Abnormal urinary acidification in infants with hydronephrosis.

Distal renal tubular abnormalities have been observed in patients with dilated urinary tract disorders. The present study was undertaken to look for patterns in urinary acidification in infants with varying degrees of hydronephrosis due to either reflux or obstruction and occurring as unilateral or bilateral disease. Three groups of infants (mean age 3.7+/-3.8 months) were studied prospectively. Groups IA and IB included patients with hydronephrosis who were acidotic and non-acidotic, respectively. Group II served as controls and consisted of patients with diarrhea and secondary metabolic acidosis with no known renal disease. Serum electrolytes, creatinine, and urine pH were measured in all patients. Urinary titratable acidity, ammonium (NH4), and net acid excretion (NAE) were measured by the titrimetric method. Infants with hydronephrosis demonstrated lower urinary buffering capacity, reflected in low NAE in the face of acidosis. Deficiencies were noted in both titratable acid and NH4 excretion compared with control infants. Acidosis was as common in unilateral as in bilateral disease, regardless of severity score. These data confirm a defect in distal urinary acidification in infants with hydronephrosis, whether unilateral or bilateral. Immaturity and endogenous acid load may play a significant role in the manifestation of metabolic acidosis with unilateral disease.