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Urinary > Session 3 > Flashcards

Session 3 Flashcards

1
Q

What does the vasa recta do

A

Absorb nutrients and solutes

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2
Q

Corticopapillary gradient is established by

A

Countercurrent multiplication (solutes)
Urea recycling

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3
Q

Corticopapillary gradient is maintained by

A

Vasa recta

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4
Q

What happens as you go down the descending limb of loop of henle

A

Increase in solute concentration, decrease in osmolality

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5
Q

The loop of Henle over view

A
  • Responsible for 25% Na+ reabsorption
  • Thin descending limb: permeable to water, Na+ and Cl-
  • Thin ascending limb: impermeable to water, minimal Na+ and Cl- transport
  • Thick ascending limb: impermeable to water, Na+K+2Cl- co transporter apical membrane
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6
Q

What happens at thick ascending limb for concentrated urine

A

Na+ pumped out
Osmolarity increases in interstitium due to gain of sodium
Osmolarity decreases in thick ascending limb due to loss of sodium

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7
Q

What happens as a result of sodium being pumped out of thick ascending limb

A

Filtrate in descending limb must equilibrate until osmolarity is same inside and outside

Water leaves LOH and Na+ and Cl- enter - tubular fluid becomes more concentrated

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8
Q

Overall result of loop of henle countercurrent multiplication

A

Vasa recta plasma descends in opposite direction to tubule
Always has lower osmolality
Always diffusion gradient from tubule to interstitium and interstitium to plasma

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9
Q

Thick ascending limb of Loop of Henle can maintain a difference of

A

200mOsm/kg between interstitium and tubular fluid

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10
Q

Loop of Henle normal plasma osmolality

A

300mOsm/kg

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11
Q

Maximum osmolality of interstitium

A

1400mOsm/kg

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12
Q

Fluid leaving LOH is

A

Hypotonic (100mOsm/kg)

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13
Q

5 features of vasa recta

A
  • Hairpin arrangement- permeable to solutes and water
  • Descend: absorb solutes, water lost
  • Ascend: loss of solutes, reabsorb water
  • Slow flow: can equilibrate at each stratification level and minimise washout
  • Absorbs water released from CD in presence of ADH (maintains high osmolality of interstitium)
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14
Q

What does urea recycling do

A

Help to maintain the medullary hypertonicity

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15
Q

How much urea is reabsorbed in proximal convoluted tubule

A

50% filtered urea re absorbed

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16
Q

What happens to tubular concentration of urea as it goes from medulla into lumen in descending limb

A

Increases as it diffuses down concentration gradient (110% at base of LOH)

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17
Q

What happens to urea at ascending limb

A

Ascending limb and early DCT impermeable to urea to concentration increases as solutes and water reabsorbed

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18
Q

ADH causes

A

Urea transporter UT1 to increase expression. Urea flows down conc grad. 70% filtered urea reabsorbed by UT1 and 40% excreted

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19
Q

How is urea recycled

A

Urea secreted back into LOH and goes back up to DCT/CD and is recycled

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20
Q

What do diuretics do

A

Act on the kidney to increase the production of urine and to eliminate water from the body

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21
Q

3 main things diuretics do as a result of eliminating water

A
  • Reduce plasma volume and cardiac output
  • Reduce blood pressure
  • Reduce oedema/ascites
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22
Q

What are diuretics

A

Drugs that increase renal excretion of sodium and water resulting in increase in urine volume

23
Q

What is diuresis

A

Process of excretion of water in the urine

24
Q

What is Natriuresis

A

Process of excretion of sodium in the urine

25
Q

5 main classes of diuretics

A
  • Carbonic anhydrase inhibitors
  • Osmotic diuretics
  • Loop diuretics
  • Potassium sparing diuretics
  • Thiazide and thiazide-like diuretics
26
Q

How do most diuretics act

A

By interfering with the normal sodium reabsorption by the renal tubules resulting in Na+ and water excretion

27
Q

Which diuretics act at proximal tubule

A

Carbonic anhydrase inhibitors
Amiloride a little bit
SGLT-2 inhibitors (not diuretics)

28
Q

Which diuretics act at ascending limb of loop of Henle

A

Loop diuretivcs

29
Q

Which diuretics act at distal convoluted tubule/ early collecting duct

A

Thiazide and thiazide-like diuretics
(Amiloride)

30
Q

Which diuretics act at collecting duct

A

Potassium sparing diuretics

31
Q

How do carbonic anhydrase inhibitors work

A

Proximal tubule, stop bicarbonate being converted into water and carbon dioxide, this inhibits sodium transport out

32
Q

What do SGLT-2 inhibitors (Flozins) do

A

Reduce Na+ absorption in PCT

33
Q

Osmotic diuretics key points

A

Mannitol- administered via IV
Increase water excretion with relatively little effect on Na+ (water diuresis)

34
Q

Effects of osmotic diuretics

A

Expands the extracellular fluid volume initially, decrease blood viscosity, inhibit renin release, increase renal blood flow

35
Q

Uses of osmotic diuretics

A

Acute renal failure due to shock or trauma
Acute drug poisoning- need to eliminate drugs that are reabsorbed from renal tubules
To lower intracranial and intra ocular pressure before ophthalmic or brain procedures

36
Q

Side effects of osmotic diuretics

A
37
Q

What do loop diuretics work on

A

Prevent Na+K+2CL- transporter, reduce resorption of magnesium and calcium too

38
Q

What are the most potent diuretics (high ceiling)

A

Loop diuretics- bumetanide and Furosemine

39
Q

Key points of loop diuretics

A

Given orally or IV
Fast onset of action
Increase urine volume
Suitable for emergency situations

40
Q

When are loop diuretics useful

A
  • Severe oedema associated with congestive heat failure, nephrotic syndrome
  • Treatment for Oliguric ARF
  • Treatment of hypercalcaemia
  • Acute pulmonary oedema
  • Acute hyperkalaemia, hypercalcaemia
  • Toxicity of Br, F, and I
41
Q

Side effects of loop diuretics

A
  • Hypovolemia
  • Hyponatraemia (decreased blood Na+)
  • Hypokaemia (decreased blood K+)
  • Hypomagnasemia
  • Hypocalcae,is
  • Metabolic alkalosis
  • Postural hypotension
42
Q

What can be done to reduce the side effect of hypokalemia with loop diuretics

A

Dietary K supplementation or K sparing diuretics should be used to avoid hypokalemia

43
Q

How so thiazide and thiazide like diuretics work

A

Stop the Na+ Cl- transporter
Helps reabsorb calcium

44
Q

Uses of thiazide and thiazide like diuretics

A

1st line antihypertensive (Bendroflumethiazide, Indapamide)

Used for treatment of :
- Essential hypertension
- Mild heart failure
- Calcimu nephrolithiasis due to hypercalciuria
- Osteoporosis
- Nephrogenic diabetes insipidus polyuria

45
Q

Excretion and absorption affected by thiazide

A

Increase urinary excretion of: NaCl, K, Mg

Increase absorption of: calcium

Decrease excretion of: Uric acid, urinary calcium

46
Q

What usually happens with aldosterone at the collecting duct

A

Binds to receptor
Causes increased expression of ENAC and ROMK
Get more reabsorption of sodium, greater loss of potassium

47
Q

What do potassium sparing diuretics do and where do they work

A

Block the potassium channels so inhibits ROMK

Late DCT/CD

48
Q

What do aldosterone antagonists do and where do they work

A

Stop aldosterone being released, reduces ENAC

Late DCT/CD

49
Q

Why might you give loop diuretic at the same time as potassium sparing/aldosterone antagonist

A

Ensure not too much Potassium is lost

50
Q

Example of potassium sparing

A

Amiloride

51
Q

Example of aldosterone antagonists

A

Spironolactone

52
Q

What do potassium sparing and aldosterone antagonist diuretics do

A

Increase urinary sodium excretion
Decrease urinary potassium excretion
Decrease H+ excretion

53
Q

Uses of potassium sparing and aldosterone antagonists

A

Secondary hyperaldosteronism
CHF, hepatic cirrhosis, nephrotic syndrome
Treatment of hypertension (combined with thiazide or loop diuretics to correct for hypokalemia)

54
Q

Potassium sparing and aldosterone antagonists are contraindicated in

A

Hyperkalaemia (as in chronic renal failure, K+ supplementation, Beta blockers or ACE inhibitors needed)

Liver disease (dose adjustment needed)

Urinary (20 decks)

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