Disorders of Vasopressin - Clinical Case Flashcards
A 48 year old mother of two teenage children sees her GP to discuss some symptoms that have been troubling her. For the last few months she has had very disrupted sleep. She has no difficulty falling asleep but wakes up at least three times per night needing to pass urine. She also notices that before she goes back to sleep, she needs to drink a large glass of water because she is so thirsty. She works as a school administrator and has noticed that she is also passing urine frequently in the daytime, having to leave her desk to go to the toilet at least six times per day. She has a large bottle of water at her desk at work and fills this up several times per day.
What is the differential diagnosis (4)?
- Diabetes Mellitus (Type I / Type II)
- Diabetes Insipidus (Cranial / Nephrogenic)
- Psychogenic Polydipsia
- UTI
A 48 year old mother of two teenage children sees her GP to discuss some symptoms that have been troubling her. For the last few months she has had very disrupted sleep. She has no difficulty falling asleep but wakes up at least three times per night needing to pass urine. She also notices that before she goes back to sleep, she needs to drink a large glass of water because she is so thirsty. She works as a school administrator and has noticed that she is also passing urine frequently in the daytime, having to leave her desk to go to the toilet at least six times per day. She has a large bottle of water at her desk at work and fills this up several times per day.
Thinking about your differential diagnosis, what tests could the GP do next and how could these help?
(DM 4 / DI 3 / PP 1 / UTI 1)
- Tests for DM: HbA1c / Fasting glucose / Urine dipstick (ketones, glucose) / Oral glucose tolerance test
- Test for DI: Water deprivation test / Plasma & urinal osmolality / Urine dipstick (Specific gravity (dilute))
- Psycogenic Polydepsia: Water deprivation test
- UTI: Urine dipstick (nitrites)
A 48 year old mother of two teenage children sees her GP to discuss some symptoms that have been troubling her. For the last few months she has had very disrupted sleep. She has no difficulty falling asleep but wakes up at least three times per night needing to pass urine. She also notices that before she goes back to sleep, she needs to drink a large glass of water because she is so thirsty. She works as a school administrator and has noticed that she is also passing urine frequently in the daytime, having to leave her desk to go to the toilet at least six times per day. She has a large bottle of water at her desk at work and fills this up several times per day.
Blood results:
Fasting plasma glucose 5.4mmol/L
HbA1c 36 mmol/mol (< 42 mmol/mol)
Serum sodium 148 mmol/L (135-145 mmol/L)
How do these results help you with the differential diagnosis?
- Fasting plasma glucose & HbA1c are normal -> Exclude DM
- Serum sodium elevated -> High plasma osmolarity -> Probably DI
A 48 year old mother of two teenage children sees her GP to discuss some symptoms that have been troubling her. For the last few months she has had very disrupted sleep. She has no difficulty falling asleep but wakes up at least three times per night needing to pass urine. She also notices that before she goes back to sleep, she needs to drink a large glass of water because she is so thirsty. She works as a school administrator and has noticed that she is also passing urine frequently in the daytime, having to leave her desk to go to the toilet at least six times per day. She has a large bottle of water at her desk at work and fills this up several times per day.
Blood results:
Fasting plasma glucose 5.4mmol/L
HbA1c 36 mmol/mol (< 42 mmol/mol)
Serum sodium 148 mmol/L (135-145 mmol/L)
The patient is then referred to the Endocrinology clinic at the local hospital and the decision is made to further investigate the patient using a water deprivation test.
This was closely monitored, with body weight measured before the urine sample collection on each occasion. The clinical staff carrying out the test were told to stop the test if the patient lost more than 3% of her body weight.
Work through the water deprivation test results. What would be the response to water deprivation in a healthy person? How does that compare to the test results here?
For a normal person, there would be an increase in urine osmolarity and eventually plateu. This patient, there are minor fluctuations, but overall it plateus from the beginning, suggesting DI.
A 48 year old mother of two teenage children sees her GP to discuss some symptoms that have been troubling her. For the last few months she has had very disrupted sleep. She has no difficulty falling asleep but wakes up at least three times per night needing to pass urine. She also notices that before she goes back to sleep, she needs to drink a large glass of water because she is so thirsty. She works as a school administrator and has noticed that she is also passing urine frequently in the daytime, having to leave her desk to go to the toilet at least six times per day. She has a large bottle of water at her desk at work and fills this up several times per day.
Blood results:
Fasting plasma glucose 5.4mmol/L
HbA1c 36 mmol/mol (< 42 mmol/mol)
Serum sodium 148 mmol/L (135-145 mmol/L)
The patient is then referred to the Endocrinology clinic at the local hospital and the decision is made to further investigate the patient using a water deprivation test.
This was closely monitored, with body weight measured before the urine sample collection on each occasion. The clinical staff carrying out the test were told to stop the test if the patient lost more than 3% of her body weight.
Why do we monitor weight during the test?
If the patient loses 3% of their weight, they are really dehydrated, making it dangerous for them and even lethal if not stopped immediatel.
A 48 year old mother of two teenage children sees her GP to discuss some symptoms that have been troubling her. For the last few months she has had very disrupted sleep. She has no difficulty falling asleep but wakes up at least three times per night needing to pass urine. She also notices that before she goes back to sleep, she needs to drink a large glass of water because she is so thirsty. She works as a school administrator and has noticed that she is also passing urine frequently in the daytime, having to leave her desk to go to the toilet at least six times per day. She has a large bottle of water at her desk at work and fills this up several times per day.
Blood results:
Fasting plasma glucose 5.4mmol/L
HbA1c 36 mmol/mol (< 42 mmol/mol)
Serum sodium 148 mmol/L (135-145 mmol/L)
The patient is then referred to the Endocrinology clinic at the local hospital and the decision is made to further investigate the patient using a water deprivation test.
This was closely monitored, with body weight measured before the urine sample collection on each occasion. The clinical staff carrying out the test were told to stop the test if the patient lost more than 3% of her body weight.
What is the diagnosis?
Cranial Diabetes Insipidus (Vasopressin Deficiency)
A 48 year old mother of two teenage children sees her GP to discuss some symptoms that have been troubling her. For the last few months she has had very disrupted sleep. She has no difficulty falling asleep but wakes up at least three times per night needing to pass urine. She also notices that before she goes back to sleep, she needs to drink a large glass of water because she is so thirsty. She works as a school administrator and has noticed that she is also passing urine frequently in the daytime, having to leave her desk to go to the toilet at least six times per day. She has a large bottle of water at her desk at work and fills this up several times per day.
Blood results:
Fasting plasma glucose 5.4mmol/L
HbA1c 36 mmol/mol (< 42 mmol/mol)
Serum sodium 148 mmol/L (135-145 mmol/L)
The patient is then referred to the Endocrinology clinic at the local hospital and the decision is made to further investigate the patient using a water deprivation test.
This was closely monitored, with body weight measured before the urine sample collection on each occasion. The clinical staff carrying out the test were told to stop the test if the patient lost more than 3% of her body weight.
How should this patient be treated?
Desmopressin nasal spray daily or oral tablets
