Estimated kidney function in children and young adults with spina bifida: A retrospective cohort study

Characteristics and predictors of chronic kidney disease in children with myelomeningocele: a nationwide cohort study

BACKGROUND

Myelomeningocele (MMC) is highly prevalent in developing countries, and MMC-related neurogenic bladder is an important cause of childhood chronic kidney disease (CKD). This nationwide study aimed to evaluate demographic and clinical features of pediatric patients with MMC in Turkey and risk factors associated with CKD stage 5.

METHODS

Data from children aged 0-19 years old, living with MMC in 2022, were retrospectively collected from 27 pediatric nephrology centers. Patients > 1 year of age without pre-existing kidney abnormalities were divided into five groups according to eGFR; CKD stages 1-5. Patients on dialysis, kidney transplant recipients, and those with eGFR < 15 ml/min/1.73 m2 but not on kidney replacement therapy at time of study constituted the CKD stage 5 group.

RESULTS

A total of 911 (57.8% female) patients were enrolled, most of whom were expectantly managed. Stages 1-4 CKD were found in 34.3%, 4.2%, 4.1%, and 2.4%, respectively. CKD stage 5 was observed in 5.3% of patients at median 13 years old (range 2-18 years). Current age, age at first abnormal DMSA scan, moderate-to-severe trabeculated bladder on US and/or VCUG, and VUR history were independent risk factors for development of CKD stage 5 (OR 0.752; 95%; CI 0.658-0.859; p < 0.001; OR 1.187; 95% CI 1.031-1.367; p = 0.017; OR 10.031; 95% CI 2.210-45.544; p = 0.003; OR 2.722; 95% CI 1.215-6.102; p = 0.015, respectively). Only eight CKD stage 5 patients underwent surgery related to a hostile bladder between 1 and 15 years old.

CONCLUSION

MMC-related CKD is common in childhood in Turkey. A proactive approach to neurogenic bladder management and early protective surgery in selected cases where conservative treatment has failed should be implemented to prevent progressive kidney failure in the pediatric MMC population in our country.

Stratification of neurogenic bladder risk in spina bifida using the urinary peptidome

Neurogenic bladder poses a major morbidity in children with spina bifida (SB), and videourodynamic studies (VUDS) are used to stratify this risk. This small-scale pilot study utilized current mass-spectrometry-based proteomic approaches to identify peptides or proteins in urine that may differentiate children at high risk of developing renal complications from a neurogenic bladder. Twenty-two urine samples of which nine had high bladder pressure storage that put the upper urinary tract at risk, while 13 with a lower risk for renal compromise were analyzed. More than 1,900 peptides across all 22 samples were quantified, and 115 peptides differed significantly (P < 0.05) between the two groups. Using machine learning approaches five peptides that showed the greatest differences between these two clinical categories were used to build a classifier. We tested this classifier by blind analysis of an additional six urine samples and showed that it correctly assigned the unknown samples in their proper risk category. These promising results indicate that a urinary screening test based on peptides could be performed on a regular basis to stratify the neurogenic bladder into low or high-risk categories. Expanding this work to larger cohorts as well as across a broad spectrum of urodynamics outcomes may provide a useful diagnostic test for neurogenic bladder.NEW & NOTEWORTHY This approach could help risk stratify the neurogenic bladder in patients with spina bifida and could allow us to safely defer on up to 1/3 of urodynamic studies. These pilot data justify a larger trial before this approach becomes a clinical tool.

Neurogenic Lower Urinary Tract Dysfunction

Neurogenic lower urinary tract dysfunction (NLUTD) remains a formidable challenge to pediatric urologists to achieve the goals of renal preservation and the reduction of urinary tract infections as well as the attainment of continence and independence as children grow toward adulthood. Tremendous progress has occurred over the past 50 years which have witnessed an evolution in focus from mere survival to optimal quality of life. This review presents four separate guidelines for the medical and surgical care of pediatric NLUTD, most commonly related to spina bifida, to highlight the change in approach from expectant to more proactive management.

Impairments and comorbidities in adults with cerebral palsy and spina bifida: a meta-analysis

Introduction

Aging with a childhood-onset disability, such as cerebral palsy (CP), spina bifida (SB), and muscular diseases (MD), comes along with significant impairments and comorbidities. Despite the increasing evidence an overall picture is lacking. This study aimed to review the literature about adults with CP/SB/MD and impairments and comorbidities to perform a meta-analysis.

Materials and methods

Embase, PubMed, Cinahl, and Google Scholar were searched (2000-2020). Search terms included adults with one of the aforementioned disabilities combined with impairments and comorbidities. If specific impairments or comorbidities were reported by at least four studies, these were included in the study. Pooled prevalence (95% Confidence Interval) of impairments/comorbidities were calculated.

Results

The search yielded 7,054 studies of which 95 were included in the meta-analysis (64 CP, 31 SB, 0 MD). In total estimates were calculated for 26 (CP) and 11 (SB) outcomes. In adults with CP, pain [56.4% (95%CI 48.8-63.8)], deformities [44.2% (95%CI 12.9-78.4)], intellectual disability [37.2% (95%CI 26.7-48.3)], and fatigue [36.9% (95%CI 24.6-50.1)] were most prevalent; renal disease [3.0% (95%CI 2.1-4.2)] and stroke/rheumatic diseases {4.8% (95%CI 3.4-6.5; 4.8% (95%CI 1.5-9.9)] respectively} were least prevalent. For adults with SB, bladder incontinence [60.0% (95%CI 50.5-69.2)], bowel incontinence [49.2% (95%CI 34.5-64.0)], pain [44.1% (95%CI 27.4-61.5)], and sleeping problems [30.3% (95%CI 4.7-65.8)] were most prevalent; diabetes [4.8% (95%CI 2.8-7.3)] and renal disease [8.7% (95%CI 2.0-19.9)] were least prevalent. The included studies showed large heterogeneity.

Conclusions

More research is needed to study health issues in adults with MD. Adults with CP or SB deal with a variety of health issues. More attention for the mental health of these adults is needed. There also is a need for accessible and adequate screening, preventive measures and clinical follow-up.

Estimating the Glomerular Filtration Rate in Pediatric Patients With Neurogenic Bladder: A Comparison Between Creatinine- and Cystatin C-Equations

Background and objective Patients with neurogenic bladder (NB) are at a higher risk of developing chronic kidney disease (CKD). Due to their lower muscle mass, the estimated glomerular filtration rate (eGFR) based on creatinine (Cr) may be overestimated and delay the diagnosis of renal failure. This study compared eGFR calculated with different equations based on Cr and/or cystatin C (CysC) in children with NB, and the differences between patients with lower muscle mass (underdeveloped lower limbs) and those with independent gait (less muscle depletion). Methods We calculated the eGFR in pediatric patients with NB and CKD stages 1 and 2 by using the following equations: Chronic Kidney Disease in Children equation for serum creatinine (CKiD-Cr), CKiD-CysC, CKiD combined-Cr/CysC, Zappitelli-CysC, and Zappitelli combined-Cr/CysC. Results We evaluated a total of 47 patients, 74.5% with CKD stage 1, with a median age of 14.1 years. Of these participants, 59.6% had lipo/myelomeningocele. The CKiD-Cr and CysC-based equations led to significantly lower calculated eGFR ​​(p<0.05), specifically CKiD-CysC (p<0.001), Zappitelli-CysC (p<0.001), CKiD-Cr/CysC (p<0.001), and Zappitelli combined-Cr/CysC (p<0.05). When CKiD-CysC was used, 68% of the patients moved to a more advanced CKD stage. In patients without independent gait, with lower muscle mass (55.3%), the median eGFR calculated using the CKiD-Cr and CKiD combined-Cr/CysC equations was significantly higher (p<0.05). However, there were no differences between the two groups when using the other CysC-based equations. Conclusion In patients with NB and poor muscle mass, the CKiD-Cr equation may overestimate renal function. CysC-based equations seem more reliable in these patients, especially in those with greater muscular atrophy.

Age-based risk of end-stage kidney disease in patients with myelomeningocele

OBJECTIVE

We aimed to quantify end-stage kidney disease (ESKD) risk after infancy in individuals with myelomeningocele (MMC) followed by urology in the modern medical era and to assess if ESKD risk was higher after surgery related to a hostile bladder.

METHODS

We retrospectively reviewed patients with MMC followed by urology at our institution born ≥ 1972 (when clean intermittent catheterization was introduced) past 1 year of age (when mortality is highest, sometimes before establishing urology care). ESKD was defined as requiring permanent peritoneal/hemodialysis or renal transplantation. Early surgery related to hostile bladder included incontinent vesicostomy, bladder augmentation, detrusor Botulinum A toxin injection, ureteral reimplantation, or nephrectomy for recurrent urinary tract infections. Survival analysis and proportional hazards regression were used. Sensitivity analyses included: risk factor analysis with only vesicostomy, timing of surgery, including the entire population without minimal follow-up (n = 1054) and only patients with ≥ 5 years of follow-up (n = 925).

RESULTS

Overall, 1029 patients with MMC were followed for a median of 17.0 years (49% female, 76% shunted). Seven patients (0.7%) developed ESKD at a median 24.3 years old (5 hemodialysis, 1 peritoneal dialysis, 1 transplantation). On survival analysis, the ESKD risk was 0.3% at 20 years old and 2.1% at 30 years old (Figure). This was ∼100 times higher than the general population (0.003% by 21 years old, p < 0.001). Patients who underwent early surgery for hostile bladder had higher ESKD risk (HR 8.3, p = 0.001, 6% vs. 1.5% at 30 years). On exploratory analyses, gender, birth year, shunt status and wheelchair use were not associated with ESKD risk (p ≥ 0.16). Thirty-year ESKD risk was 10% after early vesicostomy vs. 1.4% among children without one (p = 0.001). Children undergoing bladder surgery between 1.5 and 5 years old had a higher risk of ESKD. No other statistically/clinically significant differences were noted.

COMMENT

Patients with MMC remain at risk of progressive renal damage throughout life. We relied on the final binary ESKD outcome to quantify this risk, rather than imprecise glomerular filtration rate formulas. Analysis was limited by few people developing ESKD, inconsistent documentation of early urodynamic findings and indications for bladder-related surgery.

CONCLUSIONS

While ESKD is relatively uncommon in the MMC population receiving routine urological care, affecting 2.1% of individuals in the first 3 decades, it is significantly higher than the general population. Children with poor bladder function are likely at high risk, underlining the need for routine urological care, particularly in adulthood.

Integrated Ultrasound With Urodynamics Illustrates Effect of Bladder Volume on Upper Tract Dilation: Should we Trust Surveillance Ultrasounds?

OBJECTIVE

To evaluate if ultrasound during urodynamics (uUS) will show that traditional ultrasound (tUS) routinely underestimates the potential magnitude of upper tract dilation (UTD).

METHODS

Prospective pilot study of 10 consecutive patients ≥ 5 years of age undergoing same day uUS and tUS. Using randomized images, the study pediatric radiologist determined anterior-posterior renal pelvic diameter (APD), bladder volume, vesicoureteral reflux (VUR) and UTD grades. A single pediatric urologist determined urodynamic bladder capacity and assigned either hostile, intermediate, abnormal but safe, or normal national spina bifida patient registry classification (NSBPR).

RESULTS

Bladder volume on tUS was significantly smaller than final bladder volume on uUS (180 vs 363 ml: P<.001). On average, patient reported maximum catheterized/voided volumes were also 82 ml greater than final bladder capacity on uUS. UTD was upgraded in 25% of kidneys and APD increased by 0.6 cm on uUS over that seen on tUS (P=.001). Units with VUR had greater increases in APD (1.2 P=.007 vs. 0.3 cm P=0.06). Changes in APD stratified by NSBPR revealed average increases of up to 1.3 cm.

CONCLUSION

Despite instructions to the contrary, patients come for tUS with a relatively empty bladder as compared to either their urodynamic or patient-reported capacity. This translates to a significant underestimation of UTD with tUS, most notably in those with VUR. Alternatives to traditional protocols include insisting patients wait until their bladder is truly full for tUS, retrograde filling their bladder, or performing uUS. Accurate assessment of UTD severity may help guide long term management.

Are Tubular Injury Markers NGAL and KIM-1 Useful in Pediatric Neurogenic Bladder?

The lack of early biomarkers of renal damage in children with neurogenic bladder (NB) prompts us to investigate the role of promising proteins: neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). This prospective analysis was conducted on 58 children with NB and 25 healthy children. We assessed urinary levels of NGAL and KIM-1 in both groups. Age, sex, anthropometric measurements, activity assessment, renal function, and urodynamics parameters were analyzed. The differences between the median uNGAL and uKIM-1 in the NB group compared to control were recorded. However, only uNGAL levels were statistically significantly higher. Statistically significant correlation was found between gender, recurrent urinary tract infections, bladder trabeculation, its compliance, activity assessment, and uNGAL. To conclude, elevated levels of uNGAL may be considered a biomarker of tubular injury in children with NB due to MMC in contrast to uKIM-1.

Diagnostic Test Characteristics of Ultrasound Based Hydronephrosis in Identifying Low Kidney Function in Young Patients with Spina Bifida: A Retrospective Cohort Study

PURPOSE

Kidney dysfunction in spina bifida is usually detected by low estimated glomerular filtration rate or ultrasound based hydronephrosis. We assessed the diagnostic test characteristics of hydronephrosis for detecting low estimated glomerular filtration rate, hypothesizing that hydronephrosis has low sensitivity compared to cystatin C based estimated glomerular filtration rate.

MATERIALS AND METHODS

We conducted a single center, retrospective cohort study, including patients with spina bifida from 2012-2017 with 2 kidneys and complete data needed to calculate estimated glomerular filtration rate via multiple pediatric (age 1-17.9 years) or adult (age ≥18 years) estimating equations. We evaluated the association of hydronephrosis status (high grade, low grade or none) with estimated glomerular filtration rate, adjusting for small kidney size and scarring, and calculated diagnostic test characteristics of hydronephrosis for low estimated glomerular filtration rate.

RESULTS

We analyzed 247 patients (176 children and 71 adults). Mean±SD age was 13.7±6.6 years, and 81% of patients had myelomeningocele. Hydronephrosis (77% low grade) was found in 35/176 children and 18/71 adults. Hydronephrosis was associated with low estimated glomerular filtration rate in stepwise fashion, independent of kidney size and scarring. However, across cystatin C based pediatric equations, any hydronephrosis (compared to none) had 23%-48% sensitivity, and high grade hydronephrosis (compared to none or low grade) had 4%-15% sensitivity for estimated glomerular filtration rate <90 ml/min/1.73 m2, which remained unchanged after excluding small kidneys and scarring. Across cystatin C based adult equations, any and high grade hydronephrosis had 55%-75% and 40%-100% sensitivity, respectively, for estimated glomerular filtration rate <90 ml/min/1.73 m2, although with wide confidence intervals. Specificity was higher with high grade vs any hydronephrosis. Sensitivities were higher for estimated glomerular filtration rate <60 ml/min/1.73 m2.

CONCLUSIONS

Hydronephrosis was associated with low estimated glomerular filtration rate but had poor sensitivity for cystatin C based estimated glomerular filtration rate <90 ml/min/1.73 m2, especially among children with spina bifida.

Non-invasive markers in the management of pediatric neurogenic bladder over the last two decades - A review

Neurogenic bladder (NB) is one of the most challenging problems in nephro-urological management in pediatrics. It is an important risk factor of secondary upper urinary tract damage. A complete clinical evaluation is necessary and requires life-long extensive medical attention including invasive procedures that affect patients' quality of life. Potential non-invasive biomarkers would be desirable, especially in the pediatric population. The aim of this review was to analyze two decades of data regarding potential non-invasive biomarkers in the assessment and follow-up of children with NB. This paper summarizes and appraises the knowledge about both biochemical and imaging-based markers in 3 aspects: markers of urinary tract infections (UTIs), bladder and renal function, and this paper looks at their prospective application in everyday clinical care.

Variability in Kidney Function Estimates in Emerging Adults With Spina Bifida: Implications for Transitioning From Pediatric to Adult Care

OBJECTIVE

To examine the variability of estimated glomerular filtration rate (eGFR) in emerging adults with spina bifida (SB) by comparing multiple equations across the transitional age period, hypothesizing that creatinine (Cr)-based equations show greater variability than cystatin-C (CysC)- or combination-based equations.

METHODS

A retrospective cohort study was performed from 2012 to 2017 at a multidisciplinary SB clinic. Emerging adults were defined as patients ages 18-28 years old. Four pediatric, 3 adult, and 3 averaged eGFR equations were considered. Cross-sectional variability in eGFR data was assessed using coefficients of variation, chronic kidney disease (CKD) stage classification, and pairwise percent relative difference in eGFR between analogous pediatric and adult equations based on included lab values. Longitudinal changes in eGFR over time were compared across equations using a covariance pattern model accounting for repeated measures.

RESULTS

Seventy-five emerging adults with SB (median age 21.8 years; 55% female; 83% with myelomeningocele) were included in cross-sectional analyses. Adult equations gave higher median eGFRs by 22%-27% and generally milder CKD stage classification than analogous pediatric equations. In longitudinal analyses (median follow-up of 22 months), all equations conferred negative eGFR changes over time (range -1.9 to -4.3 mL/min/1.73m² per year) that were not significantly different.

CONCLUSION

In emerging adults with SB, adult equations demonstrated higher median eGFRs by 22%-27% compared to analogous pediatric equations, even with Cystatin-C, and generally downstaged CKD stage classification. The same eGFR equation should be used for serial kidney function monitoring in emerging adults with SB who transition care from pediatric to adult services.

Cystatin C as a biomarker of chronic kidney disease: latest developments

INTRODUCTION

Chronic kidney disease (CKD) is common, occurring in over 10% of individuals globally, and is increasing in prevalence. The limitations of traditional biomarkers of renal dysfunction, such as serum creatinine, have been well demonstrated in the literature. Therefore, augmenting clinical assessment with newer biomarkers, such as serum cystatin C, has the potential to improve disease monitoring and patient care.

AREAS COVERED

The present paper assesses the utility and limitations of serum cystatin C as a biomarker for CKD in light of the current literature.

EXPERT OPINION

Serum cystatin C has been well established as an early and accurate biomarker of CKD that is particularly helpful in patients for whom creatinine is an inadequate marker or for whom more cumbersome methods of glomerular filtration rate (GFR) measurement are impractical. Current research questions are no longer focused on if, but rather when and how often cystatin C should be used in the evaluation of CKD patients. However, transition of all reagents and estimated GFR equations to the newly established International Standard is critical for developing generalizable data.

Kidney Function Surveillance in the National Spina Bifida Patient Registry: A Retrospective Cohort Study

PURPOSE

Chronic kidney disease affects 25% to 50% of patients with spina bifida. Guidelines recommend kidney function surveillance in these patients but practice patterns are unknown. Variations in kidney function surveillance were assessed in patients with spina bifida based on the hypothesis that the treating clinic and spina bifida type would be associated with kidney function surveillance.

MATERIALS AND METHODS

A retrospective cohort study was conducted of U.S. patients in the National Spina Bifida Patient Registry from 2013 to 2018. Followup was anchored at the 2013 visit. Participants with either an outcome event within 2 years of followup or more than 2 years of followup without an outcome event were included. Primary outcome was kidney function surveillance, defined as at least 1 renal ultrasound and serum creatinine within 2 years of followup. Primary exposures were clinic and spina bifida type, which were analyzed with covariates including sociodemographic and clinical characteristics in logistic regression models for their association with the outcome. Sensitivity analyses were performed using different kidney function surveillance definitions.

RESULTS

Of 8,351 patients 5,445 were included with a median followup of 3.0 years. Across 23 treating clinics kidney function surveillance rates averaged 62% (range 6% to 100%). In multivariable models kidney function surveillance was associated with treating clinic, younger patient age, functional lesion level, nonambulatory status and prior bladder augmentation. Treating clinic remained a significant predictor of kidney function surveillance in all sensitivity analyses.

CONCLUSIONS

Within the National Spina Bifida Patient Registry wide variation exists in practice of kidney function surveillance across treating clinics despite adjustment for key patient characteristics.

Trends in Procedures to Initiate Renal Replacement Therapy among People Living with Spina Bifida

PURPOSE

Given the increasing prevalence of chronic kidney disease in people with spina bifida, we sought to determine if this is associated with an increase in end stage kidney disease. We examined population based data to measure the frequency of procedures to establish renal replacement therapy-a marker for end stage kidney disease-among patients with spina bifida.

MATERIALS AND METHODS

We used the Healthcare Cost and Utilization Project State Inpatient Database and State Ambulatory Surgery and Services Database from Florida, Kentucky, Maryland and New York (2000 to 2014), which include encounter level data. With a diagnosis code based algorithm we identified all procedural encounters made by patients with spina bifida. We determined the percentage of these encounters that were for facilitating renal replacement therapy (ie arteriovenous anastomosis, renal transplantation). We assessed for changes over time in this percentage with the Cochran-Armitage trend test. Bivariate analysis was performed using chi-square test.

RESULTS

Of all procedures performed on patients with spina bifida over this time the proportion of procedures performed to establish renal replacement therapy significantly decreased in both the inpatient and outpatient settings (p=0.042 and p <0.001, respectively). People with spina bifida undergoing procedures to establish renal replacement therapy were, on average, young adults (mean age 34.5 and 36.0 years) with a high prevalence hypertension (75.8% of inpatients, 68.6% of outpatients).

CONCLUSIONS

The frequency of surgeries to initiate renal replacement therapy among people with spina bifida undergoing procedures is low and is not increasing. This highlights the importance of consistent care throughout adolescence and young adulthood, and hypertension screening.

Chronic kidney disease and upper tract concerns after congenital and acquired urinary tract abnormalities: considerations for transition of care in teens and young adults

PURPOSE

To emphasize the burden that chronic kidney disease (CKD) and its complications place on overall health and well-being over the lifetime in individuals with congenital and acquired urinary tract abnormalities.

METHODS

Topic-based literature review was performed and professional opinion was obtained to describe the scope of medical challenges faced by both teens and adults and their health care providers in the context of congenital and acquired urinary tract abnormalities.

RESULTS

Challenges include accurate assessment of glomerular filtration rate; engaging for consistent surveillance of blood pressure, proteinuria, and medical complications of CKD that increase the risk of progression to end-stage renal disease and affect general health; achieving early referral to nephrology for better outcomes; managing renal complications within the unique limitations of lower urinary tract function; treating upper tract urolithiasis in the atypical urinary tract; and preparing for successful renal transplant.

CONCLUSION

In individuals with congenital or acquired abnormalities of the urinary tract, there is an inherent risk of CKD with its associated morbidity and increased mortality risk. Interplay between the upper and lower urinary tract impacts CKD progression. Collaborative management between urology and nephrology is highly recommended to address the unique challenges for each individual over the lifetime.