The Impact of Obesity on Urine Composition and Nephrolithiasis Management

Method development with high-throughput enhanced matrix removal followed by UHPLC-QqQ-MS/MS for analysis of grape polyphenol metabolites in human urine

Grape and grape derived products contain many bioactive phenolics which have a variety of impacts on health. Following oral ingestion, the phenolic compounds and their metabolites may be detectable in human urine. However, developing a reliable method for the analysis of phenolic compounds in urine is challenging. In this work, we developed and validated a new high-throughput, sensitive and reproducible analytical method for the simultaneous analysis of 31 grape phenolic compounds and metabolites using Oasis PRiME HLB cleanup for sample preparation combined with ultra-performance liquid chromatography with triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). Using this new method, the accuracy achieved was 69.3 % ∼ 134.9 % (except for six compounds), and the recovery achieved was 52.4 % ∼ 134.7 % (except for two very polar compounds). For each of the 31 target analytes, the value of intra-day precision was less than 14.3 %. The value of inter-day precision was slightly higher than intra-day precision, with a range of 0.7 % ∼ 19.1 %. We report for the first time on the effect of gender and BMI on the accuracy and recovery of human urine samples, and results from analysis of variance (ANOVA), and principal component analysis (PCA) indicated there was no difference in the value of accuracy and recovery between different gender or BMI (>30) using our purposed cleanup and UHPLC-QqQ-MS/MS method. Overall, this newly developed method could serve as a powerful tool for analyzing grape phenolic compounds and metabolites in human urine samples.

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.

Effect of Two Different Dietary Weight Loss Strategies on Risk Factors for Urinary Stone Formation and Cardiometabolic Risk Profile in Overweight Women

Overweight has been suggested to increase the risk of kidney stone formation. Although weight reduction might affect risk factors for urolithiasis, findings on the impact of different dietary weight loss strategies are limited. This randomized, controlled study evaluated the effect of a conventional energy-restricted modified diet with (MR group) or without meal replacement (C group) on risk factors for stone formation in overweight women without a history of urolithiasis. Of 105 participants, 78 were included into the per-protocol analysis. Anthropometric, clinical, biochemical, and 24 h urinary parameters were collected at baseline and after 12 weeks. Although both dietary interventions resulted in a significant weight reduction, relative weight loss and rate of responders were higher in the MR group. Weight loss improved cardiometabolic risk profile in both groups. Unfortunately, the benefit of decreased GPT activity in the C group was offset by a significant increase in homocysteine and a decline in GFR. While the relative supersaturation of calcium oxalate decreased significantly in both groups, a significant decline in serum uric acid concentration and relative supersaturation of uric acid was observed only in the MR group. Finally, the energy-restricted modified diet with meal replacement showed significant advantages over the energy-restricted modified diet alone.

Role of insulin resistance and the gut microbiome on urine oxalate excretion in ob/ob mice

Ob/ob mice have recently emerged as a model for obesity-related hyperoxaluria as they are obese and excrete more urine oxalate compared to wild type mice. Ob/ob mice are deficient of leptin and develop obesity with hyperphagia and hyperinsulinemia. We hypothesized that insulin resistance and the gut microbiome contribute to hyperoxaluria in ob/ob mice. We developed a new liquid chromatography-mass spectrometry assay for urine oxalate and first compared urine oxalate excretion in ob/ob mice before and after ablation of intestinal bacteria with a standard antibiotic cocktail. We then compared urine oxalate excretion in ob/ob mice before and after leptin replacement or pioglitazone treatment, two maneuvers that reduce insulin resistance in ob/ob mice. Ob/ob mice excreted more oxalate into the urine in a 24-h period compared to wild type mice, but antibiotic, leptin, or pioglitazone treatment did not change urine oxalate excretion in ob/ob mice. Unexpectedly, we found that when food intake was carefully matched between ob/ob and wild type mice, the amount of 24-h urine oxalate excretion did not differ between the two mouse strains, suggesting that ob/ob mice excrete more urine oxalate because of hyperphagia. Since the level of urine oxalate excretion in wild type mice in our study was higher than those reported in prior studies, future work will be needed to standardize the measurement of urine oxalate and to define the range of urine oxalate excretion in wild type mice so that accurate and valid comparisons can be made between wild type mice and ob/ob mice or other mouse models.

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.

Association between hyperlipidemia and calcium oxalate lower urinary tract uroliths in dogs

Background

Metabolic syndrome is associated with formation of calcium oxalate (CaOx) uroliths in humans.

Objectives

To investigate the association between obesity and hyperlipidemia with CaOx lower urinary tract uroliths in client‐owned dogs.

Animals

Dogs with (n = 55, U [uroliths]‐dogs) and without (n = 39, UF [uroliths‐free]‐dogs) CaOx lower urinary tract uroliths.

Methods

Case‐control study. U‐dogs were retrospectively enrolled and compared to UF‐dogs. Body condition score (BCS; 1‐9 scoring scale), serum triglyceride (TG) and total cholesterol (CH) concentrations and glycemia (after >12‐hour food withholding) were recorded in both groups.

Results

On univariate logistic regression, when excluding Miniature Schnauzers, odds of having uroliths increased by a factor of 3.32 (95% CI 1.38‐11.12) for each mmol/L of TG (P = .027), of 39 (95% CI 9.27‐293.22) for each mmol/L of glycemia (P < .0001), and of 2.43 (95% CI 1.45‐4.45) per unit of BCS (P = .002). In multivariable models, the effect of TG was retained when all breeds were included for analysis and odds of having uroliths increased by a factor of 4.34 per mmol/L of TG (95% CI 1.45‐19.99; P = .02).

Conclusions and Clinical Importance

Serum lipid screening in dogs diagnosed with CaOx uroliths might be recommended to improve their medical staging and management.

Association between hypertension and 24-h urine composition in adults without urolithiasis in China

PURPOSE

To explore the association between hypertension and 24-h urine composition in adults without urolithiasis in China.

MATERIALS AND METHODS

Blood test and 24-h urine analysis were performed on 958 non-stone formers in six cities to select eligible participants. Eligible participants were divided into hypertension group and non-hypertension group according to WHO guidelines. The 24-h urine compositions between two groups were compared using univariate and multivariate logistic regressions.

RESULTS

A total of 584 adults without urolithiasis were included in this analysis. Compared with non-hypertension group, hypertension group had significantly older age, higher BMI, higher prevalence of diabetes mellitus and higher levels of total cholesterol and LDL, but lower eCCr value, lower levels of serum creatinine and serum sodium (all P value < 0.05). In univariable comparisons, hypertension patients had significantly higher level of urine potassium (mean difference [MD] = - 3.89 mmol, 95% confidence interval [CI] - 7.37 to - 0.42, P = 0.014) but lower levels of urine creatinine (MD = 0.80 mmol, 95% CI 0.21-1.39, P = 0.004) and pH (MD = 0.12, 95% CI - 0.01 to 0.25, P = 0.033) than non-hypertension adults. However, no significant difference was found in all 24-h urinary components between two groups (all P value > 0.05) in multivariate Logistic regression analyses.

CONCLUSIONS

Our study demonstrated that hypertension did not independently influence the 24-h urine composition in adults without urolithiasis in China; however, we cannot make such an arbitrary conclusion that hypertension was not a risk factor for urolithiasis.

Investigation of Variations in the Human Urine Metabolome amongst European Populations: An Exploratory Search for Biomarkers of People at Risk-of-Poverty

SCOPE

According to Eurostat 2016, approximately 119 million European citizens live at-risk-of-poverty (ROP). This subpopulation is highly diverse by ethnicity, age, and culture in the different EU states, but they all have in common a low income that could represent an increased risk of nutrient deficiencies due to poor nutritional habits. This study aims to investigate the human urine metabolome in the search of common biomarkers representing dietary deficiencies amongst European populations at ROP.

METHODS AND RESULTS

2732 urine samples were collected from 1391 subjects across five different European countries, including the United Kingdom, Finland, Italy, Lithuania, and Serbia, and analyzed using ¹ H-NMR spectroscopy. The resulting urine metabolome data were explored according to study design factors including economic status, country, and gender.

CONCLUSION

Partitioning of the effects derived from the study design factors using ANOVA-simultaneous component analysis (ASCA) revealed that country and gender effects were responsible for most of the systematic variation. The effect of economic status was, as expected, much weaker than country and gender, but more pronounced in Lithuania than in other countries. Citrate and hippurate were among the most powerful ROP biomarkers. The possible relationship between these markers and nutritional deficiencies amongst the ROP population is discussed.

Obesity and metabolic stone disease

PURPOSE OF REVIEW

In this article, we aim to review the data regarding associations between obesity and nephrolithiasis to assist with workup and treatment of these intersecting disorders. As obesity has a multifactorial influence on the risk for urinary stone disease, the complicated mechanisms will be discussed to improve diagnosis and management.

RECENT FINDINGS

Obesity and metabolic syndrome interact with nephrolithiasis risk factors to produce a myriad of bodily responses that induce stone formation. For this reason, many societies recommend prompt metabolic workup to evaluate the precise causes of stone formation. Data have shown that dietary and directed medical therapies can produce an excellent therapeutic response in this patient population, although the response may be blunted compared with nonobese patients.

SUMMARY

Given the increasing number of obese and overweight patients, the urologist should be familiar with the pathophysiology, workup, and treatment of metabolic stone disease in this population, which are outlined here.

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.

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.

Efficacy and safety of mini percutaneous nephrolithotomy in obese patients

Purpose

We aimed to evaluate the effect of obesity on surgical outcomes of mini percutaneous nephrolithotomy (Mini-PNL).

Methods

Hundred and eighty two Mini-PNL procedures were performed between May 2013 and January 2015 and their results were evaluated retrospectively. Patients were classified as non-obese (BMI, 18.5–30 kg/m²) and obese (≥30 kg/m²) groups. Obese and non-obese patients were compared according to pre-operative demographic values, intra-operative surgery techniques and post-operative results.

Results

BMI values of 133 patients were lower than 30 kg/m² while 49 patient’s BMI values were higher than 30 kg/m². There were no significant difference between operation time, fluoroscopy time, number of access and access sites when two groups were compared. No significant difference was found in total length of hospital stay, hemoglobin drop, and complication rates. Stone-free rates were 70.7 % in the non-obese and 71.4 % in the obese group (p = 0.9).

Conclusions

Mini-PNL procedure is a safe and effective treatment modality, which should be strongly considered for obese patients with appropriate sized stones.

Nomogram to predict uric acid kidney stones based on patient's age, BMI and 24-hour urine profiles: A multicentre validation

INTRODUCTION

We performed a multicentre validation of a nomogram to predict uric acid kidney stones in two populations.

METHODS

We reviewed the kidney stone database of two institutions, searching for patients with kidney stones who had stone composition analysis and 24-hour urine collection from January 2010 to December 2013. A nomogram to predict uric acid kidneys stones based on patient age, body mass index (BMI), and 24-hour urine collection was tested. Receiver-operating curves (ROC) were performed.

RESULTS

We identified 445 patients, 355 from Cleveland, United States, and 90 from Sao Paulo, Brazil. Uric acid stone formers were 7.9% and 8.9%, respectively. Uric acid patients had a significantly higher age and BMI, as well as significant lower urinary calcium than calcium stone formers in both populations. Uric acid had significantly higher total points when scored according to the nomogram. ROC curves showed an area under the curve of 0.8 for Cleveland and 0.92 for Sao Paulo. The cutoff value that provided the highest sensitivity and specificity was 179 points and 192 for Cleveland and Sao Paulo, respectively. Using 180 points as a cutoff provided a sensitivity and specificity of 87.5% and 68% for Cleveland, and 100% and 42% for Sao Paulo. Higher cutoffs were associated with higher specificity. The main limitation of this study is that only patients from high volume hospitals with uric acid or calcium stones were included.

CONCLUSION

Predicting uric acid kidneys stone based on a nomogram, which includes only demographic data and 24-hour urine parameters, is feasible with a high degree of accuracy.

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

The objective of this study was to identify the independent effect of visceral fat on urine constituent excretion in a stone forming population. Using a database of 382 kidney stone patients with available visceral fat quantification, we created multiple linear regression models predicting changes in urinary solutes based on visceral fat area and body mass-index, divided by gender. Chi-square tests were used to compare stone composition by body mass-index and visceral fat area. Visceral fat predicts increases in urinary creatinine, sodium, and volume in men, but only urinary phosphate in women. In women, total body mass-index does not appear to modify this effect, but in men it is more pronounced in overweight patients for creatinine and volume only. Elevated visceral fat is associated with increased probability of uric acid stone composition. Different fat compartments likely effect urine composition in different ways. This effect appears to be different in men and women. Understanding and quantifying the effects of different fat compartments is probably important to understanding the metabolism of urolithiasis.

Distinguishing characteristics of idiopathic calcium oxalate kidney stone formers with low amounts of Randall's plaque

BACKGROUND

Overgrowth of calcium oxalate on Randall's plaque is a mechanism of stone formation among idiopathic calcium oxalate stone-formers (ICSFs). It is less clear how stones form when there is little or no plaque.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Participants were a consecutive cohort of ICSFs who underwent percutaneous nephroscopic papillary mapping in the kidney or kidneys containing symptomatic stones and a papillary tip biopsy from a representative calyx during a stone removal procedure between 2009 and 2013. The distribution of Randall's plaque coverage was analyzed and used to divide ICSFs into those with a high (≥5%; mean, 10.5%; n=10) versus low (<5%; mean, 1.5%; n=32) amount of plaque coverage per papilla. Demographic and laboratory features were compared between these two groups.

RESULTS

Low-plaque stone formers tended to be obese (50% versus 10%; P=0.03) and have a history of urinary tract infection (34% versus 0%; P=0.04). They were less likely to have multiple prior stone events (22% versus 80%; P=0.002) and had a lower mean 24-hour urine calcium excretion (187±86 mg versus 291±99 mg; P<0.01). Morphologically, stones from patients with low amounts of plaque lacked a calcium phosphate core by microcomputed tomography. Papillary biopsies from low plaque stone-formers revealed less interstitial and basement membrane punctate crystallization.

CONCLUSIONS

These findings suggest that other pathways independent of Randall's plaque may contribute to stone pathogenesis among a subgroup of ICSFs who harbor low amounts of plaque.

The impact of obesity on the presentation of primary hyperparathyroidism

CONTEXT

Obesity has been associated with elevated serum PTH (sPTH) in the general population. Obesity may also alter the clinical presentation in patients with primary hyperparathyroidism (PHPT).

OBJECTIVES

The objectives of the study were to compare the clinical presentation of obese (OB) vs nonobese (NO) PHPT patients and to assess the impact of obesity on the presentation of PHPT independent of serum calcium and PTH.

PATIENTS

Consecutive PHPT patients who underwent parathyroidectomy between 2003 and 2012 by a single surgical group participated in the study.

SETTING

The study was conducted at an academic medical center.

DESIGN

Cross-sectional review of records of preoperative demographic, historical, laboratory, and densitometry findings and intraoperative pathological findings were compared in OB vs NO patients.

MAIN OUTCOME MEASURES

The prevalence of nephrolithiasis and osteoporosis was measured.

RESULTS

Two hundred forty-seven PHPT patients were included in this analysis. Fifty percent were OB and 79% were women. Mean body mass index was 25.3 ± 3.3 and 36.0 ± 5.2 kg/m(2) in the NO and OB groups, respectively. Age, gender, and race distribution was similar between the two groups. Serum calcium was similar between the groups (11.0 ± 0.7 mg/dL in NO vs 11.1 ± 0.9 mg/dL in OB, P = .13), whereas sPTH was higher in OB (151 ± 70 vs 136 ± 69 pg/mL, P = .03). The OB group exhibited higher prevalence of hypercalciuria (urine calcium > 400 mg per 24 h) (41% vs 23% in NO, P = .01) and nephrolithiasis (36% vs 21% in NO, P = .03). Despite higher sPTH, OB patients showed higher bone mineral density and a lower rate of osteoporosis (21% vs 35%, P = .05). Differences in the prevalence of hypercalciuria and osteoporosis between the groups persisted after adjustment for age, race, estimated glomerular filtration rate, gender, sPTH, and calcium.

CONCLUSIONS

In PHPT patients, obesity is a risk factor for hypercalciuria and nephrolithiasis and is protective against osteoporosis. The impact of parathyroidectomy on the clinical features of obese PHPT patients merits further evaluation.

Does body mass index effect the success of percutaneous nephrolithotomy?

OBJECTIVE

In obese patients, the management of renal calculi presents a number of challenges for urologists. In this study, we aimed to evaluate the efficacy and safety of percutaneous nephrolithotomy (PNL) procedure in obese and morbidly obese patients.

MATERIAL AND METHODS

We retrospectively reviewed the medical files of 2360 patients treated with PNL between March 2002 and April 2013. The patients were stratified into four groups according to the World Health Organization (WHO) classification of body mass index (BMI): <25 kg/m(2) (average), 25-29.9 kg/m(2) (overweight), 30-39.9 kg/m(2) (obese), and >40 kg/m(2) (morbidly obese). Patients under 18 years of age and those with a body mass index under 18 kg/m(2) were excluded from the study. Intra-, and postoperative outcomes of PNL were compared between groups.

RESULTS

A total of 2102 patients with a mean age of 43±13.62 years were enrolled in the study. The mean stone size, mean number of stones, staghorn stone rate and history of previous shock wave lithotripsy were similar in all groups. The overall stone-free rate was 82 percent. The mean operation time was longer in the morbidly obese group but it was not significantly different from that in the other groups. No differences were observed in hospital stay, complication or stone-free rate among four study groups.

CONCLUSION

Percutaneous nephrolithotomy is a safe and effective treatment for renal stone disease. Body mass index does not affect the success or complication rate in PNL.

Twenty-five years of idiopathic calcium nephrolithiasis: has anything changed?

Idiopathic calcium nephrolithiasis (ICN) is a disease whose prevalence is rising. Our aim was to assess whether lifestyle indicators and habits of calcium stone formers in Italy have changed over the last 25 years, trying to establish a connection with the diffusion of Internet access. Therefore we examined the database of the Stone Clinic of Parma University Hospital and extracted 1952 (1192 M, 760 F) patients with ICN who underwent a full clinical and laboratory evaluation from 1986 to 2010. Laboratory evaluation included data on urinary 24-h volume, pH, sodium, potassium, chloride, calcium, phosphate, uric acid, magnesium, oxalate, and citrate. Patients were split in three groups on a chronological basis, according to official EUROSTAT-ISTAT data of Internet connection among families in Italy: Group 1, pre-Internet era (1986–1998, 853 patients); Group 2, narrow-band era (1999–2004, 467 patients); Group 3, broad-band era (2005–2010, 632 patients). Over the time we found a significant increase in water intake (1.37 vs. 1.78 L in men and 1.21 vs. 1.55 L in women, Group 1 vs. Group 3, p-trend<0.001) and a decrease in urinary sodium and chloride for both genders and calcium and magnesium only for males, while females experienced a slight increase in oxalate excretion. Supersaturation indexes for calcium and uric acid stones dramatically fell for both genders. The percentage of stone formers performing physical activity significantly rise (41% Group 3 vs. 8% Group 1, p<0.001) and we also found a trend of reduction in mean blood pressure. Therefore, the lifestyle of Italian idiopathic calcium stone formers has changed over the last 25 years, and the rising Internet access may have played a great role in driving this change.

Dyslipidemia and kidney stone risk

PURPOSE

We studied the impact of dyslipidemia on 24-hour urinalysis and stone composition.

MATERIALS AND METHODS

We retrospectively identified patients with nephrolithiasis who underwent 24-hour urinalysis and lipid profile evaluation within 3 months. Patients were divided into groups based on total cholesterol, high density lipoprotein, nonhigh density lipoprotein and triglycerides. The groups were compared based on demographic data, diabetes, hypertension and each component of 24-hour urinalysis and stone composition. Multivariate analysis and linear regression were performed to control for potential confounders, including age, gender, body mass index, diabetes and hypertension.

RESULTS

A total of 2,442 patients with a mean age of 51.1 years were included in study. On multivariate analysis patients with high total cholesterol had significantly higher urinary potassium and calcium, those with low high density lipoprotein or high triglycerides had significantly higher urinary sodium, oxalate and uric acid with lower pH, and those with high nonhigh density lipoprotein had higher urinary sodium and uric acid. Regarding stone composition, high total cholesterol and triglycerides were significantly associated with a higher uric acid stone rate (p = 0.006 and <0.001, respectively). Linear regression showed a significant association of nonhigh density lipoprotein with higher urinary sodium (p = 0.011) and uric acid (p <0.001) as well as triglycerides and higher uric acid (p = 0.017), and lower urinary pH (p = 0.005).

CONCLUSIONS

There is a link between dyslipidemia and kidney stone risk that is independent of other components of metabolic syndrome such as diabetes and obesity. Specific alterations in the patient lipid profiles may portend unique aberrations in urine physicochemistry and stone risk.