Influence of Body Mass Index on Quantitative 24-Hour Urine Chemistry Studies in Children With Nephrolithiasis

Comprehensive analysis of pediatric urolithiasis in a tertiary care center and insights into demographics, risk factors, and management outcomes

BACKGROUND

Pediatric urolithiasis is a growing global health concern, with increasing incidence and potential risks for chronic kidney disease if untreated. Contributing factors include metabolic disorders, genetic predisposition, dietary influences, and regional variations. Despite advancements in diagnosis and treatment, management remains challenging, particularly in high-risk infants.

OBJECTIVE

This study investigates the clinical characteristics, metabolic risk factors, and treatment outcomes of pediatric urolithiasis in a tertiary care center in Türkiye. Special attention is given to infants, assessing their distinct metabolic and clinical features, treatment responses, and the effectiveness of conservative management. Additionally, factors influencing stone burden and recurrence are evaluated to support individualized, risk-based management.

METHODS

We retrospectively analyzed 308 children (0-18 years) diagnosed with urinary stones. Demographic data, clinical presentation, laboratory and imaging findings, treatment strategies, and outcomes were reviewed. Metabolic evaluations included urinary levels of citrate, oxalate, and calcium. Treatment approaches varied based on stone size, location, and symptoms, ranging from conservative management to medical therapy and surgical interventions.

RESULTS

The median age at diagnosis was 12.5 months (range: 0-214), with a high prevalence of infant-onset cases. A family history of urolithiasis was present in 59.9 %, and parental consanguinity in 31.2 %. At the first visit, hypocitraturia (46.5 %), hyperoxaluria (36 %), and hypercalciuria (11.3 %) were common. Infants had higher rates of bilateral and multiple stones, while older children had larger stones (>5 mm, p < 0.001). Among infants with bilateral, multiple stones, hypocitraturia and hyperoxaluria were detected in 68.7 % and 66.1 %, respectively at follow-up, emphasizing the need for serial metabolic assessments. Nearly 70 % of patients received medical therapy, primarily Shohl's solution, while 28.2 % were managed conservatively. Among those with stones ≤5 mm, one-third were observed without intervention, with no significant difference in stone-free rates. Surgical interventions included extracorporeal shock wave lithotripsy (21.8 %), percutaneous nephrolithotomy (8.8 %), ureterorenoscopy (12.3 %), and open surgery (2.3 %).

DISCUSSION

Comparable stone-free rates between treated and untreated small stones (≤5 mm) support the role of conservative management in selected cases without metabolic risk factors. However, the high rate of surgical interventions highlights the need for individualized treatment. Early-onset urolithiasis is frequently bilateral and multiple, reinforcing the importance of serial urine testing for accurate diagnosis.

CONCLUSION

Pediatric urolithiasis generally has a favorable prognosis with early diagnosis and tailored management. High-risk infants require proactive metabolic evaluation and long-term follow-up, as metabolic abnormalities may not be present at initial diagnosis. These findings support a risk-based, individualized approach to pediatric urolithiasis management.

Symptomatic recurrence rate of upper urinary tract calculi in children after endourological procedures

INTRODUCTION

The recurrence rate of paediatric urolithiasis was less reported, especially in Asians. Our aim was to verify the symptomatic recurrence rate of Chinese paediatric urolithiasis and to determine the predictive factors for stone recurrence.

MATERIALS AND METHODS

We performed a retrospective review of children who presented with first upper urinary tract calculi from June 2014 to September 2019. For the follow-up, we generated Kaplan-Meier plots with time to stone recurrence and Cox proportional hazard regression analyses were applied. The recurrence was defined as a new symptomatic stone on ultrasound and/or computerized tomography.

RESULTS

A total of 230 children with a median age of 5 yr (IQR 4-8) were included. Calcium oxalate was found in 72% of stones, and calcium apatite was found in 32% of stones. After a median follow-up of 39.5 months, 34 (14.8%) children had stone recurrence. Median time to stone recurrence was 31 months. Among them, 31 (91.2%) required surgical intervention. Older children (P < 0.01), higher BMI (HBM) (P < 0.01) and higher stone burden (P < 0.01) were shown to be associated with stone recurrence in the univariate analysis. The multivariate Cox regression analysis showed that children with stone burden > 2 cm³ had a higher risk of recurrence (HR 4.84, 95%CI 2.28-10.3). Children with HBM had an increased recurrence rate compared to normal BMI children (HR 2.99, 95%CI 1.36-6.56).

CONCLUSIONS

The symptomatic recurrence rate of paediatric urolithiasis in Chinese is not as high as that reported in Caucasians. HBM and higher stone burden are associated with higher recurrence rates.

Effect of age, BMI, and gender on urinary risk factors in pediatric idiopathic stone formers

INTRODUCTION

The incidence of pediatric urolithiasis has been increasing over the years; however, the etiology of this increase is not well understood. Age, body mass index, and gender have been examined as possible risk factors for stone disease, but with inconsistent and variable associations.

OBJECTIVE

We aim to investigate the urine chemistry factors, as assessed by 24-h urinary parameters, in pediatric stone formers at a large volume tertiary referral center in the highest areas in the United States, the Southeast, based on age, body mass index, and gender.

STUDY DESIGN

We retrospectively reviewed all pediatric stone formers who completed a 24-h study between 2005 and 2016. Patients were stratified by age (3-10 versus 11-18 years of age), overweight status (above versus below the 85th percentile for body mass index), and gender (male versus female) (Summary Figure). Statistical analysis included analysis of variance and logistic regression.

RESULTS

243 patients were included in our analysis. Patients in the first decade of life were found to have greater numbers of urinary risk factors than those in the second decade. Non-overweight patients were more likely to have hyperoxaluria and hyperuricosuria, while overweight patients were more likely to have hypocitraturia. Female patients were more likely to have higher hyperoxaluria, while male patients were more likely to have hypercalciuria.

DISCUSSION

In contrast to prior publications, obesity is not linked to increased risk of urolithiasis with non-overweight individuals having a greater number of risk factors than the overweight cohort. Despite stone disease being more prevalent in adolescents, the greatest number of risk factors were present in the first decade of life. Lastly, female children had more urinary risk factors than males. Further understanding of the underlying causes of stone disease in various pediatric populations is warranted.

CONCLUSION

While more urinary risk factors were identified in younger, non-overweight, and female patients, there remains no consensus on the urinary risk factors for pediatric urolithiasis. Further study is needed to elucidate the risk factors and pathophysiology of pediatric stone disease.

Influence of Body Mass Index on the Surgical Outcomes of Flexible Ureteroscopy for Pediatric Upper Urinary Tract Aalculi-A Single Surgeon Experience

OBJECTIVE

To examine the association between body mass index (BMI) and surgical outcomes of flexible ureteroscopy (FURS) for pediatric upper urinary tract calculi and to estimate the influence of BMI percentile on the learning curve of pediatric FURS.

MATERIALS AND METHODS

We reviewed our prospectively maintained database containing children who had kidney or ureteral stones from June 2014 to April 2019. We calculated BMI and plotted it on the Centers for Disease Control and Prevention growth chart for sex and age to estimate BMI percentile. Patient demographics, intraoperative data, stone characteristics, stone-free rate (SFR), and complication rate (CR) were analyzed. Learning curves stratified by BMI percentile groups were generated.

RESULTS

The final analysis included 161 children, of whom 63 (39.1%) had upper body weight percentile (UBW), 64 (39.8%) had normal body weight percentile (NBW), and 34 (21.1%) had lower body weight percentile (LBW). The median stone burden of the 3 groups were 1.14 (IQR 0.50-3.41), 1.13 (IQR 0.70-3.14), and 0.95 (IQR 0.50-1.77), respectively (P = .17). The SFRs were 90.5% (57/63) in the UBW group, 81.2% (52/64) in the NBW group and 70.6% (24/34) in the LBW group (P = .04). The CRs were 15.9% (10/63), 21.9% (14/64), and 29.4% (10/34), respectively (P = .29). The learning curves showed that the SFR of FURS could be improved after about 100 cases. And decreasing BMI could steepen the learning curve of SFR.

CONCLUSIONS

BMI is associated with the SFR of FURS. LBW children had the lowest SFR compared to UBW and NBW children. Lower BMI percentile makes the success of FURS more challenging.

Stone recurrence among childhood kidney stone formers: results of a nationwide study in Iceland

OBJECTIVES

To examine the stone recurrence rate among childhood kidney stone formers in the Icelandic population.

MATERIALS AND METHODS

We retrospectively examined kidney stone recurrence in a recently reported population-based sample of 190 individuals who experienced their first stone before 18 years of age in the period 1985-2013. Of these 190 individuals, 112 (59%) were females and the median (range) age at the incident stone diagnosis was 15.0 (0.2-17.9) years. Stone recurrence was defined as an acute symptomatic episode with imaging confirmation or self-reported stone passage, new stone detected by imaging in asymptomatic patients, and suspected clinical stone episode without verification. The Kaplan-Meier method was used to assess stone-free survival and the Chi-square, Fisher's exact, Wilcoxon rank-sum and the log-rank tests to compare groups.

RESULTS

A total of 68 (35%) individuals experienced a second stone event, 1.7 (0.9-18.9) years after the initial diagnosis. The recurrence rate was 26%, 35%, 41% and 46% after 5, 10, 15 and 20 years of follow-up, respectively. The 5-year recurrence rate increased with time and was 9%, 24% and 37% in the periods 1985-1994, 1995-2004 and 2005-2013, respectively (P = 0.005). No difference in stone recurrence was observed between the sexes (P = 0.23).

CONCLUSIONS

In our population-based sample of childhood kidney stone formers, the stone recurrence rate is similar to that reported for adults. The observed rise in stone recurrence with time may be related to closer patient follow-up in recent years or increased stone risk in general.

Risk factors for recurrent urolithiasis in children

PURPOSE

To identify risk factors associated with recurrent kidney stones in a paediatric cohort in a Belgian tertiary centre.

STUDY DESIGN AND METHODS

Medical records of children with the first episode of urolithiasis between 1998 and 2016, followed at Ghent University Hospital initially and at least one-year follow-up were retrospectively reviewed. Patient characteristics, past medical history, presenting symptoms, the results of laboratory investigations and the applied management strategy were analysed. The significant variables from the univariate analysis were integrated into a backward conditional multivariate model.

RESULTS

Ninety-seven children were included in the analysis, of which 33 (34%) presented with at least one episode of stone recurrence. In the univariate analysis, body mass index (BMI) > 85th percentile and asymptomatic stones at initial presentation were associated with 1.8 and 0.1 times lower risk of recurrent stones, respectively (p = 0.020, 95% confidence interval (CI):0.368-8.749 and p = 0.017, 95% CI:0.014-0.921). In contrast, immobilization resulted in a 10-times higher risk (p = 0.002, 95% CI:1.968-50.005) and the need for technical intervention was associated with a 3.2- times higher risk (p = 0.017, 95% CI:1.297-8.084) of developing recurrent stones. On multivariate analysis only BMI >85th percentile was associated with a 15 times lower risk of stone recurrence (p = 0.030, 95% CI:0.006-0.739).

DISCUSSION

A possible explanation of reduced risk in patients with a BMI > 85th percentile may lie in a different metabolic profile. Immobilization as a risk factor can be explained by calcium metabolism, which is influenced by immobilization due to fractures, paralysis or motor disability because it causes resorption of the skeleton resulting in elevated blood calcium levels. This study showed that patients who presented without symptoms when the stones first occurred were less likely to have recurring kidney stones compared with patients with symptoms at initial presentation. When technical intervention was needed, we believe this is partly due to a larger stone burden, however we could not find an evidence-based explanation. The institutional protocol, which allowed to create a database with a limited number of patients, was lost to follow-up. Despite the retrospective setting some data were missing. There might also be a bias because the patients were followed-up at a tertiary centre. Possibly, our conclusions cannot be generalized toward the entire paediatric population.

CONCLUSION

Of all the factors investigated in our cohort, BMI >85 th percentile and asymptomatic stones are associated with a lower risk of stone recurrence. Conversely, immobilized patients and those who require technical intervention at initial presentation may benefit from an intense follow-up after the first episode of urolithiasis.

Influence of BMI in nephrolithiasis in an Appalachian pediatric population: A single-center experience

INTRODUCTION

The prevalence of pediatric nephrolithiasis has increased significantly in the past 20 years. Metabolic abnormalities predisposing adults to nephrolithiasis in obese patients include increased urinary sodium and uric acid excretion as well as low urine pH; however, limited data are available in the pediatric population.

OBJECTIVE

The aim was to investigate whether obese pediatric patients presenting with nephrolithiasis have a unique metabolic profile similar to reported findings in obese adults with nephrolithiasis.

STUDY DESIGN

A retrospective chart review was performed in children aged 1-18 years seen at Kentucky Children's Hospital between 2010 and 2016. Inclusion criteria included all patients with documented stones confirmed by ultrasonography or computed tomography.

RESULTS

A total of 111 patient charts were reviewed in the study with a mean age of 11.8 ± 4.2 years. Seventy patients (63%) had a normal BMI and 41 patients (37%) were considered overweight/obese. There was no statistically significant relationship between BMI and stone recurrence. Obese patients had significantly decreased levels of urinary citrate, oxalate, magnesium, and potassium with significant elevations of urinary urea nitrogen, ammonia, and low urine pH compared with normal weight patients (Summary Figure).

DISCUSSION

Several groups have reported on metabolic findings within obese and non-obese pediatric patients. A Turkish study reported increased oxalate excretion and hypocitraturia in obese patients while a Korean study also reported increased rates of hypocitraturia in recurrent stone formers. Similar to these studies, we did find significant differences in citrate within our study population; however, we found significantly lower levels of urinary oxalate in obese patients. The majority of these studies do not report an association with BMI and urine pH although this has been reported in the adult population and our findings support an inverse relationship between body mass index (BMI) and pH. Our group found a higher level of calcium phosphate stones, supporting of Eisner's findings that high BMI is associated with increased supersaturation of calcium phosphate. Limitations of our study include being a single center and retrospective in nature.

CONCLUSION

Our study demonstrates differences in types of stones and urinary metabolites in an obese pediatric population suggestive of different metabolic profiles contributing to stone disease. We report similar association between BMI and urine pH, urinary potassium, and citrate. This study confirmed our primary hypothesis that obese pediatric patients would have a different urinary mineral profile as evidenced by lower levels of citrate and potassium and low urine pH; however, obese patients did not exhibit significantly elevated urinary sodium and uric acid when normalized to weight, as described in the adult population. Our study did not confirm our secondary hypothesis that stone composition would be associated with BMI status or stone recurrence.

Stones in pregnancy and pediatrics

Urinary stone disease is a highly prevalent condition affecting approximately 10% of the population, and has increased in incidence significantly over the past 20 years. Along with this, the rate of stone disease among women and children is also on the rise. The management of stone disease in specific populations, such as in children and during pregnancy can present unique challenges to the urologist. In both populations, a multi-disciplinary approach is strongly recommended given the complexities of the patients. Prompt and accurate diagnosis requires a high degree of suspicion and judicious use of diagnostic imaging given the higher risks of radiation exposure. In general, management proceeds from conservative to more invasive approaches and must be individualized to the patient with careful consideration of the potential adverse effects. However, innovations in endourologic equipment and techniques have allowed for the wider application of surgical stone treatment in these patients, and significant advancement in the field. This review covers the history and current advances in the diagnosis and management of stone disease in pregnant and pediatric populations. It is paramount for the urologist to understand the complexities of properly managing stones in these patients in order to maximize treatment efficacy, while minimizing complications and morbidity.

Prospective evaluation of urinary incontinence in severely obese adolescents presenting for weight loss surgery

BACKGROUND

Obesity has been associated with daytime urinary incontinence (UI), likely due to increased intra-abdominal pressure.

OBJECTIVES

To assess incontinence symptoms in severely obese adolescents before and 3 years after bariatric surgery.

SETTING

Tertiary care pediatric hospitals in the United States.

METHODS

The Teen-Longitudinal Assessment of Bariatric Surgery is a prospective, multicenter study designed to evaluate efficacy and safety of bariatric surgery in adolescents. Patients<19 years of age undergoing bariatric surgery at 5 centers between 2007 and 2012 were enrolled. Trained study staff collected baseline and postoperative anthropometric and clinical data. Presence and severity of UI were determined by standardized interview.

RESULTS

A total of 242 patients (76% female) were evaluated at baseline. The mean age was 17.1 years at baseline, and 72% were of white race. The preoperative median body mass index was 50.5 kg/m2. At baseline, 18% of females and 7% of males reported UI. Prediction analysis at baseline indicated that females, white race, and increasing body mass index had greater odds for UI. UI prevalence in females and males decreased to 7% and 0%, respectively, at 6 months after surgery (P<.01) and remained stable out to 36 months postoperatively. Furthermore, older patients were less likely to achieve 3-year UI remission or improvement.

CONCLUSIONS

In adolescents undergoing bariatric surgery, UI was more common in females than in males. Incontinence status significantly improved by 6 months and was durable to 3 years after surgery, suggesting that bariatric surgery favorably affects anatomic or physiologic mechanisms of bladder control in both males and females.

24 Hour urine metabolic differences between solitary and multiple stone formers: Results of the Collaboration on Urolithiasis in Pediatrics (CUP) working group

INTRODUCTION

Specific factors associated with the risk of developing pediatric urinary stone disease remain unclear, especially those that may be associated with recurrent stone disease.

OBJECTIVE

We compared the results of 24-h urine collections in children with a solitary stone episode to those with multiple stone episodes to determine if there is a difference that may be associated with multiple stone formation in children.

STUDY DESIGN

A multi-institutional retrospective analysis was completed to assess 24-h urinary metabolic profiles in children with urolithiasis aged 2-18 years old. Differences in mean urine collections between the two groups were assessed using chi-square tests to test the associations among gender, stone type, and multiple stone status, as well as multivariate analyses using general linear models.

RESULTS

We analyzed 142 solitary stone patients and 136 multiple stone patients from four centers were included. Multiple stone patients were older than solitary stone patients (mean 13.4 ± 3.6 years vs. 12 ± 3.9 years, p = 0.002). Females were more likely to have multiple stones (58% vs. 39%, p = 0.002). BMI was not associated with multiple stones (p = 0.8467). Multiple stone formers had lower urine volumes, although this did not reach statistical significance when compared with solitary stone formation (20.4 mL/kg/day ± 11.5 vs. 22.9 ± 13.0, p = 0.0880). Higher values for super-saturation of calcium oxalate were associated with multiple stone disease in univariate (p = 0.0485) and multivariate analysis (p = 0.0469) (Figure). Centers located in the Southeast of the United States saw a higher proportion of children with multiple stones (Tennessee 62.7%, Virginia 44.4%, Oregon 31.6%, Michigan 27.3%, p < 0.0001).

DISCUSSION

In a large multi-institutional retrospective analysis we found that multiple stone disease was associated with higher super-saturations of calcium oxalate. Many urinary parameters changed with patient age, highlighting that the values should be interpreted with respect to patient age. The inability to comment on follow-up because of the nature of our dataset is a limitation of this study.

CONCLUSION

Multiple stone disease in children is associated with higher super-saturation calcium oxalate, while lower urinary volume may also be associated with multiple stones; however, further study is required. Early metabolic evaluation may help risk stratify children likely to form multiple stones.

Influence of body mass index on pediatric urolithiasis

OBJECTIVE

In recent years, there has been increased incidence of urolithiasis in children. Changing nutritional patterns and sedentary lifestyles predispose to urolithiasis, as well as to the global rise in obesity. It has been established that the prevalence of high body mass index (BMI) is increasing in the pediatric population. The aim of the present study was to incorporate 24-h urine metabolic analysis results with BMI values to evaluate the tendency towards stone formation in children.

METHODS

Eighty-four children were recruited to the study, stratified into three BMI categories as low, normal, or upper. All patients were evaluated with 24-h urine analysis results. Patients with a secondary cause of stone formation such as hyperparathyroidism, cystinuria, primary hyperoxaluria, inflammatory bowel disease, cystic fibrosis, history of prematurity and/or use of drug, recurrent urinary tract infection, and urinary tract anomaly were excluded. Additionally, it was ensured that none of the patients were taking specific medication or diet that could alter their acid-base metabolism and calcium, oxalate, and uric acid levels.

RESULTS

Mean BMI of patients was 21.6 ± 2.9 kg/m(2). LBMI was found in 52 (61.9%), N-BMI in 20 (23.8%), and U-BMI in 12 (14.3%) of the patients. No significant differences were present between the three groups for stone sizes and numbers. The patients' characteristics and 24-h urine parameters for BMI groups are presented in the Table.

DISCUSSION

In the literature, several studies have focused on the relationship between obesity and pediatric urinary stone disease. However, only a few evaluated the urinary metabolic analysis in pediatric patients. We have encountered different results from mainly adult studies and some pediatric studies. Our study shows that U-BMI children are not under greater risk for urolithiasis than the other groups. An important portion of our study group was in the L-BMI group; nevertheless we cannot conclude that having a low BMI predisposes to urolithiasis based on the urinary metabolic evaluation as well as the stone sizes and numbers. The N-BMI group has increased risk factors for urolithiasis rather than the other groups, according to results of 24-h urine analysis.

CONCLUSION

The results of our study indicate that BMI itself could not be considered as a separate and definite risk factor for urolithiasis development in children. Although the mechanisms and causative factors for urinary stone formation are better defined in adults, further studies investigating these parameters in children are warranted.

Clinical, demographic, and laboratory characteristics of children with nephrolithiasis

While the incidence of pediatric kidney stones appears to be increasing, little is known about the demographic, clinical, laboratory, imaging, and management variables in this patient population. We sought to describe various characteristics of our stone-forming pediatric population. To that end, we retrospectively reviewed the charts of pediatric patients with nephrolithiasis confirmed by imaging. Data were collected on multiple variables from each patient and analyzed for trends. For body mass index (BMI) controls, data from the general pediatrics population similar to our nephrolithiasis population were used. Data on 155 pediatric nephrolithiasis patients were analyzed. Of the 54 calculi available for analysis, 98 % were calcium based. Low urine volume, elevated supersaturation of calcium phosphate, elevated supersaturation of calcium oxalate, and hypercalciuria were the most commonly identified abnormalities on analysis of 24-h urine collections. Our stone-forming population did not have a higher BMI than our general pediatrics population, making it unlikely that obesity is a risk factor for nephrolithiasis in children. More girls presented with their first stone during adolescence, suggesting a role for reproductive hormones contributing to stone risk, while boys tended to present more commonly at a younger age, though this did not reach statistical significance. These intriguing findings warrant further investigation.

Dyslipidaemia in overweight children and adolescents is associated with an increased risk of kidney stones

AIM

There is conflicting evidence about the role of obesity in paediatric nephrolithiasis. This Polish study explored the influence of nutritional status and lipid disturbances on urinary lithogenic factors and the risk of kidney stone formation in children and adolescents from three to 18 years of age.

METHODS

We carried out serum lipid profile evaluations and 24-h urine chemistry analyses on 493 overweight/obese paediatric participants (mean age 13 years) without nephrolithiasis and 492 healthy normal weight sex and age-matched controls.

RESULTS

A third (33%) of the study group had blood lipid disturbances, with more acidic urine, lower urinary citrate excretion and a higher fraction of ionised calcium and higher Bonn Risk Index than the controls. The participants' body mass index standard deviation score (BMI Z-score) was positively correlated with urinary oxalate and uric acid and negatively correlated with citrate excretion. Total cholesterol, low-density lipoprotein cholesterol and triglycerides correlated negatively with citraturia, while high-density lipoprotein cholesterol correlated positively.

CONCLUSION

The main factor that predisposed overweight and obese children to kidney stones was hypocitraturia. Urinary citrate excretion was related to both BMI Z-scores and all lipid fraction abnormalities. However, hypercholesterolaemia and particularly low-density lipoprotein hypercholesterolaemia seemed to play a major role.

The new epidemiology of nephrolithiasis

Historically nephrolithiasis was considered a disease of dehydration and abnormal urine composition. However, over the past several decades, much has been learned about the epidemiology of this disease and its relation to patient demographic characteristics and common systemic diseases. Here we review the latest epidemiologic studies in the field.

Prospective evaluation of urinary metabolic indices in severely obese adolescents after weight loss surgery

BACKGROUND

Observational studies in obese adults have found abnormal urinary metabolic indices that predispose to nephrolithiasis. Few studies have been performed in severely obese adolescents.

OBJECTIVES

To assess urinary stone risk factors in severely obese adolescents and in those undergoing 2 types of weight loss surgery.

SETTING

Children's hospital, United States.

METHODS

A prospective cross-sectional study was performed to assess urinary metabolic profiles in severely obese adolescents who either have not undergone any gastrointestinal surgery or who have undergone Roux-en-Y gastric bypass (RYGB) or vertical sleeve gastrectomy (SG). Twenty-four-hour urine collections were performed at home and evaluated at a central laboratory. Established normal reference ranges for adults were used in the analysis. A linear regression analysis was performed assessing the relationship of the study group with each of the outcomes.

RESULTS

A total of 55 samples were analyzed from 14 severely obese adolescents and from 17 severely obese adolescents after bariatric surgery (RYGB, 10; SG, 7). Median body mass index was similar between the RYGB and SG groups. The median 24-hour excretion of oxalate was significantly elevated in the RYGB group. Calcium and uric acid excretion and the median supersaturation of calcium oxalate, calcium phosphate, and uric acid were similar among all groups.

CONCLUSIONS

Elevated excretion of oxalate in the urine of severely obese adolescents and in those who have undergone RYGB may portend increased risk for kidney stone formation. Larger longitudinal studies are needed to verify these findings and to determine the clinical risk of developing stone disease in these patient populations.

Correlation of the body mass index and calcium nephrolithiasis in adult population

Introduction:

Prevalence of the kidney stones (renal calculi) increase in several countries in parallel with the increase of overweight, diabetes (type 2 diabetes) and hypertension.

Goal:

The goal of our research was to evaluate the connection between the calcium nephrolithiasis and overweight, as quantified using the Body Mass Index (BMI) of the adult population, with a particular reflection on the age groups within it.

Material and methods:

The research was prospective and it was implemented at the Clinical Center of Banja Luka, at the Urology Clinic in the period from 1^st April 2012 to 1^st January 2013. The trial encompassed 120 patients with calcium nephrolithiasis of the upper part of the urinary tract and 120 patients without nephrolithiasis. A group of patients with the calcium nephrolithiasis presented a working group, while a group of patients without nephrolithiasis presented a control group. The BMI obtained on the basis of bodily weight and height of the patient, where the age and sex of specific reference values of the BMI were developed by the Center for Disease Control and Prevention (CDC) were not used in the calculation of the BMI.

Results:

Analyzing the values of the BMI in relation to age groups, where there was a statistically significant difference in the working group, whereas in the control group there was a statistically high significant difference, testing of statistical significance of the average value of the BMI was done by observed age groups of working and control group, as well as to the total sample of work and control group using the Chi-Square test and T-test for independent samples. Having observed the age group of 20-40 years, statistically significant differences have been noted at the level of risk of 10%, which confirms that there is a connection between the categories of the BMI and the group, which the patient comes from (Chi-Square test p-0.05), that is, T-test has shown that the values are different at the level of 10%, i.e. p<0.1 (p=0.073). Having observed the age group 40-60, there was no dependency between the category of the BMI and the group, that is, the differences are not statistically significant, p>0.05 (t-test p=0.314). In addition to this, the average BMI values are not significantly different, p>0.05 (t-test p=0.871). Having observed the age group of the older than 60, there was no dependency between the category of the BMI and the group, that is, the differences are not statistically significant, p>0.05 (Chi-square test p=0.167). Having observed the total sample of the working and control group, there was no dependency of the category of the BMI and the group (or urolithiasis), p>0.05 (Chi-Square test p=1.208), whereas the results of the T-test showed that there was no statistically significant difference of the arithmetic mean values of the BMI working group and control group, p>0.05 (t-test p=0.620).

Conclusion:

Overweight in younger age groups of adult population may be connected to the occurrence of calcium nephrolithiasis, thus we suggest that urolithiasis should be considered with them, as part of overweight, by which a change of living habits and the manner of food consumption could prevent this disease.

Obesity might not be a disadvantage for SWL treatment in children with renal stone

AIM

Although the management of urinary stones in obese patients is a challenge and the impact of the patient-related parameter has been well studied in adults: No study has evaluated the possible impact of obesity in terms of body mass index related SWL success in pediatric population. In this present study, we aimed to evaluate the safety and efficiency of SWL in obese children in a comparative manner with the cases in normal BMI value limits.

PATIENTS AND METHODS

A total of 66 children (45 boys and 21 girls, M/F:2.1) with renal calculi were treated with SWL. Depending on the BMI values, the children were divided into two groups as; Group 1 (n:50) children with normal BMI values (mean: 16.1) and Group 2 (n:16) obese children with higher BMI values (mean: 20.3). The success rates, complications, and need for auxiliary procedures after SWL were evaluated between two groups of patients in a comparative manner. While majority of the cases were treated under general anesthesia (n:61), a limited number of cases were treated under neurolept anesthesia with PiezoLith 3000 (Richard Wolf GmbH) lithotripter. Evaluation of efficiency was based on radiological examinations using abdominal radiography, ultrasonography, or CT scan when needed.

RESULTS

Both the mean age and mean stone size values were similar in both groups. While the mean age was 62 months (24-148) in Group 1, this value was 68 months (24-137) in Group 2. Again mean stone size was 10.26 mm(5-25 mm) in Group 1 and 10.12 mm (6-20 mm) in Group 2. The mean number of SWL sessions and the number of SW's applied were similar in both groups (2.06 vs. 2.0 and 1975 vs. 1835, respectively). Evaluation of success rates after 3-months again did not show any statistically significant difference with respect to stone-free rates in both groups (47/50-94 %, 16/16-100 %, respectively). However, 3 children in Group 1 did show residual fragments (≤3 mm) which were followed closely with regular visits without any problem. In another 3 cases, again fragments migrated to involved ureter after lithotripsy and these fragments were successfully treated in situ with further SWL. With respect to auxiliary procedures, there was no specific procedure has been done in Group 2, but 3 cases did undergo further SWL for ureteral stones in Group 1. Stone location did not affect the final outcome of the procedure in a significant manner in both groups. Lastly, no serious complication could be demonstrated in both groups either during or after SWL procedures.

CONCLUSIONS

In the light of the successful treatment outcomes with limited need for auxiliary procedures in both groups, we may say that obesity might not be a disadvantage for SWL in children with renal stones.

Is urolithiasis in children associated with obesity or malnutrition?

BACKGROUND

Although it is known that obesity predisposes to urolithiasis, a tendency for malnutrition in children with urolithiasis owing to recurrent urinary infections and abdominal pain also makes sense.

AIMS

In this study, we aimed to determine the nutritional status of infants and children with urolithiasis, and to observe whether obesity or malnutrition is more prevalent in that population.

METHODS

One hundred eighty-seven children aged 4 months to 17 years (mean, 4.9 ± 4.4 years) with urolithiasis, and 278 age- and sex-matched children without any chronic diseases were included. Anthropometric evaluations, including weight and height standard deviation score (SDS), body mass index, and triceps and subscapular skinfold thickness (SFT), were performed.

RESULTS

Mean weight SDSs of the patients was statistically lower than that of the control subjects (P < .0001). Malnutrition rate was statistically higher in the patients with urolithiasis when evaluated according to weight SDS and percentiles of body mass index and SFT. When the age factor was taken into account, the percentage of malnutrition, determined by the percentiles of triceps and subscapular SFT measurements, was found to be higher in children younger than 2 years. Short stature was more prevalent in older children.

CONCLUSION

Malnutrition among children with urolithiasis is not as rare as thought previously. A careful anthropometric evaluation should be included in the clinical assessment of those children.

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.

Body fat composition and occurrence of kidney stones in hypercalciuric children

In the last 10 years, the incidence of kidney stones has increased in the pediatric population, and this rise has been paralleled by a significant increase in pediatric obesity rates in the USA. The purpose of this study was to evaluate percentage body fat (%BF) measured by dual energy X-ray absorptiometry (DXA) in hypercalciuric children with and without kidney stones. A retrospective chart review was performed on children with idiopathic hypercalciuria based on a 24-h urine calcium excretion of >4 mg/kg/day or >200 mg/day who had undergone DXA scanning. Patients were then classified by sex and by %BF (3 categories; normal: <27% girls, <21% boys; at risk for obesity: 27-36% girls, 21-30% boys; obese: >36% girls, >30% boys). The 2003-2004 NHANES data were used as a control. Fifty patients (24 males) were analyzed, of whom 26% were assessed as having a normal %BF, 44% as being at risk for obesity, and 30% as being obese. Children with an increased %BF had a significantly higher occurrence of kidney stones (p = 0.03) than those with a normal %BF. No significant differences were noted in 24-h urine chemistries between the groups. In conclusion, an increased %BF was associated with an increased occurrence of kidney stones in children with idiopathic hypercalciuria.

Association between body mass index and urolithiasis in children

PURPOSE

The prevalence of obesity and urolithiasis in children has increased with time. We evaluated the relationship between body mass and urolithiasis in children.

MATERIALS AND METHODS

We performed a matched case-control study in a network of 30 primary care pediatric practices. Cases included subjects with ICD-9 codes for urolithiasis and controls were matched on age, duration of observation before the index date and clinical practice. Age and sex specific body mass index z scores at the time of the stone episode were calculated. Continuous body mass index z scores and clinical weight categories were evaluated with covariates, including race, ethnicity, gender and payer status. The OR and 95% CI were calculated using multivariate conditional logistic regression.

RESULTS

We identified 110 cases and 396 matched controls, of whom 1.9% and 4.3% were overweight, and 3.7% and 4.5% were obese, respectively. On multivariate conditional logistic regression analysis the continuous body mass index z score (OR 0.84, 95% CI 0.63-1.12, p = 0.18), overweight status (OR 0.13, 95% CI 0.01-1.18) and obese status (OR 0.18, 95% CI 0.02-1.40) were not associated with urolithiasis. However, black race (OR 0.35, 95% CI 0.15-0.85) and Medicaid payer status (OR 0.47, 95% CI 0.24-0.93) were associated with a significant decrease in the odds of urolithiasis.

CONCLUSIONS

High body mass was not associated with urolithiasis in our primary care pediatric practice network. However, black race and Medicaid payer status were associated with decreased odds of urolithiasis.

An update on the changing epidemiology and metabolic risk factors in pediatric kidney stone disease

Nephrolithiasis in children is a painful and costly disease that may also have detrimental long-term effects on kidney function. Recent data provide evidence that the incidence of nephrolithiasis in children is rising. Children who are white, female, and adolescent seem to have the highest risk for forming symptomatic kidney stones. Although the reasons for the rising incidence and demographic discrepancies in pediatric nephrolithiasis are not yet clear, recent investigations into urine chemistry provide clues regarding predisposing metabolic risk factors. As more data emerge regarding epidemiologic and metabolic characteristics of pediatric kidney stone formers, we hope to gain a better understanding of the causes of kidney stone disease and, ultimately, provide better strategies for stone prevention in children.

Use of Google Insights for Search to track seasonal and geographic kidney stone incidence in the United States

OBJECTIVE

To determine whether Internet search volume for kidney stones has seasonal and geographic distributions similar to known kidney stone incidence.

MATERIAL AND METHODS

Google Insights for Search analyzes a portion of Google web searches from all Google domains to compute how many searches are performed for a given term relative to the total number of searches done over a specific time interval and geographic region. Selected terms related to kidney stones were examined to determine which most closely tracked kidney stone incidence. Google Insights for Search data were correlated with hospital admissions for the emergent treatment of nephrolithiasis found through the Nationwide Inpatient Sample. Ambient temperature in Seattle and New York were compared with search volume for these regions to display qualitative relationships.

RESULTS

The term "kidney stones" had the highest seasonal correlation of terms examined (r = .81, P = .0014). Google Insights for Search output and national Inpatient Sample admissions also correlated when regions were compared (r = .90, P = .005). Qualitative relationships between ambient temperatures and kidney stone search volume do exist.

CONCLUSIONS

Internet search volume activity for kidney stones correlates with temporal and regional kidney stone insurance claims data. In the future, with improved modeling of search detection algorithms and increased Internet usage, search volume has the potential to serve as a surrogate for kidney stone incidence.

The increasing pediatric stone disease problem

While once thought to be relatively rare in developed nations, the prevalence of pediatric urolithiasis appears to be increasing, and a number of factors may be contributing to this increase. Many theories are plausible and such theories include the increasing childhood obesity epidemic, a changing sex predilection, climate change, alterations in dietary habits and improving diagnostic modalities. Yet, unlike adult patients, rigorous epidemiologic studies do not exist in pediatric populations. Thus, in the setting of an increasing prevalence of childhood stone disease, improved research is critical to the development of uniform strategies for pediatric urolithiasis management.

Difference in urinary stone components between obese and non-obese patients

The prevalence and incidence of urinary stone disease have been reported to be associated with body weight and body mass index (BMI). The aim of the study was to determine the difference in stone components among different BMI groups in patients with urolithiasis. Between Dec 2005 and Jan 2008, 907 urinary calculi were collected and analyzed by infrared spectroscopy. Most of the stones had been passed spontaneously, and some were collected during surgical manipulations. The data on patients' gender, age, BMI at diagnosis, and stone composition were collected. The patients were classified as normal weight (18.5≤ BMI <24), overweight (24≤ BMI <27), or obese (BMI ≥27). Of the 907 patients with urinary stone disease, 27.7% had normal weight, 33.5% were overweight, and 38.8% were obese. The prevalence of calcium oxalate stones in the normal weight, overweight, and obese groups were 23.1, 30.6, and 34.9%, respectively (P = 0.002), and the prevalence of uric acid stones in the different groups was 2.8, 7.2, and 7.7%, respectively (P = 0.002). The prevalence of calcium oxalate and uric acid stones, but not that of calcium phosphate stones, increased with body size. There was a significant correlation between BMI and uric acid stones in the overweight and obesity groups, with odds ratios of 3.28 and 4.35, respectively. The prevalence and incidence of urinary stone disease were found to be associated with BMI. The percentage of uric acid and calcium oxalate stones was higher in obese than in non-obese patients. There was no apparent difference in the prevalence of calcium phosphate stones between obese and non-obese patients.

Pediatric urolithiasis--does body mass index influence stone presentation and treatment?

PURPOSE

Pediatric obesity is a major public health concern in the United States. We investigated the association of body mass index with presentation and outcome in children with urolithiasis.

MATERIALS AND METHODS

We identified all patients 2 to 18 years old at our institution with a radiographically confirmed first renal or ureteral stone between January 2003 and June 2008. Data abstracted included demographics, stone characteristics, treatment and metabolic evaluation. Patients were stratified into 3 body mass index categories, including lower (10th percentile or less for age), normal (10th to 85th percentile) and upper (85th percentile or greater) percentile body weight.

RESULTS

Of the children 62 boys (55.4%) and 50 girls (44.6%) were evaluable. Mean age at diagnosis was 11.8 years. Body mass index stratification showed lower percentile body weight in 11 patients (9.8%), normal percentile body weight in 55 (49.1%) and upper percentile body weight in 46 (41.1%). Mean stone diameter was 5.0 mm. Of the stones 31 (27.7%) were in the kidney or ureteropelvic junction and 81 (72.3%) were in the ureter. Surgery was done in 87 patients (78.9%) and stone clearance was accomplished by 1 (69.0%) or 2 (31.0%) procedures in all. Lower percentile body weight patients presented earlier than normal and upper percentile body weight patients (9.0 vs 12.2 and 12.0 years, respectively, p = 0.04). Neither stone size nor the number of procedures required for stone clearance differed significantly by body mass index.

CONCLUSIONS

Upper percentile body weight was not associated with earlier stone development, larger stones or the need for multiple surgical procedures. In lower percentile body weight patients symptomatic renal stones developed significantly earlier than in normal or upper percentile body weight patients. Stone size and the surgical intervention rate were similar regardless of body mass index. Further research may identify potential factors predisposing children with lower percentile body weight to early stone development.

Increasing incidence of kidney stones in children evaluated in the emergency department

OBJECTIVE

To test the hypothesis that there is an increase in the incidence of childhood nephrolithiasis in the state of South Carolina.

STUDY DESIGN

We analyzed demographic data from a statewide database on incidence of kidney stones from emergency department data and financial charges. Data were compared with population data from the US Census to control for population growth.

RESULTS

There was a significant increase in the incidence of kidney stones in children between 1996 and 2007. The greatest rate of increase was seen in adolescents, pre-adolescents, and Caucasian children. Infants, toddlers, and African-American children did not show significantly increased incidence in the period. Girls show a growing predominance in our population. The amount of money charged for care of children with kidney stones has gone up >4-fold in our state.

CONCLUSION

The incidence of kidney stone disease has risen dramatically in the state of South Carolina since 1996. Further studies investigating potential contributing factors are needed to prevent this costly and painful condition.