Control of sodium homeostasis in children with recurrent urinary tract infections and reduced glomerular filtration rates.

Abstract

SummaryBasal sodium excretion and rapid response to oral and intravenous sodium loads have been studied in children with recurrent urinary tract infections and a wide range of glomerular filtration rates. Basal sodium excretion related to body surface was remarkably stable in all children studied and thus independent of glomerular filtration rate. The rapid response to an oral or an intravenous sodium load was reduced in patients with low filtration rates. The urinary sodium excretion rate following oral sodium load was correlated to the glomerular filtration rate with high statistical significance. In patients with high filtration rates saline infusion resulted in a rather prompt inhibition of tubular sodium reabsorption with consequent increase in urinary sodium excretion. In patients with low filtration rates inhibition of tubular sodium reabsorption following intravenous saline load was much less pronounced. During the transition from hydropenia to water diuresis without extra sodium supply both the patients with low and with high filtration rates increased the absolute as well as the fractional sodium excretion concomitantly with an increase in the filtered load of sodium. The results are compatible with, but do not prove the existence of an additional natriuretic factor that keeps the basal sodium excretion constant in the diseased kidney.