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49 Cards in this Set
- Front
- Back
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What is a normal GFR for adults?
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men 125 +/- 15/1.73m2
women 110 +/- 15 /1.73m2 |
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What is normal GFR for newborns?
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50% of normal adjusted for body surface area
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How does GFR change?
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decreases 1%/year above age 40
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What things increase GFR?
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afternoon, pregnancy, increased dietary ptoein intake
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What decreases GFR?
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nighttime, exercise
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Why do you use inulin to measure GFR?
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filtred by glomerulus, not secreted/reabsorbed in tubules
GFR rate equivalent to inulin clearance |
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How do you measure clearance of inulin?
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infuse inulin IV to steady state, measure plasma and urine inulin levels simultaneously
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How do you calculate GFR from Cin?
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Uin x V = Cin = GFR
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What should you use instead of inulin?
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iohexol
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Why do you use creatinine clearance?
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released from muscle at a constant rate, filtered completely by glomerulus, not reabsorbed by tubules, minimally secreted by tubules
excretion is equal to creatinine filtered |
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How do you calculate GFR from creatinine clearance?
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Ccr = (UcrV) /PCr
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What is UcrV
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creatinine excretion, equal to creatinine production, dependent on muscle mass
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What does higher serum creatinine mean?
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worse kidney function
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What is a normal creatinine?
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.6 - 1.2
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What is the relationship between serum creatinine and GFR?
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inverse curvilinear
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How do you determine serum creatinine?
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24h urine collection
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What is normal serum creatinine?
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.6 - 1.2 mg/dl
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How much creatinine would be expected to be excreted in women?
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15-25 mg/kg/d
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How much creatinine would be expected to be excreted in men?
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20-30 mg/kg/d
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How much creatinine would be expected to be excreted in the elderly?
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10 mg/kg/d
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How much creatinine would be expected to be excreted in children?
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14.7 + (0.45 x age) mg/kg/d
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What decreases muscle mass (and creatinine excretion)?
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corticosteroids, inactivity, old age
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What is the Cockroft-Gault formula?
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GFR = ((140-age) x lean body weight in kg) / (72 x serum creatinine)
x .85 for women |
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What's wrong with MDRD formula?
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underestimates GFR when near normal
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What is normal BUN?
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7-21 mg/dl
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What does BUN do in kidney failure?
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increases
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Upon what is BIUN dependent?
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protein intake, catabolism, liver function, volume status
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What increases BUN?
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increased protein intake, catabolism, low volume states
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What decreases BUN?
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cirrhosis, high volume states
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What is normal VUN?
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60% of creatinine or inulin clearance
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Why do you use BUN?
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assess dietary protein intake, catabolism, volume status, renal perfusion, GFR
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How do lab values change in AKI?
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GFR falls, creatinine excretion decreases, serum creatinine and BUN rise, not in steady state
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When do lab values normalize with AKI?
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at about 14 days, GFR improves, creatinine plateaus and falls to normal
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What do you not use to measure GFR with AKI?
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24h urine, Cockroft-Gault, MDRD
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Why do you use fractional excretion?
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determine parts of renal function
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How do you calculate fractional excretion?
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clearance of substance/clearance of ideal GFR marker
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What do you test for with urinalysis?
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specific gravity, pH, glucose, ketones, blood, protein, bilirubin, urobilinogen, nitrite, leukocytes, cells, casts, formed elements
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What is specific gravity?
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dependent on the number, size, density of particles in the urine
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What is omsolality?
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depends on number of particles in the urine
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What is normal urine pH?
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4.5 - 8
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What pH comes with calcium phosphate stones?
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high
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What pH comes with urea splitting organisms?
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high pH
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What pH comes with uric acid stones?
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low pH
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How do you determine proteinuria?
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add 20% sulfasalicylic acid to urine, makes urine look cloudy
measure protein with 24h urine |
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What values give you microalbuminuria?
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30 mg/g creatinine - 300 mg/d, early diabetic nephropathy
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What constitutes nephrotic proteinuria?
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> 3g/d of proteinuira
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What do you see in obstructive jaundice?
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increased urobilinogen
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What do you see in non-obstructive jaundice?
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increaesd urinary urobilinogen
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Why do you test for nitrite?
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gram negative bacteria, will not test for enterococcus or organisms that don't produce nitrite
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