Aim Review of current knowledge on assessing renal function in term and preterm neonates. Methods Literature review and analysis of own data. Results Prematurity, genetic, environmental and maternal factors may alter peak nephron endowment and life‐long renal function. Nephrogenesis continues until 34‐36 weeks of gestation, but it is altered with premature delivery. Variability of nephron endowment has a substantial impact on the clearance of renally excreted drugs. Postnatally, glomerular function rate (GFR) increases daily, doubles by two weeks, and slowly reaches full maturity at 18 months of age. Ideally, renal function biomarkers should be expressed as age‐independent z‐scores, and evidence suggests indexing these values to post‐conceptual age rather than chronological age. Newborn and maternal serum creatinine correlate tightly for more than 72 hours after delivery, rendering this biomarker unsuitable for the assessment of neonatal renal function. Cystatin C does not cross the placenta and may be the preferred biomarker in the neonate. Here, we provide preliminary data on the natural evolution of the cystatin C eGFR in infancy. Conclusion Cystatin C may be superior for GFR estimation in neonates, but the best approach to drug dosing of renally excreted drugs remains to be established.

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Nephrolithiasis is a condition in which crystals precipitate out of the urine forming kidney stones in the renal calyces and pelvis. Approximately 80% of stones are composed of calcium oxalate and calcium phosphate. In recent years, there has been a significant increase in the prevalence of nephrolithiasis across populations, specifically in that of the pediatric population. The etiology of stone disease is multifactorial, and includes environmental, dietary, hormonal, and genetic factors. Evidence for monogenic causation (also known as Mendelian or single-gene disorders) in nephrolithiasis includes the finding that 30% of children with stone disease report a positive family history, with monogenic nephrolithiasis accounting for approximately 30% of cases. Monogenic nephrolithiasis can occur in isolation or may be the result of an underlying genetic disorder including autosomal dominant hypocalcemia (ADH), primary hyperoxalurias, and hereditary hypophosphatemic rickets with hypercalciuria (HHRH), to name a few. Currently, there are 41 known genes that represent monogenic causes of human nephrolithiasis. Since early detection of these mutations can in some cases prevent the progression to end stage kidney disease in pediatric patients, establishing the genetic basis for nephrolithiasis is increasingly important. Here we provide an overview of kidney stone disease in children with a focus on monogenic causation in the pediatric population.