From Hypercalciuria to Hypocitraturia—A Shifting Trend in Pediatric Urolithiasis?

Risk factors for recurrence in pediatric urinary stone disease

BACKGROUND

Children's urinary system stones may develop from environmental, metabolic, anatomical, and other causes. Our objective is to determine the recurrence and prognosis, demographic, clinical, and etiological characteristics of children with urolithiasis.

METHODS

Medical records of patients were evaluated retrospectively. Patients' demographic data and medical history, serum/urine biochemical and metabolic analysis, blood gas analysis, stone analysis, imaging findings, and medical/surgical treatments were recorded.

RESULTS

The study included 364 patients (male 187). Median age at diagnosis was 2.83 (IQR 0.83-8.08) years. The most common complaints were urinary tract infection (23%) and urine discoloration (12%). Sixty-two percent had a family history of stone disease. At least one metabolic disorder was found in 120 (88%) of 137 patients having all metabolic analyses: hypercalciuria was found in 45%, hypocitraturia in 39%, and hyperoxaluria in 37%. Anatomical abnormalities were detected in 18% of patients. Of 58 stones analyzed, 65.5% were calcium and 20.6% were cystine stones. Stone recurrence rate was 15% (55/364). Older age (> 5 years), family history of stone disease, stone size (≥ 5 mm), and urinary system anatomical abnormalities were significantly associated with stone recurrence (p = 0.027, p = 0.031, p < 0.001, and p < 0.001, respectively). In adjusted logistic regression analysis, stone size ≥ 5 mm (OR 4.85, 95% CI 2.53-9.3), presence of urinary system anatomical abnormalities (OR 2.89, 95% CI 1.44-5.78), and family history of stone disease (OR 2.41, 95% CI 1.19-4.86) had increased recurrence rate.

CONCLUSIONS

All children with urolithiasis should be evaluated for factors affecting stone recurrence. Children at higher risk of recurrence need to be followed carefully.

Dietary management of hypocitraturia in children with urolithiasis: results from a systematic review

PURPOSE

Hypocitraturia is a low urinary excretion of citrate and a well-known risk factor for kidney stone development in children. This systematic review aimed to evaluate the dietary management of hypocitraturia in children with urolithiasis.

METHODS

Literature search was performed on 30th September 2022 using Embase, PubMed, and Cochrane Central Controlled Register of Trials. Studies were included if children with stones and hypocitraturia were managed with diet supplements.

RESULTS

Six papers were included. Four studies evaluated the role of oral potassium citrate associated with high fluid intake on stone resolution and recurrence. Two studies assessed the impact of oral potassium citrate on long-term stone recurrence after percutaneous nephrolithotomy and shock wave lithotripsy. All studies demonstrated that the association of potassium citrate and high fluid intake was well tolerated with no side effects and restored normal urine citrate excretion, allowed a reduction in stone size, and, following definitive treatments, was associated with a lower rate of stone regrowth and recurrence compared with controls. These effects were demonstrated across all pediatric ages.

CONCLUSIONS

Our review infers that oral potassium citrate and high fluid assumption are safe and effective in restoring urine citrate excretion, treating and preventing stone recurrence with no serious adverse events, and should probably be the first-line treatment of pediatric patients with asymptomatic stones and hypocitraturia.

The Impact of Water and Other Fluids on Pediatric Nephrolithiasis

Pediatric nephrolithiasis cases have been on the rise in the past several years, resulting in increased healthcare costs and other burdens on the juveniles with this ailment. Recent research has shown that present trends in pediatric nephrolithiasis have changed as a result of fluid intake, including water consumption, nutrition, obesity prevalence, lifestyle, and imaging procedures. A specific cause, meanwhile, is still elusive. Trends in pediatric nephrolithiasis need to be thoroughly researched. Furthermore, variables specific to pediatric nephrolithiasis that could cause greater difficulties in an affected child elevate the level of worry with cumulative prevalence. Doctors should rigorously assess patients who present with kidney stones when they have dynamics such as varied clinical presentation, high recurrence of kidney stones linked to metabolic and urinary tract problems, and the potential existence of rare genetic kidney stone illnesses. This review aims to identify adaptive risk factors and anomalies that call for specialized treatment and prescription. More specifically, the major goals of medical and surgical treatments are to eliminate kidney stone risk and stop relapse while concurrently lowering interventional barriers. A dedicated nephrolithiasis clinic run by a pediatric nephrologist, nutritionist, urologist, and clinical nurse may sometimes be beneficial for patients in serious danger. Such a clinic offers significant chances to learn more about pediatric nephrolithiasis, which has been linked to water consumption and hence fosters urgently required study in this area.

Proteomic analysis of inhibitory protein profiles in the urine of children with nephrolithiasis: implication for disease prevention

PURPOSE

In this study we aimed to screen for the presence of biomarkers that are downregulated in children with nephrolithiasis (RS) compared to healthy controls (HC) using a proteomic approach. We hypothesized that RS and HC would display unique inhibitory protein profiles that could be used for comparative pathway analysis.

METHODS

This is a prospective, controlled, pilot study of pooled urine from RS (N = 30, 24 females, mean age 12.95 ± 4.03 years) versus age- and gender-matched HC, using liquid chromatography-mass spectrometry. The criteria for protein selection were: (1) patient/control abundance ratio of < 0.5; and (2) ≤ 0.05 p-value for the Fisher's Exact Test. Results were confirmed by ELISA testing in individual samples.

RESULTS

67 proteins were downregulated in RS group, and 17 of those were significantly different compared to controls. Of those seventeen proteins, five (two actins, annexin A5, keratin 6B, and serpin B4) were completely absent in the urine of stone patients but were found in controls. The remaining twelve proteins were significantly less abundant in the patient's urine compared to healthy controls. Protein-protein interaction modeling of significant proteins identified syndecan-1 as the key node, a protein associated with adhesion pathways. ELISA analysis by subgroups showed statistically significant difference in the urinary excretion of osteopontin (5.1 ± 3.22 ng/mg creatinine vs 14.1 ± 9.5 ng/mg creatinine, p = 0.046) between stone patients with hypocitraturia and controls. Urinary osteopontin concentration was positively correlated with urinary citrate excretion (r = 0.417, p = 0.03).

CONCLUSIONS

Children with RS have a different urinary inhibitory polypeptide profile compared to HC. Decreased urinary excretion of these proteins indicates their potential inhibitory role in renal stone formation, especially of the adhesion phase. Lower concentration of urinary osteopontin in children with nephrolithiasis and hypocitraturia suggests its potential involvement in the pathogenesis of this disease. Further characterization of these proteins in a larger sample is imperative.

Comparison of infants and children with urolithiasis: a large case series

We evaluated the demographic features, etiologic risk factors, treatment strategies, and outcome of the infants and children with urolithiasis (UL). A retrospective multicenter study was conducted including 23 Pediatric Nephrology centers in Turkey. The medical records of 2513 children with UL were reviewed. One thousand, three hundred and four boys and 1209 girls (1.1:1) were reported. The mean age at diagnosis was 39.5 ± 35 months (0.4-231 months), and 1262 patients (50.2%) were in the first year of life (infants). Most of the cases with infantile UL were diagnosed incidentally. Microlithiasis (< 3 mm) was found in 794 patients (31.6%), and 64.5% of the patients with microlithiasis were infants. Stones were located in the pelvis-calyces in 63.2% (n: 1530) of the cases. The most common stone type was calcium oxalate (64.6%). Hypocitraturia was the most common metabolic risk factor (MRF) in children older than 12 months, but in infancy, hypercalciuria was more common. Fifty-five percent of the patients had received at least one medical treatment, mostly potassium citrate. At the end of a year's follow-up, most of the patients with microlithiasis (85%) showed spontaneous remission. The rate of spontaneous stone resolution in infants was higher than in children. Spontaneous remission rate was higher in cases with MRF ( - ) stones than in MRF ( +) stones. However, remission rate with medical treatment was higher in cases with MRF ( +) stones. This study represents the results of a large series of infants and children with UL and showed that there are several differences such as underlying metabolic and anatomic abnormalities, clinical course, and stone remission rates between infants and children with urinary stone disease.

Prevalence of metabolic abnormalities in patients with urolithiasis in Kinshasa, Democratic Republic of Congo

Introduction

metabolic abnormalities are key factors in urolithiasis patients because they can be modified to prevent the risk of urinary stones. The objectives of this study were to estimate the frequency of metabolic abnormalities in the urine of patients with urolithiasis and to determine their possible link with the chemical composition of stones.

Methods

we conducted a cross-sectional study evaluating 73 patients referred for urolithiasis in 8 clinics in Kinshasa, between January 2017 and September 2019. Twenty four-hour or early morning urine were collected and analyzed in the Tenon Hospital in Paris. Parameters analyzed included pH, specific gravity, creatinine, uric acid, calcium, phosphate, oxalate, citrate and magnesium. Chi square test or chi-square likelihood-ratio and student's t test were used as statistical tests.

Results

overall, 89% (n=65) of patients with lithiasis had metabolic abnormalities. Mean (SD) age of patients was 47.0 (14.2) years with male to female ratio of 1.6: 1. The mean (SD) 24-hour diuresis was 1836.4 (1216.9) ml; the mean (SD) urine density was 1.018 (0.007); and the mean (SD) pH was 6.1(0.8). Hypocitraturia was the most frequently observed metabolic abnormality and was found in 76.7% patients. Other significant metabolic abnormalities were low magnesuria (35.6%), hyperoxaluria (11%), and low sulphaturia (74%). Whewellite (73.5%) was the main chemical component. The mean pH was higher in patients with carbapatite and struvite stones (p=0.031).

Conclusion

this study suggests that inadequate diuresis and hypocitraturia were important lithogenic factors. The population should be encouraged to increase water intake to limit the frequency of urine super saturation with crystals.

Age-Specific Excretion of Calcium, Oxalate, Citrate, and Glycosaminoglycans and Their Ratios in Healthy Children and Children with Urolithiasis

We analyzed children with urolithiasis with age- and gender-matched healthy children. Calcium (mmol/mmol creatinine) and the calcium/citrate ratio (mol/mmol) are the only variables that differentiate children before puberty from healthy children (ROC analysis confirmed only calcium/citrate as a significant variable with cut-off value > 0.84). Peri-pubertal children are distinguished from age- and gender-matched healthy children by the following variables: citrate (mmol/mol creatinine), calcium/citrate (mol/mmol), oxalate/glycosaminoglycans (mmol/g), oxalate/citrate ratios (mmol/mmol) and oxalate/(citrate × glycosaminoglycans) (mol oxalate × mol creatinine)/(mol citrate × g glycosaminoglycans). All variables were confirmed by ROC analysis with cut-off values ≤ 327.87, >1.02, >11.24, >0.12 and >0.03, respectively. These results indicate a different risk of urinary stones development before puberty vs. pubertal/postpubertal children and increasing importance (deficiency) of citrate and glycosaminoglycans in such children. J48 classifier confirmed the importance of the oxalate/(citrate × glycosaminoglycans) and the calcium/citrate ratios (Ox/Cit × GAG 0.22 and Cit/GAG 0.612) with the practically applicable classification tree for distinguishing between pubertal/postpubertal children with urolithiasis with age- and gender-matched healthy children.

Metabolic risk factors and the role of prophylaxis in pediatric urolithiasis

Suppose that the recurrence in pediatric urolithiasis has a close relationship with metabolic abnormalities and is affected by residual burden and prophylaxis. If so, the recurrence rates could be reduced with effective surgery and appropriate prophylaxis. Here we retrospectively evaluate the metabolic risk factors data of 148 children who were operated on between January 2005 and March 2013 due to kidney stones. All patients underwent percutaneous nephrolithotomy (PCNL), and all were children. Thirteen children had a history of surgery performed to treat urological anomalies. Twenty-four-hour urine analysis, the residual status of surgery, BMI levels, and the number of metabolic abnormalities were noted. Only 18 (15%) of 122 patients without residual stones after PCNL had recurrence at follow-up whereas; nine (26%) of 26 patients with residual stones developed recurrence (p = 0.017). Recurrence was observed in 14 (16%) of 89 patients with a metabolic abnormality, and 13 (30%) of 44 patients with two or more metabolic abnormalities had recurrence at follow-up (p = 0.024). Those patients with no metabolic abnormalities did not develop recurrence. Stone recurrence was seen in six (8%) of 78 children who were given metabolic prophylaxis, compared to 21 (30%) of 70 patients who did not receive metabolic prophylaxis (p = 0.02). No stone recurrence was seen in nine children who were given Shohl's, whereas four (67%) of six patients who did not take Shohl's had recurrence (p = 0.022). Complete removal of stones by a suitable surgical method is essential to avoid recurrences. Detailed clinical and laboratory evaluations should be performed in children with urolithiasis. Appropriate specific prophylactic treatment (e.g., potassium citrate and Shohl's) and non-specific prophylactic treatment (e.g., avoiding animal proteins, salt, simple sugars, and increased water intake) should be given to prevent reformation of stones in patients with pediatric urolithiasis.

Imaging modalities and treatment of paediatric upper tract urolithiasis: A systematic review and update on behalf of the EAU urolithiasis guidelines panel

BACKGROUND

Prompt diagnosis and treatment of paediatric urolithiasis are required to avoid long term sequelae of renal damage.

OBJECTIVE

To systematically review the literature regarding the diagnostic imaging modalities and treatment approaches for paediatric urolithiasis.

STUDY DESIGN

PubMed, Science Direct, Scopus and Web of Science were systematically searched from January 1980-January 2019. 76 full-text articles were included.

RESULTS

Ultrasound and Kidney-Ureter-Bladder radiography are the baseline diagnostic examinations. Non-contrast Computed Tomography (CT) is the second line choice with high sensitivity (97-100%) and specificity (96-100%). Magnetic Resonance Urography accounts only for 2% of pediatric stone imaging studies. Expectant management for single, asymptomatic lower pole renal stones is an acceptable initial approach, especially in patients with non-struvite, non-cystine stones<7 mm. Limited studies exist on medical expulsive therapy as off-label treatment. Extracorporeal shock wave lithotripsy (SWL) is the first-line treatment with overall stone free rates (SFRs) of 70-90%, retreatment rates 4-50% and complication rates up to 15%. Semi-rigid ureteroscopy is effective with SFRs of 81-98%, re-treatment rates of 6.3-10% and complication rates of 1.9-23%. Flexible ureteroscopy has shown SFRs of 76-100%, retreatment rates of 0-19% and complication rates of 0-28%. SFRs after first and second-look percutaneous nephrolithotomy (PNL) are 70.1-97.3% and 84.6-97.5%, respectively with an overall complication rate of 20%. Open surgery is seldom used, while laparoscopy is effective for stones refractory to SWL and PNL. Limited data exist for robot-assisted management.

CONCLUSIONS

In the initial assessment of paediatric urolithiasis, US is recommended as first imaging modality, while non-contrast CT is the second option. SWL is recommended as first line treatment for renal stones <20 mm and for ureteral stones<10 mm. Ureteroscopy is a feasible alternative both for ureteral stones not amenable to SWL as well as for renal stones <20 mm (using flexible). PNL is recommended for renal stones >20 mm.

Pediatric Nephrolithiasis: Risk Factors, Evaluation, and Prevention

Pediatric nephrolithiasis is a disease of increasing prevalence and economic burden, with data showing a rising trend among girls and adolescents. Kidney stones in children tend to have a high recurrence rate related to underlying risk factors, and the aim of evaluation should be to understand such causes so that targeted therapy can be provided to decrease recurrence and complications. Metabolic, anatomic, and genetic abnormalities as well as environmental risk factors have all been implicated in the pathogenesis of nephrolithiasis. Recent studies have focused on identifying monogenic causes of nephrolithiasis and/or nephrocalcinosis in young patients that would result in personalization of treatment as well as future diagnostic implications for family members. Treatment aims to decrease stone burden and recurrence as well as minimize complications and is guided by stone size and location as well as surgical expertise. Multidisciplinary care for these patients has been on the rise to provide a more comprehensive medical and surgical support. [Pediatr Ann. 2020;49(6):e262-e267.].

Dietary risk factors for urinary stones in children

PURPOSE OF REVIEW

As the incidence of urinary stone disease in children is increasing, identifying dietary risk factors becomes vitally important, especially in the context of targeting interventions to reduce risk for stone formation. Indiscriminant dietary restrictions are not appropriate for paediatric patients.

RECENT FINDINGS

Although large, prospective studies are still needed to better quantify dietary risk factors for paediatric stone formers, a number of smaller studies provide data to identify common risk factors to help prevent stone formation, while minimizing inappropriate dietary restrictions.

SUMMARY

Interpretation of 24-h urine samples to identify individualized dietary risk factors is crucial for implementing a strategy for prevention of further urinary stone formation in children. Clinicians should avoid generalized dietary restrictions in stone-forming children uninformed by laboratory data.

Educational review: role of the pediatric nephrologists in the work-up and management of kidney stones

BACKGROUND

The incidence of nephrolithiasis in children and adolescents is increasing and appears to double every 10 years. The most important role of the pediatric nephrologist is to diagnose and modify various metabolic and non-metabolic risk factors, as well as prevent long-term complications especially in the case of recurrent nephrolithiasis.

OBJECTIVE

The purpose of this review is to summarize the existing literature on the etiology and management of pediatric nephrolithiasis.

RESULTS

The incidence of kidney stones is increasing; dietary and environmental factors are probably the main causes for this increased incidence. In most pediatric patients, the etiology for the kidney stones can be identified. Metabolic factors, such as hypercalciuria and hypocitraturia, urinary tract infection, and urinary stasis, constitute leading causes. Herein, we review the etiologies, diagnostic work-up, and treatment options for the most prevalent causes of kidney stones. The detrimental effects of excessive dietary sodium, reduced fluid intake, and the benefits of plant-based over animal-based protein consumption on urinary crystal formation are discussed. We also review the long-term complications.

CONCLUSIONS

Pediatric nephrologists have an important role in the diagnostic work-up and prevention of recurring nephrolithiasis.

The association between dietary intakes and stone formation in patients with urinary stones in Shiraz

Background: Kidney stone is a common and costly disease, but it may be improved by a healthy diet. The aim of this study was to evaluate the association between dietary intake and stone formation in patients with urinary stones in Shiraz. Methods: In this cross sectional study, 110 patients with kidney stone were selected from Faghihi hospital, Shiraz. Demographic information was collected, and anthropometric indices, disease-related variables, physical activity (using IPAQ), and dietary intake (using food frequency questionnaire, analyzed by Nut 4 software, to estimate micro and macro nutrients) were evaluated. Independent sample t test and one-way ANOVA were used to compare the quantitative variables between the 2 groups and multi groups, respectively. Chi square test was also used to compare qualitative variables. The correlation between variables was determined using Pearson test. Results: Out of 110 participants in this study, 37 (33.6%) were female, with the mean BMI of 27.0 ± 4.68 kg/m2, and 73 (66.4%) were male, with the mean BMI of 24.21±2.96 kg/m2. The mean intake of calcium-containing foods (p=0.02) and high-fructose beverages (p=0.03) was significantly greater in patients with calcium stones compared to those with uric acid stones. The mean intake of high-purine foods was significantly higher in patients with uric acid stones than in those with calcium stones (p=0.007). The mean intake of vitamin A (p=0.02), beta-carotene (p=0.03), and fructose (p=0.03) was significantly higher in patients with calcium stones than in those with uric acid stones, while caffeine intake was significantly higher in patients with uric acid than in those with calcium stones (p=0.01). There was a significant correlation between consumption of high-oxalic beverages (p=0.005, correlation coefficient = 0.26) and high-fructose (p=0.048, correlation coefficient = 0.18) with spontaneous stone expulsion. Conclusion: There was a significant relationship between consuming vitamin A, beta-carotene, and foods containing calcium, purine, fructose, and oxalate and formation of kidney stones. Therefore, adopting a healthy diet and increasing physical activity may be effective in the treatment of kidney stones.

CLINICAL-EPIDEMIOLOGICAL PROFILE OF 106 PEDIATRIC PACIENTS WITH UROLITHIASIS IN RIO DE JANEIRO, BRAZIL

Objective:

To describe the frequency, clinical profile and treatment of patients with urolithiasis in the Pediatric Nephrology Department of a public state hospital in Rio de Janeiro, Brazil.

Methods:

Retrospective study. Data from pediatric patients (age: 1 month - 18 years) with urolithiasis admitted between January/2012 and December/2014 were reviewed from hospital charts. The studied variables were: demographic and anthropometric data, clinical status, family history of urolithiasis, urinary tract infection and use of lithogenic drugs, diagnostic procedures, associated abnormalities, metabolic disorders, treatment and recurrence.

Results:

The frequency of urolithiasis was 13.6%. Main characteristics of the patients: male gender, white race, eutrophy, aged between 5 and 10 years, family history of urolithiasis, previous urinary infection and spontaneous stone passage. Abdominal and flank pain and macroscopic hematuria were the most common complaints. The most frequent metabolic disorders were hypercalciuria, hyperuricosuria and hypocitraturia. Hypocitraturia was associated with previous urinary infection (p=0.004). Abdomen/urinary tract ultrasonography was the most commonly used diagnostic test. Hydronephrosis occurred in 54.4% of the cases, 81.1% of the stones were in the kidneys, and bilateral stones were associated to a family history of urolithiasis (p=0.030). Recurrence rate was 29.3% (most patients had a metabolic disorder). In 12.3%, the patients underwent lithotripsy, 24.5% were surgically treated (mainly pyelolithotomy), and only 7.6% had their stones analyzed (calcium oxalate was the main finding in the examined stones).

Conclusions:

The frequency of urolithiasis in these pediatric patients was similar to that reported by the literature. A metabolic evaluation is required and the composition of stones should be better evaluated.

The ability of a limited metabolic assessment to identify pediatric stone formers with metabolic abnormalities

INTRODUCTION

American Urological Association guidelines recommend a urinary metabolic evaluation after the first stone event in all pediatric stone patients. Prior studies identified hypercalciuria and urine hypovolemia as the most common abnormalities in children with urolithiasis. Recent data suggest that hypocitraturia is most prevalent. It was hypothesized that a limited evaluation would detect the majority of clinically significant metabolic abnormalities in pediatric stone formers.

MATERIAL AND METHODS

A retrospective analysis of all children (<18 years of age) with renal/ureteral calculi evaluated at the study institution from 2005 to 2015 was performed. Children with ≥ one 24-h urinary metabolic profile after a clinical visit for renal/ureteral calculi were included. Those with bladder stones and those with undercollection or overcollection or missing urinary creatinine were excluded. Demographics and data from the first urinary metabolic profile and stone analyses were collected. The sensitivity, specificity, and positive and negative predictive value (NPV) of a limited urinary metabolic evaluation consisting of four parameters (24-h calcium, citrate, and oxalate and low urinary volume) were compared to a complete urinary metabolic profile. The number and type of metabolic abnormalities that would have been missed with this limited evaluation weredetermined.

RESULTS

Of 410 patients, 21 were excluded for age ≥18 years, 13 for bladder stones, 248 for overcollections, 38 for undercollections, and 10 for missing creatinine. This left 80 patients for inclusion: median age 11.4 years, 60% female, and 96.3% white. Of the entire cohort, 69.6% had hypocitraturia, 52.5% had low urine volume, and 22.5% had hypercalciuria. Sensitivity was 87.5%. Specificity could not be calculated because no patients had a normal complete metabolic evaluation. The NPV was zero, and the positive predictive value was 100%, but these are artifacts resulting from the absence of patients with a normal complete metabolic evaluation. Of the 80 patients, 10 had at least one abnormality missed by a limited metabolic evaluation (Table 1). The missed abnormalities were high pH (n = 6), abnormal 24-h phosphorus (low in 1 patient and high in 1 patient), low 24-h magnesium (n = 3), low 24-h potassium (n = 3), and high 24-h sodium (n = 4).

DISCUSSION

A limited urinary metabolic evaluation would have detected the vast majority of clinically significant metabolic abnormalities in the study sample. Approximately two-thirds of the study patients submitted inadequate 24-h urine specimens.

CONCLUSIONS

A simplified approach to metabolic evaluation in first-time stone formers with a stone analysis available was proposed. This streamlined approach could simplify the metabolic evaluation and reduce health care costs.

Analyte variations in consecutive 24-hour urine collections in children

PURPOSE

The metabolic evaluation of children with nephrolithiasis begins with a 24-h urine collection. For adults, the diagnostic yield increases with consecutive collections; however, little is known regarding the variability of multiple 24-h studies in the pediatric population. We sought to evaluate the variability of consecutive 24-h urine collection in children through a multi-institutional study hypothesizing that compared with a single collection, consecutive 24-h urine collections would reveal a greater degree of clinically useful information in the evaluation of children at risk for nephrolithiasis.

MATERIALS AND METHODS

Including data from six institutions, we identified children less than 18 years of age considered at risk for recurrent nephrolithiasis, undergoing metabolic evaluation. We evaluated a subset of patients performing two collections with urine creatinine varying by 10% or less during a 7-day period. Discordance between repeat collections based on normative urine chemistry values was evaluated.

RESULTS

A total of 733 children met inclusion criteria, and in over a third both urine calcium and urine volume differed by 30% or more between samples. Urine oxalate demonstrated greater variation between collections in children <5 years than among older children (p = 0.030) while variation in other parameters did not differ by age. Discordance between repeat samples based on normative values was most common for urine oxalate (22.5%) and the derived relative supersaturation ratios for both calcium phosphate (25.1%) and calcium oxalate (20.5%). The proportion of discordant samples, based on normative thresholds, as well as variability greater ≥30% and 50%, respectively, are shown in the table.

CONCLUSIONS

Our analysis indicates that stone risk in as many as one in four children may be misclassified if normative values of only a single 24-h urine are used. In light of these findings, repeat 24-h urine collections prior to targeted intervention to modify stone risk are advised to increase diagnostic yield in children at risk for nephrolithiasis.

The Modern Metabolic Stone Evaluation in Children

OBJECTIVE

To evaluate metabolic abnormalities in a contemporary pediatric population after their first stone episode. The incidence of pediatric nephrolithiasis is increasing and therefore the etiologies contributing to today's pediatric stone formation may also be changing.

MATERIALS AND METHODS

A retrospective review of all consecutive children presenting after their first kidney stone between 2000 and 2014 was performed. We compared demographic data, serum chemistry results, and 24-hour urine results and treatments.

RESULTS

One hundred thirteen children with a mean age of 11 years (5 months to 18 years) who presented with their first kidney stone episode between 2000 and 2014 were evaluated. Sixteen patients (14%) were found to have an underlying genetic or systemic disease. Overall, there was a low rate of serum chemistry abnormalities. The most common abnormalities found within the 24-hour urine evaluation included low urine volume (89%) and hypocitraturia (68%). Hypercalciuria occurred rarely (11%).

CONCLUSION

We identified a low rate of underlying genetic or systemic diseases contributing to modern pediatric stone presentation and an increased proportion of idiopathic stones. Our study differs from historical findings by identifying a low rate of hypercalciuria and a high rate of low urine volume and hypocitraturia, suggestive of changing metabolic abnormalities contributing to modern pediatric stone disease.

Metabolic disturbances in Chinese children with urolithiasis: a single center report

Urinary stones and urine composition are the first steps in the process of recurrence prevention, but data concerning the association between the two compositions are scarce in Chinese children with urolithiasis. We retrospectively analyzed the records of children (age range 0-18 years) with urolithiasis in our center between March 2004 and December 2013. Stone analysis was carried out in 382 children and 24-hour urine analysis in 80 children. Analysis of both stone and 24-hour urine composition was completed in 56 children. Stone samples were analyzed by Fourier transform-infrared spectrometry. The major stone constituents were calcium oxalate (78.8 %). Of 80 children with 24 h urine analysis, only 2.5 % were without urinary metabolic abnormalities. Hypocitraturia was recorded in 97.5 %, high sodium excretion in 50.0 %, cystinuria in 48.7 %, hypercalciuria in 18.8 %, small urine volumes in 12.5 %, hyperoxaluria in 5.0 % and hyperuricosuria in 1.3 %. Interestingly, higher urine volumes were recorded in girls than in boys (73.2 ± 58.5 vs 51.3 ± 45.3 mL/kg, p = 0.036). Urine sodium (p = 0.002) and oxalate (p = 0.004) were significantly higher in children >9 year old. Moreover, compared with calcium oxalate stone formers, the urine volume (p = 0.040), citrate (p = 0.007) and cystine (p = 0.004) were higher in patients with cystine stones. Hypocitraturia was the common abnormality among Chinese children with urolithiasis. The surprisingly high incidence of cystinuria is of note.

Pediatric Kidney Stones - Avoidance and Treatment

Pediatric stone disease is increasing in incidence and healthcare costs. With more years at-risk for stone recurrence during their lifetimes, children with nephrolithiasis constitute a high-risk patient population that requires focused intervention through both medical and surgical means. Through high-quality future studies to compare methods of stone prevention and treatment, the burden of stone disease on the youngest members of society may be ameliorated.

A Comparison between Clinical and Metabolic Features of Renal Calyceal Microlithiasis and Overt Urolithiasis in Different Pediatric Age Groups

INTRODUCTION

This study assesses the differences in the presentations, complications and metabolic abnormalities of children with renal calyceal microlithiasis (RCM) and overt urolithiasis in different pediatric ages.

MATERIALS AND METHODS

A total of 465 children with urolithiasis were investigated retrospectively. Patients were categorized based on their ages to infancy, early childhood, middle childhood and adolescence. When the hyperechogenic spots on ultrasound imaging were <3 mm, they were considered RCM, and if they were ≥3 mm, they were considered overt urolithiasis.

RESULTS

Metabolic abnormalities were detected in 71%; hyperuricosuria in infants, hyperoxaluria in younger children and hypocitraturia in older children were the most common metabolic abnormalities. Hypercalciuria was the only metabolic abnormality that was significantly associated with overt urolithiasis in all pediatric ages (OR 2.25, 95% CI 1.21-4.19). The clinical presentations were not significantly different between RCM and overt urolithiasis; however, complications such as urinary tract infection was significantly higher with overt urolithiasis in infancy (p = 0.01), early childhood (p = 0.02), middle childhood (p = 0.007) and adolescence (p = 0.01). Also, growth retardation was significantly higher with overt urolithiasis in infancy and early childhood (p = 0.02).

CONCLUSIONS

Most children with urolithiasis have underlying urinary metabolic abnormalities that differ according to the child's age. Despite these differences, hypercalciuria is significantly associated with overt urolithiasis in all pediatric ages. Clinical and laboratory features cannot differentiate RCM and overt urolithiasis; however, complications are significantly higher with overt urolithiasis.

National multi-institutional cooperative on urolithiasis in children: Age is a significant predictor of urine abnormalities

INTRODUCTION

Pediatric nephrolithiasis is a growing problem and prior studies have shown the greatest increase in nephrolithiasis in the adolescent population. Metabolic abnormalities have historically been cited as the primary cause of pediatric nephrolithiasis; however, dietary and other factors such as obesity have also been studied with mixed results.

OBJECTIVE

We reviewed the charts of pediatric patients with a history of nephrolithiasis to determine the number and types of metabolic abnormalities present on 24-h urine analysis.

STUDY DESIGN

We retrospectively reviewed the charts of all pediatric patients with a history of nephrolithiasis from 1999-2013 across four different institutions. The subjects were excluded if they had a history of spina bifida, neurogenic bladder, cerebral palsy, isolated bladder stones, or if they were on medical therapy for nephrolithiasis before the first 24-h urine collection.

RESULTS

There were 206 subjects included in the analysis with an average age of 13 (±3.9) years. The patients were stratified into two age groups based on an apparent bimodal distribution of metabolic abnormalities, ≤10 years and >10 years of age. Metabolic abnormalities were present in 130 children (63.1%) and there was a difference between the groups, with children ≤10 years more likely to have a metabolic abnormality compared with those >10 years of age (75% vs. 60.6%, p = 0.0443) on univariate analysis. In children ≤10 years hypercalciuria was the most common disorder present (48.4%), and in children >10 years hypocitraturia was the most common disorder present (26.1%). Children ≤10 years of age were more likely to have normal volume (p = 0.006), elevated urinary oxalate (p = 0.0351), elevated urinary calcium (p < 0.001), elevated supersaturation of calcium phosphate (p < 0.001), and elevated supersaturation of calcium oxalate (p = 0.002). On multivariate analysis, children ≤10 years of age were more likely to have normal volume, hyperoxaluria, elevated supersaturation of calcium phosphate and a trend towards hypercalciuria (Table).

DISCUSSION

Our study reveals that younger children are more likely to have a metabolic abnormality present on 24-h urine analysis. This has important implications when deciding on treatment options, with younger children potentially requiring more aggressive management with medical therapy. Older children were more likely to have low urinary volume and their most common metabolic abnormality was hypocitraturia. Although dietary factors have not been established as the definitive reason behind the rising incidence of nephrolithiasis in the adolescent population, older children may benefit more from diet modification with a strong focus on increasing volume intake.

CONCLUSION

We found differences in younger compared with older age groups in terms of the number and types of metabolic disorders present. Children ≤10 years of age were more likely to have a metabolic disorder including elevations in calcium, oxalate and supersaturation of calcium phosphate, while children >10 years of age were more likely to have low urinary volume. These differences have important implications for future investigative studies on the rising incidence as well as the best course of treatment for children with nephrolithiasis.

Patient and stone characteristics associated with surgical intervention in pediatrics

Background

The incidence of kidney stones in children is increasing. While guidelines exist for acute surgical intervention, there is limited data to inform the decision as to when to intervene non-urgently.

Objectives

To identify patient and stone characteristics predicting stone surgery in children.

Design

Retrospective chart review.

Setting

Stollery Children’s Hospital, Edmonton, Alberta, Canada from 1990 to 2013.

Patients

Sixty-three children aged 0–18 years old who presented with a total of 142 stones.

Measurements

Patient’s surgical history, demographics, metabolic measures, and stone number, type, and location.

Methods

Univariate and multivariate analysis, controlling for presentation number and individual-level variation by repeated measures analysis were conducted to assess for patient and stone characteristics associated with surgical intervention.

Results

Sixty-five percent (41/63) required surgery during a mean follow-up of 19 months. Stone characteristics associated with surgical intervention by multivariate analysis included larger stone size (>6 mm), and stone composition of calcium oxalate.

Limitations

Single center study with a limited sample size and duration of follow up, thereby limiting predictive power. There were some missing data (i,e. stone type was not always available). Despite this, stone type remained significant in multivariate modeling.

Conclusion

Stone size > 6mm and composition with calcium oxalate but not patient age or symptoms associated with presentation predicted surgical intervention. These observations can be used to inform decisions as to whether urolithiasis should be surgically managed electively or observed.

Electronic supplementary material

The online version of this article (doi:10.1186/s40697-015-0057-6) contains supplementary material, which is available to authorized users.

Evaluation and medical management of kidney stones in children

PURPOSE

We review the current literature on the diagnostic evaluation and dietary and pharmacological management of children with nephrolithiasis.

MATERIALS AND METHODS

We searched MEDLINE(®), Embase(®) and the Cochrane Library from their inceptions to March 2014 for published articles in English on kidney stones and therapy in children 0 to 18 years old. Based on review of the titles and abstracts, 110 of the 1,014 articles (11%) were potentially relevant to the diagnostic evaluation and medical management of nephrolithiasis in children. We summarized this literature and drew on studies performed in adult populations to augment areas in which no studies of sufficient quality have been performed in children, and to highlight areas in need of research.

RESULTS

During the last 25 years the incidence of nephrolithiasis in children has increased by approximately 6% to 10% annually and is now 50 per 100,000 adolescents. Kidney stones that form during childhood have a similar composition to those that form in adulthood. Approximately 75% to 80% of stones are composed of predominantly calcium oxalate, 5% to 10% are predominantly calcium phosphate, 10% to 20% are struvite and 5% are pure uric acid. The recurrence rate of nephrolithiasis in patients with stones that form during childhood is poorly defined. Ultrasound should be used as the initial imaging study to evaluate children with suspected nephrolithiasis, with noncontrast computerized tomography reserved for those in whom ultrasound is nondiagnostic and the suspicion of nephrolithiasis remains high. Current treatment strategies for children with kidney stone disease are based largely on extrapolation of studies performed in adult stone formers and single institution cohort or case series studies of children. Tamsulosin likely increases the spontaneous passage of ureteral stones in children. Increased water intake and reduction of salt consumption should be recommended for all children with a history of kidney stones. Potassium citrate is a potentially effective medication for children with calcium oxalate stones and concomitant hypocitraturia, as well as children with uric acid stones. However, long-term compliance with therapy and the effect on decreasing stone recurrence in children are unknown. Based largely on efficacy in adult populations, thiazide diuretics should be considered in the treatment of children with calcium based stones and persistent hypercalciuria refractory to reductions in salt intake.

CONCLUSIONS

The incidence of kidney stone disease in children is increasing, yet few randomized clinical trials or high quality observational studies have assessed whether dietary or pharmacological interventions decrease the recurrence of kidney stones in children. Collaborative efforts and randomized clinical trials are needed to determine the efficacy and effectiveness of alternative treatments for children with nephrolithiasis, particularly those with calcium oxalate stones and concomitant hypercalciuria and hypocitraturia. Additional areas in need of study are the optimal length of time for a trial of stone passage in children, the cost-effectiveness of medical expulsive therapy vs analgesics alone, and the size and location of stones for which medical expulsive therapy is most effective.

Demographic characteristics and metabolic risk factors in Croatian children with urolithiasis

The aim of this study was to assess demographic data, clinical presentation, metabolic features, and treatment in 76 children with urolithiasis presented from 2002 to 2011. Urolithiasis is responsible for 2.5/1,000 pediatric hospitalizations, with new cases diagnosed in 1.1/1,000 admissions. From the observed period, two-fold rise of incidence rate was observed. Compiling the data from other pediatric institutions in our country, we estimated present overall incidence rate in Croatia as 6.5/100,000 children under 18 years. There were 41 boys and 35 girls (ratio 1.17:1). The mean age at diagnosis was 9.7 (range 0.8-16) years and follow-up duration was 5.3 (range 1.8-10) years. Renal colic (75.0 %) and hematuria (57.89 %) were the main symptoms. In 65.78 % of children, stones were unilateral. Stones were located in kidney in 52.63 %, in the ureter in 26.32 %, and in bladder in 6.58 % cases. Stone analysis showed calcium oxalate in 75.0 % of the cases. Associated urinary tract abnormalities were found in 19.73 % children. Most common metabolic disturbances were hypercalciuria (47.37 %) and idiopathic or mild hyperoxaluria (18.42 %). Urine saturation (EQUIL2) was elevated in 61.84 % cases. Spontaneous stone evacuation occurred in 51.21 % children. Extracorporeal shock wave lithotripsy, surgical evacuation, and endoscopic removal of calculi were performed in 21.0, 6.58, and 5.26 % of cases, respectively. Follow-up conservative therapy, consisting of fluid/diet recommendations and additional potassium citrate and/or chlorothiazide in children with increased risk, was sufficient for stone recurrence prevention in 92.1 % of children. In conclusion, the study gave insight in epidemiology and metabolic disturbances of urinary stone disease in Croatian children.

Urinary citrate excretion in healthy children depends on age and gender

BACKGROUND

Hypocitraturia is considered a major risk factor for calcium stone formation. However, there is no widely accepted reference database of urinary citrate excretion in children. The aim of our study was to determine the amount of citrate eliminated in the urine over a 24-h period in a pediatric cohort and to determine an optimal unit reflecting excretion.

METHODS

The study cohort comprised 2,334 healthy boys and girls aged 2-18 years. The levels of urinary citrate were assessed by an enzymatic method in 24-hour urine and expressed in absolute values, as urinary concentration, citrate/creatinine ratio, per kilogram of body weight, in relation to 1.73 m2, and as the calcium/citrate index.

RESULTS

Similar incremental age-related citraturia rates were observed in both male and female subjects until puberty during which time citrate excretion became significantly higher in girls. Urinary citrate adjusted for creatinine and for body weight showed a significantly decreasing trend with increasing age in both sexes. Urinary citrate corrected for body surface was weakly correlated with age. Thus, the assumption of 180 mg/1.73 m2/24 h for males and 250 mg/1.73 m2/24 h for females as lower cut-off values appeared to be reliable from a practical perspective.

CONCLUSIONS

We found distinct sex-dependent differences in citraturia at the start of puberty, with significantly higher values of urinary citrate in girls than in boys. Further prospective studies are warranted to elucidate whether this difference represents a differentiated risk of urolithiasis.

Metabolic risk factors and the effect of metaphylaxis in pediatric stone disease with hypocitraturia

To describe the metabolic risk factors and investigate the effect of prophylaxis based on these factors on long-term recurrence of urolithiasis in pediatric patients with hypocitraturia. One-hundred and twenty-nine pediatric patients who underwent percutaneous nephrolithotomy between January 2008 and June 2011 were evaluated for metabolic risk factors. The patients with hypocitraturia were enrolled in this study and the data were analyzed using statistical methods for a mean period of 2 years for metabolic abnormalities, stone type, and the effect of potassium citrate prophylaxis on stone recurrence. A 24-h urine metabolite analysis revealed one or more metabolic risk factors in 115 (89.2 %) of the patients, whereas 14 (10.8 %) of the patients had no metabolic abnormalities. Eighty-two (63.5 %) of 129 patients had hypocitraturia. Of them, 43 (52 %) were male and 39 (48 %) were female, with a mean age of 9.7 ± 4.9 and 6.7 ± 4.4 (1-16) years, respectively(p = 0.102). Thirty-five (42.7 %) had pure hypocitraturia, and 47 (57.3 %) had two or more metabolic abnormalities. The most common dual metabolic abnormality was hypocitraturia and hypomagnesuria. Seventy-one patients (87 %) with hypocitraturia received medical prophylaxis and continued regularly, whereas 11 (13 %) patients did not receive medical prophylaxis despite being advised to do so. After a mean follow-up of 26.5 ± 9.4 months, the rate of recurrence was 1.4 % in the patients with hypocitraturia who continued prophylaxis and occurred in all of the patients who did not receive prophylaxis (p < 0.001). Calcium oxalate stones (95.2 %) were the most commonly found stones in the stone analysis. Detailed clinical and laboratory evaluations should be performed in children with urolithiasis. Appropriate prophylactic treatment as potassium citrate, should be given to prevent reformation of stones in patient with hypocitraturia.

The effect of dietary sodium and fructose intake on urine and serum parameters of stone formation in a pediatric mouse model: a pilot study

PURPOSE

Dietary factors have a role in stone disease in adults but little is known about the relationship in children. We tested whether diet could alter urine and serum parameters in a pediatric mouse model.

MATERIALS AND METHODS

We randomized 30 female BALB/c mice at age 3 weeks to mouse chow, a complex carbohydrate Western diet or a high fructose, high sodium Western diet. Body weight was measured twice weekly. Urine was periodically collected and mice were sacrificed on day 30. Samples were pooled to analyze serum and urine electrolyte factors.

RESULTS

There was no significant difference in body weights among the groups at any time or in kidney weight at sacrifice (each p >0.15). There was no observable increase in urine stone forming analytes across the arms except uric acid, which tended to be higher in the Western diet and high fructose, high sodium Western diet groups. There was a substantial decrease in urinary stone inhibitors (magnesium and citrate), a decrease in urinary potassium and an increase in serum calcium in the 2 Western diet groups.

CONCLUSIONS

This pilot study suggests that consuming a Western diet, especially one composed of high fructose and sodium, may alter parameters that predispose to stone formation in children by decreasing stone inhibitors. Results require validation in larger studies and ultimately in humans.