Diabetes Insipidus Flashcards
1
Q
what is DI?
A
- condition caused by hyposecretion of, or insensitivity to the effects of, antidiuretic hormone (ADH)
2
Q
Where is ADH made, transported and stored?
A
- Hypothalamus
- Neurosecretory vesicle
- PPG
3
Q
How many litres or urine would pt c DI normally pass? What will the typical osmolality be?
A
- >3 litres/24 hours
- <300 mOsmol/kg) urine
4
Q
What are the two forms of DI?
A
- Cranial DI
- decreased secretion of ADH
- Nephrogenic DI
- resistance to ADH in the kidney
5
Q
What are the other forms of DI?
A
- Gestational DI
- degradation of vasopressin by a placental vasopressinase
- Primary polydipsia (dipsogenic DI)
- primary defect in osmoregulation of thirst
- seen in TBmeningitis, MS, meurosarcoidosis
6
Q
What is the most common cause of nephrogenic DI?
A
- lithium
7
Q
What are the causes of cranial DI?
A
- idiopathic
- brain tumours
- intracranial surgery
- head injury
- granulomata (sarcoidosis, TB, Granulomatosis c Polyamgiitis)
- Infection - encephalitis, meningitis
8
Q
What are the causes of nephrogenic DI?
A
- Idiopathic.
- Hypokalaemia.
- Hypercalcaemia.
- Chronic kidney disease.
- Drugs - eg, ofloxacin, orlistat, lithium
- Renal tubular acidosis.
- Pregnancy
- Post-obstructive uropathy.
9
Q
What are the genetic causes of DI?
*think for both cranial and nephrogenic
A
Cranial
- Wolfram’s syndrome - Autosomal recessive combination of DI, diabetes mellitus, optic atrophy, deafness (DIDMOAD)
- Aut. Dom. mutation of ADH gene
Nephro
- X-linked mutation in V2 ADH-receptor gene
- Autosomal recessive defect in aquaporin 2 (AQP2) gene
10
Q
What are the sx of DI?
A
- polyuria - 3L/day
- Polydipsia
- Nocturia
- Infants
- irritability, failure to thrive, protracted crying, fever, anorexia, fatiguability, feeding problems
- Enlarged bladder
- Dehydration signs
11
Q
What are the differentials for DI?
A
- Psychogenic or primary polydipsia (PP).
- Diabetes mellitus.
- Cushing’s syndrome.
- Hypercalcaemia.
- Hyperkalaemia.
- Diuretic abuse
12
Q
What Ix would you order for DI?
A
Bloods
- Plasma glucose, U&E, urine specific gravity, urine osmolality
Bedside
- 24hr urine collection
Special test
- Fluid deprivation test with response to Desmopressin
Imaging
- MRI of pituitary, hypothalamus, pineal gland
- Renal tract US
13
Q
How would you classify DI based on the water deprivation and Desmopressin test?
A
14
Q
How would you mx DI?
A
Cranial DI
- Desmopressin
- Monitor Na levels every 1-3months
Nephrogenic
- Stop any drugs that may be causing the problem
- High-dose DDAVP + thiazide diuretic + NSAID
15
Q
What are the Cx of DI?
A
- Worsen MI - if pt on desmopressin
- bladder dysfunction and hydro-ureter/hydronephrosis
