Ultrasonographic study of initial size and postnatal growth of kidneys in preterm infants.
BACKGROUND
Preterm birth is known to be associated with risks of impaired nephrogenesis.


OBJECTIVE
To determine the normal range of renal sizes at birth in preterm infants as well as their short-term postnatal renal growth, to assess the correlation between initial renal size and growth parameters at birth and to compare the initial and serial renal sizes between appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA) preterm infants.


METHODS
Initial ultrasonography (US) was prospectively performed in 125 preterm infants within the first 72 h of life and every 2 weeks thereafter until a postmenstrual age (PMA) of 37 weeks was reached. Correlation between renal size and growth parameters was investigated. Renal lengths of AGA and SGA preterm infants were compared with those of age-matched fetuses described in the literature.


RESULTS
The renal sizes at birth in preterm infants are presented. Multiple regression analysis showed the strongest correlation between initial renal size and birth weight (p < 0.0001). Initial renal lengths of AGA infants were not significantly different from those of age-matched fetuses at ≥30 weeks' gestational age (GA), whereas those of SGA infants were significantly smaller at ≥28 weeks' GA. Serial renal lengths of SGA infants were significantly smaller than fetal renal lengths at ≥30 weeks' GA.


CONCLUSIONS
With US, the normal range of initial renal sizes of AGA preterm infants was defined according to GA. In contrast to AGA infants, SGA infants showed smaller initial renal sizes and no significant catch-up growth until a PMA of 37 weeks.
Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul, Korea.
Yun-Jung
YJ
Lim
Woo Sun
WS
Kim
Han-Suk
HS
Kim
Young Hun
YH
Choi
Jung-Eun
JE
Cheon
Su-Mi
SM
Shin
In-One
IO
Kim
Jung-Hwan
JH
Choi
D000367:Age Factors; D001724:Birth Weight; D016022:Case-Control Studies; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D007236:Infant, Small for Gestational Age; D007668:Kidney / Q000000981:diagnostic imaging* / Q000254:growth & development*; D009929:Organ Size; D011237:Predictive Value of Tests; D011446:Prospective Studies; D014463:Ultrasonography