Clinical Information

Protein in urine is normally composed of a combination of plasma-derived proteins that have been filtered by glomeruli and have not been reabsorbed by the proximal tubules and proteins secreted by renal tubules or other accessory glands. Increased amounts of protein in the urine may be due to: Glomerular proteinuria: Caused by defects in permselectivity of the glomerular filtration barrier to plasma proteins (eg, glomerulonephritis or nephrotic syndrome), Tubular proteinuria: Caused by incomplete tubular reabsorption of proteins (eg, interstitial nephritis), Overflow proteinuria: Caused by increased plasma concentration of proteins (eg, multiple myeloma, myoglobinuria).