[en] The reticuloendothelial system, including the spleen, subserves important immunologic functions. Loss of splenic function results in an increased incidence of severe bacterial infections and is accompanied by thrombocytosis. Several nephrotic children were noted to have remarkably high platelet counts and predisposition to bacterial infection with encapsulated organisms. We, therefore, investigated the splenic function of nine children with primary nephrotic syndrome and measured the phagocytic function of the spleen by sequestration of Technetium-99-labelled heat-treated autologous RBC, administered intravenously. Four children had decreased splenic function. Repeat studies performed in two of these children after remission of the nephrotic syndrome gave normal results. There were six episodes of bacterial infection (3 peritonitis, 1 septic arthritis, 1 cellulitis, and 1 Escherichia coli urinary tract infection) among the four patients with decreased splenic function. There were no episodes of bacterial infection among the five nephrotic children with normal splenic function. Nephrotic patients with decreased splenic function had significantly increased platelet counts (921,000 +/- 196,000; mean +/- SEM) compared to those with normal function (435,000 +/- 46,000; P less than 0.001). Our findings suggest the possibility that some nephrotic children may have decreased splenic function in association with increased susceptibility to bacterial infections