Diabetes Insipidus

Created by

Megan Vann

Cards (10)

Neurogenic diabetes insipidus occurs as a result of decreased levels of ADH (vasopressin) - results in excessive production of urine
Causes of neurogenic diabetes:
Mutations in the vasopressin gene
Idiopathic (25%)
Tumours - pituitary adenomas
Trauma
Infections - meningitis
Vascular
Nephrogenic diabetes insipidus is caused by a deficit in the binding of ADH to the kidneys or damage to to kidneys
Causes of nephrogenic diabetes insipidus:
Mutations in the ADH receptor gene
Mutations in the aquaporin-2 gene
Metabolic - hypercalcaemia/hyperglycaemia/hypokalaemia
Drugs - lithium interferes with the binding of ADH
Chronic kidney disease
Post obstructive uropathy
Symptoms and signs of diabetes insipidus:
Excessive urination >3 L/24hrs
Polydipsia
Nocturia
Dehydration - headache, dizziness and dry mouth
Hypotension
Dilute urine
A sign of diabetes insipidus is postural hypotension
Water deprivation test is 1st line investigation for diabetes insipidus:
Avoid all fluids for 8 hours before test
Low urine osmolarity after water deprivation = diabetes insipidus
Desmopressin (synthetic ADH) is given
Desmopressin will cause a rise in urine osmolarity if cranial diabetes insipidus
There will be no rise in osmolarity in nephrogenic diabetes insipidus as the lack of ADH is not the issue
Primary polydipsia will have high osmolality after fluid deprivation and desmopressin
Management of diabetes insipidus:
Remove underlying cause e.g. lithium
Mild cases can be managed conservatively
Cranial DI - desmopressin - monitor for hyponatraemia
Nephrogenic - high dose desmopressin and thiazide like diuretics
MRI imaging of the pituitary and hypothalamus is used to assess for cranial causes of diabetes insipidus
Patients presenting with diabetes insipidus symptoms should have their plasma glucose measures to help rule out diabetes mellitus
They also need simultaneous plasma and urine osmolarity