Acute Kidney Injuries

Question 1

What is the definition of AKI. What are the criteria for defining AKI

Answer 1

AKI is an acute decrease in glomerular function with an elevation of serum creatinine.

serum creatinine increase > 0.3 OR greater than 1.5x baselone OR urine volume < 0.5ml/kg/hr

Question 2

What are the three types of AKI

Answer 2

Pre-renal (most common)
Post-renal (second most common)
Renal (nearly a diagnosis of exclusion)

Question 3

Describe the pathophysiology of pre-renal AKI

And include examples

Answer 3

Decreased renal perfusion due to hypovolemia or hypotension.
1. volume losses from diarrhea, vomiting, hemorrhage
2. decreased cardiac output eg. CHF
3. vasodilation eg. septic shock
4. renal hypoperfusion

Question 4

Describe the pathophys of post-renal

Answer 4

Obstruction of the outflow tract anywhere from the collecting tubules to urethra.

Eg. cancer, medications, clots, stones, BPH, neurogenic bladder

Question 5

What might you find on physical exam in AKI? What would you do next?

Answer 5

pre-renal: signs of volume depletion
post-renal: palpable bladder

Action: insert foley

Question 6

What are indications for acute dialysis

Answer 6

Acidemia
Electrolytes
Intoxication
Overload
Uremia

Question 7

Intrinsic Renal failure. What are the types and what can you see on microscopy?

Answer 7

ATN-muddy casts
AGN-RBC
AIN-WBC
Most commonly due to Sepsis, renal ischemia, contrast

Question 8

What tests can you use to evaluate AKI

Answer 8

Urinalysis: concentrated in prerenal, sediment in renal, normal in post-renal
PVR: to see obstructions
FeNa: <1 in prerenal, >1 in renal (note: not for use in diuretic or CKD
FeUrea <35 is prerenal

Question 9

How do you calculate FeNa? When is it appropriate to use and what does it mean?

Answer 9

FENa = (uNa x sCr x 100) / (sNa x uCr)
Do not use in pt with diuretic, CKD. <1 indicates it is likely pre-renal AKI. However, note there are a few conditions where it is low in renal AKI eg. vasculitis, rhabdo, hemolysis, constrast, ATN