C - Renal Function Flashcards by Lottie Barot

what is the best measure of kidney function

GFR

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what is a normal GFR

120ml/min / 7.2L/hr

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3 functions of kidney

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

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what is the function of the glomerulus

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

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what is the function of the tubules

resorption of glomerular filtrate

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by how much does GFR change with each year of life

1ml/min/yr

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what can be used to estimate GFR

clearance

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what is clearance

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

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features of a suitable clearance molecule

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

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what is the equation for clearance

C = U x P

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what is the gold standard molecule to measure GFR

inulin

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why is blood urea not used as a measure of GFR

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

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where is creatinine made

muscle cells

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what does creatinine clearance depend on

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

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how is creatinine related to GFR

plasma creatinine ratio is inversely related to GFR

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does a normal plasma creatinine ratio mean GFR is normal

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

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what is the cockcroft gault equation

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

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when can cockcroft gault not be used

CKD

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what is the MDRD equation

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

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when can MDRD not be used

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

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what does the CKD-EPI equation take into account

age, sex, race, serum creatinine

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give an alternative molecule to creatinine

cystatin C

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why is cystatin C a good alternative to creatinine for eGFR

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

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name types of urine exams

urine dip
MC&S
24hr urine collection

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when is 24hr urine collection used

creatinine clearance estimate stone forming electrolytes

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

YES

what does urine dip test for

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

what proteins are detected / not detected on urine dip

albumin IS bene jones proteins are NOT

if leucocyte esterase is negative, is this significant?

YES

what does nitrities on urine dip indicate

bacteria - esp gram neg

does glucose on urine dip = DM ?

NO - can be other things

urine with RBCs in indicates what

glomerular disease or stones

urine with casts in indicates what

glomerular disease

calcium oxolate stones. what has happened?

anti freeze poisoning

Ix for ?stones

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

when do you get staghorn calculi

chronic infection

contrast GFR decline in AKI and CKD

AKI = abrupt CKD = slow

Is AKI or CKD reversible?

AKI is, CKD isn;t

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

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

define AKI

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

what 2 measures are used to differentiate severity of AKI

serum creatinine urine output

define the serum creatinine levels of the 3 levels of AKI

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

define the urine outputs of the 3 levels of AKI

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

name the 3 classifications of AKI

pre renal renal post renal

what causes pre renal AKI in general

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

causes of pre renal AKI

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

name drugs that can cause pre renal AKI

NSAIDs calcineurin inhibitors ACEi / ARB diuretics

what is ATN & is it bad

acute tubular necrosis - YES - irreversible ischaemic damage to tubules

4 causes of intrinsic renal AKI

vascular - vasculitis glomerular - nephritis tubular - ATN interstitial

3 causes of intrinsic renal injury

amyloidosis lymphoma myeloma

what causes post renal AKI in general terms

physical obstruction to urine flow

causes of post renal AKI

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

when is post renal AKI irreversible / reversible

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

prognosis of AKI (% recovery etc)

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

how does AKI heal (4 processes)

haemostasis inflammation proliferation remodelling

describe the spectrum of CKD

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

describe the 5 stages of CKD

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

what is GFR of stage 1 CKD

>90

what is GFR of stage 2 CKD

60-89

what is GFR of stage 3 CKD

30-59

what is GFR of stage 4 CKD

15-29

what is GFR of stage 5 CKD

<15 or dialysis

causes of CKD

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

name 4 consequences of CKD

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

describe features of failure of homeostatic function seen in CKD

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

Tx of failure of homeostatic function in CKD

oral sodium bicarb

features of hormonal function failure seen in CKD

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

what is ostitis fibrosa

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

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

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

how can CKD affect CVS

vascular calcification of arteries ureamic cardiomyopathy *** mortality

3 phases of uraemic cardiomyopathy

LV hypertrophy LV dilatation LV dysfunction

C - Renal Function Flashcards

(71 cards)