Reading of renal function
YY Chiou
Glomerular filtration rate
Clearance of inulin
Clearance of creatinine:normal
range
Male:120±25 mL/min
Female:95±20mL/min
Infant:17 mL/min/1.73M2
P[Inulin] × GFR = U[Inulin] ×
urine volume
Difference between inulin and
creatinine
Age effect: age >40y/o -> Ccr
decrease 1mL/min/yr
Urine Cr collection:
Age≦60y/o:male: 20-25mg/kg;
female:15-20mg/kg
Age>60y/o:10mg/kg
Plasma Cr
Condition associated with PCr increased and not changed
GFR
Increased Cr production
Rhabdomyolysis
Meat
Decreased Cr excretion
Cimetidine, triamterene, probenecid,
amiloride, trimethoprim, spironolactone
Measured bias
Endogeneous: ketone, ketoacids, glucose,
bilirubin, urate, urea, fatty acid
Exogeneous: cephalosporines, 5-FU,
phenylacetyl urea, acetoheximide
Estimate Ccr
Cockcroft and Gault equation:
CCr=[(140-age(yr)) ×BW(kg)]
÷[72×Pcr(mg/dl)]
Female: above data×0.85
1/Pcr
EsGFR(ml/min/1.73M2)=KL(body length,
cm) ÷ Pcr
K
LBW:0.33
NB-1yr:0.45
2yr-adolescent girls: 0.55
2yr-adolescent boys:0.77
BUN
Reverse relationship with GFR, but
many confounding factors
Urea nitrogen can reabsorb
paralleling with Na and H2O
resorption
BUN：Pcr = 15-20:1
Urinalysis
Urine sample: fresh (30-60min)
3000rpm, 3-5min ->
suspension with pellet
Color
Urine protein
Daily urinary
protein:150mg/day
Microalbuminuria
Detection: dipstick
Tetrabromophenol blue dye –
albumin
Sulfosalicylic acid
Protein(mg/dL)
0
1-10
15-30
40-100
150-350
>500
dipstick
0
trace
+1
+2
+3
+4
sulfosalicylic acid
no turbid
slight turbid
turbid
white without ppt
white with ppt
coarse ppt
Urine protein
24 hr daily protein loss
Spot UTP/UCr
Urine pH and osmolality
Normal range:4.5-8.0
How about alkalization urine?
Urine sp. Gr. To estimate urine
osmolality
Plasma osmolality & urine
osmolality
Urine Na excretion
Urine excretion = intake Na
amount
Urine [Na]<20meq/L
Urine [Na]>40meq/L
Significance of %FENa
ARF with %FENa <1%
Prerenal factor
ATN
Non-oliguric ATN (10%)
Chronic prerenal diseaseContrast media
Sepsis
Myoglobulinuria or hemoglobulinuria
AGN or vasculitis
Obstructive nephropathy
Urinary cast
Hyaline cast
conc. Urine or diuretics
Red cell cast
GN or vasculitis
WBC cast
TIN, APN, GN
Epithelial cast
ATN, GN
Fatty cast
GN with proteinuria, NS
Granular cast
proteinuria, degenerative cells
Waxy cast
CRF
Renal acidification evaluation
Urinary pH:
Net acid excretion:
Urinary anion gap:
Acidification loading test:
Urine pH
Fresh urine
Collect in the morning
Must rule out UTI
Many confounding factorsproton pump, electro-gradient
of membrane, buffer conc.,
diet, et. al.
Net acid excretion
Total acid excretion=titratable acid
+ NH4+
Net acid excretion=total acid
excretion – HCO3- excretion
Titratable acid= buffer solution of
H3PO4 with urea nitrogen
Def. of titratable acid excretion:the
amount of NaOH(meq) to elevate
UpH to 7.4
Urinary anion gap
Total conc. Of anions = total conc.
Of cations
Na++K++NH4++Ca+2+Mg+2=Cl+H2PO4-+SO4-+organic anions
Na++K++NH4+=Cl-+80
Urinary anion gap:Na++K+-Cl-
Urinary acid loading tests
Acid loading test
Sodium sulfate infusion test or
furosemide test
Buffer loading test
Acid loading test
NH4Cl 0.1g(1.9meq)/kg, po ->
collection urine pH and net
acid excretion for 28hr.(normal: UpH<5.5)
CaCl2
Arginine HCL
Normal urine CO2>80mmHg
Diamox test
U-B[PCO2]>30mmHg
Increase distal tubule Na conc. Test – for
proton pump or voltage-dependent defect
Furosemide test: 1mg/kg, collect
urine pH, net acid excretion and U[k],
po 5hr or iv 3hr
Reading:UpH increase in 1hr and then
UpH down to 5.5 in future 2-4hrs; U[k]
and acid increase 2 fold
Sodium sulfate
Buffer loading test
IV drip or 2-3ml/min NaHCO3 100150mEq(total) till plasma NaHCO3
≧30meq/L
Then check blood and urine pH, [HCO3-],
CO2
Calculate %FEHCO33-5%
>15%
U-B[PCO2] >20-30mmHg, when U[HCO3-]
>100-150meq/L