NDT Advance Access published online on August 4, 2008
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn431
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The effects of gestational age and growth restriction on compensatory kidney growth
1 Neonatal Intensive Care Unit 2 Radiology Department, University Hospital of Ioannina, Ioannina, Greece
Correspondence and offprint requests to: Vasileios Giapros, University Hospital of Ioannina, P.O. Box 1186, Ioannina 451 10, Greece. Tel: +30-2651097544; Fax: +30-2651097038; E-mail: vgiapros{at}cc.uoi.gr
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Abstract |
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Background. Low birth weight is associated with altered renal development, adult onset hypertension and renal disease. The aim of this prospective longitudinal study was to estimate the renal growth during the first 2 years of life in small-for-gestational age (SGA) infants of varied gestational age (GA) and with differing degrees of growth retardation (GR) at birth.
Material and methods. The study included 466 children: SGA, n = 243, and appropriate-for-gestational age (AGA), n = 223, classified according to GA into three groups (28–34, 34–36 and >36 weeks, respectively). The SGA children were also classified according to the degree of GR: birth weight <3rd percentile, and birth weight 3–10th percentiles. Serial renal ultrasonography (US) for kidney length (KL) measurement was performed at the ages of 36 and 40 weeks corrected age and 3, 6, 12 and 24 months of chronological age. The ratios of KL3 to crown to heel length (CHL), body weight (BW) and body surface area (BSA) were used as estimators of relative kidney length (RKL).
Results. A total of 1898 measurements were performed. In the full-term and near-term SGA infants (GA >36 weeks), RKL was similar to or even higher than that in AGA controls (P < 0.05 at 12 and 24 months). In two groups of preterm infants (GA 34–36, 28–34 weeks), RKL was lower than in AGA controls either after the first 6 months (GA 34–36 group, P < 0.05) or throughout the study period (GA 28–34 group, P < 0.05). The absolute KL was more severely affected in the preterm babies (GA <36 weeks) with BW <3rd percentile than in those of GA 3rd–10th percentile.
Conclusion. While in full-term and near-term SGA infants RKL is similar to or even higher than that of AGA infants, in smaller preterm babies (<36 weeks of GA) the RKL is impaired up to the second year of life.
Keywords: compensatory renal growth; growth restriction; kidney length; neonate; small-for-gestational age
Received for publication: 18.12.07
Accepted in revised form: 4. 7.08