Adult Renal Size is Not a Suitable Marker for Nephron Numbers: An Individual Patient Data Meta-Analysis

Abstract

Background: Renal size is often used as a marker for nephron numbers as estimation of glomerular numbers is not yet possible in vivo. However, the validity of an association between the two is questionable. As a proper marker for nephron number in an individual is needed in clinical practice, this study was designed to assess the association between renal size and nephron numbers. Methods: An individual patient data meta-analysis was performed on data retrieved with a PubMed and Embase search. Only studies were included that described individual human data on kidney size and nephron numbers determined by stereology, the gold standard methodology to estimate nephron numbers. As renal size increases until the end of puberty, and nephron numbers decline after the age of 60 years, only data from individuals aged 18-60 years without renal disease were included. Results: Six papers were identified that provided data on renal weight and nephron numbers from 114 individuals. Backward linear regression identified kidney weight and race as the only 2 significant factors explaining nephron numbers (R square 0.085, p=0.007). Controlling for race, there was a significant correlation between nephron number and kidney weight (r=0.231, r square=0.053, p=0.01). Conclusion: These data indicate that only ∼5% of the variation in nephron numbers is explained by differences in renal size. Renal size in adulthood should not be used as a marker for nephron numbers in an individual.

Early postnatal gentamicin and ceftazidime treatment in normal and food restricted neonatal wistar rats: Implications for kidney development

“…Nevertheless, the observed decrease in right kidney nephron numbers did not affect relative right kidney weight compared with the NF animals. This shows that kidney weight is a poor predictor for nephron number, an observation that was made previously by our group by analyzing human data (Bueters et al, ). In the end, although extrauterine growth restriction itself impairs kidney development, we did not find evidence that it modulated a potential toxicity response of gentamicin or ceftazidime treatment.…”

Does Extremely Low Birth Weight Predispose to Low-Renin Hypertension?

“…37 A subject-level meta-analysis of 190 adults (mean age, 51 years) demonstrated that the number of nephrons augments with kidney weight (r=0.17; P=0.03). 38 In our current study, we assumed that renal length reflected the number of nephrons. Even after adjustment for sex, age, and body height, kidney length was still 0.15 cm smaller in cases than controls.…”

The Impact of Kidney Development on the Life Course: A Consensus Document for Action

“…Nephron numbers have been shown to correlate with kidney weight, so renal mass has also been used as a surrogate marker for nephron numbers, although this relationship may be confounded by renal hypertrophy [51,68,69]. In all studies, glomerular numbers correlate inversely with glomerular volume, largely independent of gender and race, potentially reflecting compensatory glomerular hyperfiltration [55,61,70].…”