Influence of Gender and Age on Calcium Oxalate Crystal Growth Inhibition by Urine from Relatives of Stone Forming Patients

Hydration and Nephrolithiasis in Pediatric Populations: Specificities and Current Recommendations

Renal lithiasis is less frequent in children than in adults; in pediatrics, lithiasis may be caused by genetic abnormalities, infections, and complex uropathies, but the association of urological and metabolic abnormalities is not uncommon. The aim of this study is to provide a synthesis of nephrolithiasis in children and to emphasize the role of hydration in its treatment. As an etiology is reported in 50% of cases, with a genetic origin in 10 to 20%, it is proposed to systematically perform a complete metabolic assessment after the first stone in a child. Recent data in the field reported increased incidence of pediatric urolithiasis notably for calcium oxalate stones. These changes in the epidemiology of stone components may be attributable to metabolic and environmental factors, where hydration seems to play a crucial role. In case of pediatric urolithiasis, whatever its cause, it is of utmost importance to increase water intake around 2 to 3 L/m² per day on average. The objective is to obtain a urine density less than 1010 on a dipstick or below 300 mOsm/L, especially with the first morning urine. Some genetic diseases may even require a more active 24 h over-hydration, e.g., primary hyperoxaluria and cystinuria; in such cases naso-gastric tubes or G-tubes may be proposed. Tap water is adapted for children with urolithiasis, with limited ecological impact and low economical cost. For children with low calcium intake, the use of calcium-rich mineral waters may be discussed in some peculiar cases, even in case of urolithiasis. In contrast, sugar-sweetened beverages are not recommended. In conclusion, even if parents and patients sometimes have the feeling that physicians do not propose "fancy" therapeutic drugs, hydration and nutrition remain cornerstones of the management of pediatric 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.

Trends in pediatric urolithiasis: patient characteristics, associated diagnoses, and financial burden

BACKGROUND

The goal of this study was to examine national trends in hospitalization, emergency department (ED) utilization, secondary diagnoses, and charges associated with pediatric urolithiasis.

METHODS

Data were evaluated from the Kids' Inpatient Database of the Healthcare Costs and Utilization Project (HCUP) database from 1997 to 2012 and the HCUP National ED Sample from 2006 to 2011.

RESULTS

Pediatric nephrolithiasis discharges increased by 18%, while ureterolithiasis discharges decreased by 17%. Hospital charges increased by 20% when accounting for inflation, despite an overall decrease in discharges by 2.5%. Female patients and those aged 15-17 years were more commonly affected. Pediatric ED visits increased by 9%. The most common secondary diagnoses during 2003-2009 were urinary tract infections (UTI) (13%), asthma (9%), epilepsy (4%), and paralysis (4%).

CONCLUSIONS

Decreased hospitalizations and increased ED visits indicate a shift to outpatient care. Inpatient health care charges associated with pediatric urolithiasis continue to rise. Comorbidities include UTI, asthma, epilepsy, attention deficit hyperactivity disorder (ADHD), and mood disorders. Because of the significant health care burden and the increased risk to children of developing long-term sequelae there is a strong need for increased research into the mechanism of this systemic inflammatory disease and improved therapeutic targets.

Urine risk factors in children with calcium kidney stones and their siblings

Calcium nephrolithiasis in children is increasing in prevalence and tends to be recurrent. Although children have a lower incidence of nephrolithiasis than adults, its etiology in children is less well understood; hence, treatments targeted for adults may not be optimal in children. To better understand metabolic abnormalities in stone-forming children, we compared chemical measurements and the crystallization properties of 24-h urine collections from 129 stone formers matched to 105 non-stone-forming siblings and 183 normal, healthy children with no family history of stones, all aged 6 to 17 years. The principal risk factor for calcium stone formation was hypercalciuria. Stone formers have strikingly higher calcium excretion along with high supersaturation for calcium oxalate and calcium phosphate, and a reduced distance between the upper limit of metastability and supersaturation for calcium phosphate, indicating increased risk of calcium phosphate crystallization. Other differences in urine chemistry that exist between adult stone formers and normal individuals such as hyperoxaluria, hypocitraturia, abnormal urine pH, and low urine volume were not found in these children. Hence, hypercalciuria and a reduction in the gap between calcium phosphate upper limit of metastability and supersaturation are crucial determinants of stone risk. This highlights the importance of managing hypercalciuria in children with calcium stones.

Epidemiologic insights into pediatric kidney stone disease

The epidemiology of pediatric kidney stone has not yet been as rigorously defined as that of adult kidney stone disease. Herein, we review our recent epidemiologic works characterizing pediatric stone disease using the Kids' Inpatient Database (KID). Specifically we investigated the age and gender distribution of pediatric kidney stone disease, changes in disease prevalence over time, and medical comorbidities associated with this disorder. We identified patients by International Classification of Disease 9th Edition (ICD-9) codes for renal and ureteral calculi as the primary diagnosis. Medical comorbidities were identified using specific comorbidity software. Statistical comparisons between children with and without stone disease were performed. In the first decade of life, stone disease was more prevalent among males than females; however, in the second decade of life females were more commonly affected. Of note, there was a significant increase in treated stone disease across both genders between 1997 and 2003. We also found that the risk of kidney stone diagnosis in children younger than 6 years of age was significantly associated with hypertension and diabetes mellitus. The gender distribution among pediatric stone formers varies significantly by age, although overall females have a greater prevalence than males. There is also a strong association of stone disease and both diabetes and hypertension, although this was only observed in children less than 6 years of age. Taken all together, these findings suggest that urolithiasis in the young child is a complex systemic disease process.

Sex prevalence of pediatric kidney stone disease in the United States: an epidemiologic investigation

OBJECTIVES

To define the sex prevalence of inpatient hospital discharges for pediatric patients diagnosed with upper urinary tract stone disease.

METHODS

The study examined inpatient admissions for pediatric urolithiasis in 2003, using the Healthcare Cost and Utilization Project Kids' Inpatient Database. We used the International Classification of Disease, 9th edition, Clinical Modification codes, to identify patients with a principal diagnosis of renal (592.0) or ureteral (592.1) calculi. Sex prevalence was assessed, and the results were stratified by age group.

RESULTS

In the 2003 Kids' Inpatient Database, the sex distribution among pediatric patients with stone formation varied significantly by age. In the first decade of age, a male predominance was found that had shifted to a female predominance in the second decade. Overall, however, girls in the pediatric population were more commonly affected by stones than were boys.

CONCLUSIONS

In this nationally representative sample, the sex distribution of pediatric urolithiasis varied with age, with boys more commonly affected in the first decade of age and girls in the second decade. Although the reason for this unique epidemiologic finding is not readily apparent, additional studies can build on this hypothesis-generating work.

Association between metabolic syndrome and nephrolithiasis in an inpatient population in southern Italy: role of gender, hypertension and abdominal obesity

BACKGROUND

Metabolic syndrome (MetS) and nephrolithiasis (NL) are quite common disorders. While some of the components of MetS have been proposed as precursors of NL in population studies, no data are available about the possible association between NL and MetS as such. The primary objective of the study was to evaluate the relationship between MetS and NL. The secondary outcome was to examine the relationship between MetS single constitutive elements and NL considering the strict correlation occurring among these factors.

METHODS

We studied 2132 Caucasian inpatients of the 'Spinelli' Hospital in southern Italy (males/females = 0.95; mean age 63.8 +/- 15.8 years; body mass index 26.1 +/- 3.9 kg/m(2)). The MetS diagnosis was performed according to the Heart Association/National Heart, Lung, and Blood Institute criteria. The presence of NL was assessed by ultrasound examination of the kidneys and upper urinary tract.

RESULTS

Seven hundred twenty-five subjects (34.0%) had a positive diagnosis of MetS. Two hundred twenty subjects (10.3%) had echographic evidence of NL, while 199 subjects reported a past history of NL (9.3%). The presence of MetS, as well as the male sex, and the occurrence of a previous episode of NL (in male subjects only) were each independently related to echographic evidence of NL. Among the individual components of MetS, high blood pressure and abdominal obesity (in female individuals only) were also independently related to echographic evidence of NL.

CONCLUSIONS

MetS is significantly associated with echographic evidence of NL. A gender-related difference in the clinical expression of NL was also observed.

A new approach to the diagnosis of children's urolithiasis based on the Bonn Risk Index

Published data on the association between calcium oxalate (CaOx) crystallization and kidney stone disease in children are scarce. The aims of this study were to determine CaOx crystallization using the Bonn Risk Index (BRI) in children with urolithiasis in comparison to healthy controls, to evaluate the relationships between BRI and urinary parameters, such as pH, calciuria, oxaluria and citraturia, and to assess the association between BRI and the size of renal stones. We compared the BRI in 142 Caucasian children and adolescents (76 girls, 66 boys) aged 3-18 years with kidney stones and 210 healthy age- and sex-matched controls without urolithiasis. Urinary ionized calcium ([Ca2+]) was measured using a selective electrode, while the onset of spontaneous crystallization was determined using a photometer and titration with 40 mmol/L ammonium oxalate (Ox2-). The calculation of the BRI value was based on the Ca2+:Ox2- ratio. High-resolution renal ultrasonography was carried out to estimate the size of the renal stones. The BRI values were 15-fold higher in children with renal stones than in healthy children without stones. The same trend was shown by BRI/kg body weight (tenfold greater in children with renal stones than in healthy children without stones), BRI/per 1.73 m2 body surface (13-fold greater) and BRI/body mass index (23-fold greater). No association was observed between BRI and the diameter of stones. Children with kidney stones, both males and females, had an increased BRI compared with subjects without urolithiasis. High BRI suggests an association with lower urinary pH, hypercalciuria, hyperoxaluria or hypocitraturia, which are all risk factors of kidney stones. An increased BRI in children, although unrelated to renal stone size, reflects the risk of calcium oxalate crystallization and may indicate early metabolic disorders leading to urolithiasis.

Normative data on the Bonn Risk Index for calcium oxalate crystallization in healthy children

Bonn Risk Index (BRI) is being used for the assessment of urinary calcium oxalate (CaOx) crystallization. There are no published data regarding BRI during growth. The objective of this study was to establish age- and sex-dependent BRI values in healthy children and adolescents. A total of 1,050 Caucasian subjects aged 3-18 years (525 males, 525 females) without a history of kidney stone disease were enrolled in the cross-sectional study. The study group was divided into 15 ranges according to age, each comprising 70 subjects. Urinary ionized calcium [Ca2+] was measured using a selective electrode while the onset of spontaneous crystallization was determined using a photometer and titrating with 40 mmol/L ammonium oxalate (Ox(2-)). The calculation of BRI value was based on the ratio of [Ca2+] to the required amount of ammonium oxalate added to 200 ml of urine to induce crystallization. The median BRI was 0.26 1/L and the values of the 5th and 95th percentiles were 0.06 1/L and 1.93 1/L, respectively. BRI correlated positively with body-area-related BRI (1/L x 1.73 m2) (R = 0.18; P < 0.05), whereas a negative correlation was found between BRI and body weight (1/L x kg) (R = -0.85; P < 0.05). Neither sex nor age differences were detected in BRI across studied children and adolescents. The values of Bonn Risk Index were constant during growth and there was a limited influence of age and sex on BRI in children over 3 years of age. The BRI may be valuable in the evaluation of pediatric patients at risk for kidney stones, particularly if the BRI from stone formers is demonstrated to be higher than in normal children.

Urine protein markers distinguish stone-forming from non-stone-forming relatives of calcium stone formers

We have investigated urine protein inhibitors of calcium oxalate crystallization to determine whether variations in these proteins are associated with kidney stone disease and whether protein measurements improve the identification of stone formers compared with conventional risk factors (RF). Using Western blotting, we studied variations in the electrophoretic mobility patterns and relative abundances of crystallization-inhibitory proteins in urine from 50 stone-forming (SF) and 50 non-stone-forming (NS) first-degree relatives of calcium SF patients, matched by gender and age. Standard urine chemistry stone risk measurements were also made. Multivariate discriminant analysis was used to test the association of these proteins with nephrolithiasis. Differences in form and abundance of several urine proteins including inter-alpha-trypsin inhibitor (ITI), prothrombin fragment 1 (PF1), CD59, and calgranulin B (calB) were found to be associated with stone formation. By multivariate discriminant analysis, measurements of forms of PF1, ITI, and calB in men and ITI and CD59 in women, classified 84% of men and 76% of women correctly by stone status. In contrast, standard urine chemistry RF identified only 70% of men correctly and failed to distinguish female SF from NS. Thus a small subset of protein measurements distinguished SF from NS far better than conventional RF in a population of relatives of calcium SF, illustrating the significant association of these proteins with stone disease. Variations in these proteins may serve as markers of stone disease activity or vulnerability to recurrence and may provide new insights into mechanisms of stone formation.

Prognostic factors effecting on recurrence of urinary stone disease: a multivariate analysis of everyday patient parameters

INTRODUCTION

Since comprehensive urometabolic analyses are currently more preferred for the patients with recurrent stones and with high risk of stone recurrence, we have tried to determine simple patient data increasing stone recurrence to limit sophisticated analyses to certain cases at least in particularly deprivation districts.

MATERIALS AND METHODS

For the study 173 with first-time or recurrent urinary stone were taken. After stone treatment, various empirical metaphylaxis methods were counselled to the patients. The parameters evaluated were (a) age at onset of the disease, (b) gender, (c) urinary pH and (d) specific gravity, (e) serum calcium and (f) uric acid, (g) stone burden, (h) side, and (i) location, (j) treatment modality and (k) recurrence history. New stone formation or growing of the existing stone was considered as stone recurrence. In statistics, independent samples t, chi-square test, Kaplan-Meier, Log rank and Cox regression tests were used.

RESULTS

The mean age was 35 years. The male to female ratio was 88/85. Recurrence occurred in 49 (28%) cases at a mean of 30 months. Stone burden was significantly larger in patients with recurrent stone. In subjects treated with open surgery and with previous recurrence history, stone recurrence rate was significantly higher. In survival analyses, higher serum calcium level, larger stone burden, renal stones and previous recurrence influenced stone prognosis poorly. However in multivariate analysis, none of them was the most significant independent factor.

CONCLUSIONS

According to our study, detailed urometabolic analyses may be somewhat reserved for the patients with ordinary factors increasing risk of stone recurrence including relatively high serum calcium level, large stone burden, upper urinary stone, history of recurrence and open surgery. As a result, it has been thought that the stone risk evaluation guiding detailed laboratory examination may be partially performed with first-line clinical data under limited conditions.