Estimating Number of Nephrons in Living Pediatric Patients Using Nephrectomy Specimens

Introduction: The number of nephrons is a critical determinant of renal health, because chronic kidney disease often results from a reduction in functional nephrons. Variability in the number of nephrons is influenced by genetic, racial, prenatal, and postnatal factors. Estimating the number of nephrons is crucial for establishing a baseline, before the onset of age-related nephron loss. This study aimed to estimate number of nephrons in pediatric patients by using imaging and histological techniques. Methods: This retrospective study included pediatric patients with renal tumors, who are undergoing nephrectomy and contrast-enhanced computed tomography (CT) between January 2010 and January 2021. Postsurgical renal tissue specimens were fixed, stained, and scanned into high-resolution digital images. Nonsclerotic glomerular density was calculated using stereological methods, whereas renal cortical volume was measured using ITK-SNAP software on CT images. The total number of nephrons was estimated based on cortical volume and glomerular density. Statistical analyses were conducted to identify the correlations between the number of nephrons and clinical factors. Results: Twenty-one children met the inclusion criteria. The cohort comprised 13 boys (61.9%) and 8 girls (38.1%) with a median age at nephrectomy of 2.5 years. The median number of nephrons per kidney was 925,000 (interquartile range [IQR]:845,000-1,020,000). Higher number of nephrons was significantly correlated with older age at nephrectomy (r = 0.47, P = 0.036) and larger body surface area (BSA; r = 0.45, P = 0.034). Conclusion: This study offers new insights into pediatric nephron endowment, emphasizing the importance of early nephron assessment for predicting long-term renal outcomes.