Renal stone disease and obesity: what is important for urologists and nephrologists?

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.

Visceral Adiposity and Its Impact on Nephrolithiasis: A Narrative Review

Kidney stones represent a serious medical problem, resulting from several factors such as diet, genetics, and certain medical conditions. Visceral adipose tissue has been shown in recent research to play a significant role in kidney stone formation, making it a more precise indicator than traditional obesity indicators such as body mass index. The main aim of this review is to summarize studies on visceral obesity as a predictive marker for nephrolithiasis and to highlight new mechanistic pathways such as adipokine-mediated inflammation and its impact on kidney stone formation. This review emphasizes the importance of considering visceral fat in the prevention and management of kidney stones, suggesting that targeted strategies to reduce visceral fat could decrease the incidence of kidney stones and their management costs. Further prospective studies are needed to validate these findings and propose preventive strategies based on visceral adiposity assessments.

Refractory uric acid nephrolithiasis dissolution using phentermine/topiramate: A case report

Uric acid is one of the few kidney stone minerals that can dissolve using oral alkalinization therapies such as potassium citrate. We report an obese female whose recalcitrant uric acid stones were eliminated using the weight loss medication phentermine/topiramate (Qsymia), a metabolic stimulant and carbonic anhydrase inhibitor. Pre- and post-dissolution 24-h urine studies and computed tomography images are included with a proposed mechanism of action of this medication. This is the first description of a non-alkaline oral therapy used alone for uric acid stone dissolution. Additional investigation of this medication in obese or diabetic uric acid stone formers is warranted.

Towards an adiposity-related disease framework for the diagnosis and management of obesities

Obesity is a complex disease that relapses frequently and associates with multiple complications that comprise a worldwide health priority because of its rising prevalence and association with numerous complications, including metabolic disorders, mechanic pathologies, and cancer, among others. Noteworthy, excess adiposity is accompanied by chronic inflammation, oxidative stress, insulin resistance, and subsequent organ dysfunction. This dysfunctional adipose tissue is initially stored in the visceral depot, overflowing subsequently to produce lipotoxicity in ectopic depots like liver, heart, muscle, and pancreas, among others. People living with obesity need a diagnostic approach that considers an exhaustive pathophysiology and complications assessment. Thus, it is essential to warrant a holistic diagnosis and management that guarantees an adequate health status, and quality of life. The present review summarizes the different complications associated with obesity, at the same time, we aim to fostering a novel framework that enhances a patient-centered approach to obesity management in the precision medicine era.

The effect of nutritional factors on urolithiasis: A case-control study

Urolithiasis, a prevalent chronic kidney disease affecting all age groups, can be influenced by nutritional factors. The incidence of urolithiasis in Asian countries ranges from 1% to 19.1%, attributed to geographical and lifestyle differences. In Iran, several risk factors, including ethnicity, dietary habits, gender, and age, are associated with urolithiasis. This study aimed to assess the impact of nutritional factors on kidney and urinary tract stone formation. This case-control study enrolled 127 newly diagnosed urolithiasis patients, and 127 matched healthy participants between February to May 2017. Exclusion criteria included diabetes and acute or chronic renal failure. Data were collected using the Food Frequency Questionnaire (FFQ) and analyzed using chi-square and logistic regression tests. Water (95% CI: 0.09-0.89, OR=0.28), natural juices (95% CI: 0.10-0.65, OR=0.53), mineral water (95% CI: 0.05-0.64, OR=0.18), legumes (95% CI: 0.00-0.38, OR=0.032), butter, cream, or peppermint (95% CI: 0.09-0.95, OR=0.30), and ice cream (95% CI: 0.07-0.54, OR=0.203) had a significant protective effect against kidney and urinary tract stone formation. Conversely, tea consumption (95% CI: 1.15-7.99, OR=4.70), beverages (95% CI: 4.45-23.32, OR=23.32), coffee (95% CI: 1.63-11.78, OR=4.39), bread (95% CI: 1.1-10.59, OR=3.37), meat (95% CI: 1.01-8.01, OR=2.85), liver (95% CI: 3.37-488.90, OR=40.58), fish (95% CI: 2.89-216.39, OR=25.03), and various canned foods (95% CI: 1.34-10.25, OR=3.70) were significantly associated with kidney and urinary tract stone risk. These findings showed that the risk of urinary stones formation had a significant relationship with dietary habits. Therefore, the correct dietary pattern and sufficient fluid consumption may play an important role in 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.

Anti-Obesity Medications and Investigational Agents: An Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) 2022

Background

This "Anti-Obesity Medications and Investigational Agents: An Obesity Medicine Association Clinical Practice Statement 2022" is intended to provide clinicians an overview of Food and Drug Administration (FDA) approved anti-obesity medications and investigational anti-obesity agents in development.

Methods

The scientific information for this Clinical Practice Statement (CPS) is based upon published scientific citations, clinical perspectives of OMA authors, and peer review by the Obesity Medicine Association leadership.

Results

This CPS describes pharmacokinetic principles applicable to those with obesity, and discusses the efficacy and safety of anti-obesity medications [e.g., phentermine, semaglutide, liraglutide, phentermine/topiramate, naltrexone/bupropion, and orlistat, as well as non-systemic superabsorbent oral hydrogel particles (which is technically classified as a medical device)]. Other medications discussed include setmelanotide, metreleptin, and lisdexamfetamine dimesylate. Data regarding the use of combination anti-obesity pharmacotherapy, as well as use of anti-obesity pharmacotherapy after bariatric surgery are limited; however, published data support such approaches. Finally, this CPS discusses investigational anti-obesity medications, with an emphasis on the mechanisms of action and summary of available clinical trial data regarding tirzepatide.

Conclusion

This "Anti-Obesity Medications and Investigational Agents: An Obesity Medicine Association Clinical Practice Statement 2022" is one of a series of OMA CPSs designed to assist clinicians in the care of patients with pre-obesity/obesity.

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.

Machine learning prediction of stone-free success in patients with urinary stone after treatment of shock wave lithotripsy

BACKGROUND

The aims of this study were to determine the predictive value of decision support analysis for the shock wave lithotripsy (SWL) success rate and to analyze the data obtained from patients who underwent SWL to assess the factors influencing the outcome by using machine learning methods.

METHODS

We retrospectively reviewed the medical records of 358 patients who underwent SWL for urinary stone (kidney and upper-ureter stone) between 2015 and 2018 and evaluated the possible prognostic features, including patient population characteristics, urinary stone characteristics on a non-contrast, computed tomographic image. We performed 80% training set and 20% test set for the predictions of success and mainly used decision tree-based machine learning algorithms, such as random forest (RF), extreme gradient boosting trees (XGBoost), and light gradient boosting method (LightGBM).

RESULTS

In machine learning analysis, the prediction accuracies for stone-free were 86.0, 87.5, and 87.9%, and those for one-session success were 78.0, 77.4, and 77.0% using RF, XGBoost, and LightGBM, respectively. In predictions for stone-free, LightGBM yielded the best accuracy and RF yielded the best one in those for one-session success among those methods. The sensitivity and specificity values for machine learning analytics are (0.74 to 0.78 and 0.92 to 0.93) for stone-free and (0.79 to 0.81 and 0.74 to 0.75) for one-session success, respectively. The area under curve (AUC) values for machine learning analytics are (0.84 to 0.85) for stone-free and (0.77 to 0.78) for one-session success and their 95% confidence intervals (CIs) are (0.730 to 0.933) and (0.673 to 0.866) in average of methods, respectively.

CONCLUSIONS

We applied a selected machine learning analysis to predict the result after treatment of SWL for urinary stone. About 88% accurate machine learning based predictive model was evaluated. The importance of machine learning algorithm can give matched insights to domain knowledge on effective and influential factors for SWL success outcomes.

Biochemical Alterations in Patients with Oxalocalcic Lithiasis, the Influence of Sex, Age, and Body Mass Index

Background: Urolithiasis is a disorder that has a high prevalence in the population. Also, lithiasic patients have biochemical alterations that predispose them to the formation of stones. The knowledge of these alterations may be useful for future preventive interventions. Objectives: The objectives were to describe the metabolic characteristics of patients with oxalocalcic lithiasis, identifying the most frequent biochemical alterations, and their variation with different demographic variables. In this way, we can prevent the formation of the lithiasis before it appears, instead of treating it once established. Methods: A descriptive cross-sectional study of serum and 24 hour-urine parameters in patients with oxalocalcic lithiasis was performed. The most frequent biochemical alterations were described, and their association with age, sex, and body mass index (BMI) were assessed. Results: In this study, 100% of the 151 patients had biochemical alterations, the most frequent being hypocitraturia (84.7%), hypercalciuria (51.7%), and urinary pH decrease (44.4%). There were differences according to sex, age, and BMI with regard to the biochemical alterations. Hypouricemia, hypouricosuria, hypophosphaturia and hypomagnesuria were more frequent in women. Men had a higher percentage of hyperzinquemia, hyperphosphaturia, and excess of urinary urea. Urine density in men was slightly higher than in women. A higher percentage of hyperphosphaturia, excess urinary urea, and excess of serum urea was found in overweight patients. Patients not overweight showed a higher percentage of hypouricemia and hypomagnesuria. Urinary density was slightly higher in overweight patients. Urinary volume was higher in middle-aged subjects. Conclusions: Patients with oxalocalcic lithiasis have biochemical alterations that may predispose to stone formation. These alterations vary with sex, age, and BMI.

Obesity and stones

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Adult obesity complications: challenges and clinical impact

The complications associated with adult obesity are overwhelming national healthcare systems. No country has yet implemented a successful population-level strategy to reverse the rising trends of obesity. This article presents epidemiological data on the complications of adult obesity and discusses some of the challenges associated with managing this disease at a population and individual level.

Increased body fatness adversely relates to 24-hour urine pH during childhood and adolescence: evidence of an adipo-renal axis

BACKGROUND

Reduced net acid excretion (NAE) capacity indicates a decrease in renal function. This reduction manifests as a disproportionally low 24-h urine pH in relation to the sum of actually excreted ammonium and titratable acidity by the kidney.

OBJECTIVE

The aim of this study was to test the hypothesis that higher body fatness is one determinant of kidney function impairment with a lowered urine pH even at a young age.

METHODS

NAE, pH, urea, and creatinine were measured in 24-h urine samples from 524 healthy children and adolescents (aged 6-17 y) participating in the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study. Body fatness was assessed anthropometrically by body mass index-standard deviation score (BMI-SDS), fat mass index (FMI), body fat % (BF%), and waist circumference (WC). Multivariable linear and mixed linear regressions were used to examine cross-sectionally (n = 524 urine samples; age groups: 6-8, 9-11, 12-14, 15-17 y) and longitudinally (n = 1999 urine samples) the associations of body fatness with 24-h urine pH as the outcome variable, respectively.

RESULTS

After adjusting for the kidneys' total net acid load (24-h urinary NAE) and further relevant covariates, FMI showed significant inverse relations with urinary pH in all 4 age groups, and BMI-SDS, BF%, and WC each in 3 out of these 4 groups (P ≤ 0.02). Longitudinal results substantiated these interindividual relations and further showed intraindividual increases in body fatness to be paralleled by urine pH decreases (P ≤ 0.0002).

CONCLUSIONS

Independent of underlying acid load, an early increase in body fatness is associated with increased free proton excretion, and thus with a decline in the kidney's acid excretion function, which could potentiate the risk of renal nephrolithiasis.

Dual-Source Dual-Energy CT in Detection and Characterization of Urinary Stones in Patients With Large Body Habitus: Observations in a Large Cohort

OBJECTIVE

The objective of our study was to investigate the impact of large body habitus on dual-energy CT (DECT) image quality and stone characterization.

MATERIALS AND METHODS

We retrospectively included 105 consecutive patients with large body habitus (> 90 kg) who underwent stone protocol DECT between 2015 and 2017. The evaluation of DECT datasets was performed for image quality assessment based on European Guidelines on Quality Criteria for Computed Tomography and for determination of stone composition (i.e., uric acid vs non-uric acid). Correlation between DECT characterization and crystallography results was performed when available. The cohort was divided into two groups on the basis of body weight (≤ 104 kg and > 104 kg), and comparisons were made for image quality and stone characterization.

RESULTS

One hundred ninety-seven urinary tract calculi (size: mean ± SD, 5.7 ± 5.3 mm; range, 1.4-56 mm) were detected in 73% (79/108) of examinations in 105 patients (weight: mean ± SD, 104.0 ± 12.7 kg; range, 91-163 kg). The overall mean image quality score of blended images and color maps was 3.7 and 3.9, respectively, and the effective dual-energy FOV limitation did not hamper stone characterization. The diagnostic acceptability scores of blended images and color maps were slightly lower in patients weighing > 104 kg than in patients ≤ 104 kg (mean scores [highest score, 4 points]: blended images, 3.62 vs 3.82 [p = 0.0314]; color maps, 3.75 vs 3.98 [p = 0.0034]), but the scores were within acceptable range. Stone characterization as uric acid versus non-uric acid was achieved in 80% (158/197) of calculi (size: mean ± SD, 6.4 ± 5.7 mm; range, 1.6-56 mm), and DECT stone characterization was (95.6%) accurate with reference to crystallography. Twenty percent (39/197) of calculi could not be characterized on DECT, and these calculi were significantly smaller in size (size: mean ± SD, 2.8 ± 1.4 mm; range, 1.4-8.2 mm; p < 0.001) than those that could be characterized. The mean size of uncharacterized calculi was slightly larger in patients weighing > 104 kg (3.3 ± 1.6 mm) than in those weighing ≤ 104 kg (2.2 ± 0.6 mm).

CONCLUSION

In patients with large body habitus, dual-source DECT provides acceptable image quality and allows characterization of almost all clinically significant calculi.

Body fatness, diabetes, physical activity and risk of kidney stones: a systematic review and meta-analysis of cohort studies

We conducted a systematic review and meta-analysis to clarify the association between adiposity, diabetes, and physical activity and the risk of kidney stones. PubMed and Embase were searched up to April 22nd 2018 for relevant studies. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using random effects models. Thirteen cohort studies were included. The summary relative risk was 1.21 (95% CI 1.12-1.30, I2 = 76%, n = 8) per 5 unit increment in BMI, 1.16 (95% CI 1.12-1.19, I2 = 0%, n = 5) per 10 cm increase in waist circumference, 1.06 (95% CI 1.04-1.08, I2 = 67%, n = 3) per 5 kg increase in weight and 1.12 (95% CI 1.06-1.18, I2 = 86%, n = 3) per 5 kg of weight gain. The summary RR was 1.16 (95% CI 1.03-1.31, I2 = 51%, n = 10) for participants with diabetes compared to participants without diabetes, and 0.93 (95% CI 0.78-1.10, I2 = 80%, n = 4) for high vs. low physical activity. These results suggest a positive association between adiposity and diabetes and the risk of kidney stones, but no association with physical activity.

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.

Nephrolithiasis in elderly population; effect of demographic characteristics

Background

Kidney stone (nephrolithiasis) is one of the most common diseases. During the past several decades, its prevalence and incidence have increased markedly in elderly population.

Objectives

This study was conducted to evaluate the risk factors for nephrolithiasis in elderly population.

Patients and Methods

This study was based on the Amirkola Health and Ageing Project (AHAP). Elderly people with kidney stones in every size, type and number were considered to be the case group and other subjects without a history of kidney stones served as control group. Demographic and anthropometric data, smoking, diabetes and metabolic syndrome (MetS), calcium (Ca), vitamin D, parathyroid hormone (PTH), uric acid and urine pH were compared in both groups.

Results

In this study, 1390 elderly people with the mean age of 69.37 ± 7.42 years were evaluated which 202 (14.53%) cases had renal stones. The patients with nephrolithiasis were younger (P = 0.010) and had higher uric acid and body mass index (BMI) levels (P = 0.041 and P = 0.006, respectively). Age <75 years, male gender and BMI ≥30 kg/m² had a significant association with stone formation. The prevalence of diabetes, MetS and smoking in the patients with nephrolithiasis was lower than the subjects without it.

Conclusions

This study suggests that male gender, obesity and age <75 years might be independent risk factors for the development of nephrolithiasis. Hence, low animal protein intake and weight reduction should be included as part of the counseling of senior stone-formers.

Urological Procedures in Urolithiasis and Their Association with Chronic Kidney Disease

BACKGROUND AND OBJECTIVES

Epidemiological evidence suggests that patients with urolithiasis are at increased risk for end-stage renal disease (ESRD). It is unclear if urological intervention impacts the progression of chronic kidney disease (CKD).

METHODS

We conducted a retrospective observational cohort study of patients in the Marshfield Epidemiologic Study Area database between January 1991 and May 2007, where 1,340 patients diagnosed with urolithiasis were extracted. Of the 1,340 subjects, 446 had urological procedures for management of urolithiasis. Those that underwent these procedures were compared to those that did not. Cox proportional hazards models adjusted for age, gender, and comorbidities were performed to evaluate the risk for CKD, elevated serum creatinine, and any-cause mortality.

RESULTS

Baseline comorbidities in patients with and without procedures were not significantly different except for obesity (P<0.0001). Subjects that underwent procedures were at increased risk for elevated serum creatinine (Hazard Ratio (HR) [95% CI] =1.49 [1.19-1.85]) when compared to those that did not undergo a urologic procedure during the study period. The results did not reveal a significant difference in incidence of CKD or any-cause mortality.

CONCLUSIONS

Patients who undergo urologic procedures are at increased risk for elevated creatinine. Urological procedures do not appear to impact incidence of CKD or mortality and, in fact, may prevent long-term renal dysfunction.

Influence of body mass index on pediatric urolithiasis

OBJECTIVE

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

METHODS

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

RESULTS

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

DISCUSSION

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

CONCLUSION

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

Latent association between low urine pH and low body weight in an apparently healthy population

Low urine pH, a plausible predictor for chronic kidney disease and metabolic disorders, is often observed in obese individuals. However, the association between low urine pH and low body weight is equivocal. We examined clinical parameters including urine pH and body mass index (BMI) in a cross-sectional study of 3629 apparently healthy Japanese adults aged 25-80 years who underwent a health-screening check-up. Urine pH was lower and the prevalence of proteinuria was significantly higher in subjects with BMI of ≥ 27.0 kg/m(2) compared with those with BMI of 21.0-22.9 kg/m(2). By contrast, hematuria was more prevalent in subjects with BMI of ≤ 20.9 kg/m(2). Logistic regression analysis showed that BMI of ≥ 27.0 kg/m(2) was significantly associated with low urine pH (≤ 5.5), which remained significant after adjustment for relevant confounders including age, sex, proteinuria, estimated glomerular filtration rate, urine density, hematuria, smoking status, and daily alcohol drinking. However, the association disappeared after further adjustment for serum uric acid. In contrast, the association between low urine pH and BMI of ≤ 19.0 kg/m(2) was significant after adjustment for age and sex and rather strengthened by the further adjustment for serum uric acid. In conclusion, low urine pH may be independently associated with low BMI. However, the underlying mechanisms of low urine pH in low body weight may differ from those in high body weight.

Shock wave lithotripsy does not impair renal function in a Swine model of metabolic syndrome

PURPOSE

To determine whether shock wave lithotripsy (SWL) may be a risk factor for renal functional impairment in a swine model of metabolic syndrome (MetS).

MATERIALS AND METHODS

Nine-month-old female Ossabaw pigs were fed an excess calorie atherogenic diet to induce MetS. At 15 months of age, the MetS pigs were treated with 2000 SWs or an overtreatment dose of 4000 SWs targeted at the upper pole calyx of the left kidney (24 kV at 120 SWs/min using the unmodified Dornier HM3 lithotripter; n=5-6 per treatment group). Serum creatinine (Cr) and blood urea nitrogen (BUN) levels were measured in conscious pigs before and ∼60 days after SWL to provide a qualitative assessment of how well both kidneys were filtering (glomerular filtration rate [GFR]). Bilateral renal function was assessed at ∼65 days post-SWL in anesthetized pigs with GFR and effective renal plasma flow (ERPF) quantified by the renal clearance of inulin and para-amino hippurate, respectively.

RESULTS

Cr and BUN values were within normal limits before SWL and remained unchanged after lithotripsy in both the 2000 SW- and 4000 SW-treated pigs. GFR and ERPF of kidneys treated with SWL at either SW dose were similar to the contralateral nontreated kidney. Chronic histological changes in the SW-treated pole of the kidney included interstitial fibrosis, sclerotic glomeruli, and dilated and atrophic tubules.

CONCLUSIONS

Our results are consistent with the view that a single SWL session does not result in renal impairment, even in the presence of MetS.

Analysis of 35 cases of Xanthogranulomatous pyelonephritis

BACKGROUND

To retrospectively determine key demographic and clinical features of 35 patients with Xanthogranulomatous pyelonephritis (XGP) in a New Zealand setting and to compare it with the existing literature.

METHODS

A retrospective review of patients having a confirmed diagnosis of XGP on histopathology examination was performed. Key clinical and demographic features were analysed and compared with the published literature.

RESULTS

XGP was diagnosed in 35 patients over a 12-year (2001-2013) period in Auckland Public Hospital. Ninety-one percent of the patients were female. The population had significantly higher numbers of Maori and Pacific Island patients compared with the general population (74%). Staghorn calculi were the most common cause (51.4%) with obstructing ureteric calculi as the next most common (22.9%) cause. Twenty percent of cases were not thought to be XGP prior to nephrectomy (suspicious renal mass). Thirteen (38%) patients suffered serious complications post-operatively (Clavien 3-5).

CONCLUSION

XGP is a rare chronic inflammatory condition that appears to be overrepresented by Maori and Pacific islanders in our cohort when compared with the overall patient pool. Surgical treatment is associated with significant morbidity but remains the only definitive option. Obesity and other conditions associated with metabolic syndrome may coexist at the time of presentation and may be contributing factors to the development of XGP and poor outcomes associated with it.

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.