Renal electrolyte clearance in patients with nephrotic syndrome

BACKGROUND. Nephrotic syndrome (NS) develops with severe damage to the glomerular filter. The kidneys play a key role in the regulation of water-electrolyte homeostasis. However, the features of water-electrolyte disorders in glomerulopathy have not been studied enough. The aim of our study was to determine the main indicators of renal electrolyte transport in adult patients with NS. PATIENTS AND METHODS. 173 patients with glomerulopathy, 114 men and 81 women, were examined. The average age is 39.0±15.8 years. All of them were hospitalized during 2016-2019 years. A traditional nephrological clinical and laboratory examination was performed. Additionally, the indicators of electrolyte transport and osmotically active substances were calculated. RESULTS. Nephrotic syndrome (NS) was detected in 64 people (36.9 %). Patients with NS were characterized by lower levels of total protein, albumin, higher proteinuria, and dyslipidemia. The concentration of urea, potassium, calcium, inorganic phosphates and uric acid in the blood serum, as well as the eGFR value in the groups were comparable. Patients with NS had higher urinary clearance of sodium, potassium, and chlorine. In addition, they had a significant increase in the excreted fraction of sodium, chlorine and potassium. Hyponatremia was registered in 8.1 % and 13.1 % of patients, respectively, without and with NS. Hypocalcemia was observed in 14.5 % of patients without NS and in 22.9 % with NS. We have not revealed the relationship between the value of the excreted fraction of sodium, chlorine and potassium with the presence and severity of focal and diffuse interstitial fibrosis, depending on the nephrotic syndrome. Tubular atrophy increased the probability of an increase in the excreted fraction of sodium by 3 times, chlorine by 2.4 times. The median proportion of non-functioning glomeruli in patients with eGFR greater than 6 ml/min/1.73 m 2 and tubular atrophy was 3.0 [1.0; 5.0]. CONCLUSION. Renal electrolyte clearance is not associated with the presence of HC. The increase in the excretion of basic electrolytes is due to the severity of tubular atrophy. In patients with tubular atrophy, it is necessary not only to monitor the electrolyte composition of the blood, but also to monitor tubular functions. For this purpose, it is advisable to regularly determine the excreted sodium fraction.