Abnormal urinary acidification in infants with hydronephrosis

Distal renal tubular abnormalities have been observed in patients with dila ted urinary tract disorders. The present study was undertaken to look for p atterns in urinary acidification in infants with varying degrees of hydrone phrosis 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 hydronephro sis who were acidotic and non-acidotic, respectively. Group II served as co ntrols and consisted of patients with diarrhea and secondary metabolic acid osis with no known renal disease. Serum electrolytes, creatinine, and urine pH were measured in all patients. Urinary titratable acidity, ammonium (NH 4), and net acid excretion (NAE) were measured by the titrimetric method. I nfants with hydronephrosis demonstrated lower urinary buffering capacity, r eflected in low NAE in the face of acidosis. Deficiencies were noted in bot h titratable acid and NH4 excretion compared with control infants. Acidosis was as common in unilateral as in bilateral disease, regardless of severit y score. These data confirm a defect in distal urinary acidification in inf ants with hydronephrosis, whether unilateral or bilateral. Immaturity and e ndogenous acid load may play a significant role in the manifestation of met abolic acidosis with unilateral disease.