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Renal Physiology > Acute Kidney Injury > Flashcards

Acute Kidney Injury Flashcards

1
Q

What are three characteristics of renal failure (acute and chronic)?

A

impairment of gfr
elevation of BUN/creatinine
decreased GFR leads to accumulation of substances/drugs normally excreted by the kidney

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2
Q

What is the definition of AKI?

A

rapid deterioration of renal fxn (hours tod ays but less than 1 month)
greater than .5 mg/dl increase in serum creatinine or increase of 50% over baseline value
sometimes decreased urine output but not always
inability of kidney to regulate electrolytes/water

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3
Q

What is oliguria?

Anuria?

A

oliguria is decreased urine output below 400 ml/d

anuria is less than 100ml/day (almost none)

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4
Q

T of F:

1) AKI is usually symptomatic, discovered after pain
2) Most cases are irreversible if underlying disease is treated

A

1) False, most are asymptomatic and discovered in routine labe
2) False, most are reversible if underlying disease is treated

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5
Q

What are the three classifications of AKI?

A

Prerenal (55%)
Intrinsic Renal (40%)
Postrenal (5%)

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6
Q

What is preprenal ARF?

A

something before the kidneys is wrong, i.e. insufficient blood flow

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7
Q

What is intrinsic ARF?

A

something is damaged in the kidney

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8
Q

What is postrenal ARF?

A

something after the kidney, i.e. problem with bladder or ureter

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9
Q

What is found in the urine sediment of pts with prerenal ARF?

A

normal or few red blood cels or wbcs

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10
Q

In intrinsic ARF, what does one see in the urine sediment?

A

rbc casts, granular casts, eosinophils (primarily with allergic interstitial nephritis)

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11
Q

Tell if more characteristic of prerenal or intrinsic ARF:

Uosm: >500
Urine to plasma Osmolality: 20
Urine sediment: hyaline casts

A

Uosm>500 Prerenal
Intrin - 20 intrinsic
<10 prerenal

Hyaline casts - prerenal

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12
Q

What are things that can cause postrenal ARF?

A

prostate disease!!!!

cancer

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13
Q

What are symptoms associated with post-renal arf?

A

voiding complaints
may have distended bladder
u/a unremarkable
dx for ultrasound

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14
Q

What is the typically characteristic of the kidney on ultrasound during post-renal arf?

A

dilated calyxes

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15
Q

What is the key cause of prerenal arf?

additional causes?

A

volume depletion (gi, renal)

CHF
Shock from fluid losses, sepsis
hepatorenal syndrome
renal artery stenosis
NSAIDS
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16
Q

What do hyaline casts look like on UA (present in prerenal disorders)

A

they are clear, cylindrical rods

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17
Q

What does a Una less than 25 tell us about the type of ARF?

A

Una<25 = pre-renal (taking up all the na that it can)

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18
Q

Why is Uosm>500 in prerenal ARF?

A

all the vasopressin to fix volume depletion

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19
Q

What is hepatorenal syndrome?

A

Special case of prerenal AKI due to cirrhosis
Decreased BP despite increased ECFV
Kidneys intact and urinalysis normal (except Una)
worsening azotemia and progressive oliguria

20
Q

Explain the pathway/pathology of HepatoRenal Syndrome (HRS)

A 
portal htn
splanchnic vasodilation
decreased effective circulatory volume
activation of RAAS (leads to two things:
   Na -> Ascites
   Renal vasoconstriction -> HRS)
21
Q

When is the only time you will see renal artery stenosis?

A

when it is bilateral. when only occurring on one side, the other kidney will compensate

22
Q

What are two drug types that can lead to ARF in patients with renal artery stenosis?

Why?

A

ACEi and Angiotensin II blockers

Decreased levels of Angio II or blocking of it impairs renal auto–regulation (constrictino of efferent arterioles in RAS)

23
Q

What are the two functions of Angiotensin II?

A

Aldosterone stimulation

Constriction of efferent arterioles

24
Q

How do NSAIDs affect the kidneys?

A

they block prostaglandin synthesis, which dilate the afferent arterioles

25
Q

What pts are at risk for ARF with NSAIDS?

A

true volume depletion
CHF
cirrhosis

  • basically any time you have impaired blood flow due to volume
26
Q

What are some intrinsic ARF of the glomerulus?

A

post-strep gn, lupus, rpgn, hepatitis, IgA nephro

27
Q

What are intrinsic ARF involved with tubules?

A

ACUTE TUBULAR NECROSIS (due to prolonged HTN, meds)

Acute interstitial nephritis

28
Q

What are intrinsic ARF causes involving the vasculature?

A

vasculitis

29
Q

What can cause acute tubular necrosis?

A 
ischemic injury (i.e. when prerenal continues too long)
toxic injury from radiocontrast or meds
30
Q

Where does most ischemic injury occur?

A

in the proximal tubules and talh (where the most active transport needing 02 is occurring)

31
Q

What are clinical clues of ATN?

A

muddy brown granular casts on UA

urina Na>20 (have aldo but dying tubules cannot absorb)

32
Q

PRERENAL VS ATN

BUN/Crea >20:1

A

Prerenal

10-15:1 favors ATN

33
Q

PRERENAL VS ATN

UA with granular casts

A

ATN

hyaline casts seen in prerenal

34
Q

PRERENAL VS ATN

UNa+ <20 meq/L

A

Prerenal

> 25 meq/L is in ATN because they cannot reabsorb the Na+

35
Q

PRERENAL VS ATN

Uosm >500 mosm/kg

A

Prerenal

300-350 in ATN (isoosmotic because we cannot regulate it due to dying tubules

36
Q

What causes the muddy brown casts in the UA of ATN?

A

dead cells coming out of body in urine

37
Q

What causes the elevated BUN/Crea in ATN?

A

There is obstruction due to dead epithelial cells in the tubule, that dying, release Bun and crea and it goes back into bloodstream

38
Q

What are drugs that can cause intrarenal AKI?

A

aminoglycosides, amphotericin B

39
Q

What can cause acute interstitial nephritis (drugs)?

A

penicillins, cephalosporins, sulfonamides, NSAIDS

40
Q

What percentage of people using aminoglycosides will have an increase in creatinine?

A

10-20% (more in urine)

41
Q

Where does aminoglycoside accumulate in the kidney?

A

the proximal tubule cells

42
Q

How does contrast nephropathy lead to AKI?

A

direct vasoconstrictive effects on arterioles and tubular toxicity

43
Q

How can you avoid aKI in pts who need contrast imaging?

A

avoid volume depletion and nsaids and aCEI

44
Q

What drugs typically cause acute interstitial nephritis?

A

antibiotics (penicillins B.lactams) NSAIDS

45
Q

with mild dehydration, wil you have increased or decreased bp?

A

increased

46
Q

in severe dehydration, increased or decreased bp? why?

A

decreased bp.

aldosterone is triggered, but there isn’t enough h20 to increase bp

Renal Physiology (26 decks)

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