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chem path > Renal physiology > Flashcards

Renal physiology Flashcards

1
Q

what are normal urea levels (need to know for exam)

A

2-7

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2
Q

what is normal GFR and what happens to it with age

A

120ml/hr
decline of 1ml/hr/yr with age

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3
Q

what is clearance?

A

the volume of plasma that can be completely cleared of a marker substance in a unit of time

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4
Q

when does GFR = clearance

A

when a marker is:
1) no bound to serum proteins
2) freely filtered by the glomerulus
3) not secreted/reabsorbed by tubular cells

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5
Q

what is the gold standard measure of GFR & its limitation?

A

inulin
-requires steady state infusion & is difficult to assay

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6
Q

what is used in clinical practice to measure renal function? limitation

A

creatinine
-very variable for individual so best to monitor trend and change over time
-by product of muscle turnover. more muscular = more creatinine

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7
Q

how to estimate GFR with creatinine

A

various equations /algorithms related to age, sex, weight, ethnicity
eg. Cockcroft-Gault & MDRD

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8
Q

what can you get from a single urine sample?

A

-dipstick test
-microscopic examination
-proteinuria (protein: creatinine ratio PCR)

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9
Q

what can you get from a 24 hr urine collection?

A

-proteinuria quanitification
-creatinine clearance estimation
-electrolyte estimation
-stone forming elements

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10
Q

what can crystals in urine indicate

A

stones

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11
Q

what can RBC in urine indicate

A

stones, UTI

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12
Q

what can WBC in urine indicate

A

UTI, glomerulonephritis

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13
Q

what can casts in urine indicate

A

glomerulonephritis

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14
Q

how is AKI defined?

A
  • rise in serum creatinine >26 within 48hrs
    -50% or greater rise in serum creatinine within 7 days
    -fall in urine output to less than 0.5ml/kg/hr for more than 6 hours
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15
Q

most common cause of AKI?

A

acute tubular necrosis (ATN)

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16
Q

AKI staging?

A

stage 1 =
-serum creatinine >26 within 48hrs or increase >1.5-2 fold from baseline
-urine output <0.5ml/kg/hr for 6 hrs

stage 2=
-sCr >2-3 fold from baseline
-UO <0.5ml/kg/hr for 12 hrs

stage 3=
-sCr >3 fold from baseline or increase of >354
-iniaited on RRT (irrespective of stage)
-UO <0.3 for 24hrs or anuria fro 12hrs

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17
Q

what happens in pre-renal AKI?

A

-reduced renal perfusion without structural abnormalities to kidney
-can progress to kidney injury if leads to ischamia/necrosis - ATN

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18
Q

causes of pre-renal AKI?

A

-dehydration
-heart failure (reduced CO)
-sepsis (systemic vasodilation)
-renal artery stenosis

19
Q

what drugs can predispose to pre-renal AKI?

A

-diuretics
-NSAIDs
-calcineurin inhibiotrs (reduce afferent arteriole pressure)

20
Q

what mechanisms maintain GFR?

A

1) myogenic stretch: afferent arteriole constricts in response to increased stretch caused by high blood pressure to stabilise GFR
2)tubuloglomerular feedback: high chloride concentration in early distal tubule indicated high GFR triggering feedback mechanism that constricts afferent arteriole to decrease GFR

21
Q

what happens to renal perfusion mechanisms in pre-renal AKI?

A

normal adaptive mechanisms fail to maintain renal perfusion

22
Q

how do ACEi cause pre-renal AKI

A

reduce efferent arteriole vasoconstriction

*acEfferent

*for high renal perfusion we want dilated afferent (bringing in blood) and constricted afferent

23
Q

how do NSAIDs cause pre-renal AKI?

A

decrease afferent arteriolar dilatation

-nsAids = afferent

24
Q

how do diuretics cause pre-renal AKI?

A

decrease pre-load, affect tubular function

25
Q

how do calcineurin inhibitors cause pre-renal AKI?

A

decrease afferent arteriolar dilatation

26
Q

what causes renal AKI?

A

renal parenchyma issues
-vascular, glomerular, tubular, interstital
-ATN, AIN, glomerulonephritis

27
Q

what causes post-renal AKI?

A

obstruction to urinary flow
eg. ureteric obstruction (calculi, strictures, tumours, BPH, pelvic tumours)

28
Q

indications for dialysis?

A

AEIOU (vowels)

-Acidosis (metabolic)
-Electrolyte disturbance (refractory hyperkalaemia)
-intoxication (lithium, aspirin)
-overload (eg. pulmonary oedema)
-uraemic encephalopathy

29
Q

drugs contraindicated in AKI?

A

DAAAMN

-diuretics
-acei/arb
-aminoglycoside abx
-metformin
-nsaids

+contrast agents

30
Q

CKD stages?

A

1 = normal GFR >90
2= mild gfr 60-89
3a = 45-60
3b = 30-45
4= 15-29
5 = end stage <15 or dialysis

31
Q

commonest cause of CKD?

A

diabetes

32
Q

causes of CKD

A

-diabetes
-HTN
-atherosclerotic renal disease
-chronic glomerulonephritis
-infective/obstructive uropathy
-polycystic kidney

33
Q

consequences of CKD?

A

1) homeostasis: acidosis, hyperkalameia
2) hormones: anaemia (less EPO - normochronic/cytic) . renal osteodystrophy (low vit D causes secondary hyperparathyroidism)
3)CVD: vascular atherosclerosis & calcification, uraemic cardiomyopathy (LVH –> LV dilatation –> LV failure)
3) uraemia & death

34
Q

biggest mortality in CKD

A

CVD

35
Q

how to treat anaemia in CKD

A

darbepoieten

36
Q

what happens in fanconi syndrome

A

-PCT failure so cant reabsorb molecules (acquired or inherited)

37
Q

symptoms/signs of fanconi syndrome?

A

-polyuria/polydypsia/dehydration (glucosuria)
-growth failure
-metabolic acidosis (t2 RTA) (dec bicarb reabsoprtioN)
-hypokalaemia
-proteinuria
-hyperuricosuria

38
Q

how to treat fanconi syndrome

A

supportive

39
Q

niche cause of fanconi?

A

wilsons

40
Q

drug that prevents end stage renal failure?

A

AKI

41
Q

types of renal replacement therapy?

A

-dialysis (haemodialysis, peritoneal dialysis)
-transplant

42
Q

how does haemodialysis work?

A

-tunneled central line (tessio) or AV fistula
-around 3x a week
-not ideal for those who are still at work / needs machine at hosp

43
Q

how does peritoneal dialysis work?

A

-tenckoff catheter
-uses periotneum as dialysis membrane - insert dialysite through catheter
-can be done at home
-risk of peritoneal infections

44
Q

how is a kidney transplant done, and what is needed after?

A

-usually in right iliac fossa (rutherford morrison) - hockey stick scar
-lifelong immunosuppression eg. tacrloimus, ciclosporin

chem path (20 decks)

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