Diabetes Insipidus Flashcards
What is diabetes insipidus?
Poor sensitivity to or poor production of ADH
What are the forms of DI?
Cranial
Nephrogenic
Gestational
Primary polydipsia
What are cranial causes of DI?
Hypothalamus problems
- idiopathic
- tumours
- surgery
- infection
Stroke
What are nephrogenic causes of DI?
Idiopathic Hypokalaemia Hypercalcaemia CKD Renal tubular acidosis
What are symptoms of DI?
Polyuria
Nocturia
Urinary incontinence
Polydipsia
What is the urine output of an undiagnosed DI?
> 3L per day
How do you investigate suspected DI?
Water deprivation test
Urine dipstick
Bloods - U+Es
What is the water deprivation test?
Stage 1 = fluid deprivation
- empty bladder
- no food or drink for 8 hours
- collect urine every 2 hours
- measure osmolality and volume
- if >300mOsmo/kg proceed to stage 2
Stage 2
- give 20ug desmopressin intranasally
- measure urina osmolality hourly for 4 hours
What is a normal result of the water deprivation test?
Stage 1 urine osmolality >600mOSmol/kg
What is the result of the water deprivation test in primary polydipsia?
Urine concentrates but less than normal
400-600 mOsmol/kg
What is the result of the water deprivation test in cranial DI?
Urine osmolality increases after desmopressin
What is the result of the water deprivation test in nephrogenic DI?
No increase in osmolality after desmopressin
How is cranial DI managed?
Find and treat underlying cause
Desmopressin
How is nephrogenic DI managed?
Find and treat underlying cause
Thiazides
NSAIDs
