The pathogenesis of hematuria and proteinuria is discussed elsewhere and will only be reviewed briefly in this subsection. Abnormal red cell morphology and red cell casts are strongly suggestive of glomerular disease rather than an extrarenal disorder, such as nephrolithiasis or prostatic disease.
Proteinuria also reflects an increase in net glomerular permeability.
Glomerular proteinuria occurs when there is a defect in one or both of these barriers. In minimal change disease, for example, the often marked proteinuria is caused primarily by a loss of the charge barrier. In comparison, the GBM is directly damaged in most other glomerular diseases, leading to loss of both size selectivity and charge selectivity. Both volume and vasoconstrictor factors contribute to the hypertension that frequently occurs in the glomerulopathies. In this setting, fluid removal by use of diuretics or dialysis usually lowers the blood pressure toward normal.