Urinary lithogenic and inhibitory factors in preterm neonates receiving either total parenteral nutrition or milk formula

Nephrocalcinosis in very low birth weight infants: incidence, associated factors, and natural course

BACKGROUND

Preterm kidney is exposed to various exogenous factors that may impact its function such as nephrotoxic drugs or nephrocalcinosis. We investigated prevalence and risk factors of nephrocalcinosis (NC) in recently born very low birth weight (VLBW) infants submitted to improved biological monitoring.

METHODS

Retrospective, case-control study in very preterm infants (< 32 + 6 weeks, ≤ 1500 g) admitted to a tertiary care unit during a 6-year period. Each case (ultrasound-diagnosed NC) was matched with two controls (no NC). Data were collected at days 15 and 30 of life and 35 weeks corrected age, with follow-up at 18 months and 3 years.

RESULTS

Of 525 eligible infants, overall prevalence of NC was 17.1% at 35 weeks corrected age. Prevalence was halved between 2012 (26.1%) and 2017 (11.8%). We included 265 infants, more than half being born before 28 weeks. Cases presented with more severe morbidity than controls, but reached statistical significance only in infants born < 28 weeks (88.2% vs. 68.3%, P = 0.01). Protein, energy, calcium, phosphorus, and vitamin D intakes were similar in the two groups and did not change significantly over the study period. Weight gain was similar in the two groups. Exposure to furosemide (OR [IC95%]: 1.26 [1.02; 1.57]) and postnatal growth (1.65 [1.04; 2.67]) were independent risk factors of NC. NC resolved 12-18 months after diagnosis in 61% of infants.

CONCLUSION

Prevalence of NC is significant but can be reduced. Furosemide should be cautiously prescribed in VLBW infants, and nutritional support must be well monitored to support postnatal growth and limit risk of nephrocalcinosis.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT 04,860,583. A higher resolution version of the Graphical abstract is available as Supplementary information.

Parenteral nutrition compromises neurodevelopment of preterm pigs

BACKGROUND

Despite advances in nutritional support and intensive care, preterm infants are at higher risk of compromised neurodevelopment.

OBJECTIVE

This study evaluated the contribution of total parenteral nutrition (PN) to compromised neurodevelopment after preterm birth.

METHODS

Preterm pigs were provided PN or enteral nutrition (EN) for 10 d. Neurodevelopment was assessed by observations of motor activity and evaluation of sensory/motor reflexes, brain weight, MRI, and cerebellar histology.

RESULTS

Despite similar gains in body weight, PN pigs had smaller brains (32 ± 0.4 vs. 35 ± 0.6 g; P = 0.0002) including the cerebellum, as well as reduced motor activity (P = 0.005), which corresponded to underdeveloped myelination (P = 0.004) measured by diffusion tensor imaging. PN resulted in lower serum triglycerides (17 ± 5.9 vs. 27 ± 3.1 mg/dL; P = 0.05), total cholesterol (31 ± 9.6 vs. 85 ± 8.1 mg/dL; P = 0.04), VLDL cholesterol (3.7 ± 1.2 vs. 5.7 ± 0.7 mg/dL; P = 0.04), and HDL cholesterol (16 ± 4.6 vs. 57 ± 7.3 mg/dL; P = 0.03) and nonsignificantly lower LDL cholesterol (10.7 ± 4.4 vs. 22.7 ± 2.9 mg/dL; P = 0.09).

CONCLUSIONS

The compromised neurodevelopment caused by total PN is a novel finding, was independent of confounding variables (disease, inconsistent gestational ages, diverse genetics, extrauterine growth retardation, and inconsistent neonatal intensive care unit protocols), and highlights a need to improve current PN solutions. The preterm pig is a translational animal model for improving nutrition support to enhance neurodevelopment of preterm infants requiring PN.

Renal function and kidney length in preterm infants with nephrocalcinosis: a longitudinal study

Renal injury in early life may lead to hypertension and renal disease in adulthood. In this prospective study, we estimated renal glomerular and tubular function and kidney length (KL) during the first 2 years of life of preterm infants with nephrocalcinosis (NC) associated with prematurity. The study cohort comprised 107 preterm children, 63 with NC and 44 control subjects without NC who were matched for gender, gestational age and birth weight. Kidney function was estimated based on measurements of serum creatinine (Scr), estimated glomerular filtration rate (eGFR), fractional excretion (FE) of sodium (Na), potassium (K), phosphate (P), magnesium (Mg) and uric acid (UA) and on the ratios of urinary Ca, oxalate (UOx) and citrate (UCit) to urinary creatinine (UCa/Ucr, UOx/Ucr and UCit/Ucr, respectively) calculated from morning urine collections. KL was measured by ultrasonography. Measurements were made at 40 weeks postmenstrual age and at 3, 6, 12 and 24 months of age. At 3 and 6 months, the NC group had higher UCa/Ucr, FEK and FEUA than the control group; at 12 months, only the UCa/Ucr and FEUA was still higher. The UCa/UCit ratio was higher in the NC group. Scr and eGFR did not differ between the groups at any time point. The NC group had a shorter KL up to 12 months of life (left kidney) or 24 months (right kidney). Based on these results, we conclude that NC in the preterm infants enrolled in our study was associated with impaired renal tubular function and a shorter KL in the first year of life.

Developmental changes of oxalate excretion in enterally fed preterm infants

To further substantiate gestational age-related changes in oxalate excretion, we studied urinary oxalate excretion in 66 preterm infants born at 23.4-34.7 weeks of gestation. Spot urine of 66 preterm infants was analysed by ion chromatography as soon as they were completely orally fed with enriched breast milk and/or special preterm milk formula (days 7 to 57 of postnatal life). Infants with evidence of renal, gastrointestinal, muscular or metabolic disease were not included. Newborns on parenteral nutrition were excluded. Oxalate/creatinine ratios (Ox/Cr) decreased with gestational age (three age groups: group 1, 23 0/7-28 0/7; group 2, 28 1/7-32 0/7; and group 3, 32 1/7-35 0/7 weeks of gestation). The mean Ox/Cr was highest in group 1 (398.2 mmol/mol +/- 116.8; n = 21). Differences between groups 1 + 3 were statistically significant; p = 0.001; those between groups 1 + 2 and between groups 2 + 3 were not. Ox/Cr correlated inversely with gestational and maturational age (r = -0.41, p = 0.001; r = -0.33, p = 0.007) and positively with postnatal age (r = 0.32, p = 0.008). It correlated inversely with birth weight as well as actual weight at sample collection (r = -0.46 and -0.44, p < 0.001). Ox/Cr was significantly linked to energy and carbohydrate intake (r = 0.3 and 0.4, p = 0.03 and 0.001). These results were independent of sex. In the present study we show that urinary oxalate excretion in preterm infants depends on gestational age.

Development of nephrocalcinosis in very low birth weight infants

Premature infants undergo intensive growth during the postnatal period. Adequate mineralization is dependent on sufficient intake of calcium (Ca) and phosphorus (P). However, Ca and P supplementation can be associated with some risks, for example development of nephrocalcinosis. We investigated pathophysiological risk factors in premature very low birth weight (VLBW) infants associated with the development of nephrocalcinosis. From June 1994 to September 1995 all preterm neonates with a birth weight below 1,500 g were screened prospectively. At regular intervals of 2 weeks, ultrasonography (US) of the kidneys was performed and parameters of mineral metabolism were assessed in blood and spot urine samples. For analysis, premature infants with nephrocalcinosis (group N) were compared with infants without nephrocalcinosis (group R) and with a retrospectively pair-matched subgroup of premature infants without nephrocalcinosis (control group C) taken from the same study. Nephrocalcinosis was detected in 20 of 114 preterm neonates (group N, 17.5%). Of these 20 infants with nephrocalcinosis, 16 presented with a tendency towards systemic acidosis (pH<7.25) on day 2-7, compared with only 4 of 20 premature infants of the control group. Premature infants of group N had a lower serum P at 2 weeks of life and 5 (versus 0 patients of the control group C) had transient hypophosphatemia (serum P<1.6 mmol/l). Moreover, the Ca/creatinine ratio in spot urine specimens tended to be higher (P<0.1) in patients developing nephrocalcinosis. There were no significant differences in the duration of ventilation, the length of stay in the intensive care unit, and duration and frequency of furosemide and steroid treatment between the groups N and C. VLBW premature infants developing nephrocalcinosis frequently presented with slightly impaired acid-base homoeostasis within the 1st week, followed by signs of impaired mineralization (and immature or impaired renal function) within 2 weeks. In VLBW premature infants, close observation of acid-base status and regular analysis of spot urine specimens (Ca, P, creatinine) during the first weeks of life may help to identify those premature infants at risk for nephrocalcinosis.