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PHCY 310 > L 31 Lab test of CKD > Flashcards

L 31 Lab test of CKD Flashcards

1
Q

What are the 3 primary mechanisms of urine excretion

A
  1. glomerular filtration
  2. tubular reabsorption
  3. tubular secretion
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2
Q

Is tubular transport active or passive?

A

Both, active and passive

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3
Q

Tubular secretion what is it?

A

An additional excretory mechanism

Both active and passive

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4
Q

The RAAS system affects ….

A

Na+ and K+ measurements

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5
Q

Loop of henle reabsorbs:

A

H2O and Na+

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6
Q

Distal tubule reabsorbs

A

Na+, K+, H+, HCO3

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7
Q

Proximal tubule reabsorbs

A

H2O, electrolytes, glucose

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8
Q

What pH is controlled by?

A

By 2 things i)Lungs ii)Kidneys

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9
Q

What 2 systems regulate pH?

A

The respiratory and renal systems

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10
Q

What does the kidney do to regulate pH?

A

Kidney provides a buffering system to help regulate pH

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11
Q

pH is determined by the ratio of _____ and _______.

A

pH is determined by the ratio of [HCO₃⁻] and PaC02.

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12
Q

The kidneys regulate the concentration of Bicarbonate in the ?

A

In the plasma

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13
Q

The kidney exchanges … for ….

A

Exchanges H+ ions (out) for HCO3 (in)

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14
Q

… and … are exchanged intracellularly and extracellularly to maintain a pH balance?

A

Potassium and Hydrogen are exchanged intracellularly and extracellularly to maintain a pH balance
K+ and H+

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15
Q

How do we estimate renal function? x2

A

Creatinine clearance and eGFR

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16
Q

What is creatinine?

A

A chemical compound formed by muscle

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17
Q

Summary of creatinine?

A

Filtered by glomerulus, not reabsorbed by tubules.

Half life ~6 hours

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18
Q

Creatinine clearance (CLcr) gives us an estimate of?

A

Gives us an estimate of GFR.

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19
Q

Is serum creatinine a good biomarker?

A

Not by itself, it is influenced by factors affecting production and elimination

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20
Q

What equation is used to estimate CLcr?

A

Cockcroft and gault equation

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21
Q

What is the definition of steady state?

A

Rate of elimination =rate of production

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22
Q

Creatinine production depends or influenced by?

A

Weight, age and Sex

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23
Q

What are the Limitations to creatinine-based GFR estimators?

A
  • They overestimate GFR in elderly, obese (if use TBW), severe or end stage renal disease
  • Not for <18s
  • Not for malnourished or low body mass
  • Unreliable when renal function changes rapidly (Acute renal failure)
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24
Q

If a patient has a eGFR of 55mL/min/1.73m^2, but their BSA is actually 1.50m^2, what should their eGFR be?

A

55/1.73 = 31.79

31.79 x 47mL/min

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25
Q

Other issues with creatinine based renal estimations?

A
  • Only useful in steady state condition (not good if renal function is changing)
  • Note variability in natural creatine production and drugs that raise creatinine concentration.
26
Q

These drugs inhibit tubular secretion and therefore raise creatinine concentration x3?

A

Probenecid, trimethoprim, spironolactone

27
Q

Creatinine based eGFR equations, CKD-EPI and MDRD only be used in patients with a body-surface area (BSA) of 1.73m^2?

A

No, you can adjust it if you know the BSA so that it will be accurate.

28
Q

What is urea? How is it excreted? How is it filtered?

A

Urea is the end product of protein metabolism.
It is excreted renally
It is filtered by glomerular filtration.

29
Q

How much urea is reabsorbed in tubules?

A

50%

30
Q

If you remove a kidney what happens to eGFR?

A

Reduce EGFR but not a half will remain the same but reduce a little.

31
Q

Why is urea not an ideal marker for renal function?

A

Many non-renal conditions can affect urea

32
Q

How much filtered urea is reabsorbed in the tubules? When will this increase?

A

About 50% of urea is reabsorbed in the tubules

This increases during dehydration to increase water reabsorption.

33
Q

Where is potassium usually found in the body? What is the usual serum concentration?
What is the major role of K+ in the body?

A

Usually found in intracellular fluid.
Usual serum concentration = 3.5-5.2mmol/L
K+ plays a major role in muscle and nerve function.

34
Q

Potassium homeostasis is maintained by these 2 primary mechanisms.?

A
  1. Shifting potassium in and out of cells

2. Renal elimination

35
Q

Renal elimination controlled by ?

A

Aldosterone

Eliminated by distal tubular secretion

36
Q

How is renal elimination of K+ controlled? What are the 2 options to maintain homeostasis of K+?

A

K+ renal elimination is controlled by aldosterone.
To increase K+, the body freely filters and the completely reabsorbs K+
To decrease K+, the body eliminates it through distal tubule secretion

37
Q

Why K+ accumulation occur for CKD patients?

A

In CKD, K+ secretion is reduced thus it start accumulation of K+

38
Q

In which stage K+ remain normal of CKD?

A

In which stage K+ remain normal of CKD?

in stage 3 of CKD

39
Q

What is the compensatory response to elevated K+? What does this do?

A

Aldosterone is released which causes an increase in K+ elimination

40
Q

NOTE: hyperkalaemia can be exacerbated by …..

A

ACEI, ARBs, K-sparing diuretics

Because they stop the natural aldosterone K+ elimination.

41
Q

Hyperkalaemia is most common in which stages of CKD?

In which stages do K+ levels often remain normal?

A

Hyperkalaemia: CKD4 or CKD5

Normal K+ levels: CKD1-3

42
Q

Where is sodium usually found in the body?
What is the usual serum concentration?
What is the major role of Na+ in the body?

A

Mainly found in ECF
Usual serum conc = 135-145mmol/L
Major role = to maintain serum osmolality and water balance

43
Q

Where are sodium and water primarily reabsorbed?

Where are the major sites for regulatory control?

A

By the proximal tubule

Regulatory control sites are the distal tubule and collecting ducts

44
Q

Sodium homeostasis is controlled by…

A

Aldosterone and ADH

45
Q

How much of the filtered Na+ is excreted in normal renal function?

A

Normally, 1-3% of filtered Na+ is excreted

46
Q

As CKD progresses … excretion becomes impaired causing?

A

As CKD progresses, Na+ excretion becomes impaired causing fluid retention, volume expansion, increased BP, oedema

47
Q

In late CKD, it becomes a ….problem with CVD?

A

In late CKD, it becomes a cyclical problem with CVD

48
Q

As CKD progresses, there are high levels of … and … and … in the body?

A

Na+ and K+ and H+

49
Q

Arterial pH is at ?and how it governs by the balance between …. and ….

A

Arterial pH is normally maintained at 7.36-7.44 by governing the balance between HCO3 and CO2

50
Q

Overall, metabolic processes produce an excess of … which therefore must be ….

A

Overall, metabolic processes produce an excess of acid which therefore must be buffered

51
Q

In CKD there is impaired pH control meaning that … excretion is reduced, but … reabsorption is relatively maintained.What is the result of this?

A

In CKD there is impaired pH control meaning that H+ excretion is reduced, but HCO3 reabsorption is relatively maintained.
Result = tendency of acidosis

52
Q

Signs of acidosis

A

pH <7.35

53
Q

Acidosis contributes to (x4)

A

Bone resorption
Muscle wasting
Hyperparathyroidism
Increased CKD progression and mortality

54
Q

Which patients are at risk with a triple whammy?

A

Elderly, heart failure patients

55
Q

What is proteinuria?

A

Leakage of excess albumin/proteins into the urine.

56
Q

Where is a protein normally filtered and reabsorbed?

A

Protein is normally filtered in the glomerulus and reabsorbed by the proximal tubules.

57
Q

What measures can we use to determine proteinuria?

A

Spot urine checks and albumin: creatinine ratio (ACR)

58
Q

Microalbuminuria values?

A

30-300mg/24hrs

59
Q

Macroalbuminuria values?

A

> 300mg/24hrs

60
Q

Microalbuminuria values using ACR?

A

2.5-25mg/mmol for men, 3.5-35mg/mmol for women
Macroalbuminuria values using ACR
>25mg/mmol for men, >35mg/mmol for women

61
Q

What other situations can albuminuria occur in?

A

After exercise, fever, UTIs

62
Q

Which one of the following lab results would you expect to INCREASE when initiating an ACEI in a CKD patient?

A
  1. eGFR
  2. Potassium
  3. pH
  4. Bicarbonate
    Answer: 2. Potassium.
    Because aldosterone naturally causes K+ elimination, but blocking the aldosterone pathway will inhibit secretion = increased serum potassium levels

PHCY 310 (65 decks)

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