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

Abstract

Abstract In humans, nephrogenesis is completed 4–6 weeks after birth, resulting in a highly variable total number of nephrons, ranging from 200,000 to over 2 million. Premature birth disrupts the development and maturation of the kidneys, leading to a reduction in the final number of nephrons. Due to significant genetic variability in the number of nephrons among individuals, it is crucial to identify premature infants with fewer nephrons at birth as early as possible. These infants are more susceptible to developing renal failure with advancing age compared to those with a higher nephron endowment. Bedside ultrasound, an effective and non-invasive tool, is practical for identifying newborns with a lower nephron count. However, renal volume alone cannot reliably indicate the number of nephrons due to substantial variability at birth, influenced by gestational age when nephron maturation is incomplete. This variability in kidney volumes persists as newborns grow. In this observational study, we demonstrate that the ratio between renal volume and birth weight can serve as a valid indicator of nephron count in premature newborns with a birth weight less than 1000 grams. This finding could represent the basis for defining appropriate surveillance protocols and developing targeted therapeutic approaches.