Urine Protein Electrophoresis

Electrophoresis is a sensitive test that can help to distinguish glomerular proteinuria and tubular proteinuria by means of separating protein in urine on the basis of molecular weight.

Urine protein electrophoresis is helpful to determine the cause of protein in the urine, or as a screening test to measure the various proteins in urine. While doing urine protein electrophoresis, laboratory specialist will place the urine sample on special paper and apply and electric current. The various proteins move and form visible bands, which reveal the general amount of each protein.

In case of kidney damages, clinical meaning of urine protein electrophoresis shows as follows:

1. Middle molecule and macromolecule protein mainly reflects renal glomerular damages.

Our kidneys play the role of filtering blood, during which wastes like creatinine and urea nitrogen are excreted out with urine and meanwhile, nutrient substance like protein is kept in the body. In normal condition, middle molecule and macromolecule protein fail to go through glomerular filtration membrane which functions as a filter. Therefore, when there are lots of middle molecule and macromolecule protein in urine, glomerular damages need to be considered.

2. Small molecule protein in urine can be a presentation of renal tubular damages and interstitial damages, or overflow proteinuria.

Small molecule protein go through glomerular filtration membrane smoothly, but almost all of them are reabsorbed by renal tubules later. Thereby, in normal condition, there is not too much protein in urine. When urine is detected to contain excessive protein, it always indicates the reabsorption function of renal tubules decreases.

3. Mixed proteinuria means both glomerulus and renal tubule are damaged.

Mixed proteinuria means there are small molecule protein, middle molecule protein and macromolecular protein in urine. In svere case, both renal tubule and glomerulus can be involved and in this condition, no matter small molecule protein, but also middle molecule protein and macromolecule protein can be detected out in urine.