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Reading of renal function

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/1.73M 2. P[Inulin] × GFR = U[Inulin] × urine volume. Difference between inulin and creatinine

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Reading of renal function

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  1. Reading of renal function YY Chiou

  2. 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

  3. P[Inulin] × GFR = U[Inulin] × urine volume

  4. 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

  5. Plasma Cr

  6. 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

  7. 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

  8. BUN • Reverse relationship with GFR, but many confounding factors • Urea nitrogen can reabsorb paralleling with Na and H2O resorption • BUN：Pcr = 15-20:1

  9. Urinalysis • Urine sample: fresh (30-60min) • 3000rpm, 3-5min -> suspension with pellet • Color

  10. Urine protein • Daily urinary protein:150mg/day • Microalbuminuria • Detection: dipstick • Tetrabromophenol blue dye –albumin • Sulfosalicylic acid

  11. Protein(mg/dL) dipstick sulfosalicylic acid 0 0 no turbid 1-10 trace slight turbid 15-30 +1 turbid 40-100 +2 white without ppt 150-350 +3 white with ppt >500 +4 coarse ppt

  12. Urine protein • 24 hr daily protein loss • Spot UTP/UCr

  13. 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

  14. Urine Na excretion • Urine excretion = intake Na amount • Urine [Na]<20meq/L • Urine [Na]>40meq/L • Significance of %FENa

  15. ARF with %FENa <1% • Prerenal factor • ATN • Non-oliguric ATN (10%) • Chronic prerenal disease- • Contrast media • Sepsis • Myoglobulinuria or hemoglobulinuria • AGN or vasculitis • Obstructive nephropathy

  16. 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

  17. Renal acidification evaluation • Urinary pH: • Net acid excretion: • Urinary anion gap: • Acidification loading test:

  18. Urine pH • Fresh urine • Collect in the morning • Must rule out UTI • Many confounding factors- proton pump, electro-gradient of membrane, buffer conc., diet, et. al.

  19. 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

  20. 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-

  21. Urinary acid loading tests • Acid loading test • Sodium sulfate infusion test or furosemide test • Buffer loading test

  22. Acid loading test • NH4Cl 0.1g(1.9meq)/kg, po -> collection urine pH and net acid excretion for 2-8hr.(normal: UpH<5.5) • CaCl2 • Arginine HCL • Diamox test Normal urine CO2>80mmHg U-B[PCO2]>30mmHg

  23. 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

  24. Buffer loading test • IV drip or 2-3ml/min NaHCO3 100-150mEq(total) till plasma NaHCO3 ≧30meq/L • Then check blood and urine pH, [HCO3-], CO2 • Calculate %FEHCO3- • 3-5% • >15% • U-B[PCO2] >20-30mmHg, when U[HCO3-] >100-150meq/L

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