Urine Protein Electrophoresis (UPE, UPEP)
General: Normal proteinuria is <0.15 g/24hrs in the adult, or <0.14 g/m^2 of a child's surface area, consistent with the function of normal kidneys. Approximately 35% of normal urine protein is albumin. Parameters linked to changes in urine protein concentrations are either protein specific (molecular weight, shape, charge, serum concentration, etc.) or kidney specific (structural, toxic, etc.).
- Specific protein components
- Tamm-Horsfall protein (mucoprotein, uromucoid) - Major protein of physiologic proteinuria, and is of renal origin (ascending limb of loop of Henle in the distal tubule). Is the protein support lattice for urinary calculi.
- Pseudoalbumin - Various nonspecific proteins comprising ~40% of total protein in physiologic proteinuria, and are of urogenital origins (ureter, bladder, urethra, prostate, vaginal secretions, etc.). The term is little used now, and is generally of no clinical interest.
- Bence Jones - Immunoglobulin free light chains. Originally identified as a thermolabile precipitate.
Methods:
Interpretation:
- Pre-renal - Usually mild, benign, transient. Orthostatic (adolescents), post-prandial, after sports/physical stress, emotional stress, low temperature exposure. May be linked to reduction in renal blood flow for any reason, hypertension, toxin, etc.
- Renal - Nephron pathology.
- Glomerular - (Primary or secondary) High molecular weight proteins, dominated by albumin (>70%). Lipoid nephrosis, mesangial IgA deposits, extra-membranous, membranoproliferative, focal segmental glomerulosclerosis, diabetes, cirrhosis, autoimmune, toxins, tumors, genetic, etc.
- Tubular - (Primary or secondary) Uncommon, usually moderate total proteinuria, more likely to be transient. Diabetes, cirrhosis, various syndromes, amyloidosis, toxins, infectious, rhabdomyolysis, intravascular hemolysis, monoclonal gammopathies/free light chains, etc.
Differential Diagnosis:
Malignant (multiple myeloma, Waldenstrom macroglobulinemia, etc.) vs. "benign" monoclonal gammopathy (monoclonal gammopathy of undetermined significance).
Pre-renal, renal, glomerular, tubular, or mixed source.
Pathologic vs. transient.
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Images:
Cases:
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