Urinary 6 - Plasma osmolarity (disorders + diuretics) Flashcards Preview

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Flashcards in Urinary 6 - Plasma osmolarity (disorders + diuretics) Deck (84):
1

What are the main receptors in the body that detect changes in plasma osmolarity, and where are they located?

Hypothalamic osmoreceptors
Organum Vasculosum of Lamina Terminalis (OVLT)

2

How do the hypothalamic osmoreceptors respond if they detect increased osmolarity?

- Increase thirst stimulus
- Increase ADH secretion

3

For the hypothalamic osmoreceptors to increase the thirst response, what change in osmolarity must be detected?

Increased osmolarity by 10%

4

For the hypothalamic osmoreceptors to change ADH secretion rate, what change in osmolarity must be detected?

Increased or decreased osmolarity by 1%

5

How does an increase in ADH secretion cause reduction of plasma osmolarity?

ADH increases the insertion of AQP2 into the apical membrane of principal cells of collecting ducts = increased water reabsorption

6

Which aquaporin channels are controlled by ADH?

AQP2 in the principle cells of the collecting duct

7

ADH mediates aquaporin insertion in what part of the kidney tubule?

Collecting ducts (principle cells)

8

Which aquaporin channels are present in the apical membrane of the PCT?

AQP1
AQP7

9

Which aquaporin channels are present in the apical membrane of the descending LoH?

AQP1

10

Which aquaporin channels are present in the basolateral membranes of the PCT and descending LoH?

AQP1

11

Which aquaporin channels are present in the basolateral membrane of the collecting ducts?

AQP3
AQP4

12

List some causes of Central Diabetes Insipidus:

Damage to hypothalamus and/or pituitary gland:
- Brain injury (particularly fracture of base of skull)
- Meningitis
- Brain tumour
- Sarcoidosis
- TB
- Encephalitis
- Aneurysm
- Langerhans cells histiocytosis

13

What is the pathophysiology of central diabetes insipidus?

Damage to hypothalamus and/or pituitary gland
= lack of circulating ADH
= inadequate reabsorption of H2O from collecting ducts

14

What are the symptoms of central diabetes insipidus?

Polyuria
Polydipsia

15

What is the treatment of central diabetes insipidus?

ADH nasal spray
ADH injections

16

List some causes of Nephrogenic Diabetes Insipidus:

- Hereditary
- Acquired (Lithium, hypercalcaemia, hypokalaemia, polycystic kidney disease, sickle cell anaemia, severe pyelonephritis)

17

What is the inheritance pattern of hereditary nephrogenic diabetes insipidus?

X-Linked Recessive

18

What is the pathophysiology of nephrogenic diabetes insipidus?

Kidney is less sensitive to ADH
= Inadequate reabsorption of H2O from collecting ducts

19

What are the symptoms of Nephrogenic Diabetes Insipidus?

Polydipsia
Polyuria

20

What are the treatments for Nephrogenic Diabetes Insipidus?

Mild:
- Reduced intake of salt and protein
- Adequate water intake
More severe:
- NSAIDs
- Thiazide diuretics

21

What does SIADH stand for?

Syndrome of Inappropriate ADH secretion

22

List some causes of SIADH:

- Nervous system disorders (MS, encephalitis, infection, epilepsy)
- Brain injury
- Drug induced (Lithium, antidepressants, opiates)
- Pulmonary disorders (Infection, asthma, CF)

23

Describe the pathophysiology of SIADH:

Excessive release of ADH
= Massive volume expansion
= Hyponatraemia

24

List some symptoms of SIADH:

Nausea/Vomiting
Cramps/Tremors/Seizures
Depressed mood/Irritability/Confusion

25

What is the treatment for SIADH?

- Treat underlying cause
- Fluid restriction
- Na+ replacement (IV hypertonic saline)
- ADH receptor antagonists

26

Define diuretic:

Substance which promotes diuresis by increasing renal excretion of H2O and Na+, to decrease ECF volume

27

List the 5 classes of diuretic:

1) Loop
2) Thiazide
3) K+ Sparing
4) Carbonic Anhydrase inhibitors
5) Osmotic

28

What is the mechanism of action of Loop diuretics?

Block NKCC2 in TAL (Thick ascending limb of LoH)

29

What class of diuretic does Furesomide belong in?

Loop diuretic

30

What type of diuretic is the most powerful?

Loop diuretics

31

What conditions are Loop diuretics used to treat?

- Heart failure
- Fluid retention and oedema in Nephrotic syndrome, Liver cirrhosis and renal failure
- Hypercalcaemia

32

What are the main complications of Loop diuretics?

- Hypokalaemia
- Dehydration
- Hyperuricaemia = Gout attack
- Hyponatraemia (less common)

33

Give an example of a diuretic that acts on the TAL (Thick ascending limb of LoH):

Furosemide

34

What class of diuretics block NKCC2 channels?

Loop diuretics

35

What is the mechanism of action of Thiazide diuretics?

Block Na+/Cl- symporter in the DCT

36

What class of diuretic does Metolazone belong to?

Thiazide diuretics

37

What is the preferred diuretic used in patients with osteoporosis, and why?

Thiazide diuretics
Increase Ca2+ reabsorption

38

What condition is commonly treated with Thiazide diuretics?

Hypertension

39

Which diuretic is most commonly used to treat hypertension?

Thiazide diuretics

40

What are the main complications of Thiazide diuretics?

- Hypokalaemia
- Hyponatraemia
- Hyperuricaemia = Gout attack
- Hyperglycaemia
- Hyperlipidaemia
- Erectile dysfunction

41

Give an example of a diuretic that acts on the DCT:

Metolazone (Thiazide)
Amiloride (K+ sparing ENaC blocker)

42

Which class of diuretics block the Na+/Cl- symporter?

Thiazide diuretics

43

What is the mechanism of action of K+ sparing diuretics?

EITHER:
1 - Inhibition of ENaC in DCT and collecting duct
2 - Aldosterone antagonist

44

What class of diuretic does Amiloride belong to?

K+ Sparing (ENaC inhibition)

45

What class of diuretics does Spironalactone belong to?

K+ sparing (Aldosterone antagonist)

46

What are ENaC blockers used for?

Used alongside K+ losing diuretics, to minimise K+ loss

47

What conditions are commonly treated with Aldosterone antagonists?

- Hypertension (if caused by Conn's syndrome)
- Ascites and Oedema in Cirrhosis
- Heart failure (with loop diuretics)

48

What is the main complication of K+ sparing diuretics?

- Hyperkalaemia

49

What may increase the risk of hyperkalaemia occurring when taking K+ sparing diuretics?

- ACEi
- K+ supplements
- Renal impairment

50

To which class of diuretics do ENaC blockers belong?

K+ Sparing diuretics

51

Give an example of a diuretic that acts on the collecting ducts:

Amiloride (K+ sparing ENaC blocker)
Spironolactone (K+ Sparing aldosterone antagonist)

52

To which class of diuretics do Aldosterone antagonists belong?

K+ sparing

53

What class of diuretic does Acetazolamide belong to?

Carbonic Anhydrase inhibitor

54

What condition are Carbonic Anhydrase inhibitors used for?

Glaucoma

55

What is the main complication caused by Carbonic Anhydrase Inhibitors?

Metabolic acidosis (increases HCO3- loss)

56

What is the mechanism of action of osmotic inhibitor diuretics?

Small inert molecules increase the osmolarity of blood and filtrate
= Increased driving force for H2O loss

57

What class of diuretics does Mannitol belong to?

Osmotic Inhibitor diuretics

58

What condition can be treated with osmotic inhibitor diuretics?

Cerebral oedema

59

By what mechanisms can Loop and Thiazide diuretics cause hypokalaemia?

1 - Increased Na+ delivery to late DT/collecting ducts
= Increased Na+ reabsorption (ENaC)
= Increased K+ secretion (ROMK down favourable electrical gradient)
2 - Increased flow rate in lumen
= Secreted K+ is washed away faster (reduced local conc.)
= Increased K+ secretion (ROMK down favourable concentration gradient)
3 - Decreased ECF
= RAAS activation
= Increased Aldosterone activation
= Increased Na+ absorption and K+ secretion

60

Which diuretics can cause hypokalaemia?

Loop diuretics
Thiazide diuretics

61

Which diuretics can cause hyperkalaemia?

K+ Sparing diuretics

62

Which diuretics can cause hyponatraemia?

Thiazide diuretics
Loop diuretics (less likely)

63

Which diuretics can cause hyperuricaemia?

Loop diuretics
Thiazide diuretics

64

Which diuretics can cause hyperglycaemia and hyperlipidaemia?

Thiazide diuretics

65

Which diuretics can cause erectile dysfunction?

Thiazide diuretics

66

What is a complication of Spironolactone diuretics?

Gynaecomastia

67

Which diuretics can cause gynaecomastia?

Spironolactone

68

How do Spironolactone diuretics cause gynaecomastia?

Decreased testosterone production and Increased peripheral conversion of Testosterone to Estradiol

69

How does Alcohol cause diuresis?

Inhibits ADH release

70

How does coffee cause diuresis?

- Increased GFR
- Decreased tubular reabsorption of Na+

71

How does Lithium cause diuresis?

Inhibits ADH action on collecting ducts

72

How does hyperglycaemia cause diuresis?

Increased osmolarity of plasma and filtrate

73

How does psychogenic polydipsia cause diuresis?

Increased fluid intake = increased fluid loss

74

Which nephrons have a vertical osmotic gradient?

Juxtamedullary nephrons only

75

What is the concentration of the filtrate when it reaches the distal tubule of juxtamedullary nephrons?

100 mosm/L

76

Describe the relationship between the vasa recta and a juxtamedullary nephron:

Flow of the vasa recta is in opposite direction to the tubule:
- Desc. limb of vasa recta accompanies the asc. limb of LoH
- Asc. limb of vasa recta accompanies the desc. limb of the LoH

77

Na+, Cl- and Urea diffuse into which limb of the vasa recta?

Descending limb

78

H2O diffuses into which limb of the vasa recta?

Ascending limb

79

What type of nephrons can produce hyper/hypotonic urine?

Juxtamedullary nephrons

80

What is the maximum concentration of urine?

1200 mosm/L

81

What is the average concentration of urine?

300 mosm/L

82

ADH binds to which cells in the kidney?

Principal cells in the collecting duct

83

Where is ADH produced and secreted from?

Produced - hypothalamus
Secreted from - posterior pituitary

84

How does ADH cause increased water reabsorption across the principle cells of the collecting duct?

ADH induces the relocation of AQP2 into the apical membrane