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Urinary stasis is a risk factor for recurrent urinary tract infection (UTI). Homozygous mutant Megabladder (Mgb-/-) mice exhibit incomplete bladder emptying as a consequence of congenital detrusor aplasia. We hypothesize that this predisposes Mgb-/- mice to spontaneous and experimental UTI. Mgb-/-, Mgb+/-, and wild-type female mice underwent serial ultrasound and urine cultures at 4, 6, and 8 weeks to detect spontaneous UTI. Urine bacterial isolates were analyzed by Gram stain and speciated. Bladder stones were analyzed by x-ray diffractometry. Bladders and kidneys were subject to histologic analysis. The pathogenicity of coagulase-negative Staphylococcus (CONS) isolated from Mgb-/- urine was tested by transurethral administration to culture-negative Mgb-/- or wild-type animals. The contribution of urinary stasis to CONS susceptibility was evaluated by cutaneous vesicostomy in Mgb-/- mice. Mgb-/- mice develop spontaneous bacteriuria (42%) and struvite bladder stones (31%) by 8 weeks, findings absent in Mgb+/- and wild-type controls. CONS was cultured as a solitary isolate from Mgb-/- bladder stones. Bladders and kidneys from mice with struvite stones exhibit mucosal injury, inflammation, and fibrosis. These pathologic features of cystitis and pyelonephritis are replicated by transurethral inoculation of CONS in culture-negative Mgb-/- females, whereas wild-type animals are less susceptible to CONS colonization and organ injury. Cutaneous vesicostomy prior to CONS inoculation significantly reduces the quantity of CONS recovered from Mgb-/- urine, bladders, and kidneys. CONS is an opportunistic uropathogen in the setting of urinary stasis, leading to enhanced UTI incidence and severity in Mgb-/- mice.

Congenital obstructive nephropathy is a common cause of chronic kidney disease and a leading indication for renal transplant in children. The cellular and molecular responses of the kidney to congenital obstruction are incompletely characterized. In this study, we evaluated global transcription in kidneys with graded hydronephrosis in the megabladder (mgb (-/-)) mouse to better understand the pathophysiology of congenital obstructive nephropathy. Three primary pathways associated with kidney remodeling/repair were induced in mgb (-/-) kidneys independent of the degree of hydronephrosis. These pathways included retinoid signaling, steroid hormone metabolism, and renal response to injury. Urothelial proliferation and the expression of genes with roles in the integrity and maintenance of the renal urothelium were selectively increased in mgb (-/-) kidneys. Ngal/Lcn2, a marker of acute kidney injury, was elevated in 36% of kidneys with higher grades of hydronephrosis. Evaluation of Ngal(high) versus Ngal(low) kidneys identified the expression of several novel candidate markers of renal injury. This study indicates that the development of progressive hydronephrosis in mgb (-/-) mice results in renal adaptation that includes significant changes in the morphology and potential functionality of the renal urothelium. These observations will permit the development of novel biomarkers and therapeutic approaches to progressive renal injury in the context of congenital obstruction.

Background: Congenital obstructive nephropathy (CON) is a leading cause of pediatric chronic kidney disease (CKD). Despite optimal surgical and medical care, there is a high rate of CKD progression. Better understanding of molecular and cellular changes is needed to facilitate development of improved biomarkers and novel therapeutic approaches in CON. Methods: The megabladder (mgb) mouse is an animal model of CKD with impaired bladder emptying, hydronephrosis, and progressive renal injury. In this study, we characterize a particular microRNA, miR-205, whose expression changes with the degree of hydronephrosis in the mgb −/− kidney. Results: Expression of miR-205 is progressively increased in the adult mgb −/− mouse with worsening severity of hydronephrosis. miR-205 expression is correlated with altered expression of cytokeratins and uroplakins, which are markers of cellular differentiation in urothelium. We describe the spatial pattern of miR-205 expression, including increased expression in renal urothelium and novel miR-205 expression in medullary collecting duct epithelium in the congenitally obstructed kidney. Conclusion: miR-205 is increased with severity of CON and CKD in the mgb −/− mouse and may regulate urothelial differentiation.

In children, unilateral multicystic dysplastic kidney (MCDK) is one of the most frequently identified urinary tract abnormalities. A variety of proposed etiologies has been associated with the underlying pathogenesis of MCDK. These include genetic disturbances, teratogens, in utero infections, and urinary outflow tract obstruction. From 5–43% of the time, MCDK has associated genito-urinary anomalies, both structural and functional in nature. A review of the literature reveals that involution rates are reported to be 19–73%, compensatory hypertrophy of the contralateral kidney occurs from 24–81% of the time, and estimated glomerular filtration rates (GFRs) (by the Schwartz formula) range from 86–122 ml/min per 1.73 m 2 body surface area. Most authors suggest serial ultrasonography to monitor contralateral growth, routine blood pressure monitoring, and a serum creatinine monitoring algorithm. The risk of hypertension in those with MCDKs does not appear to be greater than that of the general population, and the rates of malignant transformation of MCDK are small, if at all increased, in comparison with those in the general population. If the patient develops a urinary tract infection or has abnormalities of the contralateral kidney, shown on ultrasound, a voiding cystourethrogram is recommended. Finally, the body of literature does not support the routine surgical removal of MCDKs.

Congenital obstructive nephropathy is the leading cause of chronic renal disease in children. As a result, it represents a tremendous societal burden in terms of morbidity and mortality, as well as in health care expenses of caring for children with chronic kidney disease and end-stage renal disease. The various diagnostic, prognostic, and therapeutic challenges associated with congenital obstructive nephropathy highlight the importance of developing effective experimental models for studying this disease process. In this review, we define the clinical entity that is congenital obstructive nephropathy, outline the current standards of diagnosis and care, and discuss the utilization of current experimental models designed to help clarify some of the clinical conundrums associated with this important disease.

Osteogenesis imperfecta (OI) is an inherited disorder characterized by bone fragility and low bone mass. Low bone density and fracture is a cause of morbidity. Limited data exists on bisphosphonate treatment in patients under 24 months of age. The objective of the study was to examine the safety and efficacy of pamidronate in children under 24 months with OI. To do so, we carried out a retrospective chart review and analysis of OI patients started on intravenous pamidronate under 24 months of age. Pamidronate was administered in three-day cycles. Growth, the number of fractures, and lumbar bone mineral densities were recorded both prior to and after treatment initiation. A total of 18 patients were reviewed. Five were classified as OI type I, seven were type III, and six were type IV. The mean age at treatment initiation was 12 months (range 11 days to 23 months). The mean lumbar z score at baseline was −3.63, which improved to −1.53 at one year ( P  < 0.01) and 0.79 ( P  < 0.01) at the end of the study. The fracture rate improved from 68 fractures in 209 months (0.32 fractures/patient-month) before treatment to 41 fractures in 1,248 months (0.03 fractures/patient-month) post-treatment ( P  < 0.05). Height standard deviation score (SDS) was conserved from baseline to end of study (−2.12 ± 2.45 vs. −2.45 ± 2.73) ( P  = 0.05) with an average follow-up of 73 months. The only adverse effect recorded in six infants was fever during the initial pamidronate infusion. Treatment with intravenous pamidronate is safe, significantly improves lumbar bone mineral density (L-BMD), and reduces fracture rates in young infants with OI while preserving linear growth.

BackgroundMost studies of neonatal acute kidney injury (AKI) have focused on the first week following birth. Here, we determined the outcomes and risk factors for late AKI (>7d).MethodsThe international AWAKEN study examined AKI in neonates admitted to an intensive care unit. Late AKI was defined as occurring >7 days after birth according to the KDIGO criteria. Models were constructed to assess the association between late AKI and death or length of stay. Unadjusted and adjusted odds for late AKI were calculated for each perinatal factor.ResultsLate AKI occurred in 202/2152 (9%) of enrolled neonates. After adjustment, infants with late AKI had higher odds of death (aOR:2.1, p = 0.02) and longer length of stay (parameter estimate: 21.9, p < 0.001). Risk factors included intubation, oligo- and polyhydramnios, mild-moderate renal anomalies, admission diagnoses of congenital heart disease, necrotizing enterocolitis, surgical need, exposure to diuretics, vasopressors, and NSAIDs, discharge diagnoses of patent ductus arteriosus, necrotizing enterocolitis, sepsis, and urinary tract infection.ConclusionsLate AKI is common, independently associated with poor short-term outcomes and associated with unique risk factors. These should guide the development of protocols to screen for AKI and research to improve prevention strategies to mitigate the consequences of late AKI.

BackgroundHypertension occurs in up to 3% of neonates admitted to the Neonatal Intensive Care Unit (NICU), and is a potentially under-recognized condition. The aim of this study was to examine the incidence of documented and undiagnosed hypertension from the 24-center Assessment of Worldwide Acute Kidney Injury Epidemiology in Neonates (AWAKEN) database, and to assess risk factors for hypertension according to gestational age.MethodsDiagnosed hypertension was documented if an infant had a discharge diagnosis of hypertension and/or discharged on antihypertensive medications. Undiagnosed hypertension was defined when infants did not have a diagnosis of hypertension, but >50% of the lowest mean, diastolic and systolic blood pressure recordings were >95th percentile for gestational age.ResultsOf the 2162 neonates enrolled in the study, hypertension was documented in 1.8%. An additional 3.7% were defined as having undiagnosed hypertension. There was a significant correlation with neonatal hypertension and acute kidney injury (AKI). Additional risk factors for neonatal hypertension were hyperbilirubinaemia, Caucasian race, outborn, vaginal delivery, and congenital heart disease. Protective factors were small for gestational age, multiple gestations, and steroids for fetal maturation.ConclusionsNeonatal hypertension may be an under-recognized condition. AKI and other risk factors predispose infants to hypertension.

BackgroundWe aimed to describe nephrotoxic medication exposure and investigate associations between exposure and acute kidney injury (AKI) in the neonatal intensive care unit during the first postnatal week.Design/methodsSecondary analysis of the AWAKEN cohort. We evaluated nephrotoxic medication exposure during the first postnatal week and associations with AKI using time-varying Cox proportional hazard regressions models. Nephrotoxic medication exposure categories were defined as: no nephrotoxic medication, nephrotoxic medications excluding aminoglycosides, aminoglycoside alone, and aminoglycoside and another nephrotoxic medication.ResultsOf 2162 neonates, 1616 (74.7%) received ≥1 nephrotoxic medication. Aminoglycoside receipt was most common (72%). AKI developed in 211(9.8%) neonates and was associated with a nephrotoxic medication exposure (p < 0.01). Nephrotoxic medication exposures including a nephrotoxic medication excluding aminoglycoside (aHR 3.14, 95% CI 1.31–7.55) and aminoglycoside and another nephrotoxic medication (aHR 4.79, 95% CI 2.19–10.50) were independently associated with AKI and severe AKI (stage 2/3), respectively.ConclusionsNephrotoxic medication exposure in critically ill infants is common during the first postnatal week. Specific nephrotoxic medication exposure, principally aminoglycosides with another nephrotoxic medication, are independently associated with early AKI.

Background High-frequency ventilation (HFV) is frequently used in critically ill preterm neonates. We aimed to determine the incidence of acute kidney injury (AKI) in neonates less than 29 weeks gestation who received HFV in the first week of life and to determine if the rates of AKI differed in those who received other forms of respiratory support. Methods This retrospective cohort study of 24 international, level III/IV neonatal intensive care units (NICUs) included neonates less than 29 weeks gestation from the AWAKEN study database. Exclusion criteria included the following: no intravenous fluids ≥ 48 h, admission ≥ 14 days of life, congenital heart disease requiring surgical repair at < 7 days of life, lethal chromosomal anomaly, death within 48 h, severe congenital kidney abnormalities, inability to determine AKI status, insufficient data on ventilation, and when the diagnosis of early AKI was unable to be made. Subjects were grouped into three groups based on ventilation modes (CPAP/no ventilation, conventional ventilation, and HFV). Results The incidence of AKI was highest in the CPAP/no ventilation group, followed by HFV, followed by conventional ventilation (CPAP/no ventilation 48.5% vs. HFV 42.6% vs. conventional ventilation 28.4% ( p  = 0.009). An increased risk for AKI was found for those on HFV compared to CPAP/no ventilation (HR = 2.65; 95% CI:1.22–5.73). Conclusions HFV is associated with AKI in the first week of life. Neonates on HFV should be screened for AKI. The reasons for this association are not clear. Further studies should evaluate the relationship between ventilator strategies and AKI in premature neonates. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information