Diabetes Insipidus Flashcards
Diabetes insipidus (DI) is an acquired (90%) or inherited (10%) condition that results in the body being unable to concentrate urine as a result of either a lack of production of antidiuretic hormone (ADH) or a loss of sensitivity to ADH within the kidneys. What is the incidence of DI?
1 - 1000 cases per 100,000
2 - 100 cases per 100,000
3 - 10 cases per 100,000
4 - 1.00 cases per 100,000
4 - 1.00 cases per 100,000
Affects men and women equally
DI = tasteless urine
T2DM = sweet urine
Does diabetes insipidus affect older or younger people more?
- younger people
Most common in infants
What is the main hormone that is affected in diabetes insipidus?
1 - cortisol
2 - anti-diuretic hormone
3 - aldosterone
4 - renin
2 - anti-diuretic hormone
Osmoreceptors in the hypothalamus detect plasma osmolality, which is the concentration of dissolved particles in plasma, with the main 3 being glucose, Na+ and blood urea nitrogen. What is the normal blood osmolality?
1 - 120-300
2 - 180-420
3 - 285-295
4 - 325-345
3 - 285-295
Urine is 300-900
High concentration of particles in blood = HIGHER osmolality (dehydration)
Low concentration of particles in blood = LOWER osmolality
During dehydration the hypothalamus detects high osmolality and increases thirst. Does the hypothalamus increase or decrease the secretion of anti-diuretic hormone (ADH), also called vasopressin as it causes smooth muscle around blood vessels to contract?
- Increase
- ADH secreted by posterior pituitary gland
- ADH binds to distal convoluted tubules and collecting ducts of the nephrons
- ADH binds vasopressin receptor 2 receptors increasing aquaporins to open and reabsorbed water back into the blood
Drinking water and increased ADH reduce blood osmolality
There are 4 types of diabetes insipidus (DI). Which of the following matches the following description?
- reduction in the production and/or secretion of anti-diuretic hormone, meaning water is not retained
1 - central DI
2 - dipsogenic DI
3 - gestational DI
4 - nephrogenic DI
1 - central DI
Central diabetes insipidus is when there is a reduction in the production or secretion of anti-diuretic hormone. Is this more commonly acquired or congenital?
- acquired accounts for 90% of cases
Most common cause is destruction of magnocellular neurons in hypothalamus.
- damaged posterior pituitary gland s
- tumours or craniopharyngioma.
- trauma or pituitary surgery
- infections including encephalitis, cryptococcal meningitis and TB meningitis
- vascular damage
Congenital causes include:
- mutation in Arginine vasopressin-neurophysin II gene (AVP-NPII)
- Wolfram syndrome
There are 4 types of diabetes insipidus (DI). Which of the following matches the following description?
- normal production and/or secretion of anti-diuretic hormone (ADH), but kidneys are unresponsive or less to ADH, meaning water it not retained.
1 - central DI
2 - dipsogenic DI
3 - gestational DI
4 - nephrogenic DI
4 - nephrogenic DI
There are a variety of clinical features that present in diabetes insipidus, of these which 2 occur in nearly all patients?
1 - Polydipsia
2 - Polyuria (dilute)
3 - Nocturia (urinate at night)
4 - Fatigue
5 - Dizziness
6 - Weakness
1 - Polydipsia
2 - Polyuria (dilute)
Typically occur insidiously over months
Fatigue, Dizziness and Weakness are all typically due to dehydration
There are 4 types of diabetes insipidus (DI). Which of the following matches the following description?
- normal production and/or secretion of anti-diuretic hormone (ADH), but placenta produces vasopressinase that degrades ADH, meaning water it not retained.
1 - central DI
2 - dipsogenic DI
3 - gestational DI
4 - nephrogenic DI
3 - gestational DI
Can begin at week 8, peaks in 3rd trimester and can last 2 months post partum
There are 4 types of diabetes insipidus (DI). Which of the following matches the following description?
- normal production and/or secretion of anti-diuretic hormone (ADH), but patient drinks far too much water
1 - central DI
2 - dipsogenic DI
3 - gestational DI
4 - nephrogenic DI
2 - dipsogenic DI
Also called psychogenic polydipsia
Damage to the thirst mechanisms may also cause this which may be due to:
- Chronic meningitis
- Multiple sclerosis
In nephrogenic diabetes, is this more likely to be congenital or acquired?
- congenital accounts for 85% of patients
Presents in childhood and causes by:
- mutation in vasopressin-2-receptor, an X-linked mutation accounts for 90% of congenital causes
Acquired causes include:
- Drug induced, most commonly lithium.
- Hypercalcaemia
- Hypokalaemia
- Kidney disease
There are 4 types of diabetes insipidus (DI). Which 2 are the most common?
1 - central DI
2 - dipsogenic DI
3 - gestational DI
4 - nephrogenic DI
1 - central DI
4 - nephrogenic DI
If central diabetes insipidus is the cause, which of the following may we expect to see if a space occupying lesion is the cause?
1 - Headaches
2 - Visual changes
3 - Seizures
4 - All of the above
4 - All of the above
In a patient with suspected diabetes insipidus (DI), which of the following is least useful when performing a history?
1 - family history of DI
2 - fluid intake
3 - liver failure
4 - trauma
5 - medications (diuretics, lithium)
3 - liver failure
If a patient is not maintaining sufficient fluid levels with diabetes insipidus, which of the following are common signs of dehydration?
1 - Dry mucous membranes
2 - Poor skin turgor
3 - Prolonged capillary refill time
4 - Tachycardia
5 - Orthostatic hypotension
6 - Palpable distended bladder
7 - All of the above
7 - All of the above
Which of the following would provide the least useful information in an attempt to confirm a diagnosis of diabetes insipidus?
1 - TFTs
2 - U&Es
3 - Urine and plasma osmolality
4 - 24-hour urine collection.
5 - Fluid intake diary
6 - Glucose (T2DM)
7 - Calcium (hypercalcaemia)
1 - TFTs
In a patient with dipsogenic diabetes insipidus, what would we expect to see following the water deprivation test?
1 - high urine osmolality
2 - low urine osmolality
1 - high urine osmolality
Unable to drink water, so urine becomes concentrates
No need to perform the desmopressin test
A water deprivation test can be performed in a patient with suspected diabetes insipidus (DI). Which 2 of the following criteria must be met to perform the water deprivation test?
1 - hypokalaemia
2 - hypernatraemia
3 - hypovolaemic
4 - hypervolaemic
2 - hypernatraemia
3 - hypovolaemic
Does not have to be both, can be one or the other
Water deprivation test:
- patient empties bladder, record volume, urine and serum osmolality
- restrict fluids for 8 hours
- measure urine and serum osmolality
Following the water deprivation test, we can perform the desmopressin test (a synthetic form of anti-diuretic hormone (ADH)). Before doing this, what must the urine osmolality level be following the water deprivation test?
1 - <900
2 - <600
3 - <300
4 - <140
3 - <600
Serum will typically be <300 in DI
Desmopressin Test:
- Urine osmolality is measured for 2-4 hours following the administration of 2mcg IM or 20mcg intranasal
- Patients are able to drink as required
- Urine osmolality measured every hour for 4 hours
In a patient with central diabetes insipidus, what would we expect to see following the water deprivation test?
1 - high urine osmolality
2 - low urine osmolality
2 - low urine osmolality
Issue is a lack of production or secretion of ADH
In a patient with central diabetes insipidus, what would we expect to see following the desmopressin test?
1 - high urine osmolality
2 - low urine osmolality
1 - high urine osmolality
Desmopressin triggers water retention so urine becomes concentrated
This would be the same result in gestational DI
In a patient with nephrogenic diabetes insipidus, what would we expect to see following the desmopressin test?
1 - high urine osmolality
2 - low urine osmolality
2 - low urine osmolality
Issue is not ADH levels, rather the kidneys are not responding so we lose too much water
In a patient with nephrogenic diabetes insipidus, what would we expect to see following the desmopressin test?
1 - high urine osmolality
2 - low urine osmolality
2 - low urine osmolality
Despite desmopressin (synthetic ADH), the kidneys do not respond
In a patient who has performed the water deprivation and desmopressin test, and a suspicion of central diabetes insipidus is suspected, what would be the 1st line test?
1 - head MRI
2 - neurological exam
3 - head CT
4 - renal ultrasound
1 - head MRI
In a patient with mild diabetes insipidus, which of the following are part of conservative management?
1 - low solute diets
2 - remove offending medication (lithium)
3 - access to water and fluid intake
4 - patient education including what to do if they become unwell
5 - all of the above
5 - all of the above
In central diabetes insipidus, what are patients given?
1 - conservative management and a urine diary
2 - desmopressin
3 - furosemide
4 - carbimazole
2 - desmopressin
Need to monitor Na+ due to risk of hyponatraemia
In nephrogenic diabetes insipidus, how can patients be treated?
1 - access to plenty of water
2 - high-dose desmopressin
3 - thiazide diuretics
4 - NSAIDs
5 - all of the above
5 - all of the above
- thiazide diuretics = decreased urine volume
- NSAIDs = constrict afferent arterioles and reduce fluid
