Low molecular weight organic acids in the urine of the newborn

The urinary excretion of seven selected low molecular weight organic acids in normal neonates was measured by gas chromatography. First and third to fourth day of life excretion of the following compounds was significantly unchanged: 3-OH-butyric acid (less than 13 mumol/mmol creatinine), succinic acid (approx. 43 mumol/mmol creatinine), adipic acid (approx. 12 mumol/mmol creatinine), 2-OH-glutaric acid (approx. 23 mumol/mmol creatinine), 3-OH-3-Me-glutaric acid (approx. 25 mumol/mmol creatinine) and citric acid (approx. 115 mumol/mmol creatinine). The excretion of 4-OH-phenyl-acetic acid increased during the first four days of life (from less than 8 mumol/mmol creatinine to approx. 20 mumol/mmol creatinine). It is postulated that urinary orgainc acid excretion in the neonate, which is clearly different from the adult urinary pattern, is a reflection of the specific neonatal metabolic situation, including a high fatty acid utilisation and a low protein catabolism.