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Z Year3 Clinical Presentations > Polyuria > Flashcards

Polyuria Flashcards

1
Q

What does polyuria and high urinary frequency have in common?

A

passing urine more often that before

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2
Q

How is polyuria different from high urinary frequency?

A

pass abnormally large volumes of clear urine each time

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3
Q

How do you check if it is true polyuria?

A

collecting 24hr urine sample (>3L = polyuria) - usually hard to rely on patient

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4
Q

What are differential diagnosis for polyuria?

A
  1. Diabetes mellitus (T1 or T2)
  2. Diuretics (e.g. diuretic medication, caffeine, alcohol, lithium)
  3. Heart failure
  4. Hypercalcaemia
  5. Hyperthyroidism
  6. Primary polydipsia
  7. Hypokalaemia
  8. Hyperuricaemia
  9. Diabetes insipidus (cranial or nephrogenic)
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5
Q

How can chronic renal failure and hypercalcaemia (e.g. due to bone metastases) cause polyuria?

A

by inducing nephrogenic diabetes insipidus

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6
Q

Why can steroids and Cushing’s syndrome cause polyuria?

A

by causing diabetes mellitus

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7
Q

What questions do you ask patient to help narrow down differential?

A
  1. Temporal pattern of urine output
  2. Fatigue, weight loss, recurrent infections
  3. Lower urinary tract symptoms
  4. Pain frequency, change in urine colour and smell
  5. PMHx
  6. DHx
  7. FHx
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8
Q

What do you ask about temporal pattern of urine output?

A

no of times day and night especially nocturia

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9
Q

What does nocturia (in absence of other causes e.g. BPH) suggest?

A

one of earliest signs of loss of concentrating ability - makes primary polydipsia less likely

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10
Q

What would fatigue, weight loss, recurrent infections and polyuria suggest?

A

DM

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11
Q

What are examples of lower urinary tract symptoms?

A
  • frequency
  • urgency
  • hesitancy
  • terminal driblling
  • incomplete voiding
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12
Q

What would symptoms of lower urinary tract suggest?

A
  1. pathology of bladder or outflow tract
  2. e.g. prostatism (men)
  3. detrusor instbaility and prolapse (women)
  4. not really polyruia
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13
Q

Why do you ask about pain frequency, change in urine colour and smell with polyuria?

A

suggestive of UTI, which could cause increased frequency but not polyuria

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14
Q

What PMHx do you ask about with polyuria?

A
  1. Hx renal problems e.g vasculitides, hypertension, chronic urinary retention
  2. Older patients, cancer (bony mets, hypercalcaemia)
  3. primary polydipsia in psychiastric disorders
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15
Q

What DHx do you ask about with polyuria?

A
  1. diuretic are potential and obvious cause of polyuria
  2. recent changes in medication or new over counter drugs
  3. lithium
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16
Q

Why can lithium cause polyuria?

A

inducing nephrogenic diabetes insipidus

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17
Q

What FHx do you ask about polyuria?

A
  1. hereditary component to DM and some forms of cancer

2. familial forms of diabetes inspidus (nephorgenic and cranial) present early in life

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18
Q

What GP tests must you request for polyruia?

A
  1. Cap blood glucose

2. Urinalysis with dipstick

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19
Q

Why do you do a cap glucose?

A

check for DM

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20
Q

Why do you do a urinalysis for polyuria?

A
  1. exclude UTI

2. see if glucosuria and ketonuria other signs of DM

21
Q

What other tests may you request for polyuria?

A
  1. Fasting plasma glucose
  2. Urine osmolarity
  3. Electrolytes
  4. Urea, creatinine and eGFR
  5. Serum calcium
  6. Thyroid function
22
Q

Why/When do you do fasting plasma glucose?

A
  1. if cap glucose is near upper limit or above normal

2. to exclude DM and calculate serum osmolarity

23
Q

What could lead to a high osmolality and volume?

A

inability to reabsorb solutes by the kidneys, solutes remain in urine and keep water with them

24
Q

What could lead to a low osmolality and volume?

A

inability to reabsorb water due to distal tubule pathology of deficient ADH pathway

25
Q

What would electrolyte levels be like in primary polydipsia?

A

serum sodium will be dilute

26
Q

What would electrolyte levels be like in other polyuria pathologies?

A

serum sodium concentrated

27
Q

Why do you need to measure potassium?

A

calculate serum osmolarity

28
Q

Why do you measure urea, creatinine and eGFR for polyuria?

A

help exclude chronic kidney failure

29
Q

Why do you measure serum calcium in polyuria?

A

exclude hypercalcaemia

30
Q

Why do you measure thyroid function in polyuria?

A

exclude hyperthyroidism

31
Q

What are the 2 types of diabetes inspidius?

A
  1. Cranial/Central

2. Nephrogenic

32
Q

What is the cranial/central inspidous?

A
  1. ADH secretion either reduced or absent due to defect in hypothalamic-pituitary axis
  2. Signal to kidneys to concentrate the urine is weak or absent
33
Q

What are the causes of cranial inspidus?

A
  1. head injury
  2. pituitary tumours
  3. craniopharyngiomas or metastases
  4. surge5y
  5. vascular lesion
  6. metastasis
34
Q

What is nephrogenic insipidus?

A

kidneys become less sensitive to ADH so do not respond to signals to concentrate the urine

35
Q

What are causes of renal damage for nephrogenic insipidus?

A
  1. low potassium
  2. high calcium
  3. lithium
  4. pyelonephirits
  5. hydronephorisis
  6. may be inherited
36
Q

What is a water deprivation?

A

distinguish between two times

37
Q

What is the process of a water deprivation test?

A
  1. Patient is fluid restricted
  2. Normal person ADH released to concentrate urine but in DI, urine dilute
  3. Desmopressin given, cranial DI will be able to concentrate urine but not nephrogenic
38
Q

What should you do before a water deprivation test?

A

ensure true polyuria with 24hr urine

39
Q

Why is a water deprivation potentially dangerous?

A

if DI as deprivation can cause hypovolemia so patients wieghed through

40
Q

When will the water deprivation test be stopped?

A

if body weight loss >3%

41
Q

What would polyuria + raised plasma glucose suggest?

A

DM

42
Q

What would polyuria + normal plasma glucose + normal urine osmolarity >300mOsm/L suggest?

A

solute diuresis (drugs, contrast agent, urea)

43
Q

What would polyuria + normal plasma glucose + low urine osmolarity <250mOsm/L + low serum sodium suggest?

A

psychogenic polydyspia

44
Q

What would polyuria + normal plasma glucose + low urine osmolarity <250mOsm/L + normal serum sodium suggest?

A

diabetes insipidus (desmopressin test to determine type)

45
Q

What is the management for cranial diabetes inspidus?

A
  1. Adequate fluid intake
  2. Investigation of underlying cause
  3. Replacement ADH
46
Q

When would you do investigation of underlying cause for CDI?

A
  • when no obvious cause is present (e.g. intercranial surgery)
  • MRI head
47
Q

When do you give replacement ADH?

A

if no reversible cause of cranial DI (e.g. pituitary tumour) patients need to take replacement ADH for life

48
Q

What medications do you use in nephrogenic but not cranial DI?

A

e.g. chlorpropamide, carbamazepine

Z Year3 Clinical Presentations (37 decks)

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