The visceral fat compartment is independently associated with changes in urine constituent excretion in a stone forming population

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.

Subcutaneous Adipose Tissue Accumulation Is an Independent Risk Factor of Urinary Stone in Young People

BACKGROUND

Urinary stones usually start at a young age and tend to recur. Therefore, preventing stone occurrence and recurrence in young people is crucial. We aimed to investigate the association between subcutaneous adipose tissue, visceral adipose tissue, and stone episodes in young people.

METHODS

We retrospectively studied patients aged below 40 years with kidney or ureteral stones. Data on demographic and metabolic characteristics, urolithiasis history, subcutaneous fat area (SFA), and visceral fat area (VFA) were collected. We evaluated the association between SFA or VFA and the occurrence or recurrence of stone episodes using binary logistic regression and Poisson regression analyses.

RESULTS

In total, 120 patients were included. Abdominal obesity, overweight or obesity, dyslipidemia, metabolic syndrome, SFA, and VFA increased with the number of stone episodes (all p < 0.05). The increase in SFA was independently associated with episode occurrence (p = 0.015). Patients with an SFA > 97 cm² had a higher risk of episode occurrence. SFA and VFA accumulation were independently associated with episode recurrence (all p < 0.05), and SFA had a stronger association than VFA did.

CONCLUSIONS

In young people, SFA accumulation is an independent and early risk factor for the occurrence and recurrence of stone episodes. Subcutaneous fat could be a convenient and effective indicator to assess the risk of stone episodes before the development of metabolic disorders.

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 Relationship Between Nephrolithiasis Risk with Body Fat Measured by Body Composition Analyzer in Obese People

BACKGROUND

Nephrolithiasis (kidney stones) continues to be a major cause of morbidity and healthcare spending that visceral and subcutaneous adipose tissue may associate with kidney stone formation. This study aimed to investigate the relationship between nephrolithiasis with visceral fat scale in obese people in Western Iran for the first time.

MATERIALS AND METHODS

In 2017, 103 participants with BMI≥30 kg/m² were selected for the present study. The participants were divided into two groups, 52 as case group (having the kidney stone) and 58 as healthy control group (no kidney stone or history of the kidney stone or any other disease). The levels of body composition were checked by body composition analyzer (BoCA x1) based on Bio Impedance mechanism.

RESULTS

Two groups were matched in terms of sex and BMI. There was a significant difference between two groups for the visceral fat to subcutaneous fat ratio (VSR) that accordingly, the mean VSR in the case group was higher than the control group. The difference for other variables between two groups was not significant.

CONCLUSIONS

The results showed that visceral and subcutaneous fat and VSR were important risk factors for kidney stone formation (nephrolithiasis). Evaluating these fats in stone formers may facilitate a tailored metabolic evaluation and treatment plan.

Arsenic and Obesity: A Comparison of Urine Dilution Adjustment Methods

INTRODUCTION

A commonly used approach to adjust for urine dilution in analyses of biomarkers is to adjust for urinary creatinine. However, creatinine is a product of muscle mass and is therefore associated with body mass. In studies of urinary analytes and obesity or obesity-related outcomes, controlling for creatinine could induce collider stratification bias. We illustrate this phenomenon with an analysis of urinary arsenic.

OBJECTIVE

We aimed to evaluate various approaches of adjustment for urinary dilution on the associations between urinary arsenic concentration and measures of obesity.

METHODS

Using data from the National Health and Nutrition Examination Survey, we regressed body mass index (BMI) and waist-to-height ratios on urinary arsenic concentrations. We compared eight approaches to account for urine dilution, including standardization by urinary creatinine, osmolality, and flow rates, and inclusion of these metrics as independent covariates. We also used a recently proposed method known as covariate-adjusted standardization.

RESULTS

Inverse associations between urinary arsenic concentration with BMI and waist-to-height ratio were observed when either creatinine or osmolality were used to standardize or as covariates. Not adjusting for dilution, standardizing or adjusting for urinary flow rate, and using covariate-adjusted standardization resulted in null associations observed between arsenic concentration in relation to BMI and waist-to-height ratio.

CONCLUSIONS

Our findings suggest that arsenic exposure is not associated with obesity, and that urinary creatinine and osmolality may be colliders on the causal pathway from arsenic exposure to obesity, as common descendants of hydration and body composition. In studies of urinary biomarkers and obesity or obesity-related outcomes, alternative metrics such as urinary flow rate or analytic strategies such as covariate-adjusted standardization should be considered. https://doi.org/10.1289/EHP1202.