Role of Overweight Status on Stone-forming Risk Factors in Children: A Prospective Study

Harnessing the Power of Donkey's Milk and Homemade Pickles: Unveiling Oxalate-Degrading Probiotics and Their Heat-Killed Cells as Antiadipogenic Agents in 3T3-L1 Adipocytes

Gut microbial dysbiosis is associated with the development of critical clinical conditions of metabolic syndrome (obesity, type II diabetes), and calcium oxalate kidney stones. The human gut microbial eubiosis with functional probiotics and their heat-killed cells of lactic acid bacteria (LAB) is considered the current therapy for metabolic syndrome (MS). In accordance with this, our study aimed to isolate oxalate-degrading, cholesterol-lowering, and anti-adipogenic bacterial strains from raw donkey's milk and homemade fermented pickles. Nine LAB strains with potential in vitro oxalate degrading, α-glucosidase inhibiting, and cholesterol-lowering activities were pre-screened from fourteen isolates. Further, the heat-killed cells of selected strains were evaluated for anti-adipogenic activity in murine 3T3-L1 adipocytes. This activity was examined by studying the lipid storage, gene, and protein expression of adipogenic and lipogenic transcription factors. Subsequently, four potential isolates demonstrated a significant reduction in lipid storage by limiting adipogenesis (reducing C/EBPα, PPARγ expression), lipid transportation (downregulating aP2 expression), and lipogenesis (reducing PLIN-1 expression). These effective isolates were characterized using 16S rRNA molecular sequencing, and were identified as closest relatives to the Enterococcus (RRLA5, RRLA1, and RRLD6) and Lactobacillus (RRLM2) genera. Further, they displayed good survivability under in vitro gastric conditions and non-haemolytic activity. Taken together, the live cells of effective isolates depicted significant in vitro oxalate degradation, and their heat-killed cells demonstrated anti-adipogenic activity through downregulating the adipogenesis and lipogenesis. Moreover, future preclinical animal model studies on the synergistic role of probiotics and their heat-killed cells in disease prevention through gut microbial modulation could provide evidence as a biotherapeutic agent.

Current Status and Prospects of Pediatric Stone Disease: A Bibliometric and Visualization Study

Pediatric stone disease, once considered rare, has emerged as a significant research area in the past two decades due to a sharp increase in its incidence. Understanding the evolving epidemiology and treatment strategies for pediatric stone disease is crucial for enhancing child health protection. This study aims to summarize the advancements in pediatric stone disease research over the last two decades through bibliometric analysis. We conducted a comprehensive search in the Web of Science Core Collection (WoSCC) for literature on pediatric stone disease from January 1, 2000 to February 20, 2024. Econometric analyses were performed using tools such as VOSviewer, CiteSpace, and the R package "bibliometrix." Our search yielded 1,208 publications, predominantly from the United States and Turkey, showing an annual increase in publications on pediatric stone disease. Leading research institutions include Dicle University, Children's Hospital of Philadelphia, and the University of Pennsylvania, with the Journal of Pediatric Urology publishing the highest number of articles. The most prolific authors were C.P. Nelson and B. Hoppe, with Caleb P. Nelson being the most co-cited author. Research themes primarily focused on risk factors and therapeutic approaches for pediatric stone disease. Emerging research hotspots are identified by keywords such as mechanism, mini-percutaneous nephrolithotomy, recurrence, and retrograde intrarenal surgery. The study forecasts a continued upward trend in global research on pediatric stone disease, with future studies likely to delve deeper into risk factors and novel therapeutic methods.

No stone unturned: The epidemiology and outcomes of paediatric urolithiasis in Manchester, United Kingdom

BACKGROUND

The epidemiology and risk factors for paediatric urolithiasis (UL) in developed countries are evolving, with increasing rates of metabolic stone-formers. In the United Kingdom (UK), only a single London cohort has been studied in the past three decades. Regional disease patterns across the UK remain unknown. UL has been associated with an increased risk of chronic kidney disease in adults, but long-term paediatric outcomes remain poorly understood.

METHODS

We assessed the epidemiology of paediatric UL by defining the demographics, incidence, aetiology, recurrence rates and outcomes at tertiary nephro-urology centres in Greater Manchester. Health records of 177 consecutive paediatric urology referrals (0-18 years) for UL between 2002 and 2015 were retrospectively included for observational analysis. Metabolic screening was performed in 105 children.

RESULTS

The incidence of paediatric urology referrals for UL was 1.77/100,000 person-years, increasing annually by 13.6%. Mean patient age was 8.2 years and the male:female ratio was 1.3:1. The upper urinary tract was involved in more than 90% of cases and 45% of children presented with multiple calculi. Metabolic abnormalities were identified in 52% of children screened: hypercalciuria (64%), hyperoxaluria (18%) and cystinuria (11%) were the most common. Significant family history was predictive of metabolic abnormalities (OR 4.9:1, 95% CI 1.4-17.0). 30% of children had infective stones, which were more common in children less than 6 years. Ultrasound was found to be 90% sensitive for UL detection. Dimercaptosuccinic acid (DMSA) imaging identified renal scarring in 33 of the 55 children tested (60%). Recurrence was observed in 18% of children over mean 6.4 year follow-up and was more common in metabolic stone-formers. Spontaneous passage was observed in 83% of stones ≤ 5 mm, 69% between 5 and 10 mm and only one calculi > 10 mm.

CONCLUSIONS

The incidence of paediatric urology referrals for UL is rising in North West England. Metabolic abnormalities were detected in half of the children tested, justifying comprehensive screening. Recurrence is common following paediatric UL, reinforcing the need for stone prevention strategies. The majority of calculi less than 10 mm were found to pass spontaneously with supportive measures, which favours an initial observation period over surgical intervention for small calculi. UL was associated with renal scarring in the analysed population and therefore, children with UL require long-term assessment of blood pressure and proteinuria.

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.

Obesity and stones

PURPOSE OF REVIEW

The incidence of urolithiasis has shown a prominent increase in the last two to three decades and evidence-based data have clearly indicated the certain role of obesity and overweight in both children and adults. As a certain component of metabolic syndrome, 'obesity' has been found to have a significant impact on the urinary metabolic risk factors which may be important in stone formation. In this present review article, we aimed to evaluate the possible association between obesity and urolithiasis and related risk factors. The epidemiology, pathophysiology, and management of stone disease in obese cases will be discussed in detail.

RECENT FINDINGS

The possible influence of overweight/obesity on the metabolic stone-forming risk factors has been subjected to several studies which in turn well demonstrated the increased risk of stone formation in this population. Although the exact underlying mechanisms are still to be outlined, some certain pathogenetic factors, namely, changes in urinary pH and increased excretion of some urinary stone components have been well demonstrated. Given this increased risk status, these cases require a more comprehensive workup for urolithiasis. Appropriate metabolic evaluation-based medical therapy alongside dietary recommendations will be effective in preventing stone formation.

SUMMARY

Patients suffering from obesity problem have particular risk factors for urolithiasis when compared with their normal-weight counterparts. All efforts should be taken to increase the awareness of this problem and necessary precautions with well-planned treatment plan are the main tasks for urologists.

Enhanced gastrointestinal passive paracellular permeability contributes to the obesity-associated hyperoxaluria

Most kidney stones (KS) are composed of calcium oxalate and small increases in urine oxalate enhance the stone risk. Obesity is a risk factor for KS, and urinary oxalate excretion increases with increased body size. We previously established the obese ob/ob ( ob) mice as a model (3.3-fold higher urine oxalate) to define the pathogenesis of obesity-associated hyperoxaluria (OAH). The purpose of this study was to test the hypothesis that the obesity-associated enhanced small intestinal paracellular permeability contributes to OAH by increasing passive paracellular intestinal oxalate absorption. ob Mice have significantly higher jejunal (1.6-fold) and ileal (1.4-fold) paracellular oxalate absorption ex vivo and significantly higher (5-fold) urine [¹³C]oxalate following oral gavage with [¹³C]oxalate, indicating increased intestinal oxalate absorption in vivo. The observation of higher oxalate absorption in vivo compared with ex vivo suggests the possibility of increased paracellular permeability along the entire gut. Indeed, ob mice have significantly higher fractions of the administered sucrose (1.7-fold), lactulose (4.4-fold), and sucralose (3.1-fold) excreted in the urine, reflecting increased gastric, small intestinal, and colonic paracellular permeability, respectively. The ob mice have significantly reduced gastrointestinal occludin, zonula occludens-1, and claudins-1 and -3 mRNA and total protein expression. Proinflammatory cytokines and oxidative stress, which are elevated in obesity, significantly enhanced paracellular intestinal oxalate absorption in vitro and ex vivo. We conclude that obese mice have significantly higher intestinal oxalate absorption and enhanced gastrointestinal paracellular permeability in vivo, which would likely contribute to the pathogenesis of OAH, since there is a transepithelial oxalate concentration gradient to drive paracellular intestinal oxalate absorption. NEW & NOTEWORTHY This study shows that the obese ob/ob mice have significantly increased gastrointestinal paracellular oxalate absorption and remarkably enhanced paracellular permeability along the entire gut in vivo, which are likely mediated by the obesity-associated increased systemic and intestinal inflammation and oxidative stress. A transepithelial oxalate concentration gradient driving gastrointestinal paracellular oxalate absorption exists, and therefore, our novel findings likely contribute to the hyperoxaluria observed in the ob/ob mice and hence to the pathogenesis of obesity-associated hyperoxaluria.

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.

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.

Reduced active transcellular intestinal oxalate secretion contributes to the pathogenesis of obesity-associated hyperoxaluria

Most kidney stones are composed of calcium oxalate, and minor changes in urine oxalate affect the stone risk. Obesity is a risk factor for kidney stones and a positive correlation of unknown etiology between increased body size, and elevated urinary oxalate excretion has been reported. Here, we used obese ob/ob (ob) mice to elucidate the pathogenesis of obesity-associated hyperoxaluria. These ob mice have significant hyperoxaluria (3.3-fold) compared with control mice, which is not due to overeating as shown by pair-feeding studies. Dietary oxalate removal greatly ameliorated this hyperoxaluria, confirming that it is largely enteric in origin. Transporter SLC26A6 (A6) plays an essential role in active transcellular intestinal oxalate secretion, and ob mice have significantly reduced jejunal A6 mRNA (- 80%) and total protein (- 62%) expression. While net oxalate secretion was observed in control jejunal tissues mounted in Ussing chambers, net absorption was seen in ob tissues, due to significantly reduced secretion. We hypothesized that the obesity-associated increase in intestinal and systemic inflammation, as reflected by elevated proinflammatory cytokines, suppresses A6-mediated intestinal oxalate secretion and contributes to obesity-associated hyperoxaluria. Indeed, proinflammatory cytokines (elevated in ob mice) significantly decreased intestinal oxalate transport in vitro by reducing A6 mRNA and total protein expression. Proinflammatory cytokines also significantly reduced active mouse jejunal oxalate secretion, converting oxalate transport from net secretion in vehicle-treated tissues to net absorption in proinflammatory cytokines-treated tissues. Thus, reduced active intestinal oxalate secretion, likely secondary to local and systemic inflammation, contributes to the pathogenesis of obesity-associated hyperoxaluria. Hence, proinflammatory cytokines represent potential therapeutic targets.

Influence of weight status on 24-hour urine composition in adults without urolithiasis: A nationwide study based on a Chinese Han population

Objectives

This study sought to explore the influence of different body weight statuses on 24-hour urine compositions in adults without urolithiasis based on a nationwide study of a Chinese Han population.

Material and methods

Twenty-four-hour urine samples from 584 Chinese Han adults without urolithiasis in six cities were analyzed. The participants were divided into four body weight status types according to their body mass indices (BMIs) according to WHO guidelines. The baseline characteristics and 24-hour urine compositions of the standard weight group were compared with those of the underweight, overweight and obese groups. The influences of different body weight statuses on the 24-hour urine compositions were explored using univariate and multivariate logistic regressions.

Results

The numbers of participants in the underweight, standard weight, overweight and obese status groups were 24, 376, 149 and 35, respectively. The overweight and obese groups suffered significantly higher risks of hypertension and diabetes mellitus than the standard weight group. In the univariate analyses, compared with the standard weight group, the overweight group had significantly higher levels of urine citrate (mean difference [MD] = 0.51 mmol, 95% confidence interval [CI]: 0.15–0.87, P = 0.001), potassium (MD = 6.63 mmol, 95% CI: 1.13–12.14, P = 0.01) and magnesium (MD = 0.38 mmol, 95% CI: 0.08–0.69, P = 0.014). Significant increases in urine citrate (MD = 0.85 mmol, 95% CI: 0.01–1.68, P = 0.046), magnesium (MD = 0.69 mmol, 95% CI: 0.13–1.25, P = 0.016) and phosphate (MD = 2.28 mmol, 95% CI: 0.03–4.54, P = 0.047) were found in the obese group. No significant differences were detected between the standard weight and underweight groups. In the multivariate logistic regression analyses, we only observed significantly higher levels of urine potassium (odds ratio [OR] = 1.02, 95% CI: 1.00–1.04, P = 0.03) in the overweight group and phosphate (OR = 1.32, 95% CI: 1.05–1.66, P = 0.018) in the obese group when compared with the standard weight group.

Conclusions

Nonstone-forming adults with overweight or obese statuses were at higher risks of hypertension and diabetes mellitus. Obese nonstone-formers might have a greater risk of urinary stone formation due to increased urinary phosphate excretion. Additionally, underweight status had no influence on 24-hour urine composition.

Risk factors evaluation for urolithiasis among children

BACKGROUND

The prevalence of pediatric urolithiasis varies from 0.01-0.03%. Urolithiasis may be caused by anatomical, metabolic and environmental factors. Recurrence varies between 16 to 67%, and it is frequently associated with metabolic abnormalities. The objective of the present work was the identification of risk factors that promote urolithiasis in a child population.

METHODS

This study included 162 children with urolithiasis and normal renal function (mean age 7.5 years). Risk factors were investigated in two stages. In the first stage, 24-hour urine, and blood samples were analyzed to assess metabolic parameters and urinary tract infection. During the second stage, the effect of calcium restriction and a calcium load on renal Ca excretion were evaluated. Data were statistically analyzed.

RESULTS

Urolithiasis was observed in 0.02% of children, 50% of them with family history of urinary stones. There were multiple risk factors for urolithiasis including hypocitraturia (70%), hypomagnesuria (42%), hypercalciuria (37%; in 11/102 was by intestinal hyperabsorption, in 13/102 was unclassified. Ca resorption or renal Ca leak were not detected). We also detected alkaline urine (21%), systemic metabolic acidosis (20%), urinary infections (16%), nephrocalcinosis with urolithiasis (11%), oliguria (8%), urinary tract anomalies, hyperuricosemia and hypermagnesemia (7% each one), hypercalcemia (6%), hyperoxaluria (2%) and hypercystinuria (0.61%).

CONCLUSIONS

Hypocitraturia and hypomagnesuria were the most frequent risk factors associated with urolithiasis, followed by hypercalciuria. High PTH values were excluded. Children presented two or more risk factors for urolithiasis.

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.

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.

Hypertriglyceridemia and low high-density lipoprotein cholesterolemia are associated with increased hazard for urolithiasis

PURPOSE

To assess the association between dyslipidemia and urolithiasis, a propensity score-matching study was performed.

PATIENTS AND METHODS

Fasting blood samples were taken, and serum lipid profiles were measured in 655 stone formers (SF) and 1965 propensity score-matched controls between 2005 and 2011. The controls, from a health-screening program, did not have a history of dyslipidemia or statin use and have any evidence of stone disease, as determined by abdominal radiography, ultrasonography examination. Propensity score-matching with respect to age, sex, and body mass index was used to minimize selection bias, and the logistic regression analysis was adjusted for other components of metabolic syndrome.

RESULTS

Compared with controls, the SF group had significantly higher mean triglyceride and lower total cholesterol, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol levels (each P<0.001). The SF group was also more likely to have hypertriglyceridemia and low HDL-cholesterolemia, and less likely to have hypercholesterolemia and high LDL cholesterolemia compared with controls (each P<0.05). When adjusted for other components of metabolic syndrome including obesity, presence of diabetes mellitus or hypertension, the odds ratio (OR) for urinary stones appeared with hypercholesterolemia (OR=0.747, P=0.003), hypertriglyceridemia (OR=1.901, P<0.001), low HDL cholesterolemia (OR=1.886, P<0.001) and high LDL cholesterolemia (OR=0.610, P<0.001).

CONCLUSIONS

Our study implies that dyslipidemia may play a crucial part in urinary stone risk.

Epidemiological gender-specific aspects in urolithiasis

PURPOSE

The incidence of urolithiasis is worldwide increasing and contributes to a rising economic and health care burden. The objective of this review is to identify gender differences in urolithiasis epidemiology in Europe and the USA as well as gender-specific risk factors for urolithiasis.

EVIDENCE ACQUISITION

A systematic review of the present literature was performed including English journals without a time limit. The MeSH terms used were as follows: ("Sex Characteristics"[Mesh]) AND "Urolithiasis"[Mesh] or ("Epidemiology"[Mesh]) AND "Urolithiasis"[Mesh]. Additionally, reference search of retrieved papers identified additional references. The MEDLINE database was searched.

EVIDENCE SYNTHESIS

The prevalence of urolithiasis is rising worldwide including both genders in different age groups. Especially women face an increase in prevalence in the USA. Overweight seems to be an important cause for this development. Additionally insulin resistance and hypertonia, conditions present in the metabolic syndrome complex, contribute to this phenomenon.

CONCLUSION

Stone prevalence across all age groups and both genders is increasing. Lifestyle changes along with increasing prevalence of obesity are key factors for this development. Female gender did significantly differ in the risk ratio of stone development in different variables including body mass index, hyperinsulinemia, and hypertension. It is important to inform the public on measures how to change lifestyle and dietary measures for preventing or lowering events of stone disease.

Preoperative evaluation of pediatric kidney stone prior to percutaneous nephrolithotomy: is computed tomography really necessary?

The objective of the study was to investigate the precise role of computed tomography (CT) in preoperative radiologic evaluation and surgical planning of kidney stone in children prior to percutaneous nephrolithotomy (PNL). A total of 113 pediatric patients (aged ≤18 years) undergoing PNL for renal stone(s) in three referral hospitals between March 2010 and August 2012 were retrospectively evaluated. Depending on the preoperative radiologic evaluation, patients were divided into two groups. Those evaluated with CT were classified as group-1 (n = 50) and the remaining cases undergoing intravenous urography (IVU) examination were classified as group-2 (n = 63). Patient- and procedure-related variables and perioperative measures were compared between the groups. The mean age, stone size and localization were similar in both groups (p = 0.07, p = 0.57, p = 0.6, respectively). Although the postoperative hemoglobin drop was found to be significantly higher in group-2 (1.5 ± 1.3 vs. 0.9 ± 0.6 g/dL, p = 0.005), the mean operation time, fluoroscopic screening time, access number, overall success and complication rates were comparable (p = 0.06, p = 0.94, p = 0.75, p = 041, and p = 0.41, respectively). However, the mean hospitalization time was significantly prolonged in group-2 than in group-1 (p = 0.03). Our findings clearly demonstrate that, despite the key role of preoperative CT in particular patients with anatomically abnormal kidneys, IVU is a valuable alternative imaging modality with comparable radiation doses in children.

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.

Influence of overweight on 24-hour urine chemistry studies and recurrent urolithiasis in children

Purpose

We investigated the influence of overweight on 24-hour urine chemistry studies and recurrent urolithiasis (UL) in children.

Materials and Methods

A retrospective cohort study was designed to assess children who presented with UL at a pediatric institution between 1985 and 2010. We calculated body mass index percentile (BMIp) adjusted for gender and age according to the 2007 Korean Children and Adolescents Growth Chart and stratified the children into 3 BMI categories: lower body weight (LBW, BMIp≤10), normal BW (NBW, 10<BMIp<85), and upper BW (UBW, BMIp≥85). Twenty-four hour urine chemistry studies (urine volume, creatinine, calcium, oxalate, citrate, and pH) were compared between the 3 BMIp groups. Univariate and multivariate analyses were performed to assess independent risk factors for stone recurrence.

Results

A total of 125 patients were included. The age of the patients in the NBW group was older than that of patients in the LBW group, but 24-hour urine chemistry studies did not differ significantly between the three groups. Mean urine citrate levels were lower (0.273±0.218 mg/mg/d vs. 0.429±0.299 mg/mg/d, p<0.05) and the incidence of hypocitraturia was higher (81.5% vs. 45.7%, p<0.05)) in the recurrent stone former group. In the univariate analysis, hypocitraturia and acidic urinary pH were risk factors, but in the multivariate analysis, only hypocitraturia was a risk factor for stone recurrence (hazard ratio, 3.647; 95% confidence interval, 1.047 to 12.703). In the Kaplan-Meier curve, the hypocitraturia group showed higher recurrence than did the normocitraturia group (p<0.05).

Conclusions

Unlike in adults, in children, overweight adjusted for gender and age was not associated with 24-hour urine chemistry studies and was not a risk factor for recurrent UL. Hypocitraturia was the only risk factor for UL in children.

Overweight and obesity: risk factors in calcium oxalate stone disease?

Introduction. Several studies showed an association of overweight and obesity with calcium oxalate stone disease (CaOx). However, there are no sufficient data on the influence of body weight on the course of the disease and the recurrence rate. Patients and Methods. N = 100 consecutive stone formers with pure CaOx were studied. Different parameters were investigated. According to the BMI, patients were divided into three groups: (1) BMI ≤ 25; (2) BMI 25.1-30; (3) BMI > 30. Results. N = 32 patients showed a BMI ≤ 25, n = 42 patients showed a BMI of 25.1-30 and n = 26 patients showed a BMI ≥ 30. The groups differed significantly concerning BMI (by definition), urine pH, and urine citrate. The recurrence rate was not significantly different. Discussion. Our study demonstrated that body weight negatively influences single risk factors in CaOx, but obesity is not a predictor for the risk of recurrence in CaOx.

Metabolic syndrome in obese adolescents is associated with risk for nephrolithiasis

OBJECTIVES

To examine the relationship between urinary pH and metabolic syndrome risk factors along with insulin resistance in obese adolescents, and to evaluate the relationship between other urinary stone-forming and -inhibiting markers and metabolic syndrome.

STUDY DESIGN

A total of 46 obese adolescents were enrolled. Twenty-four hour and randomly obtained urine samples were analyzed for urinary pH, promoters of stone formation (ie, uric acid, oxalate, and relative saturation ratio of calcium oxalate [RSR-CaOx]), and inhibitors of stone formation (ie, citrate and osteopontin). Other data collected included height, weight, blood pressure, and fasting lipid, insulin, and glucose levels.

RESULTS

The subjects had a mean age of 14.6±2.0 years and a mean body mass index of 36±6.3 kg/m(2). Random urine pH and the number of risk factors for metabolic syndrome were negatively correlated (r=-0.34; P=.02). RSR-CaOx was correlated with both homeostasis model assessment of insulin resistance score (r=0.38; P<.01) and number of risk factors for metabolic syndrome (r=0.47; P=.001)

CONCLUSION

Decreased urinary pH and increased RSR-CaOx are associated with risk factors for metabolic syndrome in obese adolescents.

Pediatric urolithiasis: causative factors, diagnosis and medical management

Childhood urolithiasis is associated with considerable morbidity and recurrence. Many risk factors--including those metabolic, genetic, anatomic, dietary and environmental in nature--have been identified in children with urinary tract calculi. As pediatric urolithiasis with a metabolic etiology is the most common disease, evaluating the metabolic risk factors in patients is necessary to both effectively treat current stones and prevent recurrence. We discuss causative risk factors of pediatric urolithiasis, as well as the diagnostic and therapeutic approaches.

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.

Management of stones in childhood

PURPOSE OF REVIEW

The purpose of this review was to report on the latest world literature relating to paediatric stone disease. Inevitably, because of the small numbers, the literature is limited and consists mainly of case series from individual centres. There is also a wide variation in criteria and techniques, making direct comparison limited.

RECENT FINDINGS

Changes in the incidence of stone disease are becoming more apparent particularly in female patients. Metabolic abnormalities can be identified in the majority of children with stones, and even in the absence of obvious physical stone, if detected warrant further follow-up. Data supporting the safety and efficacy of treatments for stones in children is improving constantly, but choosing the best option may be difficult on current evidence. Better long-term follow-up is still needed regarding adverse effects of treatment.

CONCLUSION

A high index of suspicion is required for the diagnosis of stone disease in children, especially in the very young. After exclusion of anatomical abnormalities, metabolic evaluation is important in management and prevention of recurrence. Modalities for treatment are expanding all the time, but due to overall small numbers, and variations in the availability of technology, consensus views about treatment are difficult to agree.