Pediatric nephrotic syndrome is a clinical condition characterized by severe proteinuria, hypoalbuminemia, hyperlipidemia, and generalized edema, most commonly affecting children aged 2 and 6 years. Although standard oral steroid therapy is effective in managing most cases, relapses are common during childhood. Nephrotic syndrome presents significant challenges due to frequent relapses and the potential side effects of long-term drug therapy. In Korea, the absence of a unified national clinical guideline has led physicians to manage pediatric nephrotic syndrome based on diverse clinical guidelines and individual clinical judgment. To address this, the Korean Society of Pediatric Nephrology has developed an evidence-based guideline specifically tailored to the Korean healthcare system. This guideline provides recommendations for the diagnosis and management of steroid-sensitive nephrotic syndrome in children under the age of 18 years.

The incidence of pediatric urinary tract infections (UTIs) caused by extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) has increased worldwide; however, optimal empirical treatment strategies remain controversial. This review addresses the prevalence, virulence factors, clinical impacts, and antibiotic management of UTIs caused by ESBL-PE in children. The prevalence of ESBL-PE among pediatric UTI isolates exceeds 20% in many regions, including Korea. No significant differences exist in the clinical manifestations between ESBL(+) UTIs and other UTIs. Despite in vitro resistance, third-generation cephalosporins frequently achieve therapeutic success because of their high urinary drug concentrations. Based on the patient's condition and risk factors, an initial empirical antibiotic should be selected, and early de-escalation and carbapenem-sparing strategies are essential to balance treatment efficacy and resistance prevention. Therefore, Korean guidelines for the treatment of pediatric UTIs are required.

Purpose: Sepsis is a leading cause of pediatric critical illness and a major contributor to acute kidney injury (AKI). Sepsis-associated AKI (SA-AKI) worsens outcomes, yet current diagnostic criteria based on serum creatinine and urine output lack sensitivity for early detection. This study evaluated the diagnostic performance of neutrophil gelatinase-associated lipocalin (NGAL), angiopoietin-2, and syndecan-1 for early identification of SA-AKI in children with sepsis. Methods: A prospective nested case-control study was conducted in children aged 1-18 years with sepsis. Participants were classified into SA-AKI and non-SA-AKI groups using pediatric Risk, Injury, Failure, Loss, End-stage Renal Disease (pRIFLE) criteria based on estimated creatinine clearance index (eCCI). Blood and urine samples were collected at baseline, 12, 24, and 48 hours to measure NGAL, angiopoietin-2, and syndecan-1 levels by enzyme-linked immunosorbent assay. Diagnostic accuracy was assessed using receiver operating characteristic (ROC) analysis. Results: Of 23 children enrolled, eight (34.8%) developed SA-AKI. Baseline creatinine, eCCI, urinary NGAL, and mean corpuscular volume (MCV) differed significantly between groups, whereas angiopoietin-2 and syndecan-1 did not. ROC analysis showed that 24-hour eCCI (area under the curve [AUC]=1.000; sensitivity 100%; specificity 100%) and 12- to 24-hour urinary NGAL (AUC=0.900; sensitivity 87.5%; specificity 86.7%) were the strongest predictors. MCV had moderate accuracy (AUC=0.767). Urinary NGAL correlated negatively with eCCI (r=-0.67). Conclusions: Urinary NGAL measured within 12-24 hours is a reliable early biomarker for SA-AKI in pediatric sepsis, complementing eCCI and pRIFLE criteria to enhance early diagnosis and management.

Purpose: This study aimed to evaluate the progression of renal function and clinical outcomes during the first year of life in infants with congenital abnormalities of the kidney and urinary tract (CAKUTs) detected via antenatal ultrasonography. Methods: This retrospective, observational cohort study included 55 infants, categorized into two groups: those with collecting system anomalies (CSAs) and those with renal parenchymal malformations (RPMs). The primary outcomes were the incidences of acute kidney injury (AKI) and chronic kidney disease (CKD) as well as the prognostic indicators linking the antenatal and postnatal periods. Results: CSAs were more common in both the antenatal and postnatal periods, with incidence rates of 54.5% and 56.4%, respectively. Hydronephrosis was the most frequently detected CAKUT type during the antenatal period (47.2%). Multicystic dysplastic kidney was the most predominant lesion in both antenatal and postnatal diagnoses within the RPM group, accounting for 38.2%. Although the incidence of AKI did not differ significantly between the two groups, CKD was more prevalent in the RPM group (P<0.05). Gestational age, presence of oligohydramnios, and several ultrasonographic findings (including loss of corticomedullary differentiation, bladder trabeculation, and cysts) were significantly associated with the development of AKI. In multivariate logistic regression analysis, loss of corticomedullary differentiation remained an independent predictor of AKI (odds ratio, 13.5; 95% confidence interval, 1.8-100.0; P=0.011). Conclusions: Loss of corticomedullary differentiation on postnatal ultrasound is an important predictor of AKI, highlighting the need to investigate its relevance during the prenatal period.

Milky white serum in infancy is rare and usually reflects a metabolic disorder; renal causes are distinctly uncommon. We report a 7-month-old male infant who presented with generalized edema and strikingly lipemic serum. Examination revealed lipemia retinalis, while investigations showed extreme hypertriglyceridemia and nephrotic range proteinuria. Initial tests also suggested hyperproteinemia and hyperphosphatemia, but repeat measurements confirmed hypoalbuminemia. Whole exome sequencing identified compound heterozygous variants in the NPHP1 gene, comprising one pathogenic variant and one variant of uncertain significance. Although parental testing was not performed, the combined clinical and genetic findings supported a diagnosis of congenital nephrotic syndrome. Parental testing, though not performed, combined clinical and genetic findings supported a diagnosis of congenital nephrotic syndrome. This case highlights that, although rare, congenital nephrotic syndrome can present with severe dyslipidemia and milky serum in infancy, and underscores the need to recognize potential laboratory estimation errors in lipemic samples.

Calcineurin inhibitors remain a cornerstone in the treatment of steroid-resistant nephrotic syndrome (SRNS) in pediatric patients. Hypomagnesemia, a clinically relevant yet frequently neglected complication of calcineurin inhibitors like cyclosporine, may exacerbate hypokalemia and induce neuromuscular symptoms such as tetany, challenging patient management. However, serum magnesium is not routinely monitored in many clinical settings. A 46-month-old girl with SRNS had been receiving highdose cyclosporine for over 1 year. She was admitted with vomiting, diarrhea, generalized edema, and hypovolemic shock. After stabilization, she developed persistent hypokalemia refractory to supplementation, despite normal renal function and basic electrolyte panel. On hospital day 10, carpal-type tetany prompted the first measurement of serum magnesium, revealing severe hypomagnesemia (0.14 mmol/L). Cyclosporine was temporarily withheld, and intravenous then oral magnesium was administered. Tetany resolved within 48 hours, and both serum magnesium and potassium levels normalized. This case highlights the risk of delayed recognition of symptomatic hypomagnesemia during prolonged cyclosporine therapy in children. Tetany was the first neurological manifestation of a preventable complication. Current guidelines lack clear recommendations regarding magnesium surveillance in pediatric SRNS receiving cyclosporin. This case underscores a critical gap in practice and calls for the integration of magnesium monitoring into standard care for this vulnerable population.