Use of ClearGuard HD caps in pediatric hemodialysis patients.

BACKGROUND: Bloodstream infections (BSIs) are a leading cause of hospitalizations and mortality among patients receiving hemodialysis (HD) therapy, especially those with a central venous catheter (CVC) for dialysis access. The use of chlorhexidine impregnated catheter caps (ClearGuard) has been associated with a decrease in the rate of HD catheter-related BSIs (CA-BSIs) in adults; similar data have not been published for children. METHODS: We compared CA-BSI data from participating centers within the Standardizing Care to Improve Outcomes in Pediatric Endstage Kidney Disease (SCOPE) collaborative based on the center's use of ClearGuard caps for patients with HD catheter access. Centers were characterized as ClearGuard (CG) or non-ClearGuard (NCG) centers, with CA-BSI data pre- and post-CG implementation reviewed. All positive blood cultures in participating centers were reported to the SCOPE collaborative and adjudicated by an infectious disease physician. RESULTS: Data were available from 1786 SCOPE enrollment forms completed January 2016-January 2022. January 2020 served as the implementation date for analyzing CG versus NCG center data, with this being the time when the last CG center underwent implementation. Post January 2020, there was a greater decrease in the rate of HD CA-BSI in CG centers versus NCG centers, with a decrease from 1.18 to 0.23 and 0.41 episodes per 100 patient months for the CG and NCG centers, respectively (p = 0.002). CONCLUSIONS: Routine use of ClearGuard caps in pediatric dialysis centers was associated with a reduction of HD CA-BSI rates in pediatric HD patients.

Fluid balance assessment in pediatric hemodialysis patients by using whole-body bioimpedance spectroscopy (WB-BIS).

BACKGROUND: Fluid overload is a major factor in morbidity and mortality in dialysis patients. Whole-body bioimpedance spectroscopy (WB-BIS) is a noninvasive method for assessing fluid status. We hypothesized that fluid status measurement of changes in total body water (TBW), extracellular fluid (ECF), and intracellular fluid (ICF) by WB-BIS would correlate with the weight (Wt) changes before and after hemodialysis (HD) and the amount of ultrafiltration (UF) in pediatric HD patients. We also examined the relationship between the ECF percent of total body water (ECF%) and ECF/ICF ratio with the pre-HD systolic blood pressure percentile (SBP%ile). METHODS: WB-BIS measurements were made both before and after HD on three separate occasions in each patient. Pre- and post-HD Wt, BP, and UF volumes were collected on the day of BIS measurement. RESULTS: At total of 96 measurements were obtained from 16 HD patients. There were 6 females (mean age: 13.2 ± 4.5 yrs). UF correlated with changes in weight, TBW and ECF (p < 0.001) but not with ICF changes (p = 0.345). Pre-HD SBP%ile correlated with ECF%. CONCLUSIONS: Our findings suggest that WB-BIS can be used to monitor the fluid status in pediatric HD patients. The fluid that is removed from the patient during the HD treatment primarily comes from the ECF and not the ICF. Mobilization of fluid from the ICF appears to be delayed. Patients with significantly higher pre-HD ECF% and ECF/ICF ratio had higher pre-HD systolic BP. A higher resolution version of the Graphical abstract is available as Supplementary information.

A review of ferric citrate clinical studies, and the rationale and design of the Ferric Citrate and Chronic Kidney Disease in Children (FIT4KiD) trial.

Pediatric chronic kidney disease (CKD) is characterized by many co-morbidities, including impaired growth and development, CKD-mineral and bone disorder, anemia, dysregulated iron metabolism, and cardiovascular disease. In pediatric CKD cohorts, higher circulating concentrations of fibroblast growth factor 23 (FGF23) are associated with some of these adverse clinical outcomes, including CKD progression and left ventricular hypertrophy. It is hypothesized that lowering FGF23 levels will reduce the risk of these events and improve clinical outcomes. Reducing FGF23 levels in CKD may be accomplished by targeting two key stimuli of FGF23 production-dietary phosphate absorption and iron deficiency. Ferric citrate is approved for use as an enteral phosphate binder and iron replacement product in adults with CKD. Clinical trials in adult CKD cohorts have also demonstrated that ferric citrate decreases circulating FGF23 concentrations. This review outlines the possible deleterious effects of excess FGF23 in CKD, summarizes data from the adult CKD clinical trials of ferric citrate, and presents the Ferric Citrate and Chronic Kidney Disease in Children (FIT4KiD) study, a randomized, placebo-controlled trial to evaluate the effects of ferric citrate on FGF23 in pediatric patients with CKD stages 3-4 (ClinicalTrials.gov Identifier NCT04741646).

Conversion to permanent vascular access is associated with improved markers of hemodialysis efficacy in children: Pediatric nephrology research consortium study.

BACKGROUND AND OBJECTIVES: Arteriovenous fistulae (AVF) and grafts (AVG) are preferred permanent vascular access (PVA) for chronic hemodialysis (HD) patients. Our objective was to examine the change in markers of HD efficacy after successful establishment of a PVA among children who started HD with a tunneled cuffed catheter (TCC). MATERIALS AND METHODS: Retrospective chart reviews were completed on patients from 20 pediatric dialysis centers. All patients used TCC prior to AVF/AVG, and each patient acted as his/her own control. Data on markers of HD efficacy (single-pool Kt/V, urea reduction ratio (URR), serum albumin and hematocrit (Hct)) were collected at the creation of AVF/AVG and for 2 years thereafter. Statistical methods included hypothesis testing and statistical modeling after adjusting for relevant demographic variables. RESULTS: First PVA was created in 98 individual children: 87 (89%) were AVF and 11 (11%) were AVG. The mean TCC vintage prior to AVF/AVG was 10.4 ± 17.3 months. At 1-year follow-up, Kt/V improved by 0.15 ± 0.06 (p = 0.02) and URR improved by 4.54 ± 1.17% (p < 0.0001). Furthermore, PVA was associated with improved serum albumin by 0.31 ± 0.07 g/dL (p < 0.0001) and Hct by 2.80 ± 0.65% (p < 0.0001) at 1 year. These HD efficacy markers remained statistically significant at 2nd-year follow-up. These observations were further supported by the adjusted models. Conversion to AVF was associated with statistically significant improvement in all four markers of HD efficacy at 1-year follow-up. This trend was not demonstrated for subjects who were converted to AVG. CONCLUSION: Switching to PVA was associated with improved markers of HD efficacy, single-pool Kt/V, URR, serum albumin, and Hct. This improvement was mostly demonstrated at 1 year and maintained for the 2nd year. The potential differential impact of the type of PVA on the trajectory of markers of HD efficacy should be further investigated.

Clinical evaluation of the Prismaflex™ HF 20 set and Prismaflex™ system 7.10 for acute continuous kidney replacement therapy (CKRT) in children.

BACKGROUND: Continuous kidney replacement therapy (CKRT) is a common modality for treatment of severe acute kidney injury (AKI) in children. Adult technologies routinely utilized to provide this therapy have a large extracorporeal volume. The Prismaflex™ HF20 filter set has a relatively low extracorporeal blood volume of 60 mL, which provides technological benefit for smaller children compared with current filter sets available in the USA. METHODS: We conducted a multicenter, open-label single group study to evaluate whether the Prismaflex™ HF20 filter set delivers efficacious and safe CKRT to support patients with AKI, fluid overload, or both in pediatric patients weighing ≥ 8 to 20 kg. RESULTS: Twenty-three patients were enrolled between April 24, 2016 and April 8, 2018. The mean reduction in blood urea nitrogen from baseline to 24 h was 58.12 ± 20.08% (95% CI, - 68.45 and - 47.79 (p = 0.0008)). Median cumulative normalized effluent rate at 24 h was 60.8 mL/kg/h (25.9, 83.7). None of the patients participating in the study suffered a serious adverse event; thus, no obvious safety concerns were noted. CONCLUSIONS: We suggest that the Prismaflex HF20™ filter set used in conjunction with the Prismaflex™ System Software Version 7.10 or 7.20 is a suitable alternative to larger filter sets for use in pediatric patients weighing less than 20 kg. Graphical abstract.

Predictors of time to first cannulation for arteriovenous fistula in pediatric hemodialysis patients: Midwest Pediatric Nephrology Consortium study.

BACKGROUND: Permanent vascular access (PVA) is preferred for long-term hemodialysis. Arteriovenous fistulae (AVF) have the best patency and the lowest complication rates compared to arteriovenous grafts (AVG) and tunneled cuffed catheters (TCC). However, AVF need time to mature. This study aimed to investigate predictors of time to first cannulation for AVF in pediatric hemodialysis patients. METHODS: Data on first AVF and AVG of patients at 20 pediatric dialysis centers were collected retrospectively, including demographics, clinical information, dialysis markers, and surgical data. Statistical modeling was used to investigate predictors of outcome. RESULTS: First PVA was created in 117 children: 103 (88%) AVF and 14 (12%) AVG. Mean age at AVF creation was 15.0 ± 3.3 years. AVF successfully matured in 89 children (86.4%), and mean time to first cannulation was 3.6 ± 2.5 months. In a multivariable regression model, study center, age, duration of non-permanent vascular access (NPVA), and Kt/V at AVF creation predicted time to first cannulation, with study center as the strongest predictor (p < 0.01). Time to first cannulation decreased with increasing age (p = 0.03) and with increasing Kt/V (p = 0.01), and increased with duration of NPVA (p = 0.03). Secondary failure occurred in 10 AVF (11.8%). Time to first cannulation did not predict secondary failure (p = 0.29), but longer time to first cannulation tended towards longer secondary patency (p = 0.06). CONCLUSIONS: Study center is the strongest predictor of time to first cannulation for AVF and deserves further investigation. Time to first cannulation is significantly shorter in older children, with more efficient dialysis treatments, and increases with longer NPVA duration.

Correction to: Predictors of patency for arteriovenous fistulae and grafts in pediatric hemodialysis patients.

The original version of this article unfortunately contained a mistake. The name of Vimal Chadha was presented incorrectly. The corrected author list is given above.

Predictors of patency for arteriovenous fistulae and grafts in pediatric hemodialysis patients.

BACKGROUND: Hemodialysis (HD) guidelines recommend permanent vascular access (PVA) in children unlikely to receive kidney transplant within 1 year of starting HD. We aimed to determine predictors of primary and secondary patency of PVA in pediatric HD patients. METHODS: Retrospective chart reviews were performed for first PVAs in 20 participating centers. Variables collected included patient demographics, complications, interventions, and final outcome. RESULTS: There were 103 arterio-venous fistulae (AVF) and 14 AV grafts (AVG). AVF demonstrated superior primary (p = 0.0391) and secondary patency (p = 0.0227) compared to AVG. Primary failure occurred in 16 PVA (13.6%) and secondary failure in 14 PVA (12.2%). AVF were more likely to have primary failure (odds ratio (OR) = 2.10) and AVG had more secondary failure (OR = 3.33). No demographic, clinical, or laboratory variable predicted primary failure of PVA. Anatomical location of PVA was predictive of secondary failure, with radial having the lowest risk compared to brachial (OR = 12.425) or femoral PVA (OR = 118.618). Intervention-free survival was predictive of secondary patency for all PVA (p = 0.0252) and directly correlated with overall survival of AVF (p = 0.0197) but not AVG. Study center demonstrated statistically significant effect only on intervention-free AVF survival (p = 0.0082), but not number of complications or interventions, or outcomes. CONCLUSIONS: In this multi-center pediatric HD cohort, AVF demonstrated primary and secondary patency advantages over AVG. Radial PVA was least likely to develop secondary failure. Intervention-free survival was the only predictor of secondary patency for AVF and directly correlated with overall access survival. The study center effect on intervention-free survival of AVF deserves further investigation.

Epidemiology of peritonitis following maintenance peritoneal dialysis catheter placement during infancy: a report of the SCOPE collaborative.

BACKGROUND: Maintenance peritoneal dialysis (PD) is the dialysis modality of choice for infants and young children. However, there are limited outcome data for those who undergo PD catheter insertion and initiate maintenance PD within the first year of life. METHODS: Using data from the Children's Hospital Association's Standardizing Care to Improve Outcomes in Pediatric End Stage Renal Disease (ESRD) Collaborative (SCOPE), we examined peritonitis rates and patient survival in 156 infants from 29 North American pediatric dialysis centers who had a chronic PD catheter placed prior to their first birthday. RESULTS: In-hospital and overall annualized rates of peritonitis were 1.73 and 0.76 episodes per patient-year, respectively. Polycystic kidney disease was the most frequent renal diagnosis and pulmonary hypoplasia the most common co-morbidity in infants with peritonitis. Multivariable regression models demonstrated that nephrectomy at or prior to PD catheter placement and G-tube insertion after catheter placement were associated with a nearly sixfold and nearly threefold increased risk of peritonitis, respectively. Infants with peritonitis had longer initial hospital stays and lower overall survival (86.3 vs. 95.6%, respectively; P < 0.02) than those without an episode of peritonitis. CONCLUSIONS: In this large cohort of infants with ESRD, the frequency of peritonitis was high and several risk factors associated with the development of peritonitis were identified. Given that peritonitis was associated with a longer duration of initial hospitalization and increased mortality, increased attention to the potentially modifiable risk factors for infection is needed.

Transient antenatal Bartter's Syndrome and X-linked polyhydramnios: insights from the genetics of a rare condition.

The discovery that mutations in MAGED2 cause a rare and transient form of antenatal Bartter's Syndrome may have implications beyond the very small number of affected families. Understanding the mechanism by which this severe form of Bartter's Syndrome resolves after birth could also provide new insights into the regulation of tubular transport and the response to tissue hypoxia.

Timing of continuous renal replacement therapy and mortality in critically ill children*.

OBJECTIVES: Acute kidney injury and fluid overload frequently necessitate initiation of continuous renal replacement therapy in critically ill patients admitted to the ICU. In this study, our primary objective was to determine the effect of timing of initiation of continuous renal replacement therapy on ICU mortality in children requiring renal support for management of acute kidney injury and/or fluid overload. DESIGN: Retrospective cohort study. SETTING: Tertiary level, multidisciplinary PICU. PATIENTS: Children who received continuous renal replacement therapy for management of acute kidney injury and/or fluid overload from January 2000 through July 2009 were included in the study. Patients requiring extracorporeal life support and patients initiated on continuous renal replacement therapy for indications other than acute kidney injury and/or fluid overload were excluded. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Timing of initiation was defined chronologically as time from ICU admission to continuous renal replacement therapy initiation. Three hundred eighty treatments were performed during the study period, of which 190 were eligible and included in the study. Overall ICU mortality was 47% among the study population. Median timing of initiation was higher among nonsurvivors compared with survivors (3.4 vs 2.0 d, p = 0.001). Multivariable logistic regression analysis identified timing of initiation as an independent predictor of mortality with an adjusted odds ratio of 1.05 (95% CI, 1.01, 1.11). Fluid overload, indication for continuous renal replacement therapy initiation, severity of illness at ICU admission, and active oncologic diagnosis were the other independent predictors of mortality that were identified in the final regression model. In the survival analysis, late initiators (> 5 d) had higher mortality than early initiators (≤ 5 d) with a hazard ratio of 1.56 (95% CI, 1.02, 2.37). CONCLUSIONS: Earlier initiation of continuous renal replacement therapy was associated with lower mortality in this cohort of critically ill children. Future studies should focus on early identification of such children who may benefit from early continuous renal replacement therapy initiation.

Tolvaptan increases serum sodium in pediatric patients with heart failure.

This study aimed to evaluate the use of tolvaptan in a consecutive series of pediatric patients with heart failure. Patients 18 years of age or younger with heart failure prescribed tolvaptan between January 2009 and October 2011 were retrospectively identified at Children's Medical Center Dallas. Laboratory parameters, urine output, fluid balance, and concurrent medications were recorded at baseline and at specified intervals after a single dose of tolvaptan. The 28 patients in the study had a median age of 2 years (range 1 month-18 years). The median tolvaptan dose administered was 0.3 mg/kg (range 0.1-1.3 mg/kg). The study patients had a median baseline serum sodium concentration of 127 mmol/L, and the increases in sodium were 2.5 mmol/L at 12 h, 5 mmol/L at 24 h, 4 mmol/L at 48 h, and 5 mmol/L at 72 h (all p < 0.001). Urine output was increased at 24 h (p < 0.001) and 48 h (p = 0.03), and fluid balance changes were significantly different at 24 h (p = 0.004). The changes in potassium, blood urea nitrogen, and serum creatinine were not significant at any interval. When controlling for traditional diuretic therapy, increases in serum sodium concentration and urine output remained statistically significant. A single dose of tolvaptan increased serum sodium concentrations for the majority in this small series of pediatric patients with heart failure. These results suggest that tolvaptan can be safely and effectively administered to pediatric patients. Prospective, randomized controlled trials are needed to evaluate the safety and efficacy of its use further.

Persistent Increase in Serum Ferritin Levels despite Converting to Permanent Vascular Access in Pediatric Hemodialysis Patients: Pediatric Nephrology Research Consortium Study.

Our objective was to examine serum ferritin trends after conversion to permanent vascular access (PVA) among children who started hemodialysis (HD) using tunneled cuffed catheters (TCC). Retrospective chart reviews were completed on 98 subjects from 20 pediatric HD centers. Serum ferritin levels were collected at the creation of PVA and for two years thereafter. There were 11 (11%) arteriovenous grafts (AVG) and 87 (89%) arteriovenous fistulae (AVF). Their mean TCC use was 10.4 ± 17.3 months. Serum ferritin at PVA creation was elevated at 562.64 ± 492.34 ng/mL, increased to 753.84 ± 561.54 ng/mL (p = < 0.001) in the first year and remained at 759.60 ± 528.11 ng/mL in the second year (p = 0.004). The serum ferritin levels did not show a statistically significant linear association with respective serum hematocrit values. In a multiple linear regression model, there were three predictors of serum ferritin during the first year of follow-up: steroid-resistant nephrotic syndrome as primary etiology (p = 0.035), being from a center that enrolled >10 cases (p = 0.049) and baseline serum ferritin level (p = 0.017). Increasing serum ferritin after conversion to PVA is concerning. This increase is not associated with serum hematocrit trends. Future studies should investigate the correlation of serum transferrin saturation and ferritin levels in pediatric HD patients.

Developmental changes in renal function.

PURPOSE OF REVIEW: Although nephrogenesis in a term infant is complete, there are a number of functional changes that occur in the kidney as the infant matures. Understanding these changes will aid in the evaluation of neonates to delineate what is normal development versus a pathophysiologic problem. In addition, as many drugs are either cleared by the kidneys or can affect renal function, dosing regimens are dramatically different in the neonate as compared with the adult. These differences are greatly exaggerated in the preterm infant, making it more difficult to determine if there is a pathophysiologic problem. RECENT FINDINGS: While investigators in recent years have made great strides in understanding the early embryology of the kidney and the molecular signals involved in the formation of the kidney, there remains a paucity of functional studies. The most recent studies have re-examined the changes in the serum creatinine in the newborn and how this impacts the excretion of drugs. Developmental changes in the renal tubule transport systems and their regulation have also been more extensively studied. SUMMARY: The kidney undergoes many developmental physiologic changes as the neonate adapts to extra-uterine life. Understanding these changes will help in the medical management of these infants.

Dialysis disequilibrium syndrome.

The dialysis disequilibrium syndrome is a rare but serious complication of hemodialysis. Despite the fact that maintenance hemodialysis has been a routine procedure for over 50 years, this syndrome remains poorly understood. The signs and symptoms vary widely from restlessness and headache to coma and death. While cerebral edema and increased intracranial pressure are the primary contributing factors to this syndrome and are the target of therapy, the precise mechanisms for their development remain elusive. Treatment of this syndrome once it has developed is rarely successful. Thus, measures to avoid its development are crucial. In this review, we will examine the pathophysiology of this syndrome and discuss the factors to consider in avoiding its development.

Early Fluid Accumulation and Intensive Care Unit Mortality in Children Receiving Extracorporeal Membrane Oxygenation.

Purpose of this study was to evaluate the impact of early fluid accumulation and renal dysfunction on mortality in children receiving extracorporeal membrane oxygenation (ECMO). Retrospective cohort study of neonatal and pediatric patients who received ECMO between January 2010 and December 2012 in a tertiary level multidisciplinary pediatric intensive care unit (ICU). Ninety-six patients were included, and forty-six (48%) of them received continuous renal replacement therapy (CRRT) during ECMO. Overall mortality was 38.5%. Proportion of patients with acute kidney injury (AKI) at ICU admission was 33% and increased to 47% at ECMO initiation. High-risk diagnoses, extracorporeal cardiopulmonary resuscitation (ECPR), and venoarterial (VA)-ECMO were more common among nonsurvivors. Nonsurvivors had significantly higher proportion of AKI at ICU admission (OR: 2.59, p = 0.04) and fluid accumulation on ECMO day 1 (9% vs. 1%, p = 0.05) compared with survivors. Multivariable logistic regression analysis (adjusted for a propensity score based on nonrenal factors associated with increased mortality) demonstrated that fluid accumulation on ECMO day 1 is significantly associated with increased ICU mortality (OR: 1.07, p = 0.04). Fluid accumulation within the first 24 hours after ECMO cannulation is significantly associated with increased ICU mortality in neonatal and pediatric patients. Prospective studies evaluating the impact of conservative fluid management and CRRT during the initial phase of ECMO may help further define this relationship.

Expression and role of serum and glucocorticoid-regulated kinase 2 in the regulation of Na+/H+ exchanger 3 in the mammalian kidney.

Serum and glucocorticoid-regulated kinase 2 (sgk2) is 80% identical to the kinase domain of sgk1, an important mediator of mineralocorticoid-regulated sodium (Na(+)) transport in the distal nephron of the kidney. The expression pattern and role in renal function of sgk2 are virtually uncharacterized. In situ hybridization and immunohistochemistry of rodent kidney coupled with real-time RT-PCR of microdissected rat kidney tubules showed robust sgk2 expression in the proximal straight tubule and thick ascending limb of the loop of Henle. Sgk2 expression was minimal in distal tubule cells with aquaporin-2 immunostaining but significant in proximal tubule cells with Na(+)/H(+) exchanger 3 (NHE3) immunostaining. To ascertain whether mineralocorticoids regulate expression of sgk2 in a manner similar to sgk1, we examined sgk2 mRNA expression in the kidneys of adrenalectomized rats treated with physiological doses of aldosterone together with the glucocorticoid receptor antagonist RU486. Northern blot analysis and in situ hybridization showed that, unlike sgk1, sgk2 expression in the kidney was not altered by aldosterone treatment. Based on the observation that sgk2 is expressed in proximal tubule cells that also express NHE3, we asked whether sgk2 regulates NHE3 activity. We heterologously expressed sgk2 in opossum kidney (OKP) cells and measured Na(+)/H(+) exchange activity by Na(+)-dependent cell pH recovery. Constitutively active sgk2, but not sgk1, stimulated Na(+)/H(+) exchange activity by >30%. Moreover, the sgk2-mediated increase in Na(+)/H(+) exchange activity correlated with an increase in cell surface expression of NHE3. Together, these results suggest that the pattern of expression, regulation, and role of sgk2 within the mammalian kidney are distinct from sgk1 and that sgk2 may play a previously unrecognized role in the control of transtubular Na(+) transport through NHE3 in the proximal tubule.

Three-dimensional imaging reveals ureteric and mesenchymal defects in Fgfr2-mutant kidneys.

Current techniques to morphologically characterize the processes of nephrogenesis and ureteric branching during kidney development have many limitations. Here, we used in vivo three-dimensional analysis to study renal development in mice lacking fibroblast growth factor receptor 2 in the ureteric bud (Fgfr2(UB-/-)) and in littermate controls. We found that Fgfr2(UB-/-) mice have more severe defects in ureteric branching morphogenesis than previously reported, including significantly fewer branches and tips than control mice. Furthermore, these mice had decreased ureteric volume and surface area and longer ureteric segments than control mice. We also observed previously unrecognized abnormalities in nephrogenesis, including a gradual increase in volume and surface area during maturation from renal vesicles to mature nephrons, in the mutant mice. Finally, we quantified many events of normal renal development that are either difficult or impossible to measure without this three-dimensional technique. In summary, the three-dimensional approach is a powerful and quantitative means to characterize branching morphogenesis and nephrogenesis.

Increased blood pressure in mice lacking cytochrome P450 2J5.

The cytochrome P450 (CYP) enzymes participate in a wide range of biochemical functions, including metabolism of arachidonic acid and steroid hormones. Mouse CYP2J5 is abundant in the kidney where its products, the cis-epoxyeicosatrienoic acids (EETs), modulate sodium transport and vascular tone. To define the physiological role of CYP2J5 in the kidney, knockout mice were generated using a conventional gene targeting approach. Cyp2j5 (-/-) mice develop normally and exhibit no overt renal pathology. While renal EET biosynthesis was apparently unaffected by the absence of CYP2J5, deficiency of this CYP in female mice was associated with increased blood pressure, enhanced proximal tubular transport rates, and exaggerated afferent arteriolar responses to angiotensin II and endothelin I. Interestingly, plasma 17beta-estradiol levels were reduced in female Cyp2j5 (-/-) mice and estrogen replacement restored blood pressure and vascular responsiveness to normal levels. There was no evidence of enhanced estrogen metabolism, or altered expression or activities of steroidogenic enzymes in female Cyp2j5 (-/-) mice, but their plasma levels of luteinizing hormone and follicle stimulating hormone were inappropriately low. Together, our findings illustrate a sex-specific role for CYP2J5 in regulation of blood pressure, proximal tubular transport, and afferent arteriolar responsiveness via an estrogen-dependent mechanism.