Renal tubular dysfunction in fetal alcohol syndrome

Renal function was evaluated in six patients with fetal alcohol syndrome (FAS) and eight control subjects before and after fluid restriction and acute acid loading. Baseline serum electrolytes, creatinine clearance, fractional sodium excretion, tubular reabsorption of phosphate, urine and blood pH and osmolalities, plasma renin activity, and plasma aldosterone level were normal in all subjects, but fractional potassium excretion (FEK) was lower in FAS patients than in control subjects (P less than 0.001). Despite equivalent plasma osmolalities (295 +/- 3 vs 293 +/- 2 mosmol/kg, P = 0.2), the maximum urinary osmolality after 12 h of water deprivation in patients with FAS was significantly lower compared with controls (560 +/- 107 vs 965 +/- 77 mosmol/kg; P less than 0.001) and increased to only 578 +/- 101 mosmol/kg after vasopressin administration. After ammonium chloride loading, minimum urine pH was significantly higher in patients than in controls (5.7 +/- 0.17 vs 4.81 +/- 0.19; P less than 0.001). Net acid excretion and FEK were also lower in patients than in controls (102 +/- 11 vs 139.6 +/- 11.3 microEq/min per 1.73 m2 and 23.5 +/- 1.3 vs 29 +/- 1.6%, respectively; P less than 0.001). The data indicate a subclinical renal tubular defect in urine concentration and acidification in patients with FAS.