Renal tubular acidosis in a patient with recurrent metabolic alkalosis.

A 7-month-old infant with failure to thrive and recurrent episodes of vomiting and metabolic alkalosis was evaluated. Urine pH, serum bicarbonate, and urine PCO2-blood PCO2 studies were consistent with the diagnosis of distal renal tubular acidosis (RTA-type I). Analysis of serum potassium and chloride levels during periods of alkalosis and acidosis revealed that potassium depletion and hypochloremic volume contraction served to maintain the alkalotic state despite the presence of an underlying chronic acidosis. This case represents an unusual presentation for renal tubular acidosis and suggests that, under certain conditions, renal tubular acidosis may predispose to the maintenance of a metabolic alkalosis.