

Water deprivation test cranial diabetes results

A

Kidneys still capable of responding to ADH

Urine osmolality initially low as continues to be diluted by excessive water secretion

When synthetic ADH given, kidneys respond by reabsorbing water and concentrating the urine so urine osmolality will be high

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11
Q

Water deprivation test primary polydipsia

A

8 hours of water deprivation will cause urine osmolality to be high even before the synthetic ADH is given

(high urine osmolality after 8 hours of water deprivation indicates no diabetes insipidus)

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12
Q

Management

A

If possible treat underlying cause

Desmopressin in cranial

Thiazides and low salt/ protein diet for nephrogenic

Desmopressin in higher doses for nephrogenic under close monitoring

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