Evaluation of kidney function

Evaluation of kidney function

1. Summary of normal urine specimen

   • alarming signs
     • Red cell casts predominate in acute glomerulonephritis
     • White cell casts predominate in tubulointerstitial disease
     • Broad, waxy casts represent complete disintegration of embedded components, suggesting sluggish flow
       • renal failure casts
     • Calcium deficiency
       • renal failure stage of chronic renal disease
     • low creatinine clearance
       • low GFR
     • Hyperphosphatemia, hyperuricemia and acidosis
       • do not develop until there is 70-80% loss of functional capacity

2. serum urea/creatinine ratio is normally about 15

3. Laboratory findings in specific syndromes

   • Nephrotic Syndrome
     • proteinuria > 3 g/day
     • hypoproteinemia and consequent edema
     • hyperlipidemia
   • Nephritic Syndrome
     • hematuria, proteinuria ( < 2 g/day)
     • red cell casts
   • Tubulointerstitial Disease
     • cloudy urine from high WBC
     • white cell casts
     • proteinuria ( < 1 g/day)
   • Acute Renal Failure
     • sudden oliguria
     • broad waxy casts (renal failure casts)
     • urine sodium concentration > 40 mEq/L

4. Blood test

   • Blood urea nitrogen (BUN) test
     • a rise in BUN indicates obstruction of urinary tract

5. Calculations

   • GFR = Cinulin = UV/P (inulin) ml/min
   • ERPF = CPAH = UPAHV/PPAH ml/min
   • Filtration fraction = GFR/ERPF
   • Filtered load for substance x = GFR . Px mg/min
   • Excretion rate for substance x= Ux (mg/ml) . V (ml/min) = mg/min
   • Secretion Rate= ER (mg/min) – FL (mg/min) = mg/min

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