Significance Statement: Vesicoureteral reflux (VUR) is associated with progressive kidney disease. Familial aggregation supports a hereditary basis; however, its genetic architecture remains to be elucidated. The largest VUR copy number variant analysis and genome-wide association study to date accounts for multiple modes of inheritance and sex-specific effects in VUR, identifying three study-wide significant and five suggestive loci with large effects, containing canonical developmental genes including WDPCP and WNT5A. Results of experiments in mice support novel roles of Wnt5a in urogenital development. Altogether, 6% of patients carried high-risk genotypes. These findings have important implications for VUR screening. Background: Vesicoureteral reflux (VUR) is a common, familial genitourinary disorder, and a major cause of pediatric urinary tract infection (UTI) and kidney failure. The genetic basis of VUR is not well understood. Methods: A diagnostic analysis sought rare, pathogenic copy number variant (CNV) disorders among 1737 patients with VUR. A GWAS was performed in 1395 patients and 5366 controls, of European ancestry. Results: Altogether, 3% of VUR patients harbored an undiagnosed rare CNV disorder, such as the 1q21.1, 16p11.2, 22q11.21, and triple X syndromes ((OR, 3.12; 95% CI, 2.10 to 4.54; P=6.35×10⁻⁸) The GWAS identified three study-wide significant and five suggestive loci with large effects (ORs, 1.41–6.9), containing canonical developmental genes expressed in the developing urinary tract (WDPCP, OTX1, BMP5, VANGL1, and WNT5A). In particular, 3.3% of VUR patients were homozygous for an intronic variant in WDPCP (rs13013890; OR, 3.65; 95% CI, 2.39 to 5.56; P=1.86×10^–9). This locus was associated with multiple genitourinary phenotypes in the UK Biobank and eMERGE studies. Analysis of Wnt5a mutant mice confirmed the role of Wnt5a signaling in bladder and ureteric morphogenesis. Conclusions: These data demonstrate the genetic heterogeneity of VUR. Altogether, 6% of patients with VUR harbored a rare CNV or a common variant genotype conferring an OR >3. Identification of these genetic risk factors has multiple implications for clinical care and for analysis of outcomes in VUR.

The genetic causes of multiple congenital anomalies are incompletely understood. Here, we report novel heterozygous predicted loss-of-function (LoF) and predicted damaging missense variants in the WW domain binding protein 11 (WBP11) gene in seven unrelated families with a variety of overlapping congenital malformations, including cardiac, vertebral, tracheo-esophageal, renal and limb defects. WBP11 encodes a component of the spliceosome with the ability to activate pre-messenger RNA splicing. We generated a Wbp11 null allele in mouse using CRISPR-Cas9 targeting. Wbp11 homozygous null embryos die prior to E8.5, indicating that Wbp11 is essential for development. Fewer Wbp11 heterozygous null mice are found than expected due to embryonic and postnatal death. Importantly, Wbp11 heterozygous null mice are small and exhibit defects in axial skeleton, kidneys and esophagus, similar to the affected individuals, supporting the role of WBP11 haploinsufficiency in the development of congenital malformations in humans. LoF WBP11 variants should be considered as a possible cause of VACTERL association as well as isolated Klippel-Feil syndrome, renal agenesis or esophageal atresia.

Background. Acute kidney injury (AKI) occurs in up to 30% of pediatric intensive care unit (PICU) patients and is associated with a high mortality rate. Objectives. The objective of the study was to evaluate factors associated with the outcome and to identify the prognostic factors in children receiving continuous renal replacement therapy (CRRT). Material and methods. This was a retrospective, single-center study, including 46 patients. Results. Logistic regression analysis demonstrated significant effects on patient survival exerted by the percentage of fluid overload (FO%) (odds ratio (OR): 1.030; p = 0.044). In the group of patients with FO% < 25%, the mortality was 33.3%, and in the FO%>= 25% group, the mortality was 67.9% (p < 0.001). The probability of death without multi-organ failure (MOF) was 13%, while with MOF it was 74%. There was no difference in the duration of hospitalization between the CRRT patients (mean: 21.9 days) and the general population of children hospitalized in PICU in the same period (n = 3,255; mean: 25.4 days); however, a significant difference was noted in mortality between the 2 groups of patients (54% vs 6.5%; p < 0.001). Conclusions. The mortality of PICU CRRT patients is more than 8-fold higher than the mortality of the total PICU population. Coexisting MOF increases the mortality almost 6 times. The mortality of children with FO% >= 25% was more than 2-fold higher than the mortality of children with FO% < 25%.

The aim of the study was to evaluate the influence of the intensity of mesangial C3 deposits in kidney biopsy and the serum C3 level on the clinical course and outcomes of IgAN in children. The study included 148 children from the Polish Pediatric IgAN Registry, diagnosed based on kidney biopsy. Proteinuria, creatinine, IgA, C3 were evaluated twice in the study group, at baseline and the end of follow-up. Kidney biopsy was categorized using the Oxford classification, with a calculation of the MEST-C score. The intensity of IgA and C3 deposits were rated from 0 to +4 in immunofluorescence microscopy. The intensity of mesangial C3 > +1 deposits in kidney biopsy has an effect on renal survival with normal GFR in children with IgAN. A reduced serum C3 level has not been a prognostic factor in children but perhaps this finding should be confirmed in a larger group of children.

Background/Objectives: Hemolytic uremic syndrome (HUS) is a known cause of acute kidney injury in children, but there are few recent reports on its epidemiology and outcome. We aimed to investigate trends in the incidence and the long-term outcomes of both Shiga toxin-producing Escherichia coli -HUS (STEC-HUS) and atypical HUS (aHUS) in Poland over the last 12 years (2012—2023), based on the Polish Pediatric HUS and Pediatric Renal Replacement Therapy (RRT) Registries. Methods: A total of 436 patients (301 with STEC-HUS and 135 with aHUS) were included. Results: The incidence of STEC-HUS increased during the observation period, with a mean of 3.9 cases per million age-related population (marp). The incidence of aHUS was relatively constant with a mean of 1.8/marp. The majority of patients fully recovered, although kidney sequelae were observed at 5-year follow-ups in 31% of children with STEC-HUS, 57% of aHUS subjects in the pre-eculizumab era, and 37% of aHUS subjects who had received eculizumab. The overall mortality rate was 2% for STEC-HUS and 3.7% for aHUS, with no deaths reported in children on eculizumab and mortality mainly attributed to neurological damage. A decreasing incidence of chronic kidney disease stage 5 (CKD5) due to HUS was observed. Conclusions: Despite an unchanging incidence of aHUS and an increasing incidence of STEC-HUS, the kidney outcomes of both diseases have improved significantly over the last 12 years. Mortality from HUS has dropped due to improved symptomatic treatment and the introduction of anti-C5 therapy. The development of CKD5 in childhood as a consequence of HUS has become exceptional.

Background/Aims: The recent improvements of management of patients in pediatric intensive care units (PICU) are associated with improved outcome. However, this decrease in mortality is associated with an increased number of children with acute kidney injury (AKI), especially in patients with multiorgan failure. Methods: The report presents a retrospective analysis of 25 cases of AKI (assessed based on the pRIFLE criteria) in PICU within 7 years. Results: AKI was diagnosed in 1.24% of all hospitalized children. AKI percentage duration (as compared to the total hospitalization time) in the children who died vs. the survivors was 79.55% vs. 46.19%, respectively (p<0.05). The mortality rate of AKI patients was 40% which was 4.4-times higher as compared to the total mortality rate in PICU. The final cumulative survival ratio (FCSR) of patients meeting the oliguria criterion (which was met in 48% of AKI patients) was 37% vs. 49% in non-oliguric children. Averaged urine output values in the first week of hospitalization in the deceased vs. survivors were 1.49 vs. 2.57 ml/kg/h, respectively (p<0.05). Conclusions: Oliguria should not be considered as a sensitive parameter for AKI diagnosing in children below one year of age. A decreased mean urine output in the first week of PICU hospitalization (less than 1.4 ml/kg/h) should be considered as a poor prognostic factor. In many cases AKI was diagnosed too infrequently and too late.