Selectivity of Protein Excretion in Patients with the Nephrotic Syndrome*

this relationship has been expressed graphically as a straight line whose slope characterizes the degree of selective excretion of large or small protein molecules (Figure .1). A steep slope de- notes selective filtration of small molecules, and thus suggests that the size of the glomerular "defect" is correspondingly small. Selectivity patterns of protein excretion were determined and then compared with response to steroid therapy and renal pathology in individual patients. In addition, the patterns were corre- lated with blood urea nitrogen, inulin and paraaminohippuric acid clearances, total 24-hour uri- nary protein, and duration of disease. The re- sults show that those patients with the nephrotic syndrome secondary to intrinsic renal disease (primary renal disease group), demonstrating a high degree of selective protein excretion before treatment, appear to respond best to steroid ther- apy, irrespective of the histologic findings. Fur- thermore, the selectivity pattern remained fairly constant for a given patient even though the total daily urinary protein excretion was fluctuating. Although no characteristic selectivity pattern was found for any given pathologic group, those patients with more advanced histologic changes in the glomeruli appeared to have the least selective type of proteinuria.