Obesity and urolithiasis: evidence of regional influences

Are very thin patients at a higher risk of complications when submitted to percutane-ous nephrolithotomy?

PURPOSE

To assess the impact of thinness on the outcome of the percutaneous nephrolithotomy (PCNL).

MATERIALS AND METHODS

A matched case-control study was performed using a prospectively collected database of all patients who underwent PCNL between June 2011 and October 2021. The patients were stratified into two groups according to their phenotypic characteristics, arbitrarily defined according to their body mass index (BMI): <0kg/m2 (Group 1, very thin patients, G<20) and ≥25 kg/m2 (Group 2, non-thin patients, G≥25). Patients were randomly matched based on Guy's Stone Score (GSS) according to case complexity at a ratio of 1:3.

RESULTS

A total of 204 patients were enrolled in this study: 51 patients (G<20) and 153 controls (G≥25). Complications occurred in 15.2% of the patients, with 5.4% of these complications classified as major complications (Clavien grade ≥ 3). According to complications there were no significant differences between the groups. The overall complication rates were 17.6% in the G<20 and 14.4% in the G≥25 (p = 0.653). The major complication rates were 3.9% in the G<20 and 5.8% in the G≥25 (p=0.429). No differences in transfusion or urinary fistula rates were found.

CONCLUSIONS

In this study, very thin patients were not at a higher risk of complications when submitted to PCNL than in those with a BMI of ≥25 kg/m2. Apparently, this technique can be used in these patients, just as it is used in any other type of patient, independently of their BMI.

The potential causal relationship between BMI, T1D, urolithiasis, and hydronephrosis in European ancestry: A Mendelian randomization analysis

Body mass index (BMI), type 1 diabetes (T1D), urolithiasis, and hydronephrosis are interrelated. Our aim was to analyze their causal relationships at the genetic level. Mendelian randomization is an instrumental variable analysis method that follows Mendel genetic law of random allocation of parental alleles to offspring. In observational studies, genetic variants are used as instrumental variables to infer causal relationships between exposure factors and study outcomes. All the genome-wide association study data in our study were publicly available and from published genome-wide association studies, UK Biobank, and FinnGen. Random-effects inverse variance weighted was the primary analysis method, with R Egger, weighted median, and weighted mode as supplementary methods. We examined heterogeneity, horizontal pleiotropy, and the influence of individual single nucleotide polymorphisms on the analysis. We further explored the causal relationships between BMI, T1D, urolithiasis, and hydronephrosis, as well as the robustness of the analysis results. Inverse variance weighted results showed genetic causal relationships between BMI (P = .034, odds ratio [OR] 95% confidence interval [CI] = 1.273 [1.019-1.589]), T1D (P = .028, OR 95% CI = 0.921 [0.855-0.991]), urolithiasis (P < .001, OR 95% CI = 1.361 [1.175-1.576]), and hydronephrosis. Sensitivity analyses confirmed the accuracy and robustness of these findings. Our results support significant causal roles of BMI, T1D, and urolithiasis in hydronephrosis, potentially offering new intervention strategies for preventing its development.

Protein Intake and High Uric Acid Stone Risk

Rationale & Objective

We evaluated the metabolic differences between pure and impure uric acid stone formers in this retrospective study of uric acid kidney stone formers diagnosed between 1996 and 2021.

Study Design

Demographics and medical history were compared by χ2 tests. Twenty-four-hour urine chemistries were compared using logistic regressions while controlling for demographics and comorbid conditions.

Setting & Participants

Patients from Yale Urology and Nephrology Clinics with a documented kidney stone analysis containing uric acid were included. In total, 4,294 kidney stone formers had a stone analysis, and 722 (16.8%) contained uric acid. Patients with all stone analyses  ≥ 50% uric acid were allocated to the pure group, while patients with ≥1 stone analysis <50% uric acid were allocated to the impure group.

Results

Among kidney stone formers, the prevalence of uric acid nephrolithiasis was 16.8%. Pure uric acid stone formers were more likely to be older, heavier, and were 1.5 times more likely to have chronic kidney disease. When controlling for age, sex, race, ethnicity, and body mass index, pure uric acid stone formers had lower urinary pH and lower urine citrate normalized for creatinine. Additionally, they had a higher protein catabolic rate, urine urea nitrogen, and urine sulfur normalized for creatinine, all markers of dietary protein intake. These findings persisted after controlling for chronic kidney disease.

Limitations

This is a retrospective study from a single center.

Conclusions

Pure uric acid stone formation is more common with diminished kidney function; however, after controlling for kidney function, pure uric acid stone formation is associated with protein intake, suggesting that modifying protein intake may reduce risk.

Urinary stone analysis and clinical characteristics of 496 patients in Taiwan

Evaluate urinary stone components' epidemiological features in urolithiasis individuals and explore potential correlations between stone components and patients' clinical characteristics. A retrospective analysis of urinary stone compositions in 496 patients from a northern Taiwan medical center (February 2006 to October 2021) was conducted. We investigated associations between sex, age, body mass index (BMI), hypertension, diabetes mellitus (DM), hyperlipidemia (HLP), gout, coronary artery disease (CAD), cerebral vascular accident (CVA), chronic kidney disease (CKD), habits, urine pH, and three main stone groups: calcium oxalate (CaOx), calcium phosphate (CaP), and uric acid (UA). Males accounted for 66.5% of cases, with a male-to-female ratio of 1.99:1. Males were negatively associated with CaP stones (OR 0.313, p < 0.001) and positively with UA stones (OR 2.456, p = 0.009). Age showed a negative correlation with CaOx stones (OR 0.987, p = 0.040) and a positive correlation with UA stones (OR 1.023, p < 0.001). DM had a protective effect against CaP stones (OR 0.316, p = 0.004). Gout had a positive association with UA stones (OR 2.085, p = 0.035). Smoking was adversely associated with UA stones (OR 0.350, p = 0.018). Higher urine pH was a risk factor for CaP stones (OR 1.641, p = 0.001) and a protective factor against UA stones (OR 0.296, p < 0.001). These results may provide insights into the pathogenesis of urinary stones and the development of preventative strategies for high-risk populations. Further research is required to confirm and expand upon these findings.

Association between chinese visceral adiposity index and risk of kidney stones in a health screening population: an ultrasonography based cross-sectional study

BACKGROUND

Obesity is an important risk factor for kidney stones(KS). Chinese Visceral Adiposity Index (CVAI), as a specific indicator for visceral obesity in the Chinese population, can more accurately assess the visceral fat content in Chinese individuals compared to Visceral Adiposity Index (VAI). However, the association between CVAI and risk for KS has not been studied.

METHODS

A total of 97,645 participants from a health screening cohort underwent ultrasound examinations for the diagnosis of kidney stones, along with measurements of their CVAI. Logistic regressions were utilized to determine the relationship between different quartiles of CVAI and the incidence of kidney stones. Simultaneously, subgroup analysis and the computation of dose-response curves were employed to pinpoint susceptible populations.

RESULTS

Among the participants, 2,888 individuals (3.0%) were diagnosed with kidney stones. The mean CVAI values ± standard deviation for the four groups were: Q1 (18.42 ± 19.64), Q2 (65.24 ± 10.39), Q3 (98.20 ± 9.11), and Q4 (140.40 ± 21.73). In the fully adjusted multivariable model, CVAI was positively correlated with urolithiasis (OR = 1.001; 95% CI = 1.000, 1.002). Compared with the first quartile of CVAI, the population in the fourth quartile of CVAI had a higher prevalence of kidney stones (OR = 1.231; 95% CI = 1.066, 1.415). Through subgroup analysis, a positive correlation between CVAI and the risk of kidney stones was found in non-smokers (OR = 1.001, 95%CI:1.000, 1.002), non-drinkers (OR = 1.001, 95%CI:1.000, 1.002), non-hypertensive subgroups (OR = 1.003, 95%CI:1.002, 1.003), and non-diabetes subgroups (OR = 1.001, 95%CI:1.000, 1.002).

CONCLUSION

The findings suggest that CVAI could be a reliable and effective biomarker for assessing the potential risk of kidney stone prevalence, with significant implications for the primary prevention of kidney stones and public health.

Patterns of weight change during adulthood and incidence of nephrolithiasis: a population-based study

BACKGROUND

There is some evidence to suggest that there may be a link between body mass index (BMI) and the development of kidney stones, it remains unclear whether weight change was associated with the presence of kidney stone.

AIMS

The objective of this study was to investigate the potential association between changes patterns in weight during adulthood and the incidence of kidney stone.

METHODS

This study included 14472 participants aged 30-75 years, whose BMI was recorded at both baseline and 10 years prior to the survey. We categorized individuals into five weight change patterns: stable healthy, non-obesity to obesity, obesity to non-obesity, stable obesity, and maximum overweight. Odds ratios (OR) and 95% confidence intervals (CI) relating weight change to incident kidney stone were calculated using logistic regression models adjusting for covariates. The non-linear association between absolute weight change was investigated using the restricted cubic spline (RCS) regression. The supposed population attributable fraction (PAF) for the weight change patterns was calculated.

RESULTS

After adjusting for all confounders, participants changing from non-obesity to obesity, obesity to non-obesity, and stable obesity had significantly higher risks of kidney stone than those with healthy weight during adulthood (OR = 1.59, 95% CI:1.18-2.13; OR = 1.78, 95% CI: 1.47-2.16; OR = 1.80, 95% CI: 1.48-2.19, respectively). A U-shaped association was observed, and the risk of kidney stone was lowest in participants with stable healthy BMI. If the population had maintained a healthy BMI, a 28.7% (95% CI: 18.6%-37.5%) lower incidence of kidney stones was observed.

CONCLUSIONS

This study found that changes in weight during adulthood are linked to the risk of developing kidney stones. Maintaining healthy weight during adulthood is important for reducing the risk of developing kidney stones.

Causal effects of gut microbiota on the risk of urinary tract stones: A bidirectional two-sample mendelian randomization study

Background

Recent studies increasingly suggest notable changes in both the quantity and types of gut microbiota among individuals suffering from urinary tract stones. However, the causal relationship between GMB and urinary tract stone formation remains elusive, which we aim to further investigate in this research through Mendelian Randomization (MR) analysis.

Materials and methods

Single nucleotide polymorphisms (SNPs) associated with the human GMB were selected from MiBioGen International Consortium GWAS dataset. Data on urinary tract stone-related traits and associated SNPs were sourced from the IEU Open GWAS database. To investigate the causal relationships between gut microbiota and urinary tract stones, Mendelian Randomization (MR) was applied using genetic variants as instrumental variables, utilizing a bidirectional two-sample MR framework. This analysis incorporated various statistical techniques such as inverse variance weighting, weighted median analysis, MR-Egger, and the maximum likelihood method. To ensure the reliability of the findings, a range of sensitivity tests were conducted, including Cochran's Q test, the MR-Egger intercept, leave-one-out cross-validation, and examination of funnel plots.

Results

The results revealed the causal relationship between the increase in the abundance of 10 microbial taxa, including Genus-Barnesiella (IVW OR = 0.73, 95%CI 0.73-0.89, P = 2.29 × 10-3) and Genus-Flavonifractor (IVW OR = 0.69, 95%CI 0.53-0.91, P = 8.57 × 10-3), and the decreased risk of urinary tract stone formation. Conversely, the development of urinary tract stones was observed to potentially instigate alterations in the abundance of 13 microbial taxa, among which Genus-Ruminococcus torques group was notably affected (IVW OR = 1.07, 95%CI 0.64-0.98, P = 1.86 × 10-3). In this context, Genus-Clostridium sensustricto1 exhibited a bidirectional causal relationship with urinary tract stones, while the remaining significant microbial taxa demonstrated unidirectional causal effects in the two-sample MR analysis. Sensitivity analyses did not identify significant estimates of heterogeneity or pleiotropy.

Conclusion

To summarize, the results of this study suggest a likely causative link between gut microbiota and the incidence of urinary tract stones. This insight opens up potential pathways for discovering biomarkers and therapeutic targets in the management and prevention of urolithiasis. However, further in-depth research is warranted to investigate these associations.

High perirenal fat thickness predicts a greater risk of recurrence in Chinese patients with unilateral nephrolithiasis

INTRODUCTION

The aim of this study was to evaluate the association between recurrence-free survival (RFS) and perirenal fat thickness (PFT) in a cohort of Chinese population with unilateral nephrolithiasis.

METHODS

We retrospectively reviewed the medical records of 81 patients with unilateral nephrolithiasis in our center from January 2019 to June 2019. PFT measured on computed tomography (CT) scans was evaluated. Kaplan-Meier curves and log-rank tests were used to assess significant differences in RSF between high-PFT and low-PFT groups within sexes. Univariable and multivariable Cox regression analyses were used to evaluate the potential risk factors for renal stone recurrence.

RESULTS

High PFT was significantly associated with high BMI and hyperlipidemia (p = .003 and.047, respectively). The PFT of stone-bearing kidney was significantly greater than PFT of non-stone-bearing kidney (0.77 ± 0.60 cm vs. 0.67 ± 0.58 cm, p = .002) . During the follow-up periods (median 31 months), 21 (25.9%) patients experienced ipsilateral renal stone recurrence. In addition, Kaplan-Meier survival curves showed that patients with low PFT had a significant better RFS than those with high PFT (p = .012). In the univariable Cox analyses, male sex and high PFT were significantly associated with a poor RFS (p = .042 and .018, respectively). Moreover, both male sex and high PFT retained significance in the multivariable analyses (p = .045 and .020, respectively).

CONCLUSIONS

Our findings suggested that PFT is a noninvasive and feasible parameter, which may help in the risk stratification of renal stone recurrence in the follow-up periods.

Association of body fat percentage with kidney stone Disease: a cross-sectional and longitudinal study among bus drivers

BACKGROUND

The association between body fat percentage (BFP) and kidney stone disease (KSD) among bus drivers has not been explored in the existing literature. Thus, this study was conducted to explore the influence of BFP on the risk of KSD as well as KSD development for bus drivers to fill the research gap.

METHODS

A cross-sectional and longitudinal cohort study was designed. In total, 3433 bus drivers were included in the cross-sectional analyses, and 1864 bus drivers without KSD at baseline and with regular follow-up were included in the longitudinal cohort study.

RESULTS

During a median follow-up of 2.9 years, KSD occurred in 15.0% of bus drivers. Multivariate logistic analysis found that each 5% higher BFP was not only significantly related with higher odds of KSD (odds ratio [OR] = 1.48), but also associated with higher odds of developing KSD (OR = 1.27). The risk of prevalent KSD in obesity group based on BFP was 2.47 times of the normal group; and the corresponding risk of developing KSD was 1.61 times. For obesity bus drives with age < 40, the corresponding risk increased to 4.54 times.

CONCLUSION

Bus drivers were reported to have a high prevalence of KSD as well as development of KSD. As a significant predictive factor for KSD, BFP can be used to monitor and prevent bus drivers from kidney stone formation. Bus drivers in obesity group based on BFP, especially with age < 40 years should become priority subjects for targeted prevention.

Kidney Considerations in Pediatric Obesity

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is a common condition and a major cause of morbidity and mortality in adults, but children and adolescents are also at risk for early kidney injury and development of CKD. Obesity contributes both directly and indirectly to the development of CKD. The purpose of this review is to describe obesity-related kidney disease (ORKD) and diabetic kidney disease (DKD) and their impact in the pediatric population.

RECENT FINDINGS

Although obesity-related CKD in childhood and adolescence is uncommon, nascent kidney damage may magnify the lifetime risk of CKD. Glomerular hyperfiltration is an early phenotype of both ORKD and DKD and typically manifests prior to albuminuria and progressive decline in GFR. Novel treatments for obesity and type 2 diabetes exerting protective effects on the kidneys are being investigated for use in the pediatric population. It is important to understand the impact of obesity on the kidneys more fully in the pediatric population to help detect injury earlier and intervene prior to the onset of irreversible progression of disease and to guide future research in this area.

Impact of body mass index on size and composition of urinary stones: a systematic review and meta-analysis

BACKGROUND

Several studies have explored the impact of BMI on size and composition of urinary stones. Because there were controversies, a meta-analysis was necessary to be carried out to provide some evidence of the relationship of BMI and urolithiasis.

MATERIALS AND METHODS

PubMed, Medline, Embase, Web of Science databases, and the Cochrane Library were searched up to August 12th 2022 for eligible studies. The urolithiasis patients were summarized into two groups: BMI < 25 and ≥ 25 kg/m2. Summary weighted mean difference (WMD), relative risk (RR) and 95% confidence intervals (CI) were calculated through random effects models in RevMan 5.4 software.

RESULTS

A total of fifteen studies involving 13,233 patients were enrolled in this meta-analysis. There was no significant correlation of BMI and size of urinary stone (WMD -0.13mm, 95% CI [-0.98, 0.73], p = 0.77). Overweight and obesity increased the risk of uric acid stones in both genders and in different regions (RR=0.87, [95% CI] = 0.83, 0.91, p<0.00001). There was a higher risk of calcium oxalate stones formation in overweight and obesity group in total patients (RR=0.95, [95% CI] = 0.91, 0.98, p = 0.006). The relationship of BMI and calcium phosphate was not observed in this meta-analysis (RR=1.12, [95% CI] = 0.98, 1.26, p = 0.09). Sensitivity analysis was performed and indicated similar results.

CONCLUSIONS

The current evidence suggests a positive association between BMI and uric acid and calcium oxalate stones. It would be of great guiding significance to consider losing weight when treating and preventing urinary stones.

Insights into risk factors for urolithiasis: a mendelian randomization study

BACKGROUND

Risk factors for urolithiasis have not been identified. Here, we aimed to identify potentially causal risk factors driving the risk of urolithiasis.

METHODS

Two sets of instrumental variables were used for analysis, derived from publicly available databases. Summary-level statistical data for urolithiasis were obtained from the MRC-IEU Consortium and UK biobank (Neale Lab). Mendelian randomization (MR) was conducted to identify causal risk of urolithiasis. Finally, the results of the two databases were combined and a meta-analysis was performed.

RESULTS

In the MRC-IEU consortium, the odds of urolithiasis increased per 1-SD increase of body mass index (BMI) (OR = 1.0016, 95% CI:1.0004-1.0029, p = 0.010), triglycerides (OR = 1.0016, 95% CI:1.0003-1.0029, p = 0.017), adiponectin (OR = 1.0027, 95% CI:1.0003-1.0050, p = 0.024), and body fat percentage (OR = 1.008, 95% CI:1.0001-1.0161, p = 0.047). In addition, alcohol intake also increased the incidence of urolithiasis (OR = 1.0030, 95% CI:1.0009-1.0051, p = 0.005). In the UK biobank, the odds of urolithiasis increased per 1-SD increase of waist circumference (OR = 1.0215, 95% CI:1.0061-1.0372, p = 0.008) and body fat percentage (OR = 1.0239, 95% CI:1.0043-1.0440, p = 0.020). Surprisingly, we found that the risk of urolithiasis decreased with increasing hip circumference (OR = 0.9954, 95% CI:0.9915-0.9992, p = 0.017). In a meta-analysis of MR results, higher BMI (OR = 1.0016, 95% CI:1.0004-1.0027, p = 0.009), waist circumference (OR = 1.0073, 95% CI:1.0020-1.0126, p = 0.007), adiponectin (OR = 1.0026, 95% CI:1.0008-1.0043, p = 0.004), triglycerides (OR = 1.0015, 95% CI:1.0004-1.0026, p = 0.008) and body fat percentage (OR = 1.0104, 95% CI:1.0030-1.0178, p = 0.006) increased the risk of urolithiasis. Furthermore, alcohol intake also increased the incidence of urolithiasis (OR = 1.0033, 95% CI:1.0012-1.0053, p = 0.002).

CONCLUSIONS

Our MR study found that higher BMI, triglycerides, waist circumference, adiponectin, body fat percentage, and alcohol intake increased the risk of urolithiasis.

The ABCG2 rs2231142 polymorphism and the risk of nephrolithiasis: A case-control study from the Taiwan biobank

BACKGROUND

Hyperuricemia and gout are risk factors of nephrolithiasis. However, it is unclear whether the ABCG2 gene contributes to the development of nephrolithiasis. We aimed to investigate the interaction between the ABCG2 rs2231142 variant and incident nephrolithiasis in the Taiwanese population.

METHODS

A total of 120,267 adults aged 30-70 years were enrolled from the Taiwan Biobank data-base in this retrospective case-control study and genotyped for rs2231142. The primary outcome was the prevalence of self-reported nephrolithiasis. The odds ratio (OR) of incident nephrolithiasis was analyzed by multivariable logistic regression models with adjustment for multifactorial confounding factors. Associations of the ABCG2 rs2231142 variant with serum uric acid levels, and the incident nephrolithiasis were explored.

RESULTS

The frequency of rs2231142 T allele was 53%, and 8,410 participants had nephrolithiasis. The multivariable-adjusted OR (95% confidence interval) of nephrolithiasis was 1.18 (1.09-1.28) and 1.12 (1.06-1.18) for TT and GT genotypes, respectively, compared with the GG genotype (p<0.001), specifically in the male population with hyperuricemia. Higher age, male sex, hyperlipidemia, hypertension, diabetes mellitus, hyperuricemia, smoking and overweight were independent risk factors for nephrolithiasis. In contrast, regular physical exercise is a protective factor against nephrolithiasis.

CONCLUSIONS

ABCG2 genetic variation is a significant risk of nephrolithiasis, independent of serum uric acid levels. For rs2231142 T allele carriers, our result provides evidence for precision healthcare to tackle hyperuricemia, comorbidities, smoking, and overweight, and recommend regular physical exercise for the prevention of nephrolithiasis.

Global, Regional, and National Burden of Urolithiasis from 1990 to 2019: A Systematic Analysis for the Global Burden of Disease Study 2019

Introduction

To get insight into the temporal trends of urolithiasis, and thus decrease the health burden of urolithiasis, we comprehensively investigated the specific epidemiological indicators that varied among different countries and regions according to the diversity of geographic locations, gender, age, year, and socioeconomic status.

Methods

In this study, we investigated the incidence, death, disability-adjusted life years (DALYs) of urolithiasis quantified by the number of patients, age-standardized rates, and estimated annual percentage changes based on geographic locations, gender, age, and year to decode the epidemiological characteristics using the data from 1990 to 2019 in the Global Burden of Disease database.

Results

In 2019, more than 115 million (95% uncertainty interval [95% UI] 93–140) incident cases of urolithiasis occurred worldwide, and the age-standardized incidence rate (ASIR) (per 100,000 population) decreased from 1696.2 (1358.1–2078.1) in 1990 to 1394 (1126.4–1688.2) in 2019. Nearly 13,279 (95% UI: 10616–16267) died of urolithiasis, contributing to 0.6 million (0.5–0.7) DALYs in 2019. The highest age-standardized DALY rates (33.33 per 100 000 population) in 2019 were observed in Armenia, whereas the largest negative estimated annual percentage changes of DALYs were seen in Poland. The ASIR of males was higher than females. However, the ASIR EAPC of males was lower than females from 1990 to 2019. Males aged 50–54 years old were more likely to suffer from urolithiasis. Joinpoint regression model analyses suggested that the global age-standardized incidence and DALY rates of urolithiasis encountered a trend to decline over the past 30 years. Over the years, the attenuation of this disease was pinpointed to be weakly related to the Socio-demographic index.

Conclusion

At the global level, both the incident and DALY cases experienced substantial growth compared to the absolute cases in 1990. However, global age-standardized incidence and DALY rate of urolithiasis were observed to decline from 1990 to 2019. Males’ ASIR was higher than females, while the gap narrowed over the years. A weakly positive correlation between ASIR of urolithiasis and SDI was also observed in this study.

Analysis of potential risk factors associated with urolithiasis

OBJECTIVES

Eating habits, regular fluid intake, lifestyle and body composition are a primary point of research. The research focused on urolithiasis approaching potential danger, trying to interpret risk factors responsible for urolithiasis and disease recurrence.

METHODS

Research file contains 166 patients suffering from urolithiasis, 87 (52.4%) males and 79 (47.6%) females, and 172 healthy subjects from control group. All data was accessed using fully anonymous and confidential questionnaires, then evaluated in the statistical GNU PSPP 1.4 software.

RESULTS

More than 3/4 patients have a BMI higher than 24.9 and almost 40% of subjects have obesity class I, II, or III. Patients have higher BMI than subjects (d = 1.285; p < 0.001), and females have significantly higher BMI than males (d = 0.385; p = 0.007). Female patients have higher BMI than Slovak healthy females (p < 0.001; MD = 4.581; CI: 3.24-5.93). Patients have a lower daily water intake than subjects (φc = 0.157; p = 0.04) and more than ²/3 of patients have insufficient water intake. Sedentary employment prevails markedly in patients than in subjects. Patients are much less physically active than subjects (φc = 0.633; p < 0.001) and the difference is rising with increasing age of patients (ρ = - 0.232; p = 0.003). Low physical and working activity are characteristic for patients in this study. Patients smoke more often in comparison to subjects (φc = 0.261; p < 0.001). Patients consume more meats (red and white), cocoa and lentils. A lot of patients exceed recommended daily intake of pork and beef.

CONCLUSIONS

Many conditions are different for the healthy population and patients' group. High BMI, low fluid intake, exceeded red meat consumption, and low physical activity are the strongest factors for developing urolithiasis. Patients should consume more fluids daily, exercise frequently and vigorously, and lower amount of red meat consumed.

Metabolic syndrome in calcium oxalate stones: Is it so important in this type of lithiasis?

INTRODUCTION AND OBJECTIVE

The association of the metabolic syndrome with lithogenesis has been described, especially in uric acid stones. The aim of the work was to analyze the role of the metabolic syndrome in oxalocalcic lithogenesis.

MATERIALS AND METHODS

Metabolic evaluation of 151 patients including biochemical, hormonal and 24-urine urine parameters, as well as characteristics associated with metabolic syndrome. The relationship between the characteristics associated with the metabolic syndrome and those related to lithogenesis was evaluated using Spearman's correlation coefficient (SCC), Student's t test and Fisher's exact test.

RESULTS

The average body mass index (BMI) was 25.9 (SD 3.7). The median age was 51 years (18.6-84.8) and 64.9% were men. There were no statistically significant differences between hypertension and estradiol, testosterone, triglycerides or cholesterol (P=.191, .969, .454, .345, respectively). Regarding glucose, the mean was 114.5 and 93.5mg/dl in patients with and without hypertension (P=.000). The levels of glucose, estradiol, testosterone or cholesterol did not vary with proteinuria (P=.518, P=.227, P=.095, P=.218, respectively). The mean triglycerides were 185.6 and 108.2mg/dl in patients with and without proteinuria (P=.001). Hypertension and proteinuria were not associated (P=.586). BMI correlated with serum and urinary uric acid and urinary creatinine.

CONCLUSIONS

There are few associations between the characteristics of the metabolic syndrome and the anomalies related to lithogenesis. Metabolic syndrome does not seem to have a relevant role in the development of oxalocalcic stones.

Is the visceral adiposity index a potential indicator for the risk of kidney stones?

OBJECTIVE

To determine whether the visceral adiposity index (VAI) was linked to the risk of kidney stones (KS) in the representative U.S. adults.

METHODS

We investigated 59842 participants who joined the 2007-2018 National Health and Nutrition Examination Survey. The association between the visceral adiposity index (VAI) and KS was identified by logistic regression analysis. Meanwhile, the subgroup analysis as well as the calculation of dose-response curves were also utilized to identify sensitive groups.

RESULTS

Data from 29384 participants were available, including 2781 self-reported ever experiencing KS diseases. Overall, the VAI was 0.74 (0.70, 0.78) in the KS group, while 0.55 (0.52, 0.57) in the control group. After adjusting for confounders, the prevalence of KS increased by 13% for each unit of VAI increment (OR = 1.13, 95% CI: 1.08, 1.19). Moreover, a linear relationship was found between the VAI and the prevalence of KS. By subgroup analysis, we found that a positive correlation between VAI and the risk of KS both in male (OR=1.14, 95%CI:1.07, 1.22) and female (OR=1.14, 95%CI:1.05, 1.24), White (OR=1.20, 95%CI:1.11, 1.28) and other race, all aged subgroups, nonhypertensive (OR=1.06, 95%CI:1.08, 1.25) and nondiabetic subgroups (OR=1.14, 95%CI:1.07, 1.21).

CONCLUSIONS

Elevated VAI was strongly associated with KS in representative U.S. adults, which may be a promising indicator for the risk of kidney stones.

Evaluation of the Relationship between Perirenal Fat Volume and Nephrolithiasis

OBJECTIVE

To examine the relation between perirenal fat volume, which is one of the visceral fat measurements, and kidney stones.

METHOD

169 patients admitted to our clinic between January 2018 and May 2021 were included in the study. The patients were divided into 2 groups as Control Group and Unilateral Kidney Stone Group (88 patients with unilateral kidney stones). Contrast-enhanced abdominal computed tomography scans were used to measure perirenal fat volume and the results were transferred to workstations. The total perirenal fat volumes in the bilateral kidneys of patients were compared between the two groups. The perirenal fat volume in stone-bearing and non-stone bearing kidneys of patients were also compared.

RESULTS

The total perirenal fat volume was higher in the Unilateral Kidney Stone Group than in the other groups and the perirenal fat volume of the patients in this group was higher in the stone bearing kidney (295.6±164.4cm3) than in the non-stone bearing kidney (273.1±179.6cm3). In the ROC analysis, it was concluded that total perirenal fat volume>387cm3 increased the risk of kidney stones. Presence of hypertension, presence of hyperlipidemia and total perirenal fat volume>387cm3 were found to be independent risk factors for the presence of kidney stones.

CONCLUSION

Perirenal fat volume is higher in stone bearing kidneys compared to non-stone bearing kidneys. Therefore, stone formation in a kidney is directly related to the perirenal fat volume of that kidney. Also, total perirenal fat volume>387cm3 increases the risk of kidney stones independently of body mass index, and predicts it better.

Obesity-related indices and its association with kidney stone disease: a cross-sectional and longitudinal cohort study

Obesity increases the risk of several diseases, including kidney stone disease (KSD). The study aimed to explore the relationship between KSD and various obesity-related indices. A total of 121,605 participants in the Taiwan Biobank from December 2008 to February 2020 were analyzed. The association between self-reported history of KSD and eight obesity-related indices, including body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), waist-to-hip ratio (WHR), abdominal volume index (AVI), body roundness index (BRI), conicity index, and triglyceride glucose index was examined in cross-sectional analysis; additionally, the risk of developing kidney stones was analyzed in a longitudinal cohort of 25,268 participants without KSD at baseline, which was a subset of the main cohort. Of all participants, 77,904 (64.1%) were female. Overall, 10.7% of males and 4.0% of females had KSD. Multivariate-adjusted logistic regression showed that all obesity-related indices were significantly associated with KSD. During a mean follow-up of 47 months, kidney stones occurred in 642 (2.5%) participants, and after adjusting for confounders, the risk of developing kidney stones was higher in participants with higher BMI, WC, WHtR, WHR, AVI and BRI. BMI, WC, WHtR, WHR, AVI, and BRI were found to be associated with a higher prevalence of kidney stones as well as development of incident kidney stones, which could be used as predictive factors for development of KSD in clinical practice.

Low Body Mass Index as a Predictive Factor for Postoperative Infectious Complications after Ureterorenoscopic Lithotripsy

Background and Objectives: In this study, we aimed to evaluate predictive factors of postoperative fever (POF) after ureterorenoscopic lithotripsy (URSL). Materials and Methods: A total of 594 consecutive patients who underwent URSL for urinary stone disease at Gifu Municipal Hospital and Chuno Kosei Hospital between April 2016 and January 2021 were enrolled in this study. In all patients, antibiotics were routinely administered intraoperatively and the next day after surgery. We used rigid and/or flexible ureterorenoscopes depending on the stone location for URSL. Stones were fragmented using a holmium: YAG laser. The fragments of the stone were manually removed as much as possible using a stone basket catheter. A ureteral stent was placed at the end of the surgery in all cases. Results: The median age and body mass index (BMI) in all patients were 62 years and 23.8 kg/m², respectively. The median operation duration was 52 min. The most common URSL-related complication was POF in 28 (4.7%) patients. In these patients, the rates of antibiotic administration and ureteral stent insertion before surgery were significantly higher than in those without POF. In multivariate analysis, BMI was associated with POF after URSL. There were no significant differences in predicting POF after surgery in patients who had bacteriuria or received antibiotics before surgery. Conclusions: A low BMI was significantly associated with POF after URS or URSL.

Obesity and chronic kidney disease: prevalence, mechanism, and management

The prevalence of childhood obesity is increasing worldwide at an alarming rate. While obesity is known to increase a variety of cardiovascular and metabolic diseases, it also acts as a risk factor for the development and progression of chronic kidney disease (CKD). During childhood and adolescence, severe obesity is associated with an increased prevalence and incidence of the early stages of kidney disease. Importantly, children born to obese mothers are also at increased risk of developing obesity and CKD later in life. The potential mechanisms underlying the association between obesity and CKD include hemodynamic factors, metabolic effects, and lipid nephrotoxicity. Weight reduction via increased physical activity, caloric restriction, treatment with angiotensin-converting enzyme inhibitors, and judicious bariatric surgery can be used to control obesity and obesity-related kidney disease. Preventive strategies to halt the obesity epidemic in the healthcare community are needed to reduce the widespread deleterious consequences of obesity including CKD development and progression.

Effect of a low-calorie diet on 24-hour urinary parameters of obese adults with idiopathic calcium oxalate kidney stones

Purpose:

to evaluate the effect of low-calorie diet on 24-hour urinary metabolic parameters of obese adults with idiopathic calcium oxalate kidney stones.

Materials and Methods:

Adult idiopathic calcium oxalate stone formers, with body mass index (BMI) ≥30kg/m² and a known lithogenic metabolic abnormality, were submitted to low-calorie diet for twelve weeks. After enrolment, anthropometric measures, serum exams, 24-hour urinary metabolic parameters and body impedance were collected one month prior to dietary intervention and at the end of twelve weeks. Correlations between weight loss, waist circumference loss, fat loss and variation in 24-hour urinary lithogenic parameters and calcium oxalate urinary supersaturation (CaOx SS) as per Tiselius equation were analysed.

Results:

From January 2017 to January 2018, 39 patients were enrolled to participate in this study. Median (range) prescribed diet was 1300 (1100-2100) Kcal/day. Mean age was 51.7±11.0 (29-68) years old and 69.2% were female. 30.8% of the participants shifted from obesity to BMI <30kg/m² and none to BMI <25kg/m². A significant correlation was found between baseline 24-hour urinary oxalate and weight (p=0.018) and BMI (p=0.026). No correlation was found between variation of weight, waist circumference, fat mass and 24-h urinary stone risk factors or CaOx SS.

Conclusions:

Short-term modest weight loss induced by twelve weeks of low-calorie diet is not associated with a decrease of 24-hour urinary lithogenic parameters in idiopathic calcium oxalate stone formers. Calcium oxalate urinary stone formation is probably multifactorial and driven by other factors than weight.

Distribution of APOE gene polymorphism in the Chinese Uyghur children & its association with urolithiasis

BACKGROUND & OBJECTIVES

This study was to survey the apolipoprotein E (APOE) gene polymorphism distribution among Chinese Uyghur children and to explore the relationship between APOE gene polymorphism and the occurrence of urolithiasis.

METHODS

A total of 144 Uyghur children with urolithiasis and 274 without the history of urolithiasis were enrolled in this study. Venous blood samples were collected from all participants, and APOE genotyping, derived from rs429358 and rs7412, was performed using Sanger sequencing.

RESULTS

Among the 418 children, the most prevalent genotype was E3/3, accounting for 71.3 per cent in the urolithiasis group and 71.4 per cent in the control group, followed by E3/4 and E2/3. Higher frequencies of the ɛ2 and ɛ4 alleles and lower frequencies of the ɛ3 allele were observed in the test group, and the unusual allele ɛ1 was also found in them. However, there were no significant differences between cases and controls at both rs429358 and rs7412 genotype and allele frequencies [odds ratio (OR)=0.98, 95% confidence interval (CI): 0.57-1.67; 0.98 (0.59-1.63); 1.43 (0.75-2.74) and 1.40 (0.74-2.62), respectively]. Likewise, none of significant differences was found between cases and controls at both APOE genotype and allele frequencies [OR=0.88, 95% CI: 0.51-1.53; 0.74 (0.33-1.64); 1.10 (0.73-1.66); 1.13 (0.76-1.67) and 1.14 (0.76-1.70), respectively].

INTERPRETATION & CONCLUSIONS

The present study does not support any association between APOE genotyping and urolithiasis in Uyghur children.

Obesity rates in renal stone formers from various countries

OBJECTIVE

To collect evidence on the rate of obesity in renal stone formers (RSFs) living in different climatic areas and consuming different diets.

MATERIALS AND METHODS

Data of adult renal stone formers were retrospectively collected by members of U-merge from 13 participant centers in Argentina, Brazil, Bulgaria (2), China, India, Iraq (2), Italy (2), Nigeria, Pakistan and Poland. The following data were collected: age, gender, weight, height, stone analysis and procedure of stone removal.

RESULTS

In total, 1689 renal stone formers (1032 males, 657 females) from 10 countries were considered. Average age was 48 (±14) years, male to female ratio was 1.57 (M/F 1032/657), the average body mass index (BMI) was 26.5 (±4.8) kg/m2. The obesity rates of RSFs in different countries were significantly different from each other. The highest rates were observed in Pakistan (50%), Iraq (32%), and Brazil (32%), while the lowest rates were observed in China (2%), Nigeria (3%) and Italy (10%). Intermediate rates were observed in Argentina (17%), Bulgaria (17%), India (15%) and Poland (22%). The age-adjusted obesity rate of RSFs was higher than the age-adjusted obesity rate in the general population in Brazil, India, and Pakistan, whereas it was lower in Argentina, Bulgaria, China, Italy, and Nigeria, and similar in Iraq and Poland.

CONCLUSIONS

The age-adjusted obesity rate of RSFs was not higher than the age-adjusted obesity rate of the general population in most countries. The relationship between obesity and the risk of kidney stone formation should be reconsidered by further studies carried out in different populations.

The new patterns of nephrolithiasis: What has been changing in the last millennium?

Nephrolithiasis has been increasing over the last millennium. Although early epidemiologic studies have shown that kidney stones were two to three times more frequent in males than in females, recent reports have suggested that this rate is decreasing. In parallel a dramatic increase of nephrolithiasis has also been observed among children and adolescents. Furthermore, epidemiologic studies have shown a strong association between metabolic syndrome (Mets) traits and kidney stone disease. Patients with hypertension have a higher risk of stone formation and stone formers are predisposed to develop hypertension compared to the general population. An incidence of nephrolithiasis greater than 75% has been shown in overweight and obese patients compared to those of normal weight. It has also been reported that a previous diagnosis of diabetes mellitus increases the risk of future nephrolithiasis. Additionally, an association between metabolic syndrome and uric acid stone formation has been clearly recognized. Furthermore, 24-h urinary metabolic abnormalities have been decreasing among patients with nephrolithiasis over the last decades. Finally, nephrolithiasis could cause chronic kidney disease (CKD) and end stage renal disease (ESRD), especially in women and overweight patients. According to these observations, a better understanding of these new features among stone former patients may be required. Hence, the recognition and the correction of metabolic disorders could help not only to reduce the primary disease, but also stone recurrence.

Urolithiasis, Independent of Uric Acid, Increased Risk of Coronary Artery and Carotid Atherosclerosis: A Meta-Analysis of Observational Studies

Background and Aims

Recent epidemiological evidence indicates an association between urolithiasis and atherosclerosis; however, results are incongruous. Our aim is to summarize the association between urolithiasis and arteriosclerosis risk through a detailed meta-analysis.

Methods

Relevant studies published before April 2019 were identified by searching OVID, EMBASE, PubMed, Web of Science database, and Cochrane Library. The relationship between urolithiasis and the risk of atherosclerosis was assessed by using odds ratio (OR) values and the corresponding 95% confidence intervals (CIs), and the selection of fixed- or random-effects model based on heterogeneity.

Results

The meta-analysis includes 8 observational studies that contained 70,716 samples. Pooled results showed that urolithiasis was associated with an increased adjusted and unadjusted risk estimated for atherosclerosis (P=0.017 and P=0.017 and n = 65,751/70,716) with serum uric acid levels less than 6.0 mg/dl, it still showed that urolithiasis was associated with a higher risk of atherosclerosis (P=0.017 and I² = 0.0%, P=0.017 and P=0.017 and P=0.017 and

Conclusions

Urolithiasis is associated with an increased risk for atherosclerosis, especially in coronary artery and carotid atherosclerosis. Urolithiasis may be another potential risk factor of atherosclerosis, which is independent of serum uric acid levels.

Oral chemolysis is an effective, non-invasive therapy for urinary stones suspected of uric acid content

Despite the possible benefit from avoiding stone surgery with all its possible complications, oral chemolysis is rarely performed in patients with urinary stones suspected of uric acid content. Among the reasons for its limited use is the sparse and low-quality data on its efficacy and the lack of reliable factors predicting its outcome. We thus performed a retrospective single-center cohort study of 216 patients (median patient age 63 years) with 272 renal (48%) and/or ureteral (52%) stones treated with oral chemolysis from 01/2010 to 12/2019. Patients with low urine pH (< 6), low stone density upon non-contrast enhanced computed tomography (NCCT), radiolucent urinary stones on plain radiography, and/or a history of uric acid urolithiasis were included. Potassium citrate and/or sodium/magnesium bicarbonate were used for alkalization (target urine pH 6.5–7.2). Median stone size was 9 mm, median stone density 430 Hounsfield Units. Patients with ureteral stones < 6 mm were excluded since stones this small are very likely to pass spontaneously. The stone-free status of each patient was evaluated after 3 months using NCCT. Oral chemolysis was effective with a complete and partial response rate of stones at 3 months of 61% and 14%, respectively; 25% of stones could not be dissolved. Lower stone density (OR = 0.997 [CI 0.994–0.999]; p = 0.008) and smaller stone size (OR = 0.959 [CI 0.924–0.995]; p = 0.025) significantly increased the success rate of oral chemolysis in multivariate logistic regression analysis. More precise stone diagnostics to exclude non-uric-acid stones could further improve outcome.

Characteristics of infant urolithiasis: A single center experience in western Turkey

INTRODUCTION

Urolithiasis (UL) in infancy has different incidence, etiology, presentation and course compared to UL in childhood and in adults. We evaluated the clinical, radiological, metabolic factors and course of infant UL in western Turkey.

METHODS

Medical records of the infants between 1 and 12 months of age with a diagnosis of UL were reviewed retrospectively for gender, gestational age, age at diagnosis, presenting symptoms, past medical history, parental consanguinity, family history of UL, urinary tract abnormalities, urinary tract infections, localization-size-number of stones, course of stones, treatment modality of UL (medical vs surgical) and follow up duration. Patients were grouped as those who did not require surgical intervention (Group 1) and those who underwent any kind of stone surgery (Group 2). Both groups were compared for the study parameters.

RESULTS

There were 80 infants (48 males) with a mean age of 6.0 ± 2.9 months at diagnosis. Mean follow-up duration was 29.7 ± 23.1 months. Two thirds of the patients presented with symptoms/signs not directly related to urinary system. Predisposing factors included metabolic abnormalities in 24 (30%) patients and urinary tract malformations in 9 (11%) patients. Group 1 (n = 58) and Group 2 (n = 22) were not different with respect to the study parameters except for the larger stone size and higher rate of hyperuricosuria in Group 2. Stone size of 4.5 mm has a 72.7% sensitivity and 74.1% specificity for predicting surgical intervention. Infants treated medically and those followed by hydration only did not differ for regression rate of stones and for requirement for surgical intervention. However, metabolic abnormalities were significantly higher in medically treated infants.

CONCLUSION

Every infant with urolithiasis should be evaluated for risk factors. Modification of such predisposing factors when possible may mitigate the notably high recurrence rate of UL in children. Increased awareness of infant UL may allow for earlier detection, improved evaluation and follow up, and may thereby decrease the morbidity of the disease.

Oxalate Content and Antioxidant Activity of Different Ethnic Foods

OBJECTIVE

There is not enough information on the classification of oxalate content in several foods, particularly in ethnic foods, to recommend their consumption in subjects with urolithiasis (UL). The objective of the present study was to generate reliable information on the oxalate content and antioxidant activity in different foods and classify them by very low, low, medium, high and very high oxalate content and antioxidant activity.

METHODS

The oxalate content of 109 foods including ethnic foods was assessed by an enzymatic assay, and the antioxidant activity was measured by the oxygen radical absorbance capacity to determine the oxalate/antioxidant activity ratio. Oxalate consumption was then evaluated in 400 subjects with overweight and obesity using 24-h dietary recalls.

RESULTS

The main foods with high oxalate content were raw spinach, huanzontle, purslane, chard, almond, and toasted and sweetened roasted amaranth. The highest antioxidant activity was found in strawberries, all types of chocolates, roselle, morita peppers, and pinolillo. Subjects with overweight or obesity exceed the dietary oxalate daily intake recommendation.

CONCLUSIONS

The classification of foods by their oxalate content and antioxidant activity will be very useful to generate nutritional recommendation in different diseases, mainly UL.

Anthropometric variables, physical activity and dietary intakes of patients with uric acid nephrolithiasis

To evaluate anthropometric variables, energy expenditure by physical activity and nutrient intake of uric acid stone formers (UA-RSFs) compared to non-forming subjects (C). The study included 33 consecutive male patients with a diagnosis of "pure" stones of anhydrous uric acid at infrared spectroscopy and 49 male control subjects with no history of urinary stones. A personal interview was conducted including questionnaires for physical activity and dietary intakes. Anthropometric parametric and blood pressure were measured. Mean age, weight, height, waist circumference, body mass index, systolic and diastolic blood pressure values, dietary energy, carbohydrate intake, lipid intake, dietary acid load, time spent for different physical activities and total energy expenditure for physical activity were not different in UA-RSFs with respect to C. Mean dietary protein (76.2 ± 19.6 vs 65.4 ± 14.7 g/day, P = 0.006) and ethanol intake (10.4 ± 8.8 vs 4.1 ± 8.6, P = 0.002) were higher in UA-RSFs than in C. History of renal disease, heart disease and treatment with thiazides or allopurinol were more frequent and mean serum glucose and triglycerides (104 ± 12 vs 97 ± 11 mg/dl, P = 0.043) (172 ± 77 vs 123 ± 52 mg/dl, P = 0.023) were higher in UA-RSFs. Metabolic syndrome was more frequent in UA-RSFs (57% vs 39%) but not significant (p = 0.09). Increased dietary animal protein (and ethanol) intake can act as co-factors for uric acid stone formation although a more complex and not fully elucidated metabolic background can have an even more crucial role in the pathogenesis of this disease even in the absence of overweight.

The influence of metabolic syndrome and its components on the development of nephrolithiasis

The prevalence of kidney stone disease is increasing, afflicting 7%–11% of the United States population. Multiple systemic conditions, including obesity and diabetes, are also on the rise. Further, the literature has demonstrated a strong association between metabolic syndrome, its components, and kidney stone disease. In this article, we aim to review the associations of metabolic syndrome and nephrolithiasis, discussing the pathophysiology, urinary parameters, and clinical presentations. With this knowledge, urologists will have a more comprehensive understanding of this complex population of metabolic stone formers enabling improved patient management and treatment of stone disease.

Impact of food quantity and quality on the biochemical risk of renal stone formation

OBJECTIVE

This study evaluated the role of body mass index (BMI) and dietary potential renal acid load (PRAL) with urinary saturation for calcium oxalate (US-CaOx), calcium phosphate (US-CaP) and uric acid (US-UA) in renal stone formers.

MATERIALS AND METHODS

A retrospective analysis was conducted of laboratory data collected on 442 renal stone-forming patients. Demographic information, BMI and 24 h urinary samples were collected from patients on their regular diets. PRAL was calculated as the Load of Acid to Kidney Evaluation (LAKE) score through a short questionnaire.

RESULTS

Urinary risk factors, but also inhibitors of calcium stone formation such as magnesium, tended to increase in relation to BMI (p = .000). Urinary pH (p = .002) and ammonium/sulfate ratio (p = .000) were negatively related to BMI. This resulted in a positive correlation between BMI and US-UA (p = .000), whereas US-CaOx and US-CaP were not influenced by BMI. LAKE score was positively correlated with US-CaOx (p = .022) and US-CaP (p = .000) as a consequence of the inverse relationship between LAKE score and citrate (p = .000). Multiple linear regression analysis identified BMI (p = .009) and male gender (p = .002) as independent predictors of US-UA, and LAKE score (p = .004) and age (p = .001) as independent predictors of US-CaP.

CONCLUSIONS

BMI, which depends on excessive intake of energy from food, is not related to an increased biochemical risk of calcium stone formation, which is more dependent on the renal acid load of the diet. In contrast, obesity is associated with an increased risk of uric acid stone formation due to insulin resistance, impaired ammoniagenesis and low urinary pH.

The impact of body mass index on quantitative 24-h urine chemistries in stone forming patients: a systematic review and meta-analysis

To study the impact of body mass index (BMI) on quantitative 24-h urine chemistries in stone forming patients and to explore how overweight and obesity contribute to urolithiasis. A systematic search of PubMed, EMBASE, Cochrane Library, and Web of Science was performed in July 2017 and updated in October 2017 to detect relevant studies. After that, we screened all the relevant articles in accordance with the predetermined inclusion and exclusion criteria. Data of eligible studies were extracted, and then, a meta-analysis was conducted via RevMan 5.3 software. Nine studies, involving 5965 stone forming patients who underwent 24-h urine collection for chemistry analysis, were included in our analysis. BMI was used to clarify the body size. BMI ≥ 25 kg/m² group, including overweight and obesity patients, erected more calcium (WMD 34.44 mg; 95% CI 11.33-57.55; p = 0.003), oxalate (WMD 3.44 mg; 95% CI 1.40-5.49; p = 0.001), urate (WMD 97.71 mg; 95% CI 63.05-132.38; p < 0.00001), and sodium (WMD 26.64 mg; 95% CI 18.23-35.05; p < 0.00001) in 24 h than BMI < 25 kg/m² group. However, the BMI < 25 kg/m² group showed higher pH of urine (WMD 0.12; 95% CI 0.04-0.20; p = 0.004). There was no significant difference in 24-h urine volume (WMD - 29.30 ml; 95% CI - 122.03 to - 63.42; p = 0.54), citrate (WMD - 34.03 mg; 95% CI - 72.88 to 4.82; p = 0.09), magnesium (WMD - 4.50 mg; 95% CI - 10.48 to 1.48; p = 0.14), phosphate (WMD - 89.38 mg; 95% CI - 219.23 to 40.47; p = 0.18), and creatinine (WMD - 191.98 mg; 95% CI - 395.35 to 11.38; p = 0.06) between the two groups. All the results kept the same tendency when gender was taken in consideration. Sensitivity analysis generated similar results. The current evidence suggested that patients with BMI ≥ 25 kg/m² erected more promotions but not inhibitors of urolithiasis than those with BMI < 25 kg/m², which increased the risk of urolithiasis in overweight and obesity individuals.

The Association of Uric Acid Calculi with Obesity, Prediabetes, Type 2 Diabetes Mellitus, and Hypertension

Objectives

To disclose the link between the composition of urolithiasis, especially that of uric acid calculi, and obesity, prediabetes, type 2 diabetes mellitus, and hypertension.

Materials and Methods

Patients who had urinary calculi and underwent surgical treatment were registered in the study. The composition of urinary calculi was analyzed and correlated with clinical features and biomedical profiles of the patients before surgical intervention.

Results

A total of 666 patients with urolithiasis who underwent surgical management were registered and analyzed. In those who had uric acid calculi, there was a significant association with prediabetic (OR: 20.11, 95% CI: 7.40–54.63, P < 0.001) and diabetic states (OR: 11.55, 95% CI: 4.41–29.97, P < 0.001). It also seemed that uric acid calculi were related to obesity but there was no statistical significance (OR: 2.45, 95% CI: 0.91–6.62, P = 0.078). There was no association of uric acid calculi with hypertension (OR: 1.08, 95% CI: 0.54–2.17, P = 0.822) and concurrent urinary tract infection (OR: 0.93, 95% CI: 0.44–1.96, P = 0.841).

Conclusion

There was a remarkable association of uric acid calculi with prediabetic and diabetic states. The uric acid calculi were also seemingly associated with obesity in patients with urolithiasis undergoing surgical management.

Prevalence of renal uric acid stones in the adult

The aim of this study was to estimate uric acid renal stone prevalence rates of adults in different countries of the world. PubMed was searched for papers dealing with "urinary calculi and prevalence or composition" for the period from January 1996 to June 2016. Alternative searches were made to collect further information on specific topics. The prevalence rate of uric acid stones was computed by the general renal stone prevalence rate and the frequency of uric acid stones in each country. After the initial search, 2180 papers were extracted. Out of them, 79 papers were selected after the reading of the titles and of the abstracts. For ten countries, papers relating to both the renal stone prevalence in the general population and the frequency of uric stones were available. Additional search produced 13 papers that completed information on 11 more countries in 5 continents. Estimated prevalence rate of uric acid stones was >0.75% in Thailand, Pakistan, Saudi Arabia, Iran, South Africa (white population), United States and Australia; ranged 0.50-0.75% in Turkey, Israel, Italy, India (Southern), Spain, Taiwan, Germany, Brazil; and <0.50% in Tunisia, China, Korea, Japan, Caribe, South Africa (blacks), India (Northern). Climate and diet are major determinants of uric acid stone formation. A hot and dry climate increases fluid losses reducing urinary volume and urinary pH. A diet rich in meat protein causes low urinary pH and increased uric acid excretion. On the other hand, uric acid stone formation is frequently associated with obesity, metabolic syndrome and diabetes type 2 that are linked to dietary energy excess mainly from carbohydrate and saturated fat and also present with low urine pH values. An epidemic of uric acid stone formation could be if current nutritional trends will be maintained both in developed countries and in developing countries and the areas of greater climatic risk for the formation of uric acid stones will enlarge as result of the "global warming".

Biochemical and dietary factors of uric acid stone formation

The aim of this study was to compare the clinical characteristics of "pure" uric acid renal stone formers (UA-RSFs) with that of mixed uric acid/calcium oxalate stone formers (UC-RSFs) and to identify which urinary and dietary risk factors predispose to their formation. A total of 136 UA-RSFs and 115 UC-RSFs were extracted from our database of renal stone formers. A control group of 60 subjects without history of renal stones was considered for comparison. Data from serum chemistries, 24-h urine collections and 24-h dietary recalls were considered. UA-RSFs had a significantly (p = 0.001) higher body mass index (26.3 ± 3.6 kg/m²) than UC-RSFs, whereas body mass index of UA-RSFs was higher but not significantly than in controls (24.6 ± 4.7) (p = 0.108). The mean urinary pH was significantly lower in UA-RSFs (5.57 ± 0.58) and UC-RSFs (5.71 ± 0.56) compared with controls (5.83 ± 0.29) (p = 0.007). No difference of daily urinary uric acid excretion was observed in the three groups (p = 0.902). Daily urinary calcium excretion was significantly (p = 0.018) higher in UC-RSFs (224 ± 149 mg/day) than UA-RSFs (179 ± 115) whereas no significant difference was observed with controls (181 ± 89). UA-RSFs tend to have a lower uric acid fractional excretion (0.083 ± 0.045% vs 0.107+/-0.165; p = 0.120) and had significantly higher serum uric acid (5.33 ± 1.66 vs 4.78 ± 1.44 mg/dl; p = 0.007) than UC-RSFs. The mean energy, carbohydrate and vitamin C intakes were higher in UA-SFs (1987 ± 683 kcal, 272 ± 91 g, 112 ± 72 mg) and UC-SFs (1836 ± 74 kcal, 265 ± 117, 140 ± 118) with respect to controls (1474 ± 601, 188 ± 84, 76 ± 53) (p = 0.000). UA-RSFs should be differentiated from UC-RSFs as they present lower urinary pH, lower uric acid fractional excretion and higher serum uric acid. On the contrary, patients with UC-RSFs show urinary risk factors more similar to those for calcium oxalate stones. The dietary approach in patients forming uric acid stones should be reconsidered with more attention to the quantity and quality of carbohydrate intake.