607 - Estimation of Nephron Number in Living Pediatric Kidneys: Validation Through Nephrectomy Specimens

Daishi Hirano, The Jikei university school of medicine, Ohta-ku, Tokyo, Japan; Saori Miwa, the Jikei University School of Medicine, Minato-ku, Tokyo, Japan; Haruhide Sakaguchi, The Jikei University School of Medicine, Minato-ku, Tokyo, Japan; Akira Ito, Jikei University, Machida, Tokyo, Japan; Chisato Umeda, Department of Pediatrics, the Jikei University School of Medicine, Minato-ku, Tokyo, Japan; Yoichi Takemasa, The Jikei University School of Medicine, yokohama, Kanagawa, Japan; Aya Saito, Department of Pediatrics, the Jikei University School of Medicine, Minato, Tokyo, Japan; Yosuke Shoji, The Jikei University School of Medicine, Huchu -shi, Tokyo, Japan; Shiho Yoshizawa, The Jikei University School of Medicine, Minato-ku, Tokyo, Japan; Kimihiko Oishi, The Jikei University School of Medicine, Tokyo, Tokyo, Japan

Background: Nephron endowment represents a fundamental determinant of kidney function and long-term kidney health. Chronic kidney disease (CKD) primarily occurs due to a reduction in functional nephrons. Recent studies highlighted significant variability in nephron numbers influenced by genetic, racial, prenatal, and postnatal factors. The progressive decline in functional nephrons serves as the pathophysiological cornerstone of chronic kidney disease (CKD), a global health burden with significant pediatric implications. Estimating nephron numbers in children is crucial to exclude age-related nephron loss and provide a baseline for future renal function assessments.

Objective: The primary objective of this study was to estimate total nephron number in pediatric patients by combining imaging and histological analysis of nephrectomy specimens.

Design/Methods: This retrospective study included pediatric patients with renal tumors undergoing nephrectomy and contrast-enhanced computed tomography (CT) between January 1, 2010, and January 31, 2021. Postsurgical renal tissue specimens were fixed, stained, and scanned into high-resolution digital images. The density of nonsclerotic glomeruli was calculated using stereological methods. Renal cortical volume was measured using ITK-SNAP software on CT images. The total nephron number was estimated using cortical volume and glomerular density. Statistical analyses were performed to identify correlations between nephron number and clinical factors.

Results: Twenty-one children met the inclusion criteria. The cohort consisted of 13 boys (61.9%) and 8 girls (38.1%), with a median age at nephrectomy of 2.5 years (IQR, 1.4-3.8 years). The median nephron number per kidney was 950,846 (IQR, 868,760-1,049,293). No significant correlations were identified between nephron number and gestational age or birth weight. However, nephron number was significantly positively correlated with age at nephrectomy (ρ = 0.47, P = 0.034), body surface area (ρ = 0.45, P = 0.036), and renal cortical volume (ρ = 0.51, P = 0.034).

Conclusion(s): This study provided new insights into nephron endowment in children, demonstrating higher nephron numbers compared to previous studies in adults. These findings highlight the importance of early nephron assessment in predicting long-term renal outcomes and may provide a basis for more accurate estimations of nephron endowment across diverse populations.