12.2 Acute Renal Failure Flashcards
What is the hallmark of renal failure?
Azotemia
What are the 3 etiologies of acute renal failure?
- Prerenal
- Renal
- Postrenal
Prerenal - ARF
Decreased blood flow
Renal - ARF
Intrinsic renal diseases causing ARF
Postrenal - ARF
Obstruction to the outflow
What are some signs of prerenal ARF?
Decreased GFR, azotemia and oliguria
What is the ratio of BUN:Cr in prerenal azotemia?
BUN:Cr greater than 15
What is the FENa in prerenal azotemia?
FENa less than 1%
How does aldosterone affect BUN reabsorption?
It will increase the reabsorption of BUN and increase the BUN:Cr ratio
How does postrenal obstruction lead to ARF?
It will cause back pressure against the GFR decreasing the GFR as less blood is filtered
What is the BUN:Cr in early postrenal obstruction?
BUN:Cr is greater than 15
What is the FENa in early postern obstruction?
FENa will be less than 1%
What is the main cause of ARF?
Acute Tubular Necrosis
How does ATN decrease the GFR?
Necrotic cells will obstruct the tubules and cause back pressure
What are some signs of ATN?
Brown granular epithelial casts will be seen in the urine
What is the BUN:Cr ratio in ATN?
BUN:Cr ratio will be less than 15
What is the FENa in ATN?
FENa will be greater than 2%
What are the major etiologies of ATN?
- Ischemia
- Nephrotoxicity
What can prolong prerenal azotemia lead to?
ATN
What are the main causes of nephrotoxicity?
- Aminoglycosides
- Myoglobin
- Radiocontrast dye
- Heavy metals
- Urate
- Ethylene glycol (oxalate crystals in urine)
What will happen to K+ in ATN?
Hyperkalemia
What are the main causes of acute interstitial nephritis?
Drugs - NSAIDs, penicillin, diuretics
What does the finding of eosinophils in the urine indicate?
Acute interstitial nephritis
Renal Papillary Necrosis
Necrosis of the renal papillae as a sequelae of acute interstitial nephritis
What is the presentation of renal papillary necrosis?
Hematuria and flank pain
What are some of the causes of renal papillary necrosis?
- Chronic analgesic abuse
- Diabetes
- Sickle Cell Anemia/Trait
- Severe acute pyelonephritis
