The role of bioelectrical impedance analysis, NT-ProBNP and inferior vena cava sonography in the assessment of body fluid volume in children with nephrotic syndrome

Background: Assessment of volume status and differentiating “underfill” and “overfill” edema is essential in the management of patients with nephrotic syndrome (NS). Objectives: Our aim was to evaluate the volume status of NS patients by using different methods and to investigate the utility of bioelectrical impedance analysis (BIA) in children with NS. Methods: The hydration status of 19 patients with NS (before treatment of NS and at remission) and 25 healthy controls was assessed by multifrequency BIA, serum N-terminal-pro-brain natriuretic peptide (NT-proBNP) levels, inferior vena cava (IVC) diameter, left atrium diameter (LAD) and vasoactive hormones. Results: Renin, aldosterone levels, IVC diameter and LAD were not statistically different between the groups. NT-proBNP values were statistically higher in the attack period compared to remission and the control group (p = 0.005 for each). Total body water (TBW), overhydration (OH) and extracellular water (ECW) estimated by the BIA measurement in the attack group was significantly higher than that of the remission group and controls. There were no significant correlations among volume indicators in group I and group II. However, significant correlations were observed between NT-proBNP and TBW/BSA (p = 0.008), ECW/BSA (p = 0.003) and ECW/ICW (p = 0.023) in the healthy group. TBW was found to be higher in patients with NS in association with increased ECW but without any change in ICW. NT-proBNP values were higher in patients during acute attack than during remission. Conclusions: Our findings support the lack of hypovolaemia in NS during acute attack. In addition, BIA is an easy-to-perform method for use in routine clinical practice to determine hydration status in patients with NS