The pathogenesis of edema in nephrotic syndrome has not been entirely understood. We investigated the value of the echographic parameters [inferior vena cava index (IVCI), inferior vena cava collapsibility index (IVCCI), and left atrium diameter (LAD)] to determine the volume load in children with minimal lesion nephrotic syndrome (MLNS). Twelve children with MLNS (seven boys, five girls) were included in this study. The patients were classified into three different stages (stage A: edematous; stage B: 50% decrease in weight gain; stage C: edema free) following measurement of their ideal weights. The ideal weight of patients in stage A was increased 13 +/- 7%. Serum total protein, albumin and urine sodium levels were found to be low in these patients. Plasma renin activity (PRA) and serum aldosterone levels in stage A were significantly different from those of the control group (P<0.05). PRA and serum aldosterone levels were not different from those of the control group in stage B (P>0.05). However, the increase in PRA was significant in stage C. Although a significant weight decrease was found in stages B and C, it had no effect on IVCI, LAD, and cardiothoracic index. We consider IVCI, IVCCI, and LAD measurements by echocardiography (ECHO) to be easy and reliable clinical methods for assessing the intravascular volume load in patients with MLNS.