Symptomless abnormalities proteinuria.

During the last decade enormous progress has been made in the study of the ultrastructure of the glomerular capillary wall, the mechanism of protein filtration and excretion, and the pathophysiology and biochemistry of proteinuria. However, current knowledge concerning each of these problems is incomplete. Nonetheless the mechanisms of proteinuria can be categorized, using available biochemical measurements of plasma and urinary proteins, into four groups of causes. The mechanism most commonly underlying proteinuria is a defect of glomerular permeability but proteinuria may also result from the presence in the plasma of high concentrations of low molecular weight protein, failure of the proximal tubule to reabsorb protein filtered by the normal glomerulus, and protein derived from the renal parenchyma. Glomerular proteinuria may cause the nephrotic syndrome or may persist without symptoms. Investigation and follow-up of persistent asymptomatic proteinuria is important although the natural history of this condition is still uncertain.