Differentiate between ARF and AKI
acute renal failure suggests an acute, severe decrease in renal function that leads to increased serum creatinine (prerenal, intrarenal, or post renal)
acute kidney injury is another name for intrarenal ARF, and is further categorized by the part of the kidney affected (glomerular, vessels, or interstitium)
Acute tubular necrosis is defined as impaired tubular epithelial function. What are two etiologies of ATN? How do their presentations differ? What is a common clinical finding in both etiologies?
Ischemic: focal injury to PT and thick limbs of LOH of outer medulla. histology includes flattened epithelium (brush borders are lost in "epithelial simplification"). necrosis is subtle
Nephrotoxic: more extensive widespread necrosis of tubular epithelium, with PT most susceptible.
Urinalysis will show "dirty brown" granular casts cell debris rich is cytochrome pigments are sloughed off of the epithelium
How can you differentiate between types of ARF based on BUN:Cr, and FeNa?
prerenal: BUN:Cr >15 / FeNa 500
intrarenal: BUN:Cr <15/ FeNa > 2% (tubular function not intact). kidney loses ability to concentrate urine (Uosm < 500)
postrenal: BUN:Cr >15 / FeNa < 1%, Uosm > 500)