Diabetes Insipidus

Question 1

What is it

Answer 1

A disorder caused by low levels of or insensitivity to antidiuretic hormone (ADH) leading to polyuria.
Cranial or nephrogenic in origin

Question 2

What is meant by cranial cause

Answer 2

Decreased ADH is released by the posterior pituitary gland

Question 3

Causes of cranial diabetes insipidus

Answer 3

CIVIT
Congenital defect in ADH gene
Idiopathic
Vascular
Infection - meningoencephalitis
Tumour (e.g. pituitary adenoma); Tuberculosis; Trauma

Question 4

What is meant by nephrogenic cause

Answer 4

kidney does not respond to ADH

Question 5

Causes of nephrogenic diabetes insipidus

Answer 5

DIMC
Drugs e.g. lithium
Inherited
Metabolic: low potassium, high calcium
Chronic renal disease

Question 6

Where is ADH made and released

Answer 6

Made in Hypothalamus (Supraoptic mainly)

Released from the Posterior Pituitary gland

Question 7

Signs and symptoms

Answer 7

Polydipsia
Polyuria
Dehydration

Question 8

Complications

Answer 8

Electrolyte imbalance

Dehydration

Question 9

Investigations

Answer 9

Plasma osmolarity
Urine osmolarity
Plasma sodium
24-hour urine volume
**Water deprivation test
Water deprivation test after treatment with desmopressin
MRI scan for cranial caused diabetes insipidus

Question 10

Which investigations show difference between nephrogenic and cranial cause

Answer 10

Water deprivation test after treatment with desmopressin
Cranial cause = urine becomes concentrated
Nephrogenic cause = urine does not concentrate

MRI scan for cranial cause only - look for abnormality in pituitary gland such as tumour

Question 11

What is seen for each of these investigations in diabetes insipidus of a cranial cause:
Plasma osmolarity
Urine osmolarity
Plasma sodium
24-hour urine volume
Water deprivation test
Water deprivation test after treatment with desmopressin

Answer 11

Plasma osmolarity - high
Urine osmolarity - low
Plasma sodium - high
24-hour urine volume - >2L
Water deprivation test - urine does not concentrate
Water deprivation test after treatment with desmopressin - urine becomes concentrated

Question 12

What is seen for each of these investigations in diabetes insipidus of a nephrogenic cause:
Plasma osmolarity
Urine osmolarity
Plasma sodium
24-hour urine volume
Water deprivation test
Water deprivation test after treatment with desmopressin

Answer 12

Plasma osmolarity - high
Urine osmolarity - low
Plasma sodium - high
24-hour urine volume - >2L
Water deprivation test - urine does not concentrate
Water deprivation test after treatment with desmopressin - urine does NOT concentrate

Question 13

Conservative treatment

Answer 13

Patient education
Education on how to monitor fluid levels and dietary salt levels
Advise patients to wear a MedicAlert bracelet

Question 14

Medical treatment of diabetes insipidus of cranial cause

Answer 14

Desmopressin

Question 15

How does desmopressin work

Answer 15

Synthetic replacement for vasopressin
Increases the number of Aquaporin-2 channels in distal convoluted tubules and collecting ducts
Increases water reabsorption

Question 16

Medical treatment of diabetes insipidus of nephrogenic cause

Answer 16

High-dose desmopressin
Correction of electrolyte imbalances
Thiazide diuretics
Prostglandin synthase inhibitors