Neonatal nephrocalcinosis: long term follow up

Abstract

Aims: To assess the spontaneous resolution of neonatal nephrocalcinosis and its long term effects on renal function. Methods: Fourteen very low birthweight preterm babies with nephrocalcinosis were followed up at 5-7 years of age; 14 controls were matched for sex, gestation, and birth weight. Height, weight, blood pressure, and renal symptomatology were recorded, and a renal ultrasound scan was performed. Early morning urine osmolality and creatinine ratios of albumin, phosphate, calcium, oxalate and b microglobulin were determined. Urea and electrolytes in the study group were determined, and glomerular filtration rate (GFR) and TmP/GFR (tubular reabsorption of phosphate per GFR) were calculated. Statistical analysis was performed on a group basis using the Mann-Whitney confidence interval. Results: Mean age was 6.9 years (range 5. 81-7.68). An early morning urine osmolality .700 mOsm/kg was achieved in all cases. In two cases and four controls, the calcium/creatinine ratio was .0.7 mmol/ mmol. In all cases, the GFR was normal (median 132.6 ml/min/1.73 m 2 (range 104.1-173.1)). Median TmP/GFR was 1.22 mmol/l (0.73-1.61), with two having levels below the normal range. These did not have persisting nephrocalcinosis. Nephrocalcinosis was found in three of the 12 cases scanned and one control. There were no significant differences in urine biochemistry. Conclusions: Resolution of nephrocalcinosis occurred in 75% of cases. No evidence was found to suggest that nephrocalcinosis is associated with renal dysfunction in the long term. There was evidence of hypercalciuria in the cases and controls, suggesting that prematurity may be a risk factor.

Nephrocalcinosis in preterm neonates

“…Significantly more (9/41, 22%) children with neonatal NC had hypercalciuria after a mean age of 7.4 years than expected for healthy children, in contrast to former preterms without NC (2/32, 6%) [75]. This is in keeping with the findings of other smaller studies in which hypercalciuria with or without NC is described in former preterms (Table 2) [69,71,73,74,78].…”

“…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].…”

“…Most studies found no difference in early morning urine osmolality between former preterms with and without NC [14,69,74,75]. On the other hand, two studies demonstrated early morning urine osmolality to be significantly lower in former preterms than in healthy children [6,71].…”

“…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.…”

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

“…Porter et al 18 followed up the 14 VLBW infants with NC up to at 5-7 years of age who showed the 75% resolution rate and no renal function impairment in the long time, but in this study, one preterm infant with NC developed chronic renal failure due to renal stones.…”