Factors affecting renal hydrogen ion excretion capacity in healthy children

In 560 healthy German children and adolescents aged 2.8-22.0 years from the DONALD (Dortmund Nutritional and Anthropometric Longitudinally Designed) s tudy, the relationship between urine pH and renal net acid excretion (mmol/ day/1.73 m(2)) was analysed. A quadratic model showed the best fit (r(2)=0. 608). Using logistic regression analysis three parameters (urinary phosphor us excretion, total protein intake and urinary ratio of potassium and sodiu m) had a significant effect on renal hydrogen ion excretion capacity charac terised by the probability of high or low net acid excretion with respect t o the urine pH value. Urinary osmolality, in contrast to what has been seen in a previous experimental study with low birth weight infants, along with sex and age had no significant independent effects on renal net acid excre tion with respect to the urine pH value over the range of osmolalities obse rved. In healthy children and adolescents a low fluid intake with high urin ary osmolality does not at least substantially decrease the renal capacity of hydrogen ion excretion.