Acute Kidney Injury Cases

Question 1

1. Differentiate pre-renal, intra-renal, and post renal etiologies of AKI from history.

Answer 1

pre-renal: CHF, low volume, use of ACI, gout (allopurinol)
Intra-renal: ACE inhibitor, NSAID use
post-renal: symptoms of BPH, use of anticholinergics
glomerularnephritis: history of vasculitis: Wegner’s granulomatosiss, Polyarteritis nodosa or Churg-Strauss syndrome will have pulmonary symptoms

Question 2

1. Differentiate pre-renal, intra-renal, and post renal etiologies of AKI from physical.

Answer 2

pre: orthostatic hypotension, rales, S3 gallop
intra: rash due to antibiotic toxicity/allergy

Question 3

1. Differentiate pre-renal, intra-renal, and post renal etiologies of AKI from lab and radiology.

Answer 3

Intra-renal: muddy brown casts (ATN), WCB casts (AIN)
post renal- look for obstruction, or fluid filled kidney pelvis
glomerulonephritis: RBC casts; FeNa s granulomatosis, Polyarteritis nodosa or Churg-Strauss syndrome will have abnormal CXR ie. granulomas

Question 4

2. Recognize the limitations of specific tests in differentiating the causes of AKI.

Answer 4

FE Na is only useful in differentiating pre and intra renal causes (3); FE urea is even more helpful in the setting of diuretic use

Question 5

3. Recognize acute interstitial nephritis from acute tubular necrosis.

Answer 5

acute interstitial nephritis: WBC casts

acute tubular necrosis: muddy casts (of renal tubular cells)