Urinary citrate in preterm and term babies.

Objectives: (1) To determine a normal range for urinary citrate for term babies. (2) To compare urinary citrate measured in ex preterm babies at term with this normal range. (3) To evaluate whether urinary citrate was related to presence of nephrocalcinosis (NC) and chronic Lung Disease (CLD) in these ex preterm babies.

Study Design: Urinary citrate was measured in 38 healthy term babies (mean birth weight 3.52 kg, mean gestation 41 weeks) at a mean postnatal age of 3 days (1-5 days) and in 53 ex preterm babies (<32 weeks gestation at birth) at term. These preterm babies were part of a larger study on NC in which two renal ultrasound scans were performed at 1 month and term.

Results: The normal range for urinary citrate in term babies was 0.025-2.97 (mean 1.03) mmol/l and citrate/creatinine ratio 0.0011-0.852 (mean 0.27). In the ex-preterm urinary citrate was not significantly different (mean 1.1 vs. 1.03, p=0.7232) but urine citrate/creatinine ratio was significantly higher (mean 1.27 vs. 0.27, p=0.0005). There was no significant difference in urinary citrate or ratios of citrate/creatinine and calcium/citrate in the 11 (20.7%) with NC or in the 17 (32%) babies with CLD. There was no significant relationship found between duration of TPN and urinary citrate measured at term.

Conclusion: We have determined a normal range for urinary citrate in healthy term babies in the first week of life. The range was very wide. Ex preterm babies had similar values at term and there was no association between urinary citrate and NC or CLD.