Hyponatremia – serious complication of nephrotic syndrome

Czech version

Authors: S. Szórádová; M. Chocholová; Ľ. Podracká
Authors‘ workplace: Detská klinika LFUK a NÚDCH, Bratislava, Slovensko
Published in: Čes-slov Pediat 2020; 75 (2): 103-107.
Category: Case Report

Overview

Hyponatremia (s-Na <135 mmol/L) is the most common electrolyte abnormality in hospitalized children. A decrease in serum sodium concentration leads to neurological symptomatology and in severe cases is responsible for significant morbidity and mortality. Dreaded and potentially fatal complication of a rapid hyponatremia correction is the osmotic demyelination syndrome. Important risk factors for hyponatremia include nephrotic syndrome. Only anecdotal case reports of hyponatremic encephalopathy associated with nephrotic syndrome are described in the literature. The authors present a rare case report of a severe symptomatic hyponatremia (s-Na 111 mmol/L, relative urinary potassium excretion 92%) in a 6-year-old boy with relapse of nephrotic syndrome and transient renal dysfunction (AKI pRIFLE).

The treatment of severe hyponatremia with edema is demanding and requires considerable clinical experience. According to the classical hypothesis, in the pathophysiology of nephrotic edema large proteinuria and hypoalbuminemia can lead to intravascular hypovolemia and the kidneys retain sodium and water via compensatory mechanism in an attempt to maintain adequate circulatory volume („underfill hypothesis”). On the other hand, in glomerulonephritis the primary intrarenal retention of sodium and water applies to edema formation („overfill” hypothesis). The main task for a clinician is to recognize the basic mechanism of edema and to determine the correct treatment. In practice, relative urinary potassium excretion in the initial urine sample might be helpful. Excretion index higher than 60% suggests an intravascular hypovolemia.

Conclusion: Hyponatremia is a serious complication of relapse of nephrotic syndrome. The treatment of such complication should be managed by skilled clinician. The goal of the correction is a slow and gradual increase of serum sodium concentrations by a maximum of 12 mmol/L/24 hours in hyponatremic encephalopathy.

Keywords:

hypervolemic hyponatremia – Edema – nephrotic syndrome – underfill and overfill hypothesis

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