Congenital solitary kidney size at birth could predict reduced eGFR levels later in life

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.

Predicting outcomes in children with congenital anomalies of the kidney and urinary tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most frequent causes of childhood chronic kidney disease (CKD). Using a large CAKUT cohort, we sought to identify the predictors of CKD and to develop a prediction model that informs a risk-stratified clinical pathway.

METHODS

This was a retrospective cohort study including cases with multicystic dysplastic kidneys (MCDK), unilateral kidney agenesis (UKA), kidney hypoplasia (KH), and posterior urethral valves (PUV). We identified risk factors for CKD (estimated glomerular filtration rate [eGFR] <60 ml/min/1.73 m2) and tested their performance in an adjusted multivariate binary regression model. Prediction probability scores for CKD were used to separate cases likely to develop complications from those not needing specialist follow-up.

RESULTS

We identified 452 eligible cases of CAKUT with 22% developing CKD. Strongest associations with CKD included primary diagnosis (OR 3.5, 95% CI 2.6-4.6), preterm delivery (OR 2.3, 95% CI 1.2-4.4), non-kidney anomalies (OR 1.8, 95% CI 1.1-3), first eGFR<90 (OR 8.9, 95% CI 4.4-18.1), small kidney size (OR 9, 95% CI 4.9-16.6), and additional kidney anomalies (OR 1.6, 95% CI 1.2-2.8). PUV (OR 4.7, 95% CI 1.5-15.3), first eGFR <90 (OR 4.4, 95% CI 2-9.7), and kidney length to body length ratio <7.9 (OR 4.2, 95% CI 1.9-9.2) were independent predictors of CKD. The regression model had a prediction accuracy of 80% and a prediction probability c-statistic of 0.81.

CONCLUSION

Using a large combined CAKUT cohort we identified risk factors for CKD. Our prediction model provides the first steps towards a risk-stratified clinical pathway. A higher resolution version of the Graphical abstract is available as Supplementary information.

Effects of Lockdown for COVID-19 Pandemic on Chronic Kidney Disease Progression in Children with Congenital Anomalies of the Kidney and Urinary Tract: A Retrospective Pilot Study

The coronavirus disease 2019 (COVID-19) pandemic changed adults and children's lifestyle. We focused our attention on children affected by chronic kidney disease (CKD) due to congenital abnormalities of kidney and urinary tract (CAKUT) and their behavior during the lockdown. Our aims were to evaluate the incidence of CKD progression within 6 months after the end of the first Italian lockdown and the factors associated to it. CKD progression was defined by the transition to higher CKD stage or by the drop in estimated glomerular filtration rate by a 25% or more for patients belonging to CKD stages 1 and 2. We retrospectively selected 21 children with CAKUT and CKD ≥ stage 1 observed within 3 months before and 6 months after the first Italian lockdown. We called them by phone and asked them about their lifestyle before and during lockdown focusing on physical activity, screen time, sweet/candies/sugar-sweetened beverages eaten/drunk and adherence to the Mediterranean diet (MD) (through KIDMED questionnaire). We calculated and analyzed the delta between the pre- and post- lockdown observation of all collected parameters (clinical and biochemical parameters and questionnaires scores). Analyzing the overall cohort, we found significantly increased mean BMI and mean screen time and significantly lower mean physical activity time in post- compared with pre-lockdown observations. Eleven out of twenty-one patients (52.4%) had a worsening of CKD. These patients presented higher delta of levels of uric acid and microalbuminuria and showed minor adherence to the MD and declared to have consumed more sweets or candies or sugar-sweetened beverages/week during the lockdown with a tendentially major increment of BMI compared with patients not presenting CKD progression. In conclusion, the lockdown for COVID-19 pandemic determined increase of BMI in all enrolled patients due to a "forced" negative lifestyle. About half of these patients presented CKD progression. This progression was associated to less adherence to the MD and major consumption of sweets or candies or sugar-sweetened beverages.

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.

Diagnostic Performance of the Acute Kidney Injury Baseline Creatinine Equations in Children and Adolescents with Type 1 Diabetes Mellitus Onset

Three new equations for calculating the estimated basal serum creatinine (ebSCr) in hospitalized children have been developed: the simplified acute kidney injury (AKI) baseline creatinine (ABC) equation which considered only age in the formula; the equation including age and minimum creatinine (Crmin) within the initial 72 h from hospitalization (ABC-cr); and the equation including Crmin and height, weight, and age as squared values (ABC-advanced). We aimed to test the diagnostic performance of the ABC, ABC-cr and ABC-advanced equations in diagnosing AKI in 163 prospectively enrolled children with type 1 diabetes mellitus (T1DM) onset. We considered measured basal serum creatinine (mbSCr), the creatinine measured 14 days after T1DM onset. AKI was defined by the highest/basal serum creatine (HC/BC) ratio > 1.5. On the basis of the mbSCr, the AKI was diagnosed in 66/163 (40.5%) patients. This prevalence was lower than the prevalence of AKI diagnosed on the basis of ABC ebSCr (122/163 patients; 74.8%) (p < 0.001) and similar to the prevalence of AKI diagnosed on the basis of ABC-cr ebSCr (72/163 patients; 44.2%) (p = 0.5) and to the prevalence of AKI diagnosed on the basis of ABC-advanced ebSCr (69/163; 42.3%) (p = 0.73). AKI determined using ABC ebSCr, ABC-cr ebSCr and ABC-advanced ebSCr showed, respectively, 63.5% (kappa = 0.35; p < 0.001), 87.7% (kappa = 0.75; p < 0.001), and 87.1% (kappa = 0.74; p < 0.001) agreement with AKI determined using mbSCr. Using the HC/BC ratio calculated on the basis of mbSCr as gold standard, for Bland−Altman plots the HC/BC ratio calculated on the basis of ABC formula presented higher bias and wider limits of agreement compared with the HC/BC ratio calculated on the basis of ABC-cr and ABC-advanced formulas. In the receiver−operating characteristics (ROC) curve analysis the HC/BC ratio calculated on the basis of ABC ebSCr presented lower area under the ROC curve (AUROC) (AUROC = 0.89; 95%CI: 0.85−0.95; p < 0.001) compared with HC/BC ratio calculated on the basis of ABC-cr (AUROC = 0.94; 95%CI: 0.91−0.98; p < 0.001) or ABC-advanced ebSCr (AUROC = 0.914; 95%CI: 0.91−0.97; p < 0.001). In both Bland−Altman plots and ROC curve analysis, the ABC-cr and ABC-advanced formulas performed similarly. In conclusion, the ABC-cr and ABC-advanced formulas present very good diagnostic performance toward AKI identification in a population of children with T1DM onset.

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.

Diagnostic Performance of Height-Estimated Baseline Creatinine in Diagnosing Acute Kidney Injury in Children with Type 1 Diabetes Mellitus Onset

At type 1 diabetes mellitus (T1DM) onset, acute kidney injury (AKI) is very common. To diagnose AKI, the availability of a baseline serum creatinine (bSCr) is pivotal. However, in most hospitalized children the bSCr is unknown. We aimed to test whether the bSCr estimated on the basis of height (ebSCr) could be a reliable surrogate for AKI diagnosis compared with the measured bSCr (mbSCr). As the mbSCr, we considered the creatinine measured 14 days after T1DM onset while ebSCr (mg/dL) = (k × height [cm])/120 mL/min/1.73 m2, where k = 0.55 for children and adolescent girls and k = 0.7 for adolescent boys. AKI was defined as serum creatinine values >1.5 times the baseline creatinine. Kappa statistics and the percentage of agreement in AKI classification by ebSCr−AKI versus mbSCr−AKI definition methods were calculated. Bland−Altman plots were used to show the agreement between the creatinine ratio (highest/baseline creatinine; HC/BC) calculated with mbSCr and ebSCr. The number of 163 patients with T1DM onset were included. On the basis of mbSCr, 66/163 (40.5%) presented AKI while, on the basis of ebSCr, 50/163 (30.7%) accomplished AKI definition. ebSCr showed good correlation with mbSCr using both the Spearman test (rho = 0.67; p < 0.001) and regression analysis (r = 0.68; p < 0.001). Moreover, at the Bland−Altman plots, the bias of the highest/baseline creatinine ratio calculated on the basis of the mbSCr compared to ebSCr was minimal (bias = −0.08 mg/dL; 95% limits of agreement = −0.23/0.39). AKI determined using ebSCr showed 90% agreement with AKI determined using mbSCr (kappa = 0.66; p < 0.001). Finally, we compared the area under a receiver−operating characteristic curve (AUROC) of HC/BC ratio calculated on the basis of ebSCr with AUROC of the gold standard HC/BC ratio calculated on the basis of mbSCr. As expected, the gold standard had an AUROC = 1.00 with a 95% confidence interval (CI) between 0.98 and 1.00, p < 0.001. The HC/BC ratio calculated on the basis of ebSCr also had significant AUROC (AUROC = 0.94; 95% CI: 0.90−0.97; p < 0.001). The comparison of the two ROC curves showed a p < 0.001. In conclusion, when mbSCr is unknown in patients with T1DM onset, the ebSCr calculated on the basis of height could be an alternative to orientate clinicians toward AKI diagnosis.

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.

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.

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.

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.

Renal Involvement in Children with Type 2 Diabetes Mellitus Onset: A Pilot Study

Type 2 Diabetes Mellitus (T2DM) is a main cause of chronic kidney disease (CKD) in adulthood. No studies have examined the occurrence of acute kidney injury (AKI)-that enhances the risk of later CKD-and renal tubular damage (RTD)-that can evolve to AKI-in children with onset of T2DM. We aimed to evaluate the prevalence and possible features of AKI and RTD in a prospectively enrolled population of children with onset of T2DM. We consecutively enrolled 10 children aged 12.9 ± 2.3 years with newly diagnosed T2DM. AKI was defined according to the KDIGO criteria. RTD was defined by abnormal urinary beta-2-microglobulin and/or tubular reabsorption of phosphate (TRP) <85% and/or fractional excretion of Na >2%. None of the patients developed AKI, whereas 3/10 developed RTD with high beta-2-microglobulin levels (range: 0.6-1.06 mg/L). One of these three patients also presented with reduced TRP levels (TRP = 70%). Proteinuria was observed in two out of three patients with RTD, while none of patients without RTD had proteinuria. Patients with RTD presented higher beta-2-microglobulin, acute creatinine/estimated basal creatinine ratio, and serum ketones levels compared with patients without RTD. In conclusion, in our pilot observation, we found that none of the 10 children with T2DM onset developed AKI, whereas three of them developed RTD.

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.

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.

Cardiovascular risk assessment in children and adolescents with congenital solitary kidneys

Patients with solitary kidneys (SKs) are at risk of hypertension (HT) and associated end-organ damage. The authors aimed to evaluate whether children with congenital SKs (CSKs) have higher office, ambulatory, or central blood pressure (BP), increased arterial stiffness or left ventricular mass index, or any risk for arrhythmia. With this purpose, patients with CSK and healthy controls being followed up between January 2018 and June 2019 were enrolled in the study. Demographic, biochemical, and office blood pressure (BP) data were recorded. Then, ambulatory blood pressure monitoring (ABPM) and measurements of central BP (cBP), pulse wave velocity (PWV), and augmentation index (AIx@75) were obtained. Ventricular repolarization parameters were acquired by 12-lead electrocardiography. Left ventricular mass index (LVMI) and abdominal aortic stiffness parameters including strain, pressure strain elastic modulus (Ep), and normalized Ep (Ep*) were calculated with echocardiographic measurements. Finally, 36 children with CSK and 36 healthy controls were included. Serum creatinine, uric acid, total cholesterol levels, ABPM parameters, cBP levels, and PWV values were significantly higher, and eGFR levels were significantly lower in the CSK group. VR parameters, abdominal aortic stiffness indices, and LVMI were similar between the groups. CSK increased the risk of HT in ABPM (HT_ABPM ) by 6 times. PWV was significantly correlated with Ep and Ep* in cases with CSK. Determination of cBP and PWV along with 24-hour ABPM would be a useful tool in children with CSK.

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.

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.

In children with urinary tract infection reduced kidney length and vesicoureteric reflux predict abnormal DMSA scan

BACKGROUND

To evaluate sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) of renal ultrasonography (US) in predicting renal uptake defects or reduced renal function at Tc-99m dimercaptosuccinic acid (DMSA) scan (primary outcome). We also evaluated which factors could be associated with Tc-99m DMSA renal scan anomalies.

METHODS

We retrospectively included all the patients with vesico-ureteral reflux (VUR) undergoing the first Tc-99m DMSA renal scan within 3 months from the most recent renal US between 2016 and 2018.

RESULTS

Sensitivity, specificity, PPV, and NPV of US in predicting abnormal Tc-99m DMSA scan were 38.9%, 91.5%, 71.9%, and 72.9%, respectively. Different length between the kidneys, expressed as standard deviation score (SDS), showed an area under the receiver operating characteristic curve of 0.70 (95% CI, 0.60-0.80; p < 0.0001) when evaluated as predictor of abnormal Tc-99m DMSA scan. A different length between the two kidneys >1.11 SDS had 91.5% sensitivity and 57.6% specificity. At multivariate analysis, the factors with significantly increased odds ratio of abnormal Tc-99m DMSA scan were difference in length between two kidneys >1.11 SDS and dilated VUR.

CONCLUSIONS

The Tc-99m DMSA scan remains the gold standard to detect renal parenchymal anomalies. A different length between the kidneys >1.11 SDS and dilated VUR are predictors of abnormal Tc-99m DMSA renal scan.

Effect of Body Mass Index on Estimated Glomerular Filtration Rate Levels in Children With Congenital Solitary Kidney: A Cross-Sectional Multicenter Study

RATIONALE & OBJECTIVE

The objective of this study is to evaluate the effect of body mass index (BMI) on estimated glomerular filtration rate (eGFR) levels in children with congenital solitary kidney (CSK). Moreover, we evaluated if other factors could influence this relationship.

STUDY DESIGN

Multicenter cross-sectional study.

SETTING & PARTICIPANTS

University hospital pediatrics departments.

SUBJECTS

Two hundred eighty-one patients with CSK.

PREDICTORS

Weight, height, BMI-SDS (standard deviation score), duration of overweight/obesity, pubertal stage, systolic (SBP) and diastolic (DBP) blood pressure, eGFR, and renal ultrasound were obtained at the last follow-up visit. The population was classified on the basis of nutritional status and divided in tertiles for duration of overweight/obesity. We compared eGFR levels among these categories. A simple regression was used to correlate eGFR with BMI-SDS. To evaluate if other factors could influence the relationship between eGFR and BMI-SDS, a general linear model was performed, including gender, birth weight<2.5 kg, age, BMI-SDS, SBP-SDS, DBP-SDS, RL-SDS (renal length), and presence of kidney injury at last follow-up as covariates.

RESULTS

The eGFR levels reduced gradually from underweight to obese patients (P = .047). The eGFR levels significantly increased across first and second tertiles of duration of overweight/obesity while they decreased across second and third tertiles of duration of overweight/obesity (P = .005). The eGFR and BMI-SDS at last follow-up were indirectly correlated (coefficient = -0.30, r² = 9.2%, P = .0004). A general linear model for eGFR variance (model R² = 26.37%; P = .02) confirmed an indirect and significant association of eGFR values with BMI-SDS as the only significant finding.

CONCLUSIONS

In patients with CSK, the higher the BMI-SDS and the duration of overweight/obesity, the lower the eGFR levels. Primary prevention strategies to counteract overweight/obesity are mandatory in CSK patients.