103114 acute kidney injury

Question 1

acute kidney injury is also called

Answer 1

acute renal failure

Question 2

acute kidney injury

Answer 2

reduction in GFR resulting in azotemia developing over days

usually reversible
absence of symptoms of chronic uremia
kidney size usually preserved

Question 3

what are the common causes of acute kidney injury

Answer 3

renal ischemia or toxins

Question 4

diagnositic criteria for AKI

Answer 4

abrupt (48 hr) reduction in kidney fxn defined as

an absolute increase in serum creatinine level of 0.3 mg/dl or

percentage increase in serum creatinine of greater than 50% or

reduction in urine output to

Question 5

oliguria

Answer 5

urine output under 400-500 mL/day

Question 6

azotemia

Answer 6

elevation of nitrogen waste products related to insufficient filtering of blood by kidneys

Question 7

uremia

Answer 7

illness accompanying kidney failure which results from toxic effects of abnormally high concnetrations of nitrogenous substances in blood

Question 8

what tests can be used in AKI?

Answer 8

serum creatinine
blood urea nitrogen
urinalysis

Question 9

urinalysis testing for AKI can look for what?

Answer 9

casts-caused by trapping of cellular elements in a matrix of protein secreted by renal tubule cells

granular casts (muddy brown urine) are seen in acute tubular necrosis

Question 10

how does autoregulation of GFR occur under decreased perfusion pres?

Answer 10

increased vasodilatory prostaglandins at afferent arteriole
increase angiotensin II at efferent arteriole

some cases of kidney injury can be precipitated when there’s a loss of these autoregulatory mechanisms

Question 11

how can autoregulation of GFR be altered?

Answer 11

elderly, NSAIDs, CKD–do not have normal vasodilatory prostaglandin response

ppl taking ACEi and ARBs cannot mount the normal angiotensin II constriction response

so for these ppl, even at modest decrease in MAP, they will have a decrease in GFR

Question 12

what are possible causes of pre-renal AKI?

Answer 12

volume depletion
heart failure
liver failure

Question 13

possible causes of renal AKI

Answer 13

acute tubular necrosis
interstitial nephritis
glomerulonephritis
vascular diseases

Question 14

possible causes of post-renal AKI

Answer 14

obstruction-prostate, bladder, stones, tumors

Question 15

prerenal AKI definition

Answer 15

due to decreased effective renal perfusion

decreased GFR WITHOUT ischmemic or nephrotoxic injury to tubules

Question 16

pathogenesis of prerenal AKI

Answer 16

decreased effective renal perfusion, leading to increased ang II and vasopressin, leading to increased reabosprtion of Na at proximal tubule and water, leading to CONCENTRATED URINE AND OLIGURIA

increased reabsorption of urea, leading to elevation of BUN out of proportion to creatinine (>20:1)

Question 17

renal AKI

Answer 17

acute injury involving tubules, glomeruli, interstitium or vasculature

ex:
acute tubular necrosis: ischemic, toxic, both

inflam: glomerulonephritis, tubulointerstitial neprhitis, vasculitis

embolism, thrombosis, thrombitc microangiopathy

neoplasms: infiltrating tumors

Question 18

most common cause of “renal” AKI

Answer 18

acute tubular necrosis

Question 19

mechanisms of acute tubular necrosis

Answer 19

if ischemic-can cause endothelial cell dysfxn and vasoconstriction. can cause tubule cell injury and reversible or irreversible damage. ultimately all of the above lead to reduced GFR and oliguria

Question 20

morphologic features of ATN

Answer 20

tubular dilatation
attenuation of tubular epithelium
loss of epithelial cell brush border
granular cast material
mitotic figures (regenerative change)

Question 21

how does tubule regeneration occur in ATN?

Answer 21

sublethally injured tubular epithelial cells dedifferentiate, proliferate, migrate, and reestablish cell polarity

Question 22

morphology of post renal AKI

Answer 22

hydronephrosis-distension and dilation of renal pelvis calyces

Question 23

how can you distinguish prerenal AKI from acute tubular necrosis (both have oliguria)

Answer 23

changes in urine sodium reabsoprtion–look at urine sodium excretion

in volume depletion–urine Na reabsoprtion should be increased in proximal tubules—FENa2%

Question 24

eqn for FENa

Answer 24

UNa * PCr / (PNa * UCr) multiplied by 100

Question 25

symptoms of ECF volume depletion

Answer 25

hypotension

oliguria

Question 26

in chronically hypertensive individuals, what happens to GFR autoregulatory curve?

Answer 26

shifted to the right. so when lower their BP, their BP falls out of the regulatory range even when it’s a normal BP

also, if they are on lisinopril (ACEi), they don’t have maintained efferent arteriolar tone, so can’t keep up good GFR

Question 27

is acetaminophen nephrotoxic?

Answer 27

no

Question 28

what is septic shock an ex of in terms of AKI?

Answer 28

acute tubular necrosis