Diabetes Insipidus

Question 1

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

Answer 1

4 - 1.00 cases per 100,000

Affects men and women equally

DI = tasteless urine
T2DM = sweet urine

Question 2

Does diabetes insipidus affect older or younger people more?

Answer 2

• younger people

Most common in infants

Question 3

What is the main hormone that is affected in diabetes insipidus?

1 - cortisol
2 - anti-diuretic hormone
3 - aldosterone
4 - renin

Answer 3

2 - anti-diuretic hormone

Question 4

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

Answer 4

3 - 285-295

Urine is 300-900

High concentration of particles in blood = HIGHER osmolality (dehydration)

Low concentration of particles in blood = LOWER osmolality

Question 5

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?

Answer 5

• 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

Question 6

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

Answer 6

1 - central DI

Question 7

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?

Answer 7

• 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

Question 8

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

Answer 8

4 - nephrogenic DI

Question 9

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

Answer 9

1 - Polydipsia
2 - Polyuria (dilute)

Typically occur insidiously over months

Fatigue, Dizziness and Weakness are all typically due to dehydration

Question 10

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

Answer 10

3 - gestational DI

Can begin at week 8, peaks in 3rd trimester and can last 2 months post partum

Question 10

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

Answer 10

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

Question 11

In nephrogenic diabetes, is this more likely to be congenital or acquired?

Answer 11

• 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

Question 12

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

Answer 12

1 - central DI
4 - nephrogenic DI

Question 13

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

Answer 13

4 - All of the above

Question 14

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)

Answer 14

3 - liver failure

Question 15

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

Answer 15

7 - All of the above

Question 16

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)

Answer 16

1 - TFTs

Question 17

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

Answer 17

1 - high urine osmolality

Unable to drink water, so urine becomes concentrates

No need to perform the desmopressin test

Question 17

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

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

2 - low urine osmolality

Issue is a lack of production or secretion of ADH

Question 20

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

Answer 20

1 - high urine osmolality

Desmopressin triggers water retention so urine becomes concentrated

This would be the same result in gestational DI

Question 21

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

Answer 21

2 - low urine osmolality

Issue is not ADH levels, rather the kidneys are not responding so we lose too much water

Question 22

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

Answer 22

2 - low urine osmolality

Despite desmopressin (synthetic ADH), the kidneys do not respond

Question 23

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

Answer 23

1 - head MRI

Question 24

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

Answer 24

5 - all of the above

Question 25

In central diabetes insipidus, what are patients given?

1 - conservative management and a urine diary
2 - desmopressin
3 - furosemide
4 - carbimazole

Answer 25

2 - desmopressin

Need to monitor Na+ due to risk of hyponatraemia

Question 26

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

Answer 26

5 - all of the above

• thiazide diuretics = decreased urine volume
• NSAIDs = constrict afferent arterioles and reduce fluid