Renal Calcification in Very Low Birth Weight Infants

Abstract

Between January 1990 and December 1991, serial real-time ultrasound examinations and analyses of urine were performed on a total of 50 infants with birth weights less than 1,500 g to assess the incidence of renal calcification. Five infants (10%) developed renal calcification at a mean age of 48.8 ± 14.1 days. These 5 infants with renal calcification had significantly shorter gestations (28.2 ± 0.8 vs. 30.1 ± 1.7 weeks, p < 0.0005) and lower birth weights (934 ± 45 vs. 1,311 ± 188 g, p < 0.0005) when compared with infants without renal calcification. None of the affected infants were treated with furosemide. Affected infants had a mean urine volume of 85.8 ± 11.3 ml/kg/24 h, mean urine calcium level of 5.07 ± 1.18 mg/kg/24 h, mean urine calcium to creatinine (mg/mg) ratio of 0.67 ± 0.09, and a mean urine N-acetyl-β-D-glu-cosaminidase (NAG) to creatinine (U/g) ratio of 259 ± 133. Urinalyses showed that affected infants had significantly higher urine pH values and hematuria. Alkaline phosphatase concentrations and initial parathyroid hormone levels were not different among the two groups. In summary, renal calcification occurred in 10% of very low birth weight infants and multiple risk factors seem to be contributory. The smaller, sicker and more immature infants appear to have increased risk for developing renal calcification. For earlier detection and treatment of renal calcification, follow-up screening by serial ultrasound examinations and assay of urinary excretion of calcium, creatinine and NAG are useful, and a meticulous search for the causes of renal calcification is mandatory.

Nephrocalcinosis in preterm infants: a single center experience

“…In addition, furosemide induced hypercalciuria seems not to be the main risk factor, as furosemide was not given in a third of the preterm infants with nephrocalcinosis in our study and in none in the study of Sheu et al [26]. As previously reported, calcium excretion was increased under dexamethasone and methylxanthine medication, as well as under total parenteral nutrition [11,12,[29][30][31].…”

“…Preterm infants with nephrocalcinosis were reported to be smaller and to have a lower gestational age than infants without that complication [3,16,26]. In our study, the incidence of nephrocalcinosis was higher in the group of infants with a birth weight below 1500 g. Immaturity of the kidneys, especially in preterm infants born <34 weeks gestational age, should therefore be considered to be a risk factor [27,28,32].…”

“…Campfield et al observed nephrocalcinosis in 16% of preterm infants when using a 7.5-MHz transducer, but only in 6% when using a 5-MHz transducer [24]. The extreme incidence (65%) in the study by Jacinto et al might also be explained by such a difference in technique, when compared to newer studies (7.5-vs 5-MHz transducer [3,25,26]). We used both a 5-MHz and a 7-MHz transducer for renal ultrasonographies.…”

Risk Factors and Outcome of Nephrocalcinosis in Very Low Birth Weight Infants

“…[5][6][7][8][9][10][11][12] At a low gestational age, the lower glomerular filtration ratio and the shorter loop of Henle lead to slow urinary transition, while the sensitivity for heterogeneous crystallization is high, which result in decreased calcium excretion and increased calcification. Also, during the neonatal period, VLBW infants are exposed more frequently and for a longer time to multiple risk factors associated with treatment.…”

Nephrocalcinosis in preterm neonates

“…NC is diagnosed in 7-64% of preterm neonates with gestational age <32 weeks or birth weight <1,500 g [7][8][9][10][11][12][13][14][15][16]. The wide range in prevalence of NC is a consequence of different study populations and ultrasound equipment and criteria, in addition to a moderate interobserver variation [12].…”