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Kim, Jeong, Choi, and Song: Risk Factors and Outcome of Nephrocalcinosis in Very Low Birth Weight Infants
Original Article

Korean J Perinatol 2015;26(1):35-45.

Published online: 20 March 2015

DOI: https://doi.org/10.14734/kjp.2015.26.1.35

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

Ho Sung Kim, M.D., Kumi Jeong, M.D., Young Youn Choi, M.D., Ph.D., Eun Song Song, M.D., Ph.D.

Department of Pediatrics, Chonnam National University Hospital, Gwangju, Korea

Correspondence to: Eun Song Song, M.D., Ph.D., Department of Pediatrics, Chonnam National University Hospital, 42, jebong-ro, Dong-gu, Gwangju 501-757, Korea Tel: +82-62-220-6649, Fax: +82-62-222-6103 E-mail: essong@jnu.ac.kr

Received 9 August 2014       Revised 5 October 2014       Accepted 21 October 2014

Copyright © 2015 Korean Society of Perinatology

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

The aim of this study was to determine the incidence, risk factors, and long-term outcome of nephrocalcinosis in very low birth weight (VLBW) infants.

Methods

A retrospective chart review was performed in VLBW infants between 2006 and 2012 in the neonatal intensive care unit.

Results

The incidence of nephrocalcinosis in VLBW infants was 10.2%. By univariate analysis, oligohydramnios and use of antenatal steroids were more frequent in the nephrocalcinosis group. In the nephrocalcinosis group, the gestational age and birth weight were lower and there were more number of female infants. Also, the initial blood pH, the lowest systolic blood pressure, and urine output on the first day of life were lower and bronchopulmonary dysplasia, sepsis, and urinary tract infection were more prevalent in the nephrocalcinosis group. The use of dexamethasone or ibuprofen and the lowest levels of phosphorus, protein and albumin were significantly lower in the nephrocalcinosis group. By binary logistic regression analysis, the use of antenatal steroids, female sex, 5-minute Apgar score, duration of oxygen therapy and total parenteral nutrition, and the lowest albumin level were found to be significant risk factors for nephrocalcinosis. Overall, the resolution rate was 64.1% and 88.6% within 12 months and 18 months, respectively.

Conclusions

The incidence of nephrocalcinosis in VLBW infants showed increasing trend. The risk factors of nephrocalcinosis were parameters for sick VLBW infants. Although the prognosis of nephrocalcinosis was relatively good, we should pay close attention to the development of complication.

Keywords: Nephrocalcinosis, Very low birth weight infants, Incidence, Risk factors, Outcome

Fig. 1.
Renal ultrasonographic findings at two months of life showed nephrocalcinosis in both kidneys (a maximum diameter of 3.5 mm in the left kidney) with normal renal echogenicity and size (upper two). At four and a half months of life, diffuse nephrocalcinosis (large calculi in the left kidney) and decreased size of both kidneys, more marked in the left kidney (left 2.8x1.4 cm, right 8x8 cm) with loss of corticomedullary differentiation suggesting chronic renal parenchymal disease was noted (lower two).
kjp-26-35f1.tif
Table 1.
Baseline characteristics of mothers and their infants
Variables NC group (n=52) Control group (n=458) P-value
Mother
Age (years), mean (range) 31.5 (19–40) 31.3 (17–45) 0.38
Oligohydramnios (AFI < 5), n (%) 7 (13.5) 27 (5.9) 0.04
Use of antenatal steroids, n (%) 37 (71.2) 243 (54.3) 0.04
PPROM (≥ 18 hours) 12 (23.1) 150 (32.8) 0.08
GDM or overt DM, n (%) 4 (7.7) 16 (3.5) 0.09
Histologic chorioamnionitis 20 (38.5) 151 (33.0) 0.65
Hypertensive diseases∗, n (%) 11 (21.2) 97 (21.2) 1.00
Infants
GA (weeks), mean (range) 27.6 (25.1–34.6) 29.6 (23.7–36.4) <0.01
BW (g), mean (range) 998.7 (470–1,480) 1,186.1 (570–1,490) <0.01
Small for gestational age, n (%) 10 (19.2) 74 (16.2) 0.57
Female, n (%) 32 (61.5) 210 (45.9) 0.03
1- min Apgar score, mean (range) 4.5 (0–10) 5.2 (0–10) 0.06
5-min Apgar score, mean (range) 6.4 (1–10) 7.4 (1–10) 0.01
Initial blood pH, mean (range) 7.28 (6.94–7.47) 7.32 (6.56–7.61) 0.04
Lowest systolic BP on day 1 (mmHg), mean (range) 35.0(21–65) 39.3 (21–75) <0.01
Urine output on day 1 (ml/kg/hr), mean (range) 2.1 (0.6–3.9) 2.8 (0.3–10.2) 0.01

Abbreviations: NC, nephrocalcinosis; AFI, amniotic fluid index; PPROM, Preterm premature rupture of membranes; GDM, Gestational diabetes mellitus; DM, diabetes mellitus; GA, gestational age; BW, birth weight;BP, blood pressure.

∗ Hypertensive diseases include pregnancy induced hypertension, preeclampsia, eclampsia and chronic hypertension.

Table 2.
Morbidities among very low birth weight infants
Variables NC group (n=52) Control group (n=458) P-value
PDA, n (%) 40 (76.9) 269 (58.7) 0.11
BPD, n (%) 33 (63.5) 188 (41.0) 0.02
Bacterial sepsis, n (%) 25 (48.1) 156 (34.1) 0.03
Fungal sepsis, n (%) 13 (25.0) 39 (8.5) <0.01
Urinary tract infection, n (%) 27 (51.9) 157 (34.3) 0.01

Abbreviations: NC, nephrocalcinosis; PDA, patent ductus arteriosus; BPD, bronchopulmonary dysplasia.

Table 3.
Supportive care and drug treatment
Variables NC group (n=52) Control group (n=458) P-value
Mechanical ventilation (days), mean (range) 28.8 (0–154) 11.9 (0–150) <0.01
Oxygen therapy (days), mean (range) 50.7 (0–196) 26.3 (0–235) <0.01
Initial trophic feeding (day of life), mean (range) 4.7 (1–34) 2.5 (0–23) 0.01
TPN (days), mean (range) 37.5 (5–106) 25.4 (0–116) <0.01
Phototherapy (days), mean (range) 12.5 (4–31) 13.7 (0–66) 0.14
Surfactant, n (%) 46 (88.5) 330 (72.1) 0.11
Dexamethasone, n (%) 18 (34.6) 91 (19.9) 0.01
Indomethacin, n (%) 3 (5.8) 84 (18.3) 0.32
Ibuprofen, n (%) 20 (38.4) 89 (19.4) 0.01
Furosemide, n (%) 27 (51.9) 193 (42.1) 0.23
Furosemide (days), mean (range) 4.5 (0–70) 2.1 (0–89) 0.12
Gentamicin (days), mean (range) 0.9 (0–17) 0.6 (0–21) 0.11
Cefotaxime (days), mean (range) 17.0 (0–71) 11.3 (0–52) 0.01
Ampicillin (days), mean (range) 14.3 (0–82) 10.3 (0–64) 0.07
Theophylline (days), mean (range) 27.9 (0–103) 25.4 (0–102) 0.88
Fluconazole (days), mean (range) 6.1 (0–44) 3.4 (0–41) 0.03

Abbreviations: NC, nephrocalcinosis; TPN, total parenteral nutrition.

Table 4.
Laboratory findings on admission, 2nd weeks, and 4th weeks of life
Variables NC group (n=52) mean (range) Control group (n=458) mean (range) P-value
During admission
Total calcium (mg/dL), highest 10.4 (6.5–19.4) 9.6 (8.9–20.1) 0.58
Total calcium (mg/dL), lowest 7.2 (5.3–9.2) 6.8 (4.8–9.9) 0.74
Ionized calcium (mEq/L), highest 3.0 (2.3–4.0) 2.9 (1.6–4.5) 0.09
Ionized calcium (mEq/L), lowest 2.0 (1.3–2.8) 2.1 (0.6–2.9) 0.43
Inorganic phosphorus (mg/dL), highest 7.4 (5.2–10.7) 7.5 (2.6–16.3) 0.48
Inorganic phosphorus (mg/dL), lowest 3.0 (1.0–6.1) 3.5 (0.3–7.0) 0.01
BUN (mg/dL), highest 35.7 (3.2–123.5) 25.1 (3.4–178.0) 0.03
Creatinine (mg/dL), highest 1.17 (0.2–5.7) 1.2 (0.2–16.0) 0.87
Protein (g/dL), lowest 3.8 (2.5–6.0) 4.1 (2.0–7.6) 0.01
Albumin (g/dL), lowest 2.6 (1.6–3.8) 2.7 (1.7–3.7) 0.02
2nd week
Total calcium, mg/dL 9.4 (4.8–13.9) 8.8 (5.7–17.9) 0.65
Ionized calcium, mg/dL 2.5 (2.1–4.0) 2.7 (1.4–3.6) 0.17
Inorganic phosphorus, mg/dL 4.4 (1.6–8.7) 4.9 (0.7–12.3) 0.03
BUN, mg/dL 19.0 (1.9–92.7) 11.6 (1.7–100.3) 0.07
Creatinine, mg/dL 4 0.7 (0.1–5.6) 0.6 (0.1–3.8) 0.02
Protein, g/dL 4.6 (3.8–6.0) 4.9 (2.7–6.6) <0.01
Albumin, g/dL 3.2 (2.2–4.2) 3.4 (2.0–4.6) <0.01
4th week
Total calcium, mg/dL 9.0 (5.7–10.7) 8.4 (6.4–12.4) 0.68
Ionized calcium, mg/dL 2.5 (1.5–3.5) 2.4 (1.7–3.0) 0.61
Inorganic phosphorus, mg/dL 5.4 (0.1–7.9) 6.1 (0.4–77.0) 0.13
BUN, mg/dL 7.4 (1.9–38.9) 6.7 (1.2–39.1) 0.73
Creatinine, mg/dL 0.4 (0.1–3.2) 0.3 (0–3.0) 0.03
Protein, g/dL 4.5 (3.6–5.8) 4.7 (3.2–6.3) 0.07
Albumin, g/dL 3.3 (2.5–4.0) 3.4 (2.3–4.8) 0.04

Abbreviations: NC, nephrocalcinosis; BUN, blood urea nitrogen.

Table 5.
Significance of risk factors by binary logistic regression analysis
Subject P-value Odd ratio 95% Confide ence Interval
Lower Upper
Use of antenatal steroids < 0.01 7.112 0.80 80.29
Female 0.03 0.161 0.68 59.92
Five-minute Apgar score 0.01 1.503 0.44 3.20
Oxygen therapy (days) 0.01 1.039 0.50 0.87
TPN (days) 0.02 0.947 –3.11 –0.01
Albumin (lowest) level during admission < 0.01 25.082 0.66 76.35

Abbreviations: BPD, bronchopulmonary dysplasia; TPN, total parenteral nutrition.

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