Abstract
Background and Aims
One of the major symptoms of severe nephrotic syndrome is fluid retention. Fluid overload can induce cardiovascular damage. NT-proBNP (N-terminal pro-brain natriuretic peptide) and hsTnT (high sensitivity troponin T) are well known markers of this disorder. The aim of the study was to evaluate the association between volumes of body water compartments and markers of cardiovascular damage in patients with severe nephrotic syndrome (SNS) defined as nephrotic range proteinuria and hypalbuminaemia ≤ 2.5 g/dl.
Method
40 patients with SNS and eGFR >30 ml/min/1.73m2 formed the study group (SNSG) and 40 healthy volunteers without SNS matched according to age, sex, height, body mass and kidney function formed the control group (CG). In all participants serum creatinine, serum albumin concentration, daily proteinuria, hsTnT and NT-proBNP were measured. Body water compartments such as extracellular water (ECW), intracellular water (ICW), total body water (TBW), overhydration (OH) were assessed using Body Composition Monitor, Fresenius Medical Care. For statistical analysis Spearman’s correlation coefficients, chi2 or Mann-Whitney U tests were used (Statistica v 13.1).
Results
SNSG included 28 males (70%) and 12 females. Median age was 55 years (IQR 30-65), the mean daily proteinuria was 10.5 ±5.0 g. The characteristics of the study parameters in two groups are described in the table.
Significantly higher hsTnT (18 vs 6 ng/l, p=0.0001) and NT-proBNP (294.8 vs 47.1 pg/ml, p=0.0003) levels were observed in the severe nephrotic syndrome group in comparison (SNSG) to CG.
In SNSG extracellular water was significantly higher (20.9 ±5,2 vs 17.4 ±3.3 L, p=0.001) and intracellular water (ICW) was significantly lower (18.9 ±5.2 vs 21.4 ±4.8 L, p=0.034) in comparison to CG. Interestingly total body water (TBW) did not differ between the groups (39.8 ±8.6 vs 38.8 ±7.7 L, p=0.603). Also overhydration which is a derivative of ECW, was higher in SNSG (OH: 4.2 vs 0.3 L, p<0.0001) than in CG. Significant, positive correlation was observed between OH and NT-proBNP (R=0.56, p<0.0001) as well as hsTnT (R=0.60, p<0.0001). We did not observed significant correlation between ECW and NT-proBNP or hsTnT.
Conclusion
In the severe nephrotic syndrome group fluid retention was associated with the increase in ECW and the decrease in ICW whereas TBW was the same in both groups. Such constellation can indicate for intracellular underhydration which was not describe so far. Overhydration, which is a derivative of ECW, positively correlated with markers of cardiovascular damage and can be important for patients with resistant SNS and can influence their prognosis.