The Kidney Volume-to-Birth Weight Ratio as a Surrogate Indicator for the Number of Nephrons in Extremely Low Birth Weight Preterm Infants

Abstract

Abstract Background: In humans, nephrogenesis is completed 4-6 weeks after birth. Premature birth interrupts renal development and maturation. In Neonatal Intensive Care Units (NICUs), harmful factors for premature infants increase the risk of hypertension, cardiovascular diseases, and renal failure in adulthood. The aim of this study is to identify preterm infants with a low number of nephrons at birth for appropriate surveillance and targeted care. Methods: Between March 2018 and March 2021, 29 extremely low birth weight premature infants (ELBW) were enrolled, including 25 appropriate for gestational age (AGA) and 4 small for gestational age (SGA). For each infant, body weight was recorded, and single and combined renal volume, as well as relative renal volume (the ratio of renal volume to body weight), were calculated using ultrasound. These measurements were taken one week after birth and every 2 weeks up to 38-40 weeks post-menstrual age (PMA), as well as at 6, 12, 18, and 24 months of PMA. Pearson's correlation coefficient was used to evaluate the strength of the correlation between renal volume and body weight for each infant. Results: The Pearson's coefficient showed a strong positive correlation for all infants from one week after birth to 38-40 weeks of PMA and from 38-40 weeks to 24 months of PMA. Conclusions: The ratio of kidney volume to birth weight appears to be a more reliable indicator for estimating the number of nephrons at birth. The identification of infants with a lower number of nephrons allows for more appropriate follow-up, thereby reducing the risk of developing kidney failure in adulthood.