Acute Kidney Injury

Question 1

what is this?

Answer 1

muddy brown cast of acute tubular necrosis (ATN)

Question 2

what is this?

Answer 2

RTE cell casts

pathomneumonic for ATN

Question 3

prerenal azotemia vs. ATN

compare: urine osmolality, urine [Na+], fractional excretion of sodium, ratio blood urea nitrogen/creatinine, urine microscopy

Answer 3

Question 4

3 causes of toxic ATN

Answer 4

1. aminoglycosides
2. iodinated radiocontrast
3. amphotericin B

Question 5

allergic interstitial nephritis

Answer 5

hypersensitivity rxn to NSAIDs, penicillin, diuretics

–> intra-renal azotemia

presents w/ oliguria, rash, fever days to weeks after starting drug w/ eosinophils in urine

usually resolves, but may progress to renal papillary necrosis - can tx w/ glucocorticoids in severe cases

Question 6

Answer 6

WBC casts in acute interstitial nephritis

Question 7

Answer 7

eosinophils in kidney in acute interstitial nephritis

Question 8

rhabdomyolysis

Answer 8

can result in toxin-associated AKI

two mechanisms: 1. afferent arteriolar vasoconstriction 2. direct toxicity to RTE

pink urine: heme but w/ no RBCs, but clear serum

Question 9

Answer 9

Light chain nephropathy - myeloma kidney (brittle casts w/ intense inflammatory response)

Light chains precipitate in tubules –> myeloma cast nephropathy

Question 10

uric acid and tumor lysis symptoms

Answer 10

uric acid is toxic to RTE

Question 11

distal tubular toxins (exogenous)

Answer 11

amphotericin B

cisplatinum

Question 12

AKI caused by crystals

Answer 12

causes obstruction of tubular flow and sometimes inflammatory response

• acyclovir, indinavir, sulfadiazine, methotrexate

Question 13

how does injury to tubular cells result in decreased GFR?

Answer 13

1. tubuloglomerular feedback: impaired tubular function –> more glow reaches DT –> JGA senses this and constricts afferent arteriole
2. back pressure –> injured cells form a plug
3. back leak thorugh holes in tubular basement membrane

Question 14

vascular causes of intrinsic AKI

Answer 14

large vessels: renal artery and vein

small vessels: thromboic microangiopathies

Question 15

obstructive AKI

Answer 15

freq non oliguric

reduced GFR b/c decreased flow in medullary capillaries

dx: ultrasound to look for obstruction

Question 16

indications for dialysis in AKI

Answer 16

AEIOU

acidemia unresponsive to med therapy

electrolyte abnormalities unresponsive to med therapy

Ingestion

Overload (fluid overload) unresponsive to med therapy

Uremia