Nephrology Flashcards
first step in evaluating renal failure
- PRErenal (perfusion)
- RENAL (parenchymal)
- POSTrenal (drainage)
clues renal failure is ACUTE
- normal kidney size
- normal hematocrit
- normal Ca2+
clues renal failure is CHRONIC
- smaller kidneys
- renal failure of more than 2 weeks will drop Hct (decreased erythropoietin production)
- Ca2+ levels drop (decreased vitamin D hydroxylation)
causes of PRErenal azotemia
- ANY cause of hypOperfusion
- hypOtension (SBP less than 90)
- hypOvolemia (dehydration or blood loss)
- low oncotic pressure (low albumin)
- CHF (heart can’t PUMP)
- constrictive pericarditis (heart can’t FILL)
- RAS
characteristic diagnostic tests for PRErenal azotemia
- BUN:Cr ratio of more than 15:1, and often more than 20:1
- LOW urinary Na+ (less than 20)
- urine osmolality more than 500
- may have hyaline casts on UA
treatment for PRErenal azotemia
treat UNDERLYING cause
mechanism of BUN elevation in PRErenal azotemia
low volume status, increases ADH, and ADH increases urea transporter activity in collecting duct
causes of POSTrenal azotemia (postobstructive uropathy)
- stones
- strictures
- cancer
- neurogenic bladder (MS or DM)
BUN:Cr ratio seen in POSTrenal azotemia
also more than 15:1
clues to obstructive uropathy
- distended bladder on exam
- large volume diuresis after Foley catheter placement
- B/L hydronephrosis on US
what must be true in order for postobstructive uropathy to cause renal failure?
MUST BE BILATERAL
UNIlateral obstructive cannot cause renal failure
INTRArenal causes of renal failure
- ATN (acute tubular necrosis)
- AGN (acute glomerulonephritis)
- AIN (acute interstitial nephritis)
causes of ATN (acute tubular necrosis)
- either hypOperfusion or toxic injury
- surgery
- severe burns
- aminoglycosides/amphotericin/contrast/chemotherapy
- rhabdomyolysis
causes of AGN (acute glomerulonephritis)
name 11
- Goodpasture’s syndrome
- Churg-Strauss syndrome
- Wegener’s granulomatosis
- polyarteritis nodosa
- IgA nephropathy (Berger’s disease)
- Henoch-Schonlein purpura
- poststreptococcal glomerulonephritis
- cryoglobulinemia
- lupus nephritis
- Alport syndrome
- TTP/HUS
causes of AIN (acute interstitial nephritis)
- antibiotics
- NSAIDs
- infection (e.g. Streptococcus, viral, Legionella)
characteristic diagnostic tests for INTRArenal renal failure
- BUN:Cr ratio of 10:1
- urinary sodium more than 40
- urine osmolality less than 350
how many days of use does it usually take for aminoglycosides to cause kidney damage?
4-5 days
mechanism of rapid onset of renal failure with contrast agent
- directly toxic to kidney tubules
- also, causes intense vasoconstriction of Afferent arterioles (decreased perfusion)
(hypOperfusion = LOW urine sodium)
what does UA show in ATN?
“muddy brown,” or granular casts
treatment for ATN
NO specific therapy
adverse effect of cyclophosphamide
hemorrhagic cystitis
cause of renal failure from rhabdomyolysis
direct TOXIC effect of MYOGLOBIN on kidney tubule
causes of rhabdomyolysis
- crush injury
- seizure
- cocaine toxicity
- prolonged immobility
- hypOkalemia resulting in muscle necrosis
- recent initiation of STATIN
best INITIAL test for rhabdomyolysis
UA (large blood)