Peritoneal protein loss in children with nephrotic syndrome during peritoneal dialysis

Background: The passage of proteins across the glomerular filtration barrier is mainly determined by the size of the protein. In nephrotic syndrome (NS) the glomerular permselectivity is affected, causing proteinuria. Some authors suggest the existence of a generalized basement membrane defect. The permeability characteristics of the peritoneal basement membrane in children with NS are not known. Methods: The transperitoneal transport of proteins with a different molecular weight ({beta}2-microglobulin MW 11 800 D, albumin MW 69 000 D, IgG MW 160 000 D, and &agr;2-macroglobulin MW 820 000 D) was studied in a study group (group A) consisting of six stable nephrotic children (three with glomerulosclerosis and three with congenital nephrotic syndrome, one of them with mesangial sclerosis) and compared to a control group (group B) consisting of eight stable children on peritoneal dialysis. After a dwell of 6 h with Dianeal 1.36% dialysate and serum samples were collected. For each patient the dialysate to plasma (D/P) ratio of the four proteins were calculated. The D/P ratios of the nephrotic patients in group A were compared to the D/P ratios of the patients in the control group B. Data were expressed as mean ±SD. Results: The values for the D/P ratios (in percentage) of {beta}2-microglobulin, albumin, IgG and &agr;2-macroglobulin in group A were 19.6±9.9, 2.7±1.7, 1.6±0.9, and 0.5±0.4, compared to 24.9±10.2, 4.0±2.3, 2.2±1.2, and 0.7±0.3 in the control group B. The ratios were plotted against MW on a double logarithmic scale. In all patients a linear relationship between molecular weight and D/P ratio of the proteins was obtained. The D/P ratios of the study group did no differ significantly from the control group. Conclusion: We conclude that the size selectivity of the capillary permeability is not affected in the peritoneal membrane in children with NS due to glomerulosclerosis and congenital nephrotic syndrome.