Nephrocalcinosis in preterm infants: a single center experience

Abstract

The risk of nephrocalcinosis in preterm infants is considerable, but conflicting numbers are given for the actual incidence (10-65%). Furosemide induced hypercalciuria is said to be the main risk factor. We examined retrospectively the incidence, causes and outcome of nephrocalcinosis in preterm infants born in our hospital from 1988 to 1998 ( n=2190). An abnormal renal echogenicity or nephrocalcinosis was seen in 31 infants (29.7+/-3.3 weeks gestational age; 1307+/-690 g birth weight). Nephrocalcinosis was diagnosed in 16, hyperechoic kidneys (HK) in 10 and Tamm-Horsfall kidneys in 5 infants. Main risk factors were low gestation age and birth weight, length of hospitalization, variations in acid-base status, length of assistant ventilation and hypercalciuria at diagnosis. The incidence of nephrocalcinosis was 0.73% [1.7% for low birth weight infants (VLBW)]. Taking the cases of nephrocalcinosis and HK together, incidence was calculated to be 1.2% overall and 2.5% for VLBW infants, but increased to 7% in 1998. The follow-up showed persisting nephrocalcinosis or hyperechoic kidneys in 8/26 preterm infants. In conclusion, the incidence of nephrocalcinosis was lower in our population than is usually reported. The numbers have, however, increased over the past few years. From the follow-up it was obvious that long-term observation of preterm infants is necessary and that complications might arise in the long run.

Nephrocalcinosis in preterm neonates

“…This is in contrast with results of a study by Saarela et al, who found no significant difference in GFR at a mean age of 4.7 years between 20 former preterms with and 20 without NC in the neonatal period [73]. Hoppe et al and Porter et al also observed normal GFR after 3-6 years and 5.8-7.7 years, respectively, in 12 and 14 prematurely born children with NC [14,74].…”

“…However, persistence for several years has been described [11,14,69,[71][72][73][74]. In the largest ongoing study of preterm neonates, NC persisted in 34%, 15% and 10% after 15 months, 30 months and 7.4 (±1.0) years, respectively (Fig.…”

“…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].…”

“…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]. Recent studies have noted a slightly lower prevalence of 7-41% than in the original reports [12][13][14][15][16].…”

“…NC in preterm neonates has a multifactorial aetiology, consisting of low gestational age and birth weight [1, 7-9, 13, 14, 30], often in combination with severe respiratory disease [8,13,14,30,31], and it occurs as a result of an imbalance between stone-promoting and stone-inhibiting factors (Table 1). There is a clear correlation between prevalence of NC and low gestational age [7-9, 13, 14, 30].…”