diabetes insipidus

Question 1

how to test for diabetes insipidus

Answer 1

water deprivation test with desmopressin stimulation

-physiologically fluid deprivation should result in reduced urine output
failure to reduce urine output indicates a pathological response and indicates diabetes insipidus

Question 2

what is diabetes insipidus

Answer 2

it is a type of diabetes caused by abnormal quantity (cranial) or response to anti-diuretic hormone (nephrogenic)

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

Question 3

clinical features

Answer 3

large volumes of dilute urine (>3 litres in 24 hours and a low osmolality <300mOsm/kg)

patients often tend to suffer from nocturia and excessive thirst

Question 4

cranial causes of DI

Answer 4

head trauma
inflammatory conditions ie sarcoidosis
cranial infections such as meningitis
vascular conditions
rare genetic causes

Question 5

nephrogenic causes of DI

Answer 5

drugs
BPD
intrinsic kidney disease
metabolic disturbances ie hypercalcaemia, hypokalaemia
chronic renal disease
rare genetic causes

Question 6

investigations for DI

Answer 6

urea and electrolytes
blood glucose
urine dip
paired serum and urine osmolality

> when the serum osmolality is raised = DI

also fluid deprivation test

Question 7

drug for DI

Answer 7

desmopressin

Question 8

nephrogenic diabetes insipidus

Answer 8

it is when the collecting dust the kidneys do not respond to ADH

Question 9

cranial diabetes insipidus

Answer 9

it is when the hypothalamus does not produce ADH