Defined as urinary protein excretion > 150 mg/day
Some excreted protein is normal
     20% is low molecular type such as Ig
     40% is high molecular weight albumin
     40% is mucoproteins secreted by tubules
Barriers to excretion begin in glomerulus
Proteins cross to tubular fluid in inverse proportion to their size and negative charge
Smaller proteins are largely reabsorbed
Dipstick analysis
     Trace = 10-20 mg/dL
     1+ = 30 mg/dL
     2+ = 100 mg/dL
     3+ = 300 mg/dL
     4+ = 1000 mg/dL
Causes of false-positive dipstick for proteinuria
     Gross hematuria
     Alkaline or concentrated urine
     Semen
     Presence of WBCs
Benign causes (may f/u 48 hr later)
     Fever
     Intense activity/exercise
     Dehydration
     Emotional stress
     Acute illness
Management
     If trace to 2+
          Repeat dipstick on morning voids x2 over next month; if negative: no further w/u; if positive proceed to protein quantification
     If 3+ to 4+ with inconclusive urinalysis
          Proceed to protein quantification
     Protein quantification
          >2 g/24 hr: glomerular disease--refer to specialist
          <2 g/24 hr: further workup
Workup
     24 hr urine specimen is gold standard quantification test
     Microscopic analysis of urine sediments
          Fatty casts, free fat or oval fat bodies suggest nephrotic range proteinuria (>3.5 g in 24 hr)
          Leukocytes and leukocyte casts w/o bacteria suggests renal interstitial disease

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The Compendium platform was created by David Kwinter, MD, CCFP(EM).

Dr. Kwinter is a Cayman Family Doctor. He runs a Family Medicine Clinic at Cayman Medical in George Town, Grand Cayman, Cayman Islands.