diabetes insipidus

Question 1

what

Answer 1

lack of ADH or lack of response to ADH

kidneys unable to concentrate urine leading to polyuria and polydipsia

Question 2

nephrogenic diabetes insipidus

Answer 2

CD of kidneys do not respond to ADH

Question 3

nephrogenic diabetes insipidus - causes

Answer 3

lithium
mutations of gene on X chr for ADH receptor
intrinsic kidney disease
hypokalaemia + hypercalcaemia

Question 4

cranial diabetes insipidus

Answer 4

hypothalamus does not produce ADH for pituitary to secrete

Question 5

cranial diabetes insipidus - causes

Answer 5

idiopathic 
brain tumour 
brain malformations
meningiis, encephalitis, TB 
brain surgery 
brain radiotherapy

Question 6

primary polydipsia

Answer 6

pt has. normal ADH system but drink too much water leading to excessive urine production

they dont have diabetes insipidus

Question 7

features of diabetes insipidus

Answer 7

polyuria
polydipsia 
dehydration 
postural hypotension 
hypernatraemia 
low urine osmolality 
high serum osmolality

Question 8

Ix

Answer 8

water deprivation test

aka desmopressin stimulation test

Question 9

water deprivation test - method

Answer 9

1. fluid deprivation for 8 hours
2. measure urine osmolality
3. give synthetic ADH (desmopressin)
4. measure urine osmolatity after 8hrs

Question 10

water deprivation test - cranial diabetes insipidus

Answer 10

patient lacks ADH but are still able to respond to it

initial urine osmolality high but after desmopressin given, kidneys will reabsorb water and concentrate urine

urine osmolality after desmopressin will be high

Question 11

water deprivation test - nephrogenic diabetes insipidus

Answer 11

patient unable to respond to ADH

urine osmolality will be low initially and will remain low after desmopressin given

Question 12

water deprivation test - primary polydipsia

Answer 12

fluid deprivation will cause urine osmolality to be high even before demospressin given

high urine osmolality after fluid deprivation = no diabetes insipidus

Question 13

water deprivation test - urine osmolality results in cranial diabetes insipidus

Answer 13

after deprivation = low

after ADH = high

Question 14

water deprivation test - urine osmolality results in nephrogenic diabetes insipidus

Answer 14

after deprivation = low

after ADH = low

Question 15

water deprivation test - urine osmolality results in primary polydipsia

Answer 15

after deprivation = high

after ADH = high

Question 16

water deprivation test - high urine osmolality after fluid deprivation indicates

Answer 16

no diabetes insipidus

Question 17

Mx

Answer 17

Rx underlying cause

desmopressin

• in cranial to replace ADH
• in nephrogenic in higher doses under monitoring

Question 18

desmopressin

Answer 18

synthetic ADH