Febrile urinary tract infections (fUTIs) are among the most common severe infections in the pediatric population, posing a significant risk to kidney health. The pathophysiology of fUTIs involves the direct bacterial invasion of kidney tissue, which triggers an inflammatory response. While this response is effective in eradicating the infection, it can also cause substantial kidney damage at multiple levels. In this review, we explore the various forms of kidney involvement in fUTIs, along with their clinical, radiological, and biochemical presentations. We also discuss the implications of these events for the long-term prognosis of kidney function. Understanding these manifestations can assist clinicians in making prompt diagnoses and initiating appropriate treatment to minimize complications such as sepsis, kidney scarring, and long-term kidney damage. Graphical Abstract

We investigated prevalence of and factors associated with acute kidney injury (AKI) in a group of patients hospitalized with viral bronchiolitis. We retrospectively enrolled 139 children (mean age = 3.2 ± 2.1 months; males = 58.9%) hospitalized for viral bronchiolitis in a non-pediatric intensive care unit (PICU) setting. The Kidney Disease/Improving Global Outcomes creatinine criterion was used to diagnose AKI. We estimated basal serum creatinine by back-calculating it by Hoste (age) equation assuming that basal eGFR were the median age-based eGFR normative values. Univariate and multivariate logistic regression models were used to explore associations with AKI. Out of 139 patients, AKI was found in 15 (10.8%). AKI was found in 13 out of 74 (17.6%) patients with and in 2 out of 65 (3.1%) without respiratory syncytial virus (RSV) infection (p = 0.006). No patient required renal replacement therapies, while 1 out of 15 (6.7%) developed AKI stage 3, 1 (6.7%) developed AKI stage 2, and 13 (86.6%) developed AKI stage 1. Among the 15 patients with AKI, 13 (86.6%) reached the maximum AKI stage at admission, 1 (6.7%) at 48 h, and 1 (6.7%) at 96 h. At multivariate analysis, birth weight < 10th percentile (odds ratio, OR = 34.1; 95% confidence interval, CI = 3.6–329.4; p = 0.002), preterm birth (OR = 20.3; 95% CI = 3.1–129.5; p = 0.002), RSV infection (OR = 27.0; 95% CI = 2.6–279.9; p = 0.006), and hematocrit levels > 2 standard deviation score (SDS) (OR = 22.4; 95% CI = 2.8–183.6; p = 0.001) were significantly associated with AKI.Conclusion: About 11% of patients hospitalized with viral bronchiolitis in a non-PICU setting develop an AKI (frequently mild in degree). Preterm birth, birth weight < 10th percentile, hematocrit levels > 2SDS, and RSV infection are significantly associated with AKI in the setting of viral bronchiolitis. What is Known:• Viral bronchiolitis affects children in the first months of life and in 7.5% of cases it can be complicated by acute kidney injury (AKI).• No studies investigated associations with AKI in infants hospitalized for viral bronchiolitis. What is New:• About 11% of patients hospitalized with viral bronchiolitis can develop an AKI (frequently mild in degree).• Preterm birth, birth weight <10th percentile, hematocrit levels > 2 standard deviation score, and respiratory syncytial virus infection are associated with AKI development in infants with viral bronchiolitis.

Voiding cystourethrography (VCUG) is indicated for evaluating the anatomy of the urethra and bladder. It is primarily used to diagnose vesicoureteral reflux (VUR) and posterior urethral valves (PUV), especially in cases of febrile urinary tract infections (UTIs), significant ureteral dilation on ultrasound, and—in continent children—urinary symptoms suggestive of infravesical obstruction. VCUG exposes children to a non-negligible dose of radiation and requires urethral catheterization, which can be painful—particularly in males—and carries a low but present risk of post-procedural UTI. Despite its widespread use, VCUG can miss VUR in up to 50% of cases. Moreover, recent studies report that preoperative suspicion of PUV on VCUG was present in only 46% of non-toilet-trained and 59% of toilet-trained males, likely due to challenges in interpreting the VCUG findings. In this review, we will highlight the clinical value, challenges, and areas of debate surrounding this diagnostic test, and offer practical tips to optimize its performance. Graphical abstract

We previously developed and retrospectively validated the estimated percentage of heart rate variation (EHRV) as a predictor of the composite outcome of ≥ 5% dehydration and/or acute kidney injury (AKI) in non-febrile children. The current study aimed to prospectively validate EHRV as a predictor for dehydration or AKI in a different cohort of children attending the Pediatric Emergency Department. From July 2022 to August 2023, 256 pediatric patients aged 0–18 years attending the Pediatric Emergency Department were enrolled. EHRV was calculated as follows: [(HR at admission − 50th percentile of HR for age and sex)/HR at admission] × 100. Dehydration was categorized as < 5% or ≥ 5% fluid deficit. AKI was defined according to KDIGO creatinine criteria. Statistical analyses included receiver-operating characteristic (ROC) curves and logistic regression analysis. Among enrolled patients, 52 had ≥ 5% dehydration, 50 had AKI, and 16 had both conditions. EHRV demonstrated significant predictive ability for both ≥ 5% dehydration (AUROC = 0.71; 95% confidence interval (CI), 0.63–0.78; p < 0.001) and AKI (AUROC = 0.78; 95% CI, 0.71–0.84; p < 0.001). An EHRV > 24.5% was associated with an increased odds ratio (OR), adjusted for confounders, of ≥ 5% dehydration (OR = 3.5; 95% CI, 1.6–8.0; p = 0.003) and AKI (OR = 3.4; 95% CI, 1.6–7.3; p = 0.002). The sensitivity and specificity of this cut-off were 34% and 83% for ≥ 5% dehydration and 36% and 84% for AKI, respectively.Conclusions: This study prospectively validates the clinical utility of EHRV in predicting dehydration and AKI in a pediatric emergency care setting. An EHRV > 24.5% could serve as a marker for suspecting dehydration or AKI. Further validation across diverse patient populations and settings is needed. What is Known:• An increased heart rate (HR) is a readily detectable sign of dehydration in children.• In a retrospective validation cohort, an estimated HR variation (EHRV) greater than 24.5% compared to the 50th percentile of HR was predictive of ≥ 5% dehydration and/or acute kidney injury (AKI) in non-febrile patients. What is New:• We prospectively validated the clinical utility of EHRV in predicting dehydration and AKI in a pediatric emergency care setting.• We confirmed that an EHRV greater than 24.5% is associated with increased odds of ≥ 5% dehydration and AKI.

Background: Screening for secondary hypertension is not recommended for all hypertensive patients, but missing these cases is critical. We aimed to (i) assess hypertension causes in a cohort of hypertensive children, (ii) determine the costs and contributions of an extended diagnostic work-up to screen for secondary hypertension, and (iii) compare the performance of a “short diagnostic work-up” with the protocols of the American Academy of Pediatrics (AAP) and European Society of Hypertension (ESH). Methods: We conducted a retrospective, single-center study of 70 hypertensive patients aged 1–18 years. All underwent an extended work-up to exclude secondary hypertension. Diagnostic findings, test counts, and costs were analyzed. A short work-up (serum creatinine, fasting glucose, electrolytes, urinalysis, kidney ultrasound (US), and renal artery Doppler US), as well as the AAP and ESH protocols, was evaluated for performance and costs. Results: Secondary hypertension was identified in 29 patients (41.4%). The extended protocol identified or excluded secondary causes in all patients. Kidney US had the highest diagnostic yield (37.1%). The short work-up and ESH protocol identified all secondary cases, whereas the AAP protocol missed 15 diagnoses. The extended protocol cost € 17,715.60 (€ 253.08 per patient). Direct cost savings were 64.3% with the short work-up, 92.4% with the AAP protocol, and 76.2% with the ESH protocol. Conclusions: Primary is more common than secondary hypertension in children, with kidney parenchymal disease being the leading secondary cause. As recommended by guidelines, a simplified, focused work-up may offer a cost-effective alternative to extensive screening while maintaining diagnostic accuracy. Graphical

Background/Objectives: Unlike rhabdomyolysis and neuroleptic malignant syndrome (NMS), massive asymptomatic creatine kinase elevation (MACKE) represents a condition commonly detected during routine screening in patients receiving antipsychotic drugs. In particular, current evidence indicates a greater incidence of this condition in patients without signs of NMS, rhabdomyolysis, or other causes of CK increase during exposure to second-generation antipsychotics (SGAs) than first-generation antipsychotics (FGAs) with a variable onset and duration. Although its pathophysiology is still not fully elucidated, MACKE has usually been recognized as a self-limiting condition, but drug discontinuation might also be required to successfully revert it. Overall, knowledge in this field is mainly extrapolated from adult data, while similar evidence in youths is still limited. As clinicians might often deal with MACKE, its understanding needs to be expanded to avoid misdiagnosis, potentially leading to wasteful healthcare spending and unfavorable patient outcomes. Methods: By reporting the first case of MACKE in an adolescent receiving an SGA, namely paliperidone, we also aimed to provide a comprehensive overview of this medical condition. Conclusions: Making a MACKE diagnosis is essential since its relevant clinical and economic implications are mainly related to unnecessary closer laboratory monitoring or therapeutic changes (e.g., drug discontinuation or switch to another medication).