Diabetes insipidus

Question 1

What is diabetes insipidus?

Answer 1

Condition in which kidneys are unable to concentrate urine

Question 2

What are the types of diabetes insipidus and its causes?

Answer 2

Central diabetes insipidus (CDI): insufficient or absent hypothalamic synthesis or secretion of antidiuretic hormone (ADH) from the posterior pituitary

Nephrogenic diabetes insipidus (NDI): caused by defective ADH receptors in the distal tubules and collecting ducts

Question 3

What are the clinical features of diabetes insipidus?

Answer 3

Polyuria with dilute urine
Nocturia → restless sleep, daytime sleepiness
Polydipsia (excessive thirst)

Question 4

How is diabetes insipidus diagnosed?

Answer 4

(sodium, plasma osmolality, and urine osmolality values are tested) urine osmolality of >700 mOsm/kg excludes diabetes insipidus
(water deprivation test) allows DI to be differentiated from primary polydipsia (excess water intake)
(If positive) CT or MRI of head to rule out tumours

Question 5

What is the treatment for diabetes insipidus?

Answer 5

(Lifestyle) Low sodium and low protein intake
(Central diabetes insipidus) Desmopressin
(Nephrogenic diabetes insipidus) Discontinuation of the causative agent (e.g., lithium, demeclocycline) in medication-induced NDI
Thiazide diuretics