Risk factors for renal injury in children with a solitary functioning kidney

A Case of Unilateral Renal Agenesis Detected by Abdominal Point-Of-Care Ultrasound

As the interest in point-of-care ultrasound (POCUS) for investigating pediatric abdominal emergencies has been growing, an increasing number of literatures about abdominal POCUS has been published. We describe a noteworthy instance of a systematic approach using abdominal POCUS for detecting unilateral renal agenesis (URA) in previously healthy children with suspected intussusception. A previously healthy three-year-old girl was brought to our emergency department (ED) due to abdominal pain and bloody diarrhea. POCUS was performed to investigate the presence of intussusception. POCUS was able to rule out intussusception and detect URA. The investigation led the patient to a proper nephrology follow-up. When performing abdominal POCUS to evaluate gastrointestinal pathologies, it is important to pay attention to concomitant congenital anomalies of the kidney and urinary tract (CAKUT).

Outcome of children with multicystic dysplastic kidney: Does involved side matter?

BACKGROUND

Multicystic dysplastic kidney (MCDK) is a common anomaly detected on antenatal ultrasound. We aimed to assess the profile of children with MCDK and to investigate whether the involved side has any effect on outcome.

METHODS

Thirty-nine patients with MCDK and 20 controls were enrolled. Patients who estimated glomerular filtration rate (eGFR) values over 90 mL/min/1.73 m2 were compared with controls. Comparison was made between the involved sides.

RESULTS

MKDB was right-sided in 20 (51.3%) and left-sided in 19 (48.7%) patients. 33.3% had additional urinary tract abnormality, 10.2% had systemic abnormality. 82% showed contralateral kidney enlargement. 48.7% involuted, 17.9% underwent nephrectomy. 35.8% suffered from urinary tract infection (UTI). 5.1% had renal scarring (RS). 30% developed microalbuminuria. 12.8% complicated with hypertension. 17.9% progressed to chronic kidney disease (CKD). Hypertension was independent risk factor for developing CKD. Blood pressure, cystatin C and urine microalbumin/creatinine levels were increased, and eGFR values were decreased in patients compared to controls. No significant difference was found between the two sides for rates of involution, UTI, RS, nephrectomy, and additional abnormality. Cystatin C levels were higher on the right than left sides (p = .033).

CONCLUSION

Children with MCDK predispose to renal deterioration even at normal eGFR values. Although cystatin C levels tended to increase in right-sided patients, the involved side seemed to have no significant effect on renal outcome. Hypertension was main determinant for progression to CKD in MCDK.

Why is chronic kidney disease progressive? Evolutionary adaptations and maladaptations

Despite significant advances in renal physiology, the global prevalence of chronic kidney disease (CKD) continues to increase. The emergence of multicellular organisms gave rise to increasing complexity of life resulting in trade-offs reflecting ancestral adaptations to changing environments. Three evolutionary traits shape CKD over the lifespan: 1) variation in nephron number at birth, 2) progressive nephron loss with aging, and 3) adaptive kidney growth in response to decreased nephron number. Although providing plasticity in adaptation to changing environments, the cell cycle must function within constraints dictated by available energy. Prioritized allocation of energy available through the placenta can restrict fetal nephrogenesis, a risk factor for CKD. Moreover, nephron loss with aging is a consequence of cell senescence, a pathway accelerated by adaptive nephron hypertrophy that maintains metabolic homeostasis at the expense of increased vulnerability to stressors. Driven by reproductive fitness, natural selection operates in early life but diminishes thereafter, leading to an exponential increase in CKD with aging, a product of antagonistic pleiotropy. A deeper understanding of the evolutionary constraints on the cell cycle may lead to manipulation of the balance between progenitor cell renewal and differentiation, regulation of cell senescence, and modulation of the balance between cell proliferation and hypertrophy. Application of an evolutionary perspective may enhance understanding of adaptation and maladaptation by nephrons in the progression of CKD, leading to new therapeutic advances.

Brief early life angiotensin-converting enzyme inhibition attenuates the diuretic response to saline loading in sheep with solitary functioning kidney

A solitary functioning kidney (SFK) from birth predisposes to hypertension and kidney dysfunction, and this may be associated with impaired fluid and sodium homeostasis. Brief and early angiotensin-converting enzyme inhibition (ACEi) in a sheep model of SFK delays onset of kidney dysfunction. We hypothesized that modulation of the renin-angiotensin system via brief postnatal ACEi in SFK would reprogram renal sodium and water handling. Here, blood pressure (BP), kidney haemodynamics and kidney excretory function were examined in response to an isotonic saline load (0.13 ml/kg/min, 180 min) at 20 months of age in SFK (fetal unilateral nephrectomy at 100 days gestation; term 150 days), sham and SFK+ACEi sheep (ACEi in SFK 4-8 weeks of age). Basal BP was higher in SFK than sham (∼13 mmHg), and similar between SFK and SFK+ACEi groups. Saline loading caused a small increase in BP (∼3-4 mmHg) the first 2 h in SFK and sham sheep but not SFK+ACEi sheep. Glomerular filtration rate did not change in response to saline loading. Total sodium excretion was similar between groups. Total urine excretion was similar between SFK and sham animals but was ∼40% less in SFK+ACEi animals compared with SFK animals. In conclusion, the present study indicates that water homeostasis in response to a physiological challenge is attenuated at 20 months of age by brief early life ACEi in SFK. Further studies are required to determine if ACEi in early life in children with SFK could compromise fluid homeostasis later in life.

Sex differences in long-term kidney fibrosis following neonatal nephron loss during ongoing nephrogenesis

BACKGROUND

Clinical studies suggest that female sex plays a protective role in the development and progression of kidney disease. Recent experimental studies indicate that in male rats early nephron loss under ongoing nephrogenesis is accompanied by severe long-term sequelae. In humans, nephron formation occurs mainly in the third trimester, ceasing with 36 weeks of gestation. Due to perinatal complications, preterm infants delivered during this vulnerable period may undergo acute nephron loss. In rats nephrogenesis persists until postnatal day 10, reflecting the situation of human preterms with persisting nephrogenesis. In our animal model of neonatal uninephrectomy, female and male rats were uninephrectomized at day 1 of life. Hypothesizing sex-dependent differences, long-term renal outcome was assessed after 1 year.

RESULTS

In both sexes, neonatal uninephrectomy was not followed by arterial hypertension at 1 year of age. Compensatory weight gain and glomerular hypertrophy of the remaining kidney occurred in uninephrectomized female and male animals. Selected markers of interstitial inflammation and fibrosis were regulated sex-dependently. The expression of monocyte chemoattractant protein-1 was increased in females, while tubulointerstitial infiltration by M1 macrophages was significantly higher in males after neonatal uninephrectomy. Neonatally uninephrectomized male rats had more glomerulosclerosis and podocyte damage compared to females, which was assessed by a semiquantitative score and desmin staining. RT-PCR revealed that after neonatal uninephrectomy in the remaining contralateral kidney of female rats the expression of candidate genes of renal development and function, i.e., wt-1, nephrin, synaptopodin, gdnf, and itga8 was higher than in males.

CONCLUSIONS

Based on these observations we conclude that female sex is protective in the long-term response of the kidney to acute nephron loss under active nephrogenesis.

Beneficial effects of brief early life angiotensin-converting enzyme inhibition wane with time in sheep with solitary functioning kidney

A child with a congenital solitary functioning kidney (SFK) may develop kidney disease from early in life due to hyperfiltration injury. Previously, we showed in a sheep model of SFK that brief angiotensin-converting enzyme inhibition (ACEi) early in life is reno-protective and increases renal functional reserve (RFR) at 8 months of age. Here we investigated the long-term effects of brief early ACEi in SFK sheep out to 20 months of age. At 100 days gestation (term = 150 days) SFK was induced by fetal unilateral nephrectomy, or sham surgery was performed (controls). SFK lambs received enalapril (SFK+ACEi; 0.5 mg/kg, once daily, orally) or vehicle (SFK) from 4 to 8 weeks of age. At 8, 14 and 20 months of age urinary albumin excretion was measured. At 20 months of age, we examined basal kidney function and RFR via infusion of combined amino acid and dopamine (AA+D). SFK+ACEi resulted in lower albuminuria (∼40%) at 8 months, but not at 14 or 20 months of age compared with vehicle-SFK. At 20 months, basal GFR (∼13%) was lower in SFK+ACEi compared with SFK, but renal blood flow (RBF), renal vascular resistance (RVR) and filtration fraction were similar to SFK. During AA+D, the increase in GFR was similar in SFK+ACEi and SFK animals, but the increase in RBF was greater (∼46%) in SFK+ACEi than SFK animals. Brief ACEi in SFK delayed kidney disease in the short-term but these effects were not sustained long-term.

Targeting Glomerular Hemodynamics for Kidney Protection

The kidney microcirculation is a unique structure as it is composed to 2 capillary beds in series: the glomerular and peritubular capillaries. The glomerular capillary bed is a high-pressure capillary bed, having a 60 mm Hg to 40 mm Hg pressure gradient, capable of producing an ultrafiltrate of plasma quantified as the glomerular filtration rate (GFR), thereby allowing for waste products to be removed and establishing sodium/volume homeostasis. Entering the glomerulus is the afferent arteriole, and the exiting one is the efferent arteriole. The concerted resistance of each of these arterioles is what is known as glomerular hemodynamics and is responsible for increasing or decreasing GFR and renal blood flow. Glomerular hemodynamics play an important role in how homeostasis is achieved. Minute-to-minute fluctuations in the GFR are achieved by constant sensing of distal delivery of sodium and chloride in the specialized cells called macula densa leading to upstream alternation in afferent arteriole resistance altering the pressure gradient for filtration. Specifically, 2 classes of medications (sodium glucose cotransporter-2 inhibitors and renin-angiotensin system blockers) have shown to be effective in long-term kidney health by altering glomerular hemodynamics. This review will discuss how tubuloglomerular feedback is achieved, and how different disease states and pharmacologic agents alter glomerular hemodynamics.

CAKUT: A Pediatric and Evolutionary Perspective on the Leading Cause of CKD in Childhood

The global prevalence of chronic kidney disease (CKD) is increasing rapidly, due to increasing environmental stressors through the life cycle. Congenital anomalies of kidney and urinary tract (CAKUT) account for most CKD in children, with a spectrum that can lead to kidney failure from early postnatal to late adult life. A stressed fetal environment can impair nephrogenesis, now recognized as a significant risk factor for the development of adult CKD. Congenital urinary tract obstruction is the leading cause of CKD due to CAKUT and can itself impair nephrogenesis as well as contribute to progressive nephron injury. Early diagnosis by ultrasonography in fetal life by an obstetrician/perinatologist can provide important information for guiding prognosis and future management. This review focuses on the critical role played by the pediatrician in providing timely evaluation and management of the patient from the moment of birth to the transfer to adult care. In addition to genetic factors, vulnerability of the kidney to CKD is a consequence of evolved modulation of nephron number in response to maternal signaling as well as to susceptibility of the nephron to hypoxic and oxidative injury. Future advances in the management of CAKUT will depend on improved biomarkers and imaging techniques.

Uncovering risk factors for kidney injury in children with a solitary functioning kidney

Children with a solitary functioning kidney (SFK) have an increased risk of kidney injury. The exact risk of and risk factors for kidney injury remain unknown, which impedes personalized care. Here, we recruited a nationwide multicenter cohort of 944 patients with SFK to get more insight into this by consenting patients born in 1993-2020 and diagnosed with congenital or acquired SFK before adulthood. The median follow-up was 12.8 years and four indications of kidney injury were studied: urine protein-creatinine ratios, blood pressure, estimated glomerular filtration rate and use of anti-hypertensive/proteinuric medication. For each indicator except medication use, separate cut-off values for any injury and severe injury were used. Survival analyses indicated that at 18 years of age, any or severe kidney injury were present in 75% and 39% of patients with congenital SFK, respectively. Risk factors for kidney injury included kidney agenesis as cause of the SFK, anomalies in the SFK, and high body mass index at last follow-up. Kidney agenesis and being overweight were specifically associated with proteinuria and high blood pressure, whereas anomalies in the SFK were associated with reduced estimated glomerular filtration rates. The high prevalence of kidney injury in patients with SFK emphasizes the need for long-term follow-up, in which lifestyle is an important topic to address. More research into the etiological role of risk factors will help to translate our findings into individualized care strategies. Thus, our study shows that a significant proportion of children with SFK will develop kidney injury over time.

Kidney length standardized to body length predicts outcome in infants with a solitary functioning kidney

BACKGROUND

Infants with a solitary functioning kidney (SFK) are at risk for chronic kidney injury (CKI). Lack of compensatory kidney growth (CKG) is associated with CKI, but measuring CKG is challenging since it is typically reported relative to normal kidneys. This study aims to (1) standardize SFK growth in infants, (2) investigate the relationship between standardized kidney length and clinical outcomes, and (3) use these results to develop a risk-based prediction model and local clinical pathway for SFK care.

METHODS

This was a quality improvement study of 166 infants with an SFK. Linear regression was used to assess kidney growth from 0 to 180 days of life. Univariate binary regression analysis was used to identify kidney length to body length thresholds associated with the development of CKI, defined as the composite outcome of chronic kidney disease (eGFR < 60 mL/min/1.73 m²), hypertension, or proteinuria.

RESULTS

Kidneys grew in length from 0 to 180 days, and growth was constant when standardized to body length. Over follow-up, infants with a baseline kidney length to body length ≤ 0.088 were more likely to experience CKI than the rest of the cohort (27 vs. 8%, p = 0.04). Kidney length to body length ≤ 0.088 was also significantly associated with CKI development (OR 4.17, 95% CI 1.14-15.28, p = 0.04).

CONCLUSIONS

In this study, kidney length to body length ratio was a stable CKG metric over 0-180 days, and a baseline ratio ≤ 0.088 was a risk factor for CKI. Results will aid in developing a practical, point-of-care risk assessment tool, and overarching risk-stratified clinical pathway for infants with an SFK. A higher resolution version of the Graphical abstract is available as Supplementary information.

Antenatally Diagnosed Kidney Anomalies

Congenital anomalies of the kidney and urinary tract encompass a broad spectrum of developmental conditions that together account for the majority of childhood chronic kidney diseases. Kidney abnormalities are the most commonly diagnosed congenital anomaly in children, and detection of this anomaly is increasing as a result of improved antenatal care and widespread access to more sensitive screening ultrasonography. Most paediatricians will encounter children with congenital kidney anomalies across a wide spectrum of disorders, and a broad understanding of the classification, investigation, and basis of management is important to appropriately direct their care.

Prostanoid receptors in hyperfiltration-mediated glomerular injury: Novel agonists and antagonists reveal opposing roles for EP2 and EP4 receptors

Increased fluid-flow shear stress (FFSS) contributes to hyperfiltration-induced podocyte and glomerular injury resulting in progression of chronic kidney disease (CKD). We reported that increased FFSS in vitro and in vivo upregulates PGE2 receptor EP2 (but not EP4 expression), COX2-PGE₂ -EP2 axis, and EP2-linked Akt-GSK3β-β-catenin signaling pathway in podocytes. To understand and use the disparities between PGE2 receptors, specific agonists, and antagonists of EP2 and EP4 were used to assess phosphorylation of Akt, GSK3β and β-catenin in podocytes using Western blotting, glomerular filtration barrier function using in vitro albumin permeability (P_alb ) assay, and mitigation of hyperfiltration-induced injury in unilaterally nephrectomized (UNX) mice at 1 and 6 months. Results show an increase in P_alb by PGE₂ , EP2 agonist (EP2^AGO ) and EP4 antagonist (EP4^ANT ), but not by EP2 antagonist (EP2^ANT ) or EP4 agonist (EP4^AGO ). Pretreatment with EP2^ANT blocked the effect of PGE₂ or EP2^AGO on P_alb . Modulation of EP2 and EP4 also induced opposite effects on phosphorylation of Akt and β-Catenin. Individual agonists or antagonists of EP2 or EP4 did not induce significant improvement in albuminuria in UNX mice. However, treatment with a combination EP2^ANT  + EP4^AGO for 1 or 6 months caused a robust decrease in albuminuria. EP2^ANT  + EP4^AGO combination did not impact adaptive hypertrophy or increased serum creatinine. Observed differences between expression of EP2 and EP4 on the glomerular barrier highlight these receptors as potential targets for intervention. Safe and effective mitigating effect of EP2^ANT  + EP4^AGO presents a novel opportunity to delay the progression of hyperfiltration-associated CKD as seen in transplant donors.

Evolution of congenital anomalies of urinary tract in children with and without solitary kidney

BACKGROUND

We hypothesized that children with congenital solitary functioning kidney (CSFK) present forms of congenital urinary tract anomalies (CUTA) with higher chance of spontaneous resolution compared with patients with two kidneys.

METHODS

We retrospectively selected 75 consecutive children with CUTA of the CSFK and 75 matched patients with unilateral CUTA but without CSFK (controls) with prenatal suspicion of unilateral CUTA and early evaluation. We compared the spontaneous CUTA resolution and the prevalence of kidney injury between groups at last follow-up. Patients and controls were clustered under the categories of "severe" and "non-severe" CUTA.

RESULTS

The mean age at first and last follow-up was 0.17 ± 0.07 and 8.5 ± 5.2 years. Compared with controls, patients with CSFK had lower prevalence of severe CUTA at first evaluation; lower prevalence of febrile urinary tract infections, need of surgical correction, and higher rate of spontaneous CUTA resolution during follow-up; and a similar prevalence of mild kidney injury at last follow-up. CSFK compared with controls presented higher cumulative proportion of spontaneous resolution from severe CUTA (100 vs 41.8%; p &lt; 0.001) and from the single CUTA sub-categories (severe vesicoureteral reflux, non-obstructive hydronephrosis, and megaureter).

CONCLUSIONS

CSFK patients had lower prevalence of severe forms and better outcomes of their CUTA compared with controls.

IMPACT

One-third of patients with congenital solitary functioning kidney (CSFK) present congenital urinary tract anomalies (CUTA) and manifest poorer outcomes compared with CSFK without CUTA. CSFK patients had lower prevalence of severe forms and better outcomes of their CUTA in spite of similar prevalence of kidney injury compared with controls. This adds evidence about disturbed nephrogenesis in CSFK patients and emboldens conservative management of many of their non-obstructive CUTA.

Definition, diagnosis and clinical management of non-obstructive kidney dysplasia: a consensus statement by the ERKNet Working Group on Kidney Malformations

Kidney dysplasia is one of the most frequent causes of chronic kidney failure in children. While dysplasia is a histological diagnosis, the term 'kidney dysplasia' is frequently used in daily clinical life without histopathological confirmation. Clinical parameters of kidney dysplasia have not been clearly defined, leading to imprecise communication amongst healthcare professionals and patients. This lack of consensus hampers precise disease understanding and the development of specific therapies. Based on a structured literature search, we here suggest a common basis for clinical, imaging, genetic, pathological and basic science aspects of non-obstructive kidney dysplasia associated with functional kidney impairment. We propose to accept hallmark sonographic findings as surrogate parameters defining a clinical diagnosis of dysplastic kidneys. We suggest differentiated clinical follow-up plans for children with kidney dysplasia and summarize established monogenic causes for non-obstructive kidney dysplasia. Finally, we point out and discuss research gaps in the field.

The causes and consequences of paediatric kidney disease on adult nephrology care

Adult nephrologists often look after patients who have been diagnosed with kidney disease in childhood. This does present unique challenges to the adult nephrologist, who may be unfamiliar with the underlying cause of kidney disease as well as the complications of chronic kidney disease (CKD) that may have accumulated during childhood. This review discusses common causes of childhood CKD, in particular congenital anomalies of the kidney and urinary tract (CAKUT), autosomal dominant tubulointerstitial kidney disease (ADTKD), polycystic kidney disease, hereditary stone disease, nephrotic syndrome and atypical haemolytic uraemic syndrome. The long-term consequences of childhood CKD, such as the cardiovascular consequences, cognition and education as well as bone health, nutrition and growth are also discussed.

Glomerular hyperfiltration

Circulating blood is filtered across the glomerular barrier to form an ultrafiltrate of plasma in the Bowman's space. The volume of glomerular filtration adjusted by time is defined as the glomerular filtration rate (GFR), and the total GFR is the sum of all single-nephron GFRs. Thus, when the single-nephron GFR is increased in the context of a normal number of functioning nephrons, single glomerular hyperfiltration results in 'absolute' hyperfiltration in the kidney. 'Absolute' hyperfiltration can occur in healthy people after high protein intake, during pregnancy and in patients with diabetes, obesity or autosomal-dominant polycystic kidney disease. When the number of functioning nephrons is reduced, single-nephron glomerular hyperfiltration can result in a GFR that is within or below the normal range. This 'relative' hyperfiltration can occur in patients with a congenitally reduced nephron number or with an acquired reduction in nephron mass consequent to surgery or kidney disease. Improved understanding of the mechanisms that underlie 'absolute' and 'relative' glomerular hyperfiltration in different clinical settings, and of whether and how the single-nephron haemodynamic and related biomechanical forces that underlie glomerular hyperfiltration promote glomerular injury, will pave the way toward the development of novel therapeutic interventions that attenuate glomerular hyperfiltration and potentially prevent or limit consequent progressive kidney injury and loss of function.

Brief Early Life Angiotensin Converting Enzyme Inhibition Offers Reno-Protection in Sheep with a Solitary Functioning Kidney at 8 Months of Age

Background: Children born with a solitary functioning kidney (SFK) are predisposed to develop hypertension and kidney injury. Glomerular hyperfiltration and hypertrophy contribute to the pathophysiology of kidney injury. Angiotensin converting enzyme inhibitors (ACEi) can mitigate hyperfiltration and may be therapeutically beneficial in reducing progression of kidney injury in SFK. Methods: SFK was induced in male sheep fetuses at 100 days gestation (term=150 day). Between 4-8 weeks of age, SFK lambs received enalapril (SFK+ACEi; 0.5mg/kg/day, once daily, orally) or vehicle (SFK). At 8 months we examined whether SFK+ACEi reduced elevation in blood pressure (BP) and improved basal kidney function, renal functional reserve (RFR; glomerular filtration rate (GFR) response to combined amino acid and dopamine infusion), GFR response to nitric oxide synthase (NOS) inhibition and basal nitric oxide (NO) bioavailability (basal urinary total nitrate+nitrite (NOx)). Results: SFK+ACEi prevented albuminuria, resulted in lower basal GFR (16%), higher renal blood flow (~22%), and lower filtration fraction ( 35%), but similar BP compared to ~ vehicle-treated SFK sheep. Together with greater recruitment of RFR (~14%) in SFK+ACEi animals than SFK, this indicates reduction in glomerular hyperfiltration-mediated kidney dysfunction. During NOS inhibition, the decrease in GFR ( 14%) was greater among SFK+ACEi than among SFK animals. Increased ( 85%) basal urinary total NOx in SFK+ACEi animals compared to SFK indicates elevated NO bioavailability likely contributing to improvements in kidney function and prevention of albuminuria. Conclusions: Brief and early ACEi in SFK is associated with reduced glomerular hyperfiltration-mediated kidney disease up to 8 months of age in a sheep model.

Multidisciplinary approaches for elucidating genetics and molecular pathogenesis of urinary tract malformations

Advances in clinical diagnostics and molecular tools have improved our understanding of the genetically heterogeneous causes underlying congenital anomalies of kidney and urinary tract (CAKUT). However, despite a sharp incline of CAKUT reports in the literature within the past 2 decades, there remains a plateau in the genetic diagnostic yield that is disproportionate to the accelerated ability to generate robust genome-wide data. Explanations for this observation include (i) diverse inheritance patterns with incomplete penetrance and variable expressivity, (ii) rarity of single-gene drivers such that large sample sizes are required to meet the burden of proof, and (iii) multigene interactions that might produce either intra- (e.g., copy number variants) or inter- (e.g., effects in trans) locus effects. These challenges present an opportunity for the community to implement innovative genetic and molecular avenues to explain the missing heritability and to better elucidate the mechanisms that underscore CAKUT. Here, we review recent multidisciplinary approaches at the intersection of genetics, genomics, in vivo modeling, and in vitro systems toward refining a blueprint for overcoming the diagnostic hurdles that are pervasive in urinary tract malformation cohorts. These approaches will not only benefit clinical management by reducing age at molecular diagnosis and prompting early evaluation for comorbid features but will also serve as a springboard for therapeutic development.

Prevalence of reflux nephropathy in Iranian children with solitary kidney: results of a multi-center study

Background

Given the importance of the function of the remnant kidney in children with unilateral renal agenesis and the significance of timely diagnosis and treatment of reflux nephropathy to prevent further damage to the remaining kidney, we aimed to determine the prevalence of reflux nephropathy in this subgroup of pediatric patients.

Methods

In general, 274 children referred to pediatric nephrologists in different parts of Iran were evaluated, of whom 199 had solitary kidney and were included in this cross-sectional study. The reasons for referral included urinary tract infection (UTI), abnormal renal ultrasonography, being symptomatic, and incidental screening. Demographic characteristics, including age and gender were recorded. History of UTI and presence of vesicoureteral reflux (VUR) were evaluated.

Results

Of the 274 children evaluated in this study with the mean age (SD) of 4.71 (4.24) years, 199 (72.6%) had solitary kidney. Among these, 118 (59.3%) were male and 81 (60.7%) were female, 21.1% had a history of UTI, and VUR was present in 23.1%. The most common cause of referral was abnormal renal ultrasonography (40.2%), followed by incidental screening (21.1%), being symptomatic (14.1%), and UTI (5.5%). In 116 children (58.3%), the right kidneys and in 83 (41.7%) the left kidneys were absent. Besides, 14.6% of the participants had consanguineous parents and 3% had a family history of solitary kidney. Upon DMSA scan, the single kidney was scarred in 13.1%, of which only 7.5% were associated with VUR. In addition, proteinuria and hematuria were observed in 6.5% and 1.5% of children, respectively.

Conclusions

The prevalence of reflux nephropathy was 7.5% in children with solitary kidney with a male predominance. Given the relatively high prevalence of reflux nephropathy in these children, screening for VUR in the remnant kidney appears to be essential in this population.

Early Renal Ultrasound in Patients with Congenital Solitary Kidney Can Guide Follow-Up Strategy Reducing Costs While Keeping Long-Term Prognostic Information

We aimed to evaluate the prognostic value of renal length (RL) > 2 standard deviation scores (SDS) measured by renal ultrasound (RUS), across infancy, childhood and adolescence, in identifying which patients with congenital solitary functioning kidney (CSFK) are at lower risk of developing kidney injury (KI). We also estimated the cost saving of integrating the current follow-up protocols with an early RUS algorithm (ERUSA). Fifty-six CSFK adult patients who were 1–3 months old at first observation of undergoing RUS were enrolled. KI was defined by hypertension and/or proteinuria and/or declined renal function. ERUSA was assessed by early (at 1–3 months of life) RUS and was retrospectively tested in our patients. ERUSA establishes that patients with RL > 2SDS at early RUS do not undergo further follow-ups. The others undergo another RUS at 1 year of age along with follow-ups according with current protocols, with the exception of RUS which could be no longer performed. Direct and indirect costs were calculated for each analysed protocol and the cost saving of applying ERUSA was calculated. None of the patients with early RL > 2SDS presented KI in adulthood. A RL > 2SDS was predictive of absence of KI only at 1–3 months (OR = infinity) and 1 year of age (OR = 0.13; 95%CI: 0.03–0.66; p = 0.01). ERUSA provided a total cost-sparing ranging from 38.6% to 55.3% among the analysed follow-up protocols. With ERUSA, no patients developing KI in adulthood were missed. In conclusion, only a RL > 2SDS at 1–3 months and 1 year of age predicted good prognosis in young adulthood. ERUSA can guide a cost-sparing follow-up strategy in CSFK patients while maintaining important long-term information.

Kidney injury rates after unilateral nephrectomy in childhood-a systematic review and meta-analysis

BACKGROUND

Unilateral nephrectomy is a relatively common procedure in children which results in a solitary functioning kidney (SFK). Living with an SFK predisposes to kidney injury, but it remains unknown which children are most at risk. We aimed to investigate kidney injury rates in patients who underwent unilateral nephrectomy in childhood and to investigate differences among nephrectomies performed for a congenital anomaly, malignancy or other condition.

METHODS

MEDLINE and EMBASE were searched for studies reporting kidney injury rates [i.e. proteinuria, hypertension and/or a decreased glomerular filtration rate (GFR)] of patients who underwent unilateral nephrectomy during childhood. Studies including five or more patients with at least 12 months of follow-up were eligible. Analyses were performed using random effects models and stratified by indication for nephrectomy. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines were used for reporting.

RESULTS

Over 5000 unique articles were screened, of which 53 studies reporting on >4000 patients were included in the analyses. Proteinuria, hypertension and a decreased GFR were present in 15.3, 14.5 and 11.9% of patients, respectively. Heterogeneity among the studies was large in several subgroups, impairing quantitative meta-analyses. However, none of our analyses indicated differences in injury rates between a congenital anomaly or malignancy as an indication for nephrectomy.

CONCLUSIONS

Unilateral nephrectomy during childhood results in signs of kidney injury in >10% of patients, with no clear difference between the indications for nephrectomy. Therefore, structured follow-up is necessary in all children who underwent nephrectomy, regardless of the indication.

Management of the congenital solitary kidney: consensus recommendations of the Italian Society of Pediatric Nephrology

In recent years, several studies have been published on the prognosis of children with congenital solitary kidney (CSK), with controversial results, and a worldwide consensus on management and follow-up is lacking. In this consensus statement, the Italian Society of Pediatric Nephrology summarizes the current knowledge on CSK and presents recommendations for its management, including diagnostic approach, nutritional and lifestyle habits, and follow-up. We recommend that any antenatal suspicion/diagnosis of CSK be confirmed by neonatal ultrasound (US), avoiding the routine use of further imaging if no other anomalies of kidney/urinary tract are detected. A CSK without additional abnormalities is expected to undergo compensatory enlargement, which should be assessed by US. We recommend that urinalysis, but not blood tests or genetic analysis, be routinely performed at diagnosis in infants and children showing compensatory enlargement of the CSK. Extrarenal malformations should be searched for, particularly genital tract malformations in females. An excessive protein and salt intake should be avoided, while sport participation should not be restricted. We recommend a lifelong follow-up, which should be tailored on risk stratification, as follows: low risk: CSK with compensatory enlargement, medium risk: CSK without compensatory enlargement and/or additional CAKUT, and high risk: decreased GFR and/or proteinuria, and/or hypertension. We recommend that in children at low-risk periodic US, urinalysis and BP measurement be performed; in those at medium risk, we recommend that serum creatinine also be measured; in high-risk children, the schedule has to be tailored according to kidney function and clinical data.

Bilateral Renal Tumors in Children: The First 5 Years' Experience of National Centralization in The Netherlands and a Narrative Review of the Literature

Survival of unilateral Wilms tumors (WTs) is exceeding 90%, whereas bilateral WTs have an inferior outcome. We evaluated all Dutch patients with bilateral kidney tumors, treated in the first five years of national centralization and reviewed relevant literature. We identified 24 patients in our center (2015–2020), 23 patients had WT/nephroblastomatosis and one renal cell carcinoma. Patients were treated according to SIOP-RTSG protocols. Chemotherapy response was observed in 26/34 WTs. Nephroblastomatosis lesions were stable (n = 7) or showed response (n = 18). Nephron-sparing surgery was performed in 11/22 patients undergoing surgery (n = 2 kidneys positive margins). Local stage in 20 patients with ≥1 WT revealed stage I (n = 7), II (n = 4) and III (n = 9). Histology was intermediate risk in 15 patients and high risk in 5. Three patients developed a WT in a treated nephroblastomatosis lesion. Two of 24 patients died following toxicity and renal failure, i.e., respectively dialysis-related invasive fungal infection and septic shock. Genetic predisposition was confirmed in 18/24 patients. Our literature review revealed that knowledge is scarce on bilateral renal tumor patients with metastases and that radiotherapy seems important for local stage III patients. Bilateral renal tumors are a therapeutic challenge. We describe management and outcome in a national expert center and summarized available literature, serving as baseline for further improvement of care.

Outcomes of solitary functioning kidneys-renal agenesis is different than multicystic dysplastic kidney disease

BACKGROUND

Multicystic dysplastic kidney (MCDK) disease and unilateral renal agenesis (URA) are well-known causes of a solitary functioning kidney (SFK) and are associated with long-term kidney injury. The aims of this study were to characterize the natural history of SFK at our center, define the risk factors associated with chronic kidney injury, and identify distinguishing features between URA and MCDK that predict outcome.

METHODS

This was a retrospective cohort study of 230 SFK patients. We compared MCDK (n=160) and URA (n=70) according to clinical features at diagnosis and kidney outcomes over follow-up. Univariate and multivariate binary regression analysis was used to determine independent risk factors for chronic kidney injury, defined as the composite outcome of hypertension, proteinuria, or chronic kidney disease (eGFR <60 mL/min/1.73m²).

RESULTS

URA had a higher prevalence of comorbid genetic syndromes (15 vs. 6%, p=0.04), non-renal anomalies (39 vs. 11%, p<0.001), and congenital anomalies of the kidney and urinary tract (CAKUT) (51 vs. 26%, p<0.001) than MCDK. Over follow-up, URA experienced more hypertension (19 vs. 3%, p=0.002), proteinuria (12 vs. 3%, p=0.03), and the composite outcome (19 vs. 6%, p=0.003) than MCDK. Independent risk factors for chronic kidney injury included CAKUT (OR 5.01, p=0.002) and URA (OR 2.71, p=0.04).

CONCLUSIONS

In our population, URA was more likely to have associated syndromes or anomalies, and to have worse outcomes over time than MCDK. URA diagnosis was an independent risk factor for chronic kidney injury. Our results will be used to develop a standardized clinical pathway for SFK management. A higher resolution version of the Graphical abstract is available as Supplementary information.

Atypical granular cell tumor of the urinary bladder: A case report

BACKGROUND

Granular cell tumor (GCT) is a neurogenic tumor mainly occurring in the head and neck. GCT in the genitourinary system is extremely rare and only sporadic cases of urinary bladder GCT have been reported. Most urinary bladder GCT cases are benign and only two malignant cases have been reported. Due to its rarity, no consensus criteria for the treatment of urinary bladder GCT are available at present.

CASE SUMMARY

A 62-year-old Chinese woman was found to have a urinary bladder tumor without any clinical manifestations on physical examination. Cystoscopy revealed a semispherical shaped lesion measuring approximately 4.0 cm in diameter at the junction of the left wall and roof of the bladder, which was covered with normal bladder mucosa. Computed tomography scan demonstrated a high-density lesion on the left wall of the bladder, measuring approximately 2.9 cm × 2.4 cm with clear boundaries. Contrast-enhanced pelvic magnetic resonance imaging revealed a space-occupying lesion on the left wall of the bladder (non-mucosal origin/ external pressure), which was preliminarily suspected to be a desmoplastic fibroma or leiomyoma. In the context of the above findings, a pre-operative diagnosis of bladder leiomyoma was made. The patient consequently underwent a laparoscopic partial cystectomy. The resected bladder mass looked yellowish and well-demarcated, measuring 4.0 cm × 3.5 cm and infiltrated the muscular layer. The diagnosis of urinary bladder GCT was finally made by postoperative pathology, with positive immunohistochemical S-100 staining and negative pancytokeratin. The patient has been followed for 6 mo so far, with no tumor recurrence detected.

CONCLUSION

This case highlights the biological feature and differential diagnosis of urinary bladder GCT at the pathological and molecular levels. Transurethral resection of the bladder tumor and partial cystectomy are recommended in most urinary bladder GCT cases, while radical cystectomy is recommended in malignant cases.

A Retrospective Analysis of Female Müllerian Duct Anomalies in Association With Congenital Renal Abnormalities

STUDY OBJECTIVE

Müllerian (paramesonephric) duct anomalies (MDAs) are associated with several coexisting congenital abnormalities, including renal abnormalities. Although congenital renal abnormalities may remain asymptomatic, the consequences should not be underestimated. In both the literature and clinical practice, it remains necessary to improve awareness of the co-occurrence of different congenital renal abnormalities in women with MDAs. To gain further insight into this co-occurrence and to estimate whether guidelines for women with MDAs should be optimized, this study was performed.

DESIGN

A descriptive retrospective analysis.

SETTING

University Medical Centre Utrecht in the Netherlands.

PARTICIPANTS

Women with MDAs diagnosed or treated between 1980 and 2015.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The prevalence of the co-occurrence of congenital renal abnormalities in women with MDAs.

RESULTS

Renal status was recorded in 186 of 255 women (72.9%), and the other women (27.1%) did not have a retrievable renal status. Congenital renal abnormalities were present in 90 of 186 women (48.4%) and were observed most frequently in women having a duplex uterus with obstructed hemivagina. The most common renal abnormality was unilateral renal agenesis, which was observed in 58 of 90 women (64.4%).

CONCLUSIONS

MDAs are highly associated with different congenital renal abnormalities, and these results emphasize that women with MDAs should be routinely screened for their co-occurrence. However, these results also highlight that there remains a lack of awareness of this association. Whether all women with congenital renal abnormalities should be routinely screened for MDAs requires further investigation.

The spectrum of kidney function alterations in adolescents with a solitary functioning kidney

BACKGROUND

A precise assessment of glomerular filtration rate is key to delineate the care of children with a solitary functioning kidney (SFK). Data regarding measured GFR (mGFR) in this population is restricted to a single study of 77 individuals, which suggested that a GFR estimation (eGFR) method based on creatinine and cystatin C (eGFR-CKiD2) performed better than Schwartz's equation (eGFR-Schwartz).

METHODS

We measured GFR in 210 consecutive adolescents (7 to 22 years old) with an SFK referred to our institution between 2014 and 2019 and in 43 young candidates for kidney donation (18 to 25 years old). We compared the distribution of mGFR in both groups and determined the factors associated with reduced mGFR in adolescents with an SFK. We further compared different eGFR formulas with mGFR and assessed the association of mGFR and eGFRs with PTH and FGF23, two early indicators of GFR reduction.

RESULTS

While adolescents with an SFK had a similar median mGFR to healthy controls (103 ± 24ml/min/1.73m² vs. 107 ± 12 ml/min/1.73m²), the fraction of individuals with an mGFR below 90 ml/min/1.73m² was higher in patients with SFK (23% vs. 5% in controls; P = 0.005). Multiple linear regression identified older age, ipsilateral abnormalities of the urinary tract, lack of compensatory hypertrophy, and treated hypertension as independent factors associated with reduced mGFR. A smaller bias using eGFR-Schwartz (95% confidence interval (95%CI): 3 to 7) was revealed when compared to other eGFR. Compared to eGFR-Schwartz, mGFR showed a stronger correlation with PTH (r = 0.04 vs. r = 0.1) and FGF23 (r = 0.03 vs. r = 0.05).

CONCLUSION

SFK is not a benign condition, since 20% of the patients display altered kidney function. Our results raise caution regarding the use of the cystatin-based equation. mGFR shows a better ability than eGFR-Schwartz to differentiate patients showing early homeostatic adaptation to GFR reduction.

Long-term follow-up of congenital anomalies of the kidney and urinary tract diagnosed in utero: a longitudinal study

BACKGROUND

Congenital-anomalies of the kidney-and-urinary-tract (CAKUT) are diagnosed in 3-6 per 1000 live-births. The objective of the current study was to examine the short and long-term outcomes of children diagnosed prenatally with CAKUT.

METHODS

A retrospective study was performed in 2018 on all pregnancies diagnosed with CAKUT between 2004 and 2008 at our hospital. Pregnancy outcomes and long-term morbidity were evaluated. Comparison was made between mild and severe forms of CAKUT and between unilateral and bilateral anomalies.

RESULTS

Ninety-eight children were included in the study. Most of them were born with an adequate weight for gestational-age, and were born at term by vaginal-deliveries. Children with major renal anomalies suffered significantly more frequently from recurrent UTIs (33.3% vs. 8.4%), needed more preventive antibiotics (50% vs. 20.5%), and had more renal surgeries (75% vs. 28%) than those with milder forms of CAKUT. Significantly more children with polycystic/multicystic kidney disease had recurrent UTIs (50% compared to 25% of the children with renal agenesis, and 5.6% of the children with hydronephrosis/hydroureter). There were no significant differences in the need for neurodevelopmental follow-up between the different groups of severity. Unilateral CAKUT patients required longer periods of nephrologist follow-up and repeated sonographic exams compared to bilateral CAKUT patients. Children with bilateral CAKUT more often needed special educational support than peers with unilateral disease (29.4% vs. 11.1%, P = 0.03).

CONCLUSIONS

Pregnancies whose children are diagnosed with CAKUT in utero usually deliver at term, with adequate-weight for gestational-age. The most common long-term comorbidities in children were recurrent UTIs and the use of preventive antibiotics was often needed. Expecting couples can be reassured of a generally good outcome of their children, at least during the first decade of life.

Is the prognosis of congenital single functioning kidney benign? A population-based study

BACKGROUND

We investigated the risk of kidney injury among adolescents with and without a congenital single functioning kidney (SFK).

METHODS

This retrospective study is based on a medical evaluation database of 17-year-old Israeli conscripts, born during 1989-1999. Those with congenital SFK diagnosis, verified by a pediatric nephrologist's review of the original military medical committee classifications, were compared to the rest of the cohort. Kidney injury (KI) was defined as proteinuria, high blood pressure (BP), or estimated glomerular filtration rate (eGFR) < 90 ml/min/1.73 m² prior to army recruitment. Risk factors for KI were examined using logistic regression.

RESULTS

Of 979,630 screened candidates, 353 were diagnosed with SFK. The yearly incidence of SFK gradually increased in the first years of the study, reaching a plateau in 1995 (5.5 ± 1.2/10,000 births/year). The male to female ratio was 2.7:1. Concomitant genital malformations were documented in 5.5% of those with SFK. KI was more prevalent in the SFK than the control group (42.2% vs. 23.5%, p < 0.001). All three components of KI were more common in the SFK than the control group: high BP (31.7% vs. 23.1%, p < 0.001), proteinuria (18.2% vs. 0.4%, p < 0.001), and eGFR <90 ml/min/1.73m² (12.0% vs 0.1%, p < 0.001). Multivariate analysis of the SFK group revealed associations of higher mean BMI, male sex, and smaller ultrasonographic kidney length with KI.

CONCLUSIONS

This large population-based study documents a significant risk for KI among adolescents with SFK. Obesity represents a major modifiable risk factor for KI, implicating the need for closer follow-up in this group during childhood.

Retrospective evaluation of children with unilateral renal agenesis

BACKGROUND

Children born with unilateral renal agenesis (URA) are thought to have a risk of developing hypertension, proteinuria, and progressive chronic kidney disease (CKD). The present study aimed to evaluate the long-term prognosis and clinical characteristics of children with URA.

METHODS

The study included 171 patients aged < 18 years diagnosed as URA who were followed-up for ≥ 1 year and 121 healthy controls matched for age, gender, and BMI.

RESULTS

Median age at diagnosis was 2 years (IQR: 1 month-16 years) and the incidence of URA in males (65.4%) was higher than in females. Among the patients, 21 (12.2%) had other urinary system anomalies. It was noted that 2.3% of the patients had proteinuria, 15.2% had hyperfiltration, and 2.9% had CKD. Hypertension based on ambulatory blood pressure monitoring (ABPM) was diagnosed in 18 (10.5%) of the patients, of whom 10 had masked hypertension. Diastolic blood pressure in the URA patients was significantly higher than in the healthy controls. The incidence of hypertension and CKD was significantly higher in the patients with other urinary system anomalies.

CONCLUSIONS

Patients with a single functional kidney should be periodically evaluated throughout their lifetime for urine protein, blood pressure, and kidney functions. The most remarkable finding of this study is the importance of the use of ABPM for evaluating blood pressure in pediatric URA patients, especially for the detection of masked hypertension and the non-dipper phenomenon, which cannot be achieved with office blood pressure measurement.

Renal function in children with a congenital solitary functioning kidney: A systematic review

INTRODUCTION

Abnormal renal development that results in lack of function or development of one of two kidneys is known as congenital solitary functioning kidney (CSFK). Two well characterized sub-categories of CFSK are unilateral renal agenesis (URA) and multicystic dysplastic kidney (MCDK). This systematic review sought to evaluate the change in renal function in children ≤18 years old with a CSFK as a result of URA or MCDK.

METHODS

A literature search in MEDLINE and Embase was conducted (1946 to July 13, 2020). All relevant articles were retrieved and evaluated based on pre-selected criteria by two independent researchers. Data was then extracted from variables of interest and conflicts were resolved by a third researcher. The primary outcome was renal function, and the secondary outcomes were proteinuria and hypertension.

RESULTS

Forty-five studies were included, of which 49% (n = 22) were retrospective and/or 58% (n = 26) were cohort studies. A combined total of 2148 and 885 patients were diagnosed with MCDK or URA, respectively. The proportion of children with worsened renal function at follow-up was found to be 8.4% (95% CI: 5.2%-13.4%). Among the studies reporting renal function as a group mean or median at follow-up, 84% (21/25) had a GFR/CrCl above 90 (mL/min/1.73  m²/ml/min). In terms of secondary outcomes, the proportion of children with proteinuria and hypertension was found to be 10.1% (95% CI: 6.9%-14.6%) and 7.4% (95% CI: 5.0%-10.9%), respectively.

CONCLUSION

The risk of developing proteinuria (10.1%), hypertension (7.4%), and/or worsened renal function (8.4%) for children with CFSK as a result of MCDK or URA is low. However, the level of evidence in the literature is weak. Further research is needed to identify the predisposing factors that may differentiate the small subset of children with CSFK at a higher risk of developing adverse renal outcomes.

A mouse model of prenatal exposure to Interleukin-6 to study the developmental origin of health and disease

Systemic inflammation in pregnant obese women is associated with 1.5- to 2-fold increase in serum Interleukin-6 (IL-6) and newborns with lower kidney/body weight ratio but the role of IL-6 in increased susceptibility to chronic kidney (CKD) in adult progeny is not known. Since IL-6 crosses the placental barrier, we administered recombinant IL-6 (10 pg/g) to pregnant mice starting at mid-gestation yielded newborns with lower body (p < 0.001) and kidney (p < 0.001) weights. Histomorphometry indicated decreased nephrogenic zone width (p = 0.039) with increased numbers of mature glomeruli (p = 0.002) and pre-tubular aggregates (p = 0.041). Accelerated maturation in IL-6 newborns was suggested by early expression of podocyte-specific protein podocin in glomeruli, increased 5-methyl-cytosine (LC–MS analysis for CpG DNA methylation) and altered expression of certain genes of cell-cycle and apoptosis (RT-qPCR array-analysis). Western blotting showed upregulated pJAK2/pSTAT3. Thus, treating dams with IL-6 as a surrogate provides newborns to study effects of maternal systemic inflammation on future susceptibility to CKD in adulthood.

Transcription Factor β-Catenin Plays a Key Role in Fluid Flow Shear Stress-Mediated Glomerular Injury in Solitary Kidney

Increased fluid flow shear stress (FFSS) in solitary kidney alters podocyte function in vivo. FFSS-treated cultured podocytes show upregulated AKT-GSK3β-β-catenin signaling. The present study was undertaken to confirm (i) the activation of β-catenin signaling in podocytes in vivo using unilaterally nephrectomized (UNX) TOPGAL mice with the β-galactosidase reporter gene for β-catenin activation, (ii) β-catenin translocation in FFSS-treated mouse podocytes, and (iii) β-catenin signaling using publicly available data from UNX mice. The UNX of TOPGAL mice resulted in glomerular hypertrophy and increased the mesangial matrix consistent with hemodynamic adaptation. Uninephrectomized TOPGAL mice showed an increased β-galactosidase expression at 4 weeks but not at 12 weeks, as assessed using immunofluorescence microscopy (p < 0.001 at 4 weeks; p = 0.16 at 12 weeks) and X-gal staining (p = 0.008 at 4 weeks; p = 0.65 at 12 weeks). Immunofluorescence microscopy showed a significant increase in phospho-β-catenin (Ser552, p = 0.005) at 4 weeks but not at 12 weeks (p = 0.935) following UNX, and the levels of phospho-β-catenin (Ser675) did not change. In vitro FFSS caused a sustained increase in the nuclear translocation of phospho-β-catenin (Ser552) but not phospho-β-catenin (Ser675) in podocytes. The bioinformatic analysis of the GEO dataset, #GSE53996, also identified β-catenin as a key upstream regulator. We conclude that transcription factor β-catenin mediates FFSS-induced podocyte (glomerular) injury in solitary kidney.

Evaluation of renal injury in children with a solitary functioning kidney

Objective

Children with a solitary functioning kidney have an increased risk of developing renal injury that is hypothesized to be caused by glomerular hyperfiltration. In this study, we aimed to assess the early signs of renal injury and ambulatory blood pressure profiles in children with a solitary functioning kidney.

Materials and Methods

Data of children with normal office blood pressure measurement and a solitary functioning kidney were reviewed (serum creatinine and urine albumin and β2 microglobulin excretions), and 23 age-, weight-, and height-matched healthy children were considered as a control group. The size of the kidney was measured by renal ultrasound, and the presence of compensatory hypertrophy was calculated for all the subjects. Also, the subjects were additionally assessed for blood pressure (BP) pattern and the presence of hypertension by 24-hambulatory blood pressure monitoring.

Results

The solitary functioning kidney demonstrated compensatory hypertrophy in 36 out of the patients (86%) at a mean age of 14.0 (SD 3.0) years. Increased urine albumin and β2 microglobulinuria, which are signs of kidney damage, were found in 7 (17%) and 5(12%) patients. Compared with the controls, patients had significantly higher mean blood pressure standard deviation scores (p>0,001), and ambulatory blood pressure monitoring identified masked hypertension in 7 (17%) children and prehypertension in 6 (14%) patients. Therefore, renal injury, defined as the presence of hypertension and/or albuminuria and/or β2 microglobulinuria and/or hypertension, was present in 36% of all children with a solitary functioning kidney.

Conclusion

Children with a solitary functioning kidney need prolonged follow-up to detect early signs of renal injury and prevent end-organ damage later in life. Ambulatory blood pressure monitoring is an essential tool in the diagnosis and clinical management of solitary functioning kidney patients.

Clinical Management of Children with a Congenital Solitary Functioning Kidney: Overview and Recommendations

CONTEXT

A congenital solitary functioning kidney (cSFK) is a common developmental defect that predisposes to hypertension and chronic kidney disease (CKD) as a consequence of hyperfiltration. Every urologist takes care of patients with a cSFK, since some will need lifelong urological care or will come with clinical problems or questions to an adult urologist later in life.

OBJECTIVE

We aim to provide clear recommendations for the initial clinical management and follow-up of children with a cSFK.

EVIDENCE ACQUISITION

PubMed and EMBASE were searched to identify relevant publications, which were combined with guidelines on related topics and expert opinion.

EVIDENCE SYNTHESIS

Initially, cSFK diagnosis should be confirmed and risk factors for kidney injury should be identified using ultrasound. Although more research into early predictors of kidney injury is needed, additional congenital anomalies of the kidney or urinary tract and absence of compensatory kidney hypertrophy have repeatedly been associated with a worse prognosis. The role of voiding cystourethrography and antibiotic prophylaxis remains controversial, and is complicated by the exclusion of children with a cSFK from studies. A yearly follow-up for signs of kidney injury is recommended for children with a cSFK. As masked hypertension is prevalent, annual ambulatory blood pressure measurement should be considered. During puberty, an increasing incidence of kidney injury is seen, indicating that long-term follow-up is necessary. If signs of kidney injury are present, angiotensin converting enzyme inhibitors are the first-line drugs of choice.

CONCLUSIONS

This overview points to the urological and medical clinical aspects and long-term care guidance for children with a cSFK, who are at risk of hypertension and CKD. Monitoring for signs of kidney injury is therefore recommended throughout life. Large, prospective studies with long-term follow-up of clearly defined cohorts are still needed to facilitate more risk-based and individualized clinical management.

PATIENT SUMMARY

Many children are born with only one functioning kidney, which could lead to kidney injury later in life. Therefore, a kidney ultrasound is made soon after birth, and other investigations may be needed as well. Urologists taking care of patients with a solitary functioning kidney should realize the long-term clinical aspects, which might need medical management.

Tumor Necrosis Factor-Like Weak Inducer of Apoptosis and Selected Cytokines-Potential Biomarkers in Children with Solitary Functioning Kidney

This study was performed to explore serum tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its dependent cytokines urinary excretion: monocyte chemoattractant protein-1 (MCP-1) and regulated on activation, normal T cell expressed and secreted chemokine (RANTES) with their relation to the kidney function parameters in children with solitary functioning kidney (SFK). The study included 80 children and adolescents (median age 9.75 year) with congenital and acquired (after surgical removal) SFK. Serum TWEAK and urinary MCP-1 and RANTES levels were significantly higher in SFK patients (p < 0.05). The serum TWEAK was positively related to serum creatinine (r = 0.356; p < 0.001). Moreover, in SFK the receiver operating characteristic analyses revealed good diagnostic profile for serum TWEAK with AUC (Area Under The Curve)—0.853, uRANTES—0.757, and for RANTES/cr.: AUC—0.816. Analysis carried out to identify children with impaired renal function (albuminuria and/or decreased estimated glomerular filtration rate < 90 mL/min/1.73 m² and/or hypertension) showed good profile for TWEAK (AUC—0.79) and quite good profile for uRANTES and RANTES/cr. (AUC 0.66 and 0.631, respectively). This is the first study investigating serum TWEAK and urinary excretion of MCP-1 and RANTES together in children with SFK. Obtained results indicate that TWEAK and RANTES may serve as potential markers of renal impairment.

Childhood Cancer and the Risk of ESKD

BACKGROUND

Increasing cancer incidence among children alongside improved treatments has resulted in a growing number of pediatric cancer survivors. Despite childhood cancer survivors' exposure to various factors that compromise kidney function, few studies have investigated the association between childhood cancer and future kidney disease.

METHODS

To assess the risk of ESKD among childhood cancer survivors, we conducted a nationwide, population-based, retrospective cohort study that encompassed all Israeli adolescents evaluated for mandatory military service from 1967 to 1997. After obtaining detailed histories, we divided the cohort into three groups: participants without a history of tumors, those with a history of a benign tumor (nonmalignant tumor with functional impairment), and those with a history of malignancy (excluding kidney cancer). This database was linked to the Israeli ESKD registry to identify incident ESKD cases. We used Cox proportional hazards models to estimate the hazard ratio (HR) of ESKD.

RESULTS

Of the 1,468,600 participants in the cohort, 1,444,345 had no history of tumors, 23,282 had a history of a benign tumor, and 973 had a history of malignancy. During a mean follow-up of 30.3 years, 2416 (0.2%) participants without a history of tumors developed ESKD. Although a history of benign tumors was not associated with an increased ESKD risk, participants with a history of malignancy exhibited a substantially elevated risk for ESKD compared with participants lacking a history of tumors, after controlling for age, sex, enrollment period, and paternal origin (adjusted HR, 3.2; 95% confidence interval, 1.3 to 7.7).

CONCLUSIONS

Childhood cancer is associated with an increased risk for ESKD, suggesting the need for tighter and longer nephrological follow-up.

Renal length z-score for the detection of dysfunction in children with solitary functioning kidney

AIM

To evaluate whether renal length z-scores predict renal dysfunction in children with a solitary functioning kidney (SFK).

METHODS

In a single-centre retrospective cohort of children with SFK, we correlated body mass index z-scores, extracellular volume and lean body mass to renal length z-scores. We grouped these z-scores to other markers of renal dysfunction (proteinuria, hypertension, extracellular volume and abnormal estimated glomerular function rate [eGFR]) and analysed renal length z-score with multivariate analysis, receiver-operated characteristics (ROC) plots and Youden's index to determine an appropriate cut-off.

RESULTS

111 children had a median follow-up 5.08 years, eGFR 80.8 mL/min/1.73 m² , and age at last follow-up 7.4 (3.8-13.4 years). The median renal length z-scores of those without any renal dysfunction (n = 37, 25.1%) were greater (+3.66, interquartile range 3.02-4.47) than those with renal dysfunction (median 3.11, interquartile range 1.76-4.11, P = .0107, Mann-Whitney test). Using a cut-off of z-score of >+1.911, the odds ratio for having no renal dysfunction was 0.07 (95% CI 0.002-0.459, P = .0010). However, accuracy of the renal length z-score was poor (ROC curve 0.6488).

CONCLUSION

In this cohort of children with SKF, using the renal length z-score as a biomarker of renal dysfunction at 7 years of age is not recommended.

Case Report: Uterine Anomalies in Girls With a Congenital Solitary Functioning Kidney

Unilateral renal agenesis and multicystic dysplastic kidney, resulting in a contralateral solitary functioning kidney (SFK), are part of the broad spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). In girls with SFK, screening for asymptomatic Müllerian anomalies of uterus and vagina is not yet routinely performed, and therefore often overlooked until clinical complications in the menstrual cycle or fertility process occur. In this case series, we report on four teenagers with congenital SFK presenting with menstrual problems due to a Müllerian anomaly. Routine peri-menarchal screening for Müllerian anomalies in girls with SFK may provide timely counseling, surgical treatment and prevention of associated complications such as endometriosis, infertility and miscarriages.

Early Renal Ultrasound in Congenital Solitary Kidney May Help to Select Patients at Lower Risk of Associated Vesicoureteral Reflux

BACKGROUND

Vesicoureteral reflux (VUR) may be associated with renal dysplasia and reduced renal length (RL). The diagnosis of VUR in children with congenital solitary functioning kidney (CSFK) identifies patients at risk of kidney injury but exposes to invasive procedures.

OBJECTIVE

We aimed to test the hypothesis that an RL >2 standard deviation score (SDS) in the first months of life - reflecting renal hyperplasia - could identify CSFK patients with lower probability of presenting VUR.

METHOD

We retrospectively selected 207 CSFK patients with prenatal diagnosis of CSFK and having undergone renal ultrasound (RUS) both at 0-3 and 10-13 months of life, renal scintigraphy, and cystourethrography/cysto-scintigraphy. We compared the cumulative proportion of an RL >2 SDS by Kaplan-Meier analysis and evaluated the odds to present VUR of patients with an RL >2 SDS both at the first and second RUS.

RESULTS

Overall, 3.3% of patients with VUR and 22.0% of patients without VUR presented an RL >2 SDS at the first RUS (p = 0.02). At the second RUS, 53.3% of patients with VUR and 52.5% of patients without VUR presented an RL >2 SDS (p = 0.93). Patients without VUR presented higher cumulative proportion of an RL >2 SDS at 3 months of life than those with VUR (p = 0.02). This difference however disappeared at 11 and 13 months of age (p = 0.17 and p = 0.54, respectively). An RL >2 SDS within 3 months of life presented an OR for VUR of 0.12 (95% CI: 0.02-0.92; p = 0.005), while an RL >2 SDS at 12 months of life presented an OR for VUR of 0.96 (95% CI: 0.45-2.1; p = 0.93).

CONCLUSION

Only an RUS made in the first months of life could identify CSFK patients at lower risk of presenting an associated VUR.

Side predilection in congenital anomalies of the kidney, urinary and genital tracts

BACKGROUND

There appear to be various patterns of sidedness with relation to the common urogenital malformations observed in pediatric urology. The objective of this statistical review was to synthesize this data and to assess if these patterns are significant.

MATERIALS AND METHODS

Eighteen urogenital conditions were investigated and for each condition the five largest studies that noted laterality were included. The sidedness of each condition was then analysed for statistical significance.

RESULTS

Three conditions had a statistically significant higher proportion on the right side: palpable undescended testis (63%, p = 0.0002), inguinal hernia (59%, p = 0.0001) and hydrocele (60%, p = 0.003). Three conditions were significantly more common on the left side: impalpable undescended testis (59%, p = 0.0008), renal agenesis (54%, p = 0.02) and vesico-ureteric junction obstruction (71%, p < 0.0001) while both pelvi-ureteric junction obstruction (62%, p = 0.09) and absent vas deferens (61%, p = 0.11) were trending towards significance.

CONCLUSIONS

Various urogenital malformations display a predilection for one side. Proximal malformations tend to be more frequently seen on the left side, where as inguinoscrotal malformations are more frequently observed on the right. There is an increasing body of literature regarding aetiological factors for these conditions. However, our current understanding of the pathophysiology of these conditions does not completely explain this pattern of observation.

Renal growth slope in children with congenital and acquired solitary functioning kidneys

Purpose

This study aimed to analyze the renal growth slope in children with congenital and acquired solitary functioning kidneys.

Methods

This retrospective study included all renal ultrasonography examinations performed in children in the agenesis, multicystic dysplastic kidney (MCDK), or nephrectomy group between September 2002 and February 2019. We reviewed the images and recorded the contralateral kidney size only when there was no focal lesion. Linear mixed model or piecewise linear mixed model analyses with a time point of 24 months of age were performed.

Results

There were 132 patients, including 26 patients in the agenesis group, 35 in the MCDK group, and 71 in the nephrectomy group. The nephrectomy group showed the largest baseline kidney size (7.4 cm vs. 5.3 cm in the agenesis group [P<0.001] and 5.2 cm in the MCDK group [P<0.001]) and the smallest overall growth slope (0.04 cm/mo vs. 0.06 cm/mo in the agenesis group [P=0.004] and 0.07 cm/mo in the MCDK group [P<0.001]). However, considering the time point of 24 months for reaching adult renal function, there were significant changes in slope, from 0.1 cm/mo before 24 months of age to 0.03 cm/mo after 24 months of age in all three groups (P<0.001), without a significant difference among the groups.

Conclusion

Significant changes were found in the renal growth slope before and after 24 months of age, with no significant difference between congenital and acquired solitary functioning kidneys.

Transforming Growth Factor-Beta 1 and Endoglin Levels in Congenital Solitary Functioning Kidney

Introduction:

Glomerular hyperfiltration leads to hypertension, microalbuminuria, and impaired renal function in children with congenital solitary functioning kidney (cSFK). The purpose of this study was to investigate the associations between serum transforming growth factor β-1 (TGF) and endoglin levels and hypertension, renal function or microalbuminuria in children with cSFK.

Materials and Methods:

63 patients and 36 controls were included in the study. Serum endoglin and TGF-β1 level was measured using ELISA commercial kits.

Results:

Serum TGF-β1 and endoglin levels were higher in patients than those of controls (P = 0.04 and P < 0.001, respectively). The prevalence of hypertension was found to be 45.6%. There was a positive association between endoglin levels and the presence of masked hypertension (odds ratio: 1.121, P = 0.04). TGF-β1 and endoglin levels were positively associated with microalbuminuria (OR: 1.17, P = 0.04; OR: 1.836, P = 0.01). ROC curve analysis showed that serum endoglin and TGF-β1 levels had predictive value for microalbuminuria (cut-off value: 4.86 ng/mL, sensitivity: 94.7%, specificity: 54.5%, area under the curve ± standard error [AUC ± SE]: 0.888 ± 0.025, P = 0.01 for endoglin; cut-off value 561.24 pg/mL, sensitivity: 89.5%, specificity: 73%, AUC ± SE: 0.995 ± 0.334, P = 0.02 for TGF-β1). There were no significant relationships between glomerular filtration rate and serum TGF-β1 or endoglin levels.

Conclusions:

Endoglin and TGF-β1 may play an important role in the pathophysiology of microalbuminuria in cSFK. Endoglin may have a role in the development of hypertension in children with cSFK.

Physiology and Pathophysiology of Compensatory Adaptations of a Solitary Functioning Kidney

Children born with a solitary functioning kidney (SFK) have an increased risk of hypertension and kidney disease from early in adulthood. In response to a reduction in kidney mass, the remaining kidney undergoes compensatory kidney growth. This is associated with both an increase in size of the kidney tubules and the glomeruli and an increase in single nephron glomerular filtration rate (SNGFR). The compensatory hypertrophy and increase in filtration at the level of the individual nephron results in normalization of total glomerular filtration rate (GFR). However, over time these same compensatory mechanisms may contribute to kidney injury and hypertension. Indeed, approximately 50% of children born with a SFK develop hypertension by the age of 18 and 20–40% require dialysis by the age of 30. The mechanisms that result in kidney injury are only partly understood, and early biomarkers that distinguish those at an elevated risk of kidney injury are needed. This review will outline the compensatory adaptations to a SFK, and outline how these adaptations may contribute to kidney injury and hypertension later in life. These will be based largely on the mechanisms we have identified from our studies in an ovine model of SFK, that implicate the renal nitric oxide system, the renin angiotensin system and the renal nerves to kidney disease and hypertension associated with SFK. This discussion will also evaluate current, and speculate on next generation, prognostic factors that may predict those children at a higher risk of future kidney disease and hypertension.

Augmented renal clearance in pediatric intensive care: are we undertreating our sickest patients?

Many critically ill patients display a supraphysiological renal function with enhanced renal perfusion and glomerular hyperfiltration. This phenomenon described as augmented renal clearance (ARC) may result in enhanced drug elimination through renal excretion mechanisms. Augmented renal clearance seems to be triggered by systemic inflammation and therapeutic interventions in intensive care. There is growing evidence that ARC is not restricted to the adult intensive care population, but is also prevalent in critically ill children. Augmented renal clearance is often overlooked due to the lack of reliable methods to assess renal function in critically ill children. Standard equations to calculate glomerular filtration rate (GFR) are developed for patients who have a steady-state creatinine production and a stable renal function. Those formulas are not reliable in critically ill patients with acutely changing GFR and tend to underestimate true GFR in patients with ARC. Tools for real-time, continuous, and non-invasive measurement of fluctuating GFR are most needed to identify changes in kidney function during critical illness and therapeutic interventions. Such devices are currently being validated and hold a strong potential to become the standard of practice. In the meantime, urinary creatinine clearance is considered the most reliable method to detect ARC in critically ill patients. Augmented renal clearance is clearly associated with subtherapeutic antimicrobial concentrations and subsequent therapeutic failure. This warrants the need for adjusted dosing regimens to optimize pharmacokinetic and pharmacodynamic target attainment. This review aims to summarize current knowledge on ARC in critically ill children, to give insight into its possible pathophysiological mechanism, to evaluate screening methods for ARC in the pediatric intensive care population, and to illustrate the effect of ARC on drug exposure, therapeutic efficacy, and clinical outcome.

Urinary prostaglandin E2 is a biomarker of early adaptive hyperfiltration in solitary functioning kidney

INTRODUCTION

Hyperfiltration is a major contributor to progression of chronic kidney disease (CKD) in diabetes, obesity and in individuals with solitary functioning kidney (SFK). We have proposed hyperfiltration-induced injury as a continuum of overlapping glomerular changes caused by increased biomechanical forces namely, fluid flow shear stress (FFSS) and tensile stress. We have shown that FFSS is elevated in animals with SFK and, it upregulates prostaglandin E₂ (PGE₂), cyclooxygenase-2 and PGE₂ receptor EP2 in cultured podocytes and in uninephrectomized mice. We conceptualized urinary PGE₂ as a biomarker of early effects of hyperfiltration-induced injury preceding microalbuminuria in individuals with SFK. We studied children with SFK to validate our hypothesis.

METHODS

Urine samples from children with SFK and controls were analyzed for PGE₂, albumin (glomerular injury biomarker) and epidermal growth factor (EGF, tubular injury biomarker). Age, gender, and Z-scores for height, weight, BMI, and blood pressure were obtained.

RESULTS

Children with SFK were comparable to controls except for lower BMI Z-scores. The median values were elevated in SFK compared to control for urine PGE₂ [9.1 (n = 57) vs. 5.7 (n = 72), p = 0.009] ng/mgCr and albumin [7.6 (n = 40) vs. 7.0 (n = 41), p = 0.085] μg/mgCr, but not for EGF [20098 (n = 44) vs. 18637 (n = 44), p = 0.746] pg/mgCr. Significant increase in urinary PGE₂ (p = 0.024) and albumin (p = 0.019) but not EGF (p = 0.412) was observed using additional regression modeling. These three urinary analytes were independent of each other.

CONCLUSION

Increased urinary PGE₂ from elevated SNGFR and consequently increased FFSS during early stage of CKD precedes overt microalbuminuria and is a biomarker for early hyperfiltration-induced injury in individuals with SFK.