Acute renal failure Flashcards

1
Q

Define acute renal failure or ARF or AKI

A

1) rapid decr in GFR
2) incr plasma creatinine
3) incr urea and waste products (BUN)

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2
Q

Define azotemia

A

incr BUN and creatinine

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3
Q

3 major etiologies of azotemia

A
  • Pre-renal azotemia
  • Post-renal azotemia
  • Intrinsic renal disease
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4
Q

Define prerenal azotemia

2 major categories of prerenal cause of ARF

A

decr in renal plasma flow and/or renal perfusion pressure –> decr GFR

1) hypovolemia (from hemorrhage, GI losses..)
2) low effective arterial blood volume (CHF or cirrhosis)

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5
Q

in prerenal, ___ are undamaged and function normally meaning …

A

tubules undamaged

continue reabsorb Na+ and H2O to incr volume and perfusion pressure

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6
Q

Pre-renal exam findings include:

A

1) decr weight andpostural changes in BP/pulse for volume depletion
2) hypervolemic = right heart failure sx = edema, rales, S3
3) UA = high SG (1.020 or 1.030), NO BLOOD, PROTEINS, OR CASTS
4) low FENa

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7
Q

define postrenal azotemia or obstructive nephropathy

A

decr in GFR due to obstruction of urine outflow from renal papilla to urethra

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8
Q

how does obstruction cause post-renal

A

1) incr intratubular pressure
2) back up to glomerulus and alter pressure gradients
3) decr GFR due to incr tubular hydrostatic pressure

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9
Q

where can obstruction occur and diseases assoc with each location?

A
  1. Ureters
    a. Extraureteral – a structure outside the ureter is compressing it; carcinoma of the cervix, retroperitoneal fibrosis

b. Intraureteral – an obstruction within the ureter; kidney stones, blood clots
2. Bladder – outlet obstruction from carcinoma, infection, neuropathy
3. Urethra – prostatic hypertrophy

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10
Q

Post-renal exam findings

A

1) obstruction = anuria, large changes in urine flow rate

2) UA = specific gravity is isosmotic with NO BLOOD, PROTEINS, CASTS unless have INFECTION

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11
Q

intrinsic renal disease

4 categories and diseases assoc

A

1) Tubular diseases – acute tubular necrosis (ATN) = most common
2) Glomerular diseases – glomerulonephritis, HUS
3) Interstitial diseases – acute interstitial nephritis (AIN), infection
4) Vascular disease – emboli, renal vein thrombosis

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12
Q

Renal exam findings include

A

1) Hx of exposure to renal insults assoc with ATN

2) UA for
a) ATN = isotonic, possibly heme, NO PROTEIN, pigmented granular casts and renal tubular epithelial cells
HIGH FENa

b) Glomerulonephritis = heme, protein, RBCs, RBC casts
c) vascultiis = normal to high SG, hematuria, protein, RBCs, RBC casts

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13
Q

if you see RTEs what does patient have

A

renal –> ATNs

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14
Q

if you see RBC casts what could that indicate?

A

vasculitis or glomerulonephritis

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15
Q

if you see WBC casts and eosinophils what does that indicate

A

AIN

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16
Q

Vascular factors that affect ATN and lead to ARF

A

1) decr in RBF (usual primary event)

2) decr in glomerular permeability

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17
Q

Tubular factors that affect ATN and lead to ARF

A

1) obstruction of tubule by cellular debris

2) leak of filtrate backwards across membrane

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18
Q

Mechanism of how ATN causes ARF

A

1) decr RBF
2) ischemia and injury to proximal tubule epithelial cells
3) damaged cells break away from basement membrane
4) expose tubule to back leak
5) decr GFR

6) also obstruct tubule –> incr tubular hydrostatic pressure, further decr GFR
7) ischemia can also damage autoregulation mechanisms in glomeruli

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19
Q

Signs of ATN in patient

A

1) oliguric (urine volume less than 400 mL)

2) non-oliguric
- manage with fluids/electrolytes

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20
Q

2 complications of ATN

A

1) infection due to decr leukocyte function

2) GI hemorrahge

21
Q

certain body insults assoc with developing ATN

A

1) hypotension
2) surgery with massive hemorrhage
3) transfusion reaction
4) contrast dye

22
Q

lab findings of ATN

A

1) pigmented, granular casts
2) renal tubular epithelial cells
3) sometimes blood and protein
4) SG = 1.010
5) FENa > 1% (but may not in non-oliguric ATN or rhabdo or hemolysis or contrast dye)

23
Q

what are exceptions to incr FENa > 1%

A

non-oliguric ATN
rhabdo
hemolysis
contrast dye

24
Q

how do you calculate FENa

A

FENa = UNa/PNa X PCr/UCr X 100

small #s divided by big #s

25
Q

if you see low urine Na+ concentration

A

prerenal because renal tubules still function to reabsorb Na+

26
Q

what is most common cause of sharp decr GFR

A

prerenal azotemia

27
Q

exam findings in prerenal

A

Urine Na 20

FENa

28
Q

exam findings in postrenal

A

Urine Na>20

Urine creatinine 2%

29
Q

evaluation of postrenal

A

1) renal US looking for hydronephrosis
2) if obstruct at urethra, bladder cath
3) leftover fluid after cath = post-void residual

30
Q

Decr in weight
flat neck veins
orthostatic BP and pulse
indicate what?

A

intravascular volume depletion

= prerenal

31
Q

edema
pulm rales
S3 gallop
indicate what?

A

cardiac dysfunction
prerenal AKI

hypervolemia

32
Q

Hypotension
surgery with blood loss
transfunction reactions
radiocontrast dye

indicate what?

A

renal insults

–> ATN

33
Q

anuria
intermittent anuria
indicate what?

A

urinary obstruction

34
Q

rash and fever and exposure to antibiotic suggests what

A

AIN

35
Q

incr tonicity due to incr ADH suggests what?

A

prerenal

or SIADH

36
Q

heme pigmetns without RBCs indicates what

A

rhabdo

hemolysis

37
Q

Hyaline casts indicate what

composed of what

A

benign, normal

tamm-horsfall protein secreted by tubule cells

38
Q

RBC casts mean what

WBC casts mean what

A

glomerulonephritis

AIN

39
Q

locations for cast formation

A

DCT

collecting duct

40
Q

high SG
no heme
waxy or finely granular casts

mean what

A

prerenal azotemia

41
Q

heme pigment

RBC and RBC casts mean

A

glomerulonephritis

42
Q

isotonic urine
WBC
eosinophils

mean

A

AIN

43
Q

+/- hematuria

A

vascular

44
Q

pigmented coarsely granular casts

renal tubular epith cells mean what

A

ATN

45
Q
prerenal 
urine Na
Ucr/Pcr
Uosm
FENa
A

1) 20
3) incr
4)

46
Q
ATN
urine Na
Ucr/Pcr
Uosm
FENa
A

1) >20

2) 2

47
Q

how to treat prerenal azotemia

1) chf
2) hypovolemia

A

1) improve CO in CHF

2) replace intravascular volume during hypovolemia

48
Q

how to treat postrenal

A

remove obstruction

49
Q

how to treat ATN

A

1) remove fluid
2) treat electrolytes
3) dialysis