Sodium and potassium concentrations of red blood cells and plasma in children with nephrotic syndrome, uraemia and pyelonephritis.

The sodium and potassium concentrations of the red blood cells and the plasma in 38 children with pyelonephritis (19 acute, 10 chronic and 9 healed), 5 children with uraemia, and 20 children with nephrotic syndrome were compared with those of control children. The red blood cell sodium concentration was lower in patients with acute pyelonephritis, uraemia, and steroid-treated nephrotic syndrome, and higher in those with chronic pyelonephritis and nephrotic syndrome not treated with steroids. Except in uraemic cases, these alterations were not accompanied by plasma sodium and potassium changes. The results might be explained by pathological Na+ and K+ transport processes in the red cell membrane. The possible role of extracellular fluid volume changes, sodium loss and water retention are discussed.