C - Renal Function Flashcards

1
Q

what is the best measure of kidney function

A

GFR

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2
Q

what is a normal GFR

A

120ml/min / 7.2L/hr

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3
Q

3 functions of kidney

A

waste excretion
metabolic balance including acid:base
water / urine excretion

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4
Q

what is the function of the glomerulus

A

water and low molecular weight molecules component filtrate, retains high molecular weight molecules

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5
Q

what is the function of the tubules

A

resorption of glomerular filtrate

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6
Q

by how much does GFR change with each year of life

A

1ml/min/yr

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7
Q

what can be used to estimate GFR

A

clearance

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8
Q

what is clearance

A

volume of plasma that is cleared of a substance per unit time

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9
Q

features of a suitable clearance molecule

A

not charged
not metabolised
not bound to serum proteins
freely filtered at glomerulus

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10
Q

what is the equation for clearance

A

C = U x P

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11
Q

what is the gold standard molecule to measure GFR

A

inulin

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12
Q

why is blood urea not used as a measure of GFR

A

increased by high protein intake or bleeding
decreased by liver disease and low protein intake
variable resorption by tubular cells

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13
Q

where is creatinine made

A

muscle cells

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14
Q

what does creatinine clearance depend on

A

muscle mass, age, sex, ethnicity
can decrease in surgery, starvation, steroid use

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15
Q

how is creatinine related to GFR

A

plasma creatinine ratio is inversely related to GFR

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16
Q

does a normal plasma creatinine ratio mean GFR is normal

A

NO - there is a lag between GFR dropping and plasma creatinine increasing

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17
Q

what is the cockcroft gault equation

A

eCCR = (1.23 x (140-age) x weight) / serum creatinine

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18
Q

when can cockcroft gault not be used

A

CKD

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19
Q

what is the MDRD equation

A

eGFR = (186 x (creatinine x 0.0113) ^-1.154) x age ^-0.203

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20
Q

when can MDRD not be used

A

healthy people - it’s only for CKD
pregnant people
doesn’t take into count weight so not for young / heavy

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21
Q

what does the CKD-EPI equation take into account

A

age, sex, race, serum creatinine

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22
Q

give an alternative molecule to creatinine

A

cystatin C

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23
Q

why is cystatin C a good alternative to creatinine for eGFR

A

independent from weight / muscle mass
reflects eGFR more accurately
good for xs muscle bulk patients

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24
Q

name types of urine exams

A

urine dip
MC&S
24hr urine collection

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25
Q

when is 24hr urine collection used

A

creatinine clearance estimate
stone forming electrolytes

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26
Q

if the dipstick is -‘ve for blood, is haematuria excluded?

A

YES

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27
Q

what does urine dip test for

A

pH, specific gravity, protein, blood, leucocyte esterase, nitrites, ketones, flucose

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28
Q

what proteins are detected / not detected on urine dip

A

albumin IS
bene jones proteins are NOT

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29
Q

if leucocyte esterase is negative, is this significant?

A

YES

30
Q

what does nitrities on urine dip indicate

A

bacteria - esp gram neg

31
Q

does glucose on urine dip = DM ?

A

NO - can be other things

32
Q

urine with RBCs in indicates what

A

glomerular disease or stones

33
Q

urine with casts in indicates what

A

glomerular disease

34
Q

calcium oxolate stones. what has happened?

A

anti freeze poisoning

35
Q

Ix for ?stones

A

<24hr PC = CT KUB
plain XR KUB
USS KUB - if preg / kid
IV urogram

36
Q

when do you get staghorn calculi

A

chronic infection

37
Q

contrast GFR decline in AKI and CKD

A

AKI = abrupt
CKD = slow

38
Q

Is AKI or CKD reversible?

A

AKI is, CKD isn;t

39
Q

What is the general Mx principles of AKI vs CKD in terms of aim of Tx

A

AKI = diagnose and reverse disease
CKD = limit progression and symptomatic

40
Q

define AKI

A

rapid reduction in kidney function (acid base control, electrolytes, fluid)

41
Q

what 2 measures are used to differentiate severity of AKI

A

serum creatinine
urine output

42
Q

define the serum creatinine levels of the 3 levels of AKI

A

S1 = sCr raised by >26umol/L OR 1.5 to 1.9 x reference
S2 = sCr raised by 2 to 2.9 x reference
S3 = sCr raised by >3x ref or by >354umol/L

43
Q

define the urine outputs of the 3 levels of AKI

A

S1 <0.5ml/kg/hr for 6-12 hours
S2 <0.5ml/kg/hr for >12 hours
S3 <0.3ml/kg/hr for >24 hours

44
Q

name the 3 classifications of AKI

A

pre renal
renal
post renal

45
Q

what causes pre renal AKI in general

A

poor renal perfusion (ischaemia) due to dysfunctional renin-aldosterone system

46
Q

causes of pre renal AKI

A

dehydration (true volume depletion)
low BP
oedematous - HF / liver failure
renal artery sclerosis
drugs that alter glomerular blood flow

47
Q

name drugs that can cause pre renal AKI

A

NSAIDs
calcineurin inhibitors
ACEi / ARB
diuretics

48
Q

what is ATN & is it bad

A

acute tubular necrosis
- YES - irreversible ischaemic damage to tubules

49
Q

4 causes of intrinsic renal AKI

A

vascular - vasculitis
glomerular - nephritis
tubular - ATN
interstitial

50
Q

3 causes of intrinsic renal injury

A

amyloidosis
lymphoma
myeloma

51
Q

what causes post renal AKI in general terms

A

physical obstruction to urine flow

52
Q

causes of post renal AKI

A

ureteric obstruction - stones etc
prostate / urethra obstruction - BPH, cancer
blocked catheter

53
Q

when is post renal AKI irreversible / reversible

A

irreversible = slow relief of blockage –> ischaemia, interstitial scaring, tubular damage
reversible = quick relief of obstruction

54
Q

prognosis of AKI (% recovery etc)

A

40% full recovery
20% die
40% have some damage in between

55
Q

how does AKI heal (4 processes)

A

haemostasis
inflammation
proliferation
remodelling

56
Q

describe the spectrum of CKD

A

increased risk factors –> early damage –> lowered GFR –> renal failure –> death

57
Q

describe the 5 stages of CKD

A

1 = kidney damage with normal GFR
2 = mild drop in GFR
3 = moderate drop in GFR
4 = severe drop in GFR
5 = end stage kidney failure

58
Q

what is GFR of stage 1 CKD

A

> 90

59
Q

what is GFR of stage 2 CKD

A

60-89

60
Q

what is GFR of stage 3 CKD

A

30-59

61
Q

what is GFR of stage 4 CKD

A

15-29

62
Q

what is GFR of stage 5 CKD

A

<15 or dialysis

63
Q

causes of CKD

A

DM ***** top cause
atherosclerotic renal disease
HTN
chronic glomerulonephritis
infective / obstructive uropathy
PCKD

64
Q

name 4 consequences of CKD

A

progressive failure of homeostatic function
hormal function failure
CVD
uraemia and death

65
Q

describe features of failure of homeostatic function seen in CKD

A

acidosis as can’t excrete H+ ions
muscle / protein degredation
osteopenia
heart dysfunction

66
Q

Tx of failure of homeostatic function in CKD

A

oral sodium bicarb

67
Q

features of hormonal function failure seen in CKD

A

anaemia - reduced epo producing cells
renal bone disease - fractures, pain, osteoporosis, osteomalacia, osteitis fibrosa

68
Q

what is ostitis fibrosa

A

osteoclastic resorption of calcifed bone and replaced by fibrous tissues –> browns tumours

69
Q

why can’t you just give epo to anaemic CKD patient

A

they increase BP
they won’t work if low iron, low folate, TB, Ca, hyperparathyroidism

70
Q

how can CKD affect CVS

A

vascular calcification of arteries
ureamic cardiomyopathy *** mortality

71
Q

3 phases of uraemic cardiomyopathy

A

LV hypertrophy
LV dilatation
LV dysfunction