Female preterm indigenous Australian infants have lower renal volumes than males: a predisposing factor for end-stage renal disease?

Aim: Indigenous Australians have an increased risk of developing chronic kidney disease (CKD). Indigenous women have a higher rate of CKD than men. In a cohort of Indigenous and non-Indigenous preterm neonates, we assessed total renal volume (TRV) (a proxy indicator for nephron number). We hypothesized that there would be no difference in renal volume between these two groups at term corrected (37 weeks gestation). Methods: Normally grown preterm neonates less than 32 weeks of gestation were recruited and at term corrected dates, the neonates underwent renal ultrasonography (TRV measurements), urine microalbumin-creatinine ratio and serum analysis for Cystatin C measurement for estimated glomerular filtration rate (eGFR) calculation. Results: One hundred and five neonates (38 Indigenous; 67 non-Indigenous) were recruited. Indigenous neonates were significantly more premature and of lower birth weight. At term corrected age, Indigenous neonates had a significantly smaller TRV (18.5 (4.2) vs 21.4 (5.1) cm³; P = 0.027) despite no significant difference in body weight. Despite having a smaller TRV, there was no significant difference in eGFR between Indigenous and Non-indigenous neonates (47.8 [43.2-50.4] vs 46.2 [42.6-53.3] ml/min per 1.73 m²; P = 0.986). These infants achieve similar eGFR through hyperfiltration, which likely increases their future risk of CKD. There was no difference in microalbumin-creatinine ratio. Female Indigenous neonates, however, had significantly smaller TRV compared with Indigenous male neonates (15.9 (3.6) vs 20.6 (3.6) cm³; P = 0.006), despite no difference in eGFR, birth weight, gestational age, and weight at term corrected. Conclusion: The difference in TRV is likely to be an important risk factor for the difference in morbidity and mortality from renal disease reported between male and female Indigenous adults.