Renal Parenchymal Thickness as a Measure of Renal Growth in Low-Birth-Weight Infants versus Normal-Birth-Weight Infants

Low birth weight (LBW, <2500 g) infants have a reduced number of glomeruli and nephrons and, therefore, smaller kidneys. The purpose of this pilot study was to determine whether renal parenchymal thickness might be a better indicator of renal growth. We carried out a pilot study over 12 mo to determine whether renal parenchymal thickness could be used to detect differences in renal growth between LBW and normal birth weight (NBW, 2500-4500 g) infants. Thirty-eight term infants (12 LBW and 26 NBW) underwent renal ultrasound. Parenchymal thickness, length, transverse diameter and antero-posterior diameter were measured. Mean renal parenchymal thickness was significantly lower in LBW infants than in NBW infants. Renal parenchymal thickness was closely correlated with an increase in renal volume (r = 0.76, p < 0.0001). Renal parenchymal thickness is a single measurement that could potentially be a more useful and accurate approach to monitoring renal growth in growth-restricted infants than renal volume.