Bicarbonate reabsorption and hydrogen ionexcretion in children with renal tubular acidosis

Abstract

Nine children with renal tubular acidosis have been evaluated on the basis ofbicarbonate reabsorption during intravenous infusion, and of excretion of hydrogen ion following administration of ammonium chloride. In 3, who were shown to have distal renal tubular acidosis, bicarbonate threshold and rate of reabsorption were normal; they had small amounts of bicarbonate in urine, however, even at low levels of serum bicarbonate, owing to their inability to depress urinary pH below 6.5. Six children had proximal renal tubular acidosis, primary in 4 and due to the Fanconi syndrome in 2. Although all had a low bicarbonate threshold and 4 had a low Tm, urinary pH and excretion of hydrogen ion during metabolic acidosis were within normal limits in each subject when the serum bicarbonate was below the threshold. Classification of patients with renal tubular acidosis as either proximal or distal is of importance because of major differences in clinical features, complications, and therapy.