Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1175 page)

PROTEIN (TOTAL), URINE

   Definition

   Normal urine contains up to 150 mg (1–14 mg/dL) of protein each day. This protein originates from ultrafiltration of plasma. Presence of increased amounts of proteins in urine is termed as proteinuria and is the first indication of renal disease. Proteinuria can be classified into three types:

   Prerenal: overflow proteinuria, with an increase in plasma, low molecular weight proteins spill into urine (normal proteins, acute-phase reactants, light chain immunoglobulins)

   Renal:

   Glomerular proteinuria: defective glomerular filtration barrier. This could be selective or nonselective to different proteins.

   Tubular proteinuria: defective tubular reabsorption; increase in low molecular weight proteins.

   Postrenal: proteins produced by the urinary tract, during inflammation, malignancy, or injury

   
Normal range:

   Twenty-four–hour urine: <150 mg/day

   Random urine: <200 mg/g creatinine

   Use

   Evaluation of proteinuria (see Table 16.70) (e.g., following urinalysis in which proteinuria is detected)

   Evaluation of renal diseases, including proteinuria complicating DM and the nephrotic syndromes.