Metabolic risk factors and the impact of medical therapy on the management of nephrolithiasis in obese patients

Fat Distribution and Urolithiasis Risk Parameters in Uric Acid Stone Formers and Patients with Type 2 Diabetes Mellitus

Key Points

Background

Uric acid (UA) nephrolithiasis affects approximately 10% of kidney stones, with a greater preponderance among patients with obesity and diabetes mellitus (DM). UA lithogenicity is driven by abnormally acidic urine pH. Distinguishing the contribution of intrinsic (e.g., body adiposity) versus external (e.g., dietary) factors to UA stone propensity is challenging because of uncontrolled diets in outpatients in previously published studies.

Methods

This compilation of metabolic studies with body composition examined by dual-energy x-ray absorptiometry scan and blood and urine biochemistry collected under a controlled metabolic diet was conducted across three distinct populations: 74 UA stone formers (UASF group), 13 patients with type 2 DM without kidney stones (DM group), and 51 healthy volunteers (HV group).

Results

Compared with HVs, both UASFs and patients with DM exhibited higher levels of net acid excretion (NAE) and significantly lower urine pH and lower proportion of NAE excreted as ammonium (NH4 +/NAE), all under controlled diets. UASFs exhibited significantly lower NH4 +/NAE compared with patients with DM. UASFs also showed higher total body and truncal fat compared with HVs. Among the HVs, lower NH4 +/NAE ratio correlated with higher truncal and total fat. However, this association was abolished in the UASF and DM groups who exhibit a fixed low NH4 +/NAE ratio across a range of body and truncal fat.

Conclusions

The findings suggest a dual defect of diet-independent increase in acid production and impaired kidney NH4 + excretion as major contributors to the risk of UA stone formation. There is an inverse physiologic association between body fat content and NH4 +/NAE in HVs, whereas NH4 +/NAE is persistently low in UASFs and patients with DM, regardless of body fat, representing pathophysiology.

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.

Comparison of safety and efficacy of different positions in percutaneous nephrolithotomy: a network meta-analysis

OBJECTIVES

Various new positions for percutaneous nephrolithotomy (PCNL) were proposed to reduce the limitations of the traditional position. This study was aimed to evaluate the efficacy and safety of the different PCNL positions.

METHODS

PubMed, Embase, Web of Science, and the Cochrane Library were searched for relevant randomized controlled trials (RCTs) up to 18 April 2023. The authors collected five common surgical positions used for PCNL: oblique supine position (OSP), supine position (SP), flank position (FP), split-leg oblique supine/flank position (SLP), and prone position (PP). Paired and network meta-analysis were conducted to compare relevant outcomes, including complications, operative time, stone-free rates, hospital stay, and hemoglobin loss among these different positions.

RESULTS

The study included 17 RCTs with a total of 1841 patients. The result demonstrated that SLP significantly outperformed in terms of decreasing operation time (FP vs SLP MD- MD-41.65; OSP vs SLP MD 28.97; PP vs SLP MD 34.94), hospital stay, and hemoglobin loss. Ranking probabilities showed SLP had highest stone-free rate. Prone position was more likely to occur complications than others. Based on SMAA model, the benefit-risk analysis suggested the SLP was the optimal position in PCNL.

CONCLUSIONS

For PCNL, the split-leg, flank, supine, and OSPs are as secure as the prone position. Further RCTs are necessary to confirm the outstanding safety and efficacy of split-leg position. Besides, the position should be selected regard for the patient's demands, the surgeon's preference and learning curve.

Effects of body mass index on urinary lithogenic factors in urinary system stone patients

AIM

Obesity and metabolic syndrome are becoming more prevalent these days. In addition, we know that urinary stone disease is also on the rise. In this study, we wanted to examine if body mass index (BMI) had a negative effect on the stone disease by evaluating 24-hour urinalysis in stone patients and recurrence rates in our region.

Ultrasound-guided percutaneous nephrolithotomy (PCNL) success rates in patients with elevated body mass index: a comparative study

Percutaneous nephrolithotomy (PCNL) is considered gold standard treatment of renal stones larger than 20 mm. Several studies have shown that ultrasound guidance during this procedure is more effective and safer than fluoroscopy. A higher body mass index (BMI) can make ultrasound-guided renal access more difficult and unsuccessful. We present a prospective analysis and comparison of ultrasound-guided PCNL in patients with normal and increased body mass index. We performed a prospective comparison of patients who underwent ultrasound-guided PCNL to remove renal stones by a single surgeon between 2020 and 2022. Patients with BMIs greater than 30 (mean 33.87-obese) were compared to those with BMIs less than 30 (mean 25.69-non-obese). Demographic, perioperative, and follow-up data were collected, analyzed, and included in this study. Total of 98 consecutive patients, with 49 patients in each group were analyzed. No statistically significant differences were observed in terms of stone volume (P = 0.085), stone density (P = 0.5590), location of renal access (P = 0.108), surgery duration (P = 0.38), blood loss (P = 0.54), or laboratory changes after surgery (P = 0.60). 87.76% of obese patients were stone free per CT scan at follow-up, compared to 73.47% of normal-weight patients (P = 0.1238). According to Clavien-Dindo classification, six patients in the non-obese group experienced grade II (10%) and grade III (2%) complications, as opposed to six patients in the obese group with grade I (2%), grade II (6%), and grade III (2%) complications. There was no significant correlation between body mass index and the success or safety of ultrasound-guided PCNL. Although more challenging, a higher BMI should not be an impediment to performing this approach. This method is safe, with no increased incidence of postoperative complications or compromise in stone-free status postoperatively and can diminish or avoid both patient's and medical team's exposure to ionizing radiation.

Analysis and prediction of postoperative recurrence of unilateral upper ureteral calculi in 243 cases (nomogram)

Objective: This study aimed to identify the risk factors for postoperative recurrence of unilateral upper ureteral calculi and develop a predictive nomogram. Patients and Methods: A retrospective analysis was conducted on 243 patients diagnosed with unilateral upper ureteral calculi who were treated at our hospital between January 1, 2016 and December 31, 2018. Patients were divided into two groups: recurrence or non-recurrence cohort. Differences in age, gender, smoking and/or drinking habit, laterality, stone diameter, ureteral stricture, stone incarceration, urinary tract infection, surgical intervention, operation time, body mass index, and metabolic syndrome were analyzed. Discrete risk factors were screened, and a nomogram was developed to predict the probability of stone recurrence. Results: The study found that the recurrence of ureteral calculi was associated with factors including stone diameter, ureteral stricture, stone incarceration, surgical intervention, operation time, metabolic syndrome, body mass index, triglycerides, diabetes, and high blood pressure (p < 0.05). Ureteral stricture, surgical intervention, metabolic syndrome, and triglycerides were found to be discrete risk factors for stone recurrence (p < 0.05). In addition, the study revealed that the stone recurrence rate of metabolic syndrome patients was significantly elevated (p < 0.05), as demonstrated by the survival curve. Lastly, using the nomogram, with an area under the curve value of 0.929, the recurrence rate of ureteral calculi was predicted. Conclusions: The study identified that preoperative ureteral stricture, laparoscopic ureterolithotomy, metabolic syndrome, and triglycerides are closely related to postoperative recurrence of ureteral calculi. The nomogram developed in this study can be used as a predictive tool for the recurrence rate of ureteral calculi.

The effectiveness of citrates and pyridoxine in the treatment of kidney stones

The prevalence of nephrolithiasis is increasing across all demographic groups. Apart from the morbidity associated with an acute occurrence, preventative treatment is essential for stone disease, which can become a long-term problem. Simple interventions like fluid intake optimization and dietary modification are effective for most stone types. However, patients with specific metabolic abnormalities may require pharmaceutical therapy if lifestyle changes are insufficient to reduce the risk of stone recurrence. The treatment of citrates and/or pyridoxines may help eliminate or prevent recurrences of kidney stones, especially when they are composed of uric acid, calcium oxalate, calcium phosphate, or the latter two together. In cases of struvite stones, which often necessitate a surgical approach, acetohydroxamic acid emerges as a valuable second-line treatment option. Thiol-binding agents may be needed for cystinuria, as well as lifestyle modifications. Successful treatment reduces stone recurrence and the need to remove stones surgically.

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.

Can we identify the risk factors for SIRS/sepsis after percutaneous nephrolithotomy? A meta‑analysis and literature review

With the increase in percutaneous interventions such as percutaneous nephrolithotomy (PCNL) for renal lithiasis, infectious complications are becoming more frequent. The present study performed a systematic Medline and Embase databases search, using the following words: 'PCNL' [MeSH Terms] AND ['sepsis' (All Fields) OR 'PCNL' (All Fields)] AND ['septic shock' (All Fields)] AND ['urosepsis' (MeSH Terms) OR 'Systemic inflammatory response syndrome (SIRS)' (All Fields)]. Because of the technological advances in endourology, articles published between 2012 and 2022 were searched. Of the 1,403 results of the search, only 18 articles, representing 7,507 patients in which PCNL was performed, met the criteria to be included in the analysis. All authors applied antibiotic prophylaxis to all patients and, in some cases, the infection was treated preoperatively in those with positive urine cultures. According to the analysis of the present study, the operative time has been significantly longer in patients who developed SIRS/sepsis post-operatively (P=0.0001) with the highest heterogeneity (I²=91%) compared with other factors. Patients with a positive preoperative urine culture had a significantly higher risk of developing SIRS/sepsis following PCNL (P=0.00001), OD=2.92 (1.82, 4.68) and there was also a high degree of heterogeneity (I²=80%). Performing a multi-tract PCNL also increased the incidence of postoperative SIRS/sepsis (P=0.00001), OD=2.64 (1.78, 3.93) and the heterogeneity was a little smaller (I²=67%). Diabetes mellitus (P=0.004), OD=1.50 (1.14, 1.98), I²=27% and preoperative pyuria (P=0.002), OD=1.75 (1.23, 2.49), I²=20%, were other factors that significantly influenced postoperative evolution. A total of two factors analyzed, body mass index and patient's age, did not influence the outcome, P=0.45, I²=58% and P=0.98, I²=63%.

Fluid intake recommendations in urolithiasis and general advice to patients without metabolic risk factors

Urolithiasis is a highly prevalent global disease with substantially increasing incidence in the last two decades. Data from the literature suggests that 26%-50% of patients will have a recurrence within 10 years after an initial symptomatic stone episode. Therefore, interest has been raised in preventive strategies, aiming to modify the risk factors of stone recurrence by implementing dietary and lifestyle changes and specific medical treatments for stone formers, depending on their recurrence risk factors. Certain dietary factors are thought to contribute significantly to the increased incidence of urolithiasis, particularly a diet low in fiber and high in animal protein, fat, and sodium. Fluid intake is perhaps the most important and modifiable step in the prevention of urolithiasis, irrespective of stone composition. However, the amount of fluid to be consumed and the implications of various fluid types on stone formation are still controversial. In this article, the relationship between fluid intake, beverage types and stone formation-prevention will be discussed. Moreover, general dietary recommendations for patients without metabolic risk factors will be reviewed based on the current literature.

Urinary Risk Profile, Impact of Diet, and Risk of Calcium Oxalate Urolithiasis in Idiopathic Uric Acid Stone Disease

The role of diet in the pathogenesis of uric acid (UA) nephrolithiasis is incompletely understood. This study investigated the effect of dietary intervention on the risk of UA stone formation under standardized conditions. Twenty patients with idiopathic UA stone disease were included in the study. Dietary intake and 24 h urinary parameters were collected on the usual diet of the patients and a standardized balanced mixed diet. Although urinary UA excretion did not change, the relative supersaturation of UA decreased significantly by 47% under the balanced diet primarily due to the significant increase in urine volume and pH. Urinary pH was below 5.8 in 85% of patients under the usual diet, and in 60% of patients under the balanced diet. The supersaturation of calcium oxalate declined significantly under the balanced diet due to the significant decrease in urinary calcium and oxalate excretion and the increase in urine volume. Dietary intervention is a key component in the management of UA nephrolithiasis. Urinary calcium and oxalate excretion should also be monitored in patients with pure UA calculi to reduce the risk of mixed stone formation with calcium oxalate. Lower urinary pH in UA stone patients can only be partially explained by diet.

Dietary weight loss strategies for kidney stone patients

PURPOSE

Overweight has been associated with an increased risk of incident and recurrent kidney stone disease. Weight reduction is the therapeutic consequence to decrease the risk of stone formation. This review examines the effectiveness of different weight loss strategies on weight reduction and cardiometabolic risk profile, with a particular focus on risk factors for urolithiasis.

METHODS

A selective literature search was performed using PubMed and Cochrane library.

RESULTS

Clinical evidence for the potential benefits of dietary weight loss strategies for kidney stone disease is limited. A conventional, energy-restricted diet may significantly induce weight loss and reduce urinary supersaturation of calcium oxalate in overweight individuals with or without a history of stone formation. The current data indicate that an energy-restricted diet with partial meal replacement may additionally decrease the relative supersaturation of uric acid and further improve the cardiometabolic risk profile, and, thus, may be a favourable option for overweight kidney stone patients. Studies on the Mediterranean and DASH diets on the association between weight loss and the risk of urinary stone formation are lacking.

CONCLUSION

An energy-restricted diet with or without meal replacement could be a promising weight loss strategy for overweight kidney stone patients. Further studies are needed to evaluate the impact of different weight loss strategies on urinary risk factors and cardiometabolic risk profile in urolithiasis.

Kidney stones among Iranian adults: Prevalence and socioeconomic inequality assessment in a cohort-based cross-sectional study

Background and Aims

Kidney stone disease is a crystal concretion formed usually within the kidneys. The worldwide prevalence of kidney stones could be affected by numerous differences in socioeconomic, and environmental factors. The purpose of this study is to investigate kidney stones among Iranian adults aged between 35 and 70 years and the prevalence and evaluation of socioeconomic inequalities.

Methods

In this, a cohort-based cross-sectional study was carried out among 20,427 participants of ArNCDs aged 35 and 70 years old. Kidney stone was defined as a dependent (and binary) variable while demographic and socioeconomic factors were considered independent variables. Multivariable logistic regression was used to identify the key socioeconomic factors affecting kidney stone prevalence in Ardabil.

Results

The overall prevalence of kidney stones was 17.6 (95% confidence interval [CI]: 16.1-19.2) out of which 21.53% and 14.36% pertained to men and women and 14.18% and 23.17% pertained to the poorest and richest groups, respectively. There was a significant difference in the prevalence of kidney stones between men and women in terms of age, marital status, education level, chronic disease, body mass index, and socioeconomic status (<0.001). The prevalence of kidney stones had a positive correlation with age (1.7, 95% [CI]: 1.42-2.04) and socioeconomic status (1.5, 95% [CI]: 1.34-1.69), where the odds of kidney stones increased significantly by increasing age and socioeconomic status. Moreover, the kidney stone concentration index showed a pro-rich distribution wherein it was more common among wealthy people (higher socioeconomic status) 0.062 (95% [CI]: 0.051-0.072).

Conclusion

The results of this study showed that there is significant inequality in the prevalence of kidney stones, where it was more common among the richest people. In addition, being men and old age are significantly related to kidney stones, so policymakers and physicians should consider these factors.

Obesity Is Positively Associated and Alcohol Intake Is Negatively Associated with Nephrolithiasis

The current research investigated the impacts of smoking, alcohol consumption, and obesity on the development of nephrolithiasis. We included ≥40-year-old Koreans from the Korean National Health Insurance Service-Health Screening Cohort. A total of 28,395 nephrolithiasis patients were compared with 113,580 control participants. Previous histories of smoking, alcohol consumption, and obesity were examined before the presence of nephrolithiasis. Conditional logistic regression analysis was performed to estimate the odds ratios (ORs) of smoking, alcohol consumption, and obesity for nephrolithiasis. Further analyses were conducted, according to age, sex, smoking, alcohol consumption, and obesity. The current smoking status was not linked with the presence of nephrolithiasis. Alcohol consumption was linked with a lower likelihood of the presence of nephrolithiasis (adjusted OR (aOR) = 0.89, 95% confidence intervals (CI) = 0.86−0.92, p < 0.001). Being obese was associated with a greater likelihood of the presence of nephrolithiasis ((95% CI) = 1.27 (1.22−1.31) < 1.42 (1.37−1.46) < 1.59 (1.47−1.71) for overweight < obese I < obese II). The relation of alcohol consumption and obesity with nephrolithiasis was consistent in the subgroups. The presence of nephrolithiasis was positively linked with obesity and negatively linked with alcohol consumption.

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.

Ureteroscopy Is Equally Efficient and Safe in Obese and Morbidly Obese Patients: A Systematic Review and Meta-Analysis

Background

Ureteroscopy (URS) has been established as an effective treatment for stones in obese patients (OP). However, recent studies found that the efficacy of the procedure may be lower in patients with higher body mass index (BMI). In the current study, we aim to determine if obesity might influence the effectiveness and safety of URS.

Methods

In May 2021, a comprehensive search was conducted in the PubMed, EMBASE, Web of Science, Cochrane Library, and ClinicalTrials.gov to find eligible studies. Stone-free rate (SFR), operative time, length of stay, and complication rate were assessed utilizing RevMan 5.3.

Results

Thirteen studies involving 4,583 normal-weight patients (NWP), 2,465 OP, and 291 morbidly OP (MOP) were included. Pooled results showed that statistically similar SFR existed between OP and NWP [odds ratio (OR): 1.09; 95% CI: 0.79, 1.52; p = 0.59], and between MOP and NWP (OR: 1.03; 95% CI: 0.46, 2.31; p = 0.95). The operation time was similar between OP and NWP [mean difference (MD): −2.27; 95% CI: −8.98, 4.43; p = 0.51], and between MOP and NWP (MD: 4.85; 95% CI: −5.78, 15.47; p = 0.37). In addition, no significant difference regarding length of stay existed between OP and NWP (MD: −0.07; 95% CI: −0.20, 0.07; p = 0.33), and between MOP and NWP (MD: −0.06; 95% CI: −0.25, 0.14; p = 0.58). Furthermore, we observed similar minor complication rate between OP and NWP (OR: 1.04; 95% CI: 0.81, 1.32; p = 0.78), and between MOP and NWP (OR: 1.29; 95% CI: 0.80, 2.08; p = 0.30). The differences concerning major complication rate between OP and NWP (OR: 0.97; 95% CI: 0.39, 2.43; p = 0.95), and between MOP and NWP (OR: 2.01; 95% CI: 0.55, 7.30; p = 0.29) were also not significant.

Conclusions

Our study demonstrated that URS performed in MOP and OP appears to have the same efficacy and safety as well as in NWP group.

Retrograde intrarenal surgery is a safe procedure in severe obese patients. Is it reality or prediction? A propensity score-matching analysis from RIRSearch study group

OBJECTIVE

The aim of the study was to assess whether severely obese patients have an increased risk of complications during and after retrograde intrarenal surgery.

MATERIALS AND METHODS

The data of 639 consecutive patients undergoing retrograde intrarenal surgery for the treatment of upper tract urinary stones were analyzed retrospectively. The patients were divided into two groups according to their body mass index numbers (Group 1, <35; Group 2, ≥35). The patients' demographics, stone characteristics, operative outcomes, and complication rates were compared between the groups. The primary objective was to examine whether the intraoperative and postoperative complication rates were higher in patients with a body mass index of ≥35 kg/m2.

RESULTS

After matching of confounding factors, Group 1 comprised 135 patients, and Group 2 comprised 47 patients. The baseline characteristics were similar between the groups. There were no significant differences between groups for intraoperative complication rates (11.8% and 12.8%, respectively; p=0.97). There was statistically significant difference in favor of Group 2 for postoperative complication rates (12.6% and 29.7%; respectively, p<0.01), overall complication rates (22.9% and 38.2%; respectively, p=0.02), mean operation time (56.15 minute vs 66.45 minute; respectively, p= 0.01) and length of stay (1.4 days vs 2.1 days; p=0.03). Stone free rates (75.5% vs 85.1%; respectively, p=0.17) did not differ between groups.

CONCLUSIONS

Retrograde intrarenal surgery is an efficient and feasible treatment option for upper urinary tract stones in severe obese patients. However, higher possibility of postoperative, especially infectious, complication rates should be taken into account in these patients.

Effect of obesity and metabolic health on urolithiasis: A nationwide population-based study

Purpose

To investigate the risk of symptomatic urolithiasis requiring surgical treatment according to obesity and metabolic health status using a nationwide dataset of the Korean population.

Materials and Methods

Of the 5,300,646 persons who underwent health examinations between the year 2009 and 2016, within one year after the health examination, 35,137 patients who underwent surgical treatment for urolithiasis were enrolled. Participants were classified as “obese” or “non-obese” using a body mass index (BMI) cutoff of 25 kg/m². People who developed ≥1 metabolic disease component in the index year were considered “metabolically unhealthy”, while those with none were considered “metabolically healthy”.

Results

Out of 34,330 participants excluding 843 missing, 16,509 (48.1%), 4,320 (12.6%), 6,456 (18.8%), and 7,045 (20.5%) subjects were classified into the metabolically healthy non-obese (MHNO), metabolically unhealthy non-obese (MUNO), metabolically healthy obese (MHO), and metabolically unhealthy obese (MUO) group, respectively. Mean BMI was 22.1±1.9 kg/m², 22.9±1.6 kg/m², 26.9±1.8 kg/m², and 27.9±2.4 kg/m² respectively. After adjusting the age and sex, the subjects in the MUNO group had an HR (95% CI) of 1.192 (1.120–1.268), those in the MHO group, 1.242 (1.183–1.305), and those in the MUO group, 1.341 (1.278–1.407) for either extracorporeal shockwave lithotripsy or surgery, compared to those in the MHNO group.

Conclusions

Metabolically healthy, obese individuals have a higher risk of developing symptomatic urolithiasis than non-obese, unhealthy, but have a lower risk than obese, unhealthy. It suggests that metabolic health and obesity have collaborative effects, independently affecting the development of symptomatic urinary stone diseases.

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.

The impact of metabolic syndrome components on urinary parameters and risk of stone formation

PURPOSE

To investigate the relationship between metabolic syndrome (MS) and urinary abnormalities in stone-forming patients. Additionally, to delineate whether severity of urinary derangements is impacted by the number of co-occurring MS components.

METHODS

Stone-forming patients who underwent initial metabolic workup prior to medical intervention at a comprehensive stone clinic were retrospectively reviewed and included in the study. Patients were given a six point (0-5) Metabolic Syndrome Severity Score (MSSS) based on the number of co-occurring MS components and split into six respective groups. Baseline clinical characteristics and metabolic profiles were compared between groups.

RESULTS

Four-hundred-ninety-five patients were included in the study. Median age and median BMI was 58 years and 27.26 kg/m², respectively. Several significant metabolic differences were noted, most notably a downward trend in median urinary pH (p < 0.001) and an upward trend in median urinary supersaturation uric acid (p < 0.001) across groups as MSSS increased. Multivariate analysis demonstrated an independent association between higher MSSS and increasing number of urinary abnormalities. A second multivariate analysis revealed that all MS components except hyperlipidemia were independently associated with low urinary pH. Additionally, obesity was independently associated with the greatest number of urinary abnormalities and had the strongest association with hyperuricosuria.

CONCLUSIONS

Prior research has attributed the strong association of nephrolithiasis and MS to high prevalence of UA nephrolithiasis and low urinary pH. Our findings indicate that all MS components with the exception of hyperlipidemia were independently associated with low urinary pH suggesting a mechanism independent from insulin resistance.

Investigating Fluid Intake in an Underserved Community: What Factors Are Associated with Low Urine Volume on 24-Hour Urine Collection?

Background: Stone prevention is dependent on high fluid intake, with evidence that low urine volume (LUV) can promote nephrolithiasis in the absence of other metabolic abnormalities. Herein, we investigate patient-related factors associated with LUV on initial 24-hour urine collection in an underserved population. Materials and Methods: A retrospective chart review was performed of patients treated by a single surgeon for nephrolithiasis from August 2014 to January 2019. Patients who submitted 24-hour urine samples were divided into two groups based on whether their initial collection was >2 L or not. Factors associated with 24-hour urine volume were analyzed using bivariate and multivariate analyses. As a secondary outcome, we investigated factors associated with corrected 24-hour urine volume on repeat 24-hour urine collection. Results: Two hundred eight patients (45.1%) submitted 24-hour urine collections, 63.9% (133/208) of which demonstrated a urine volume of <2 L. LUV was more common in female patients (77.1% vs 49.5%; p = 0.001) and patients with no insurance and Medicaid (no insurance [100%] vs Medicaid [74.1%] vs Medicare/private [58.6%]; p = 0.02). Female gender and insurance status were independent predictors of LUV in the multivariable analysis. Seventeen of 43 patients (39.5%) with LUV who provided a subsequent collection were able to correct their urine volume. Patients who improved their LUV were older (58.5 vs 45.9 years, p = 0.0149) and more likely to have surgical intervention for their kidney stones (94.1% vs 53.8%, p = 0.006). In our multivariable analysis, surgical intervention was associated with correcting urine volume. Conclusions: Female patients and those with no insurance or Medicaid were more likely to have LUV on an initial 24-hour urine collection. Further research into barriers to fluid intake is important for these two groups, along with directed patient education on strategies for increasing fluid intake.

Association between metabolic syndrome components and the risk of developing nephrolithiasis: A systematic review and bayesian meta-analysis

Background: There is increasing evidence that nephrolithiasis is a systemic disease, as opposed to an isolated urinary metabolic problem, after considerable links were found between nephrolithiasis and systemic diseases such as hypertension, obesity, dyslipidemia, and insulin resistance. The interplay between these four factors defines metabolic syndrome (MetS). In this review we aim to clarify the associations of MetS and its components to kidney stone incident. Methods: Online databases of EMBASE, MEDLINE, and Google Scholar were searched from January 1998 up to October 2020 to identify observational studies examining the association between metabolic syndrome components and kidney stone incident. Bayesian random-effects meta-analysis and meta-regression were performed to observe the association. Linear dose-response analysis was conducted to shape the direction of the association. Data analysis was performed using STATA, and R statistics. Results: A total of 25 potentially relevant studies (n = 934,588 participants) were eventually identified. The pooled results suggested that metabolic syndrome was associated with an increased risk of nephrolithiasis with an odds ratio (OR) of 1.769 (95% CI: 1.386 - 2.309).  The summary OR of hypertension and dyslipidemia for developing nephrolithiasis were 1.613 (95% CI: 1.213 - 2.169) and 1.586 (95% CI: 1.007 - 2.502) respectively. The presence of diabetes mellitus and obesity had an OR of 1.552 (95% CI: 1.027 - 2.344) and 1.531 (95% CI: 1.099 - 2.109) respectively. Our results revealed that the increasing number of MetS traits will increase the risk of developing nephrolithiasis, the higher the fasting plasma glucose, and body mass index, the higher the risk of kidney stones incident. Conclusions: Our results suggest that hypertension, diabetes, obesity and dyslipidemia are associated with increased risk of developing nephrolithiasis. Linear significant association between MetS components and nephrolithiasis were revealed in our study which reinforced the notion that should be considered a systemic disorder.

The effects of obesity on the human body part III: Cardiovascular, digestive, excretory, endocrine, and reproductive

This third installment of The Effects of Obesity on the Human Body discusses the endocrine, digestive, reproductive, cardiovascular, and excretory systems. Obesity is known to upset hormonal balance, leading to widespread metabolic disorders involving organs such as the liver and pancreas. Furthermore, the hypersecretion of leptin from adipose tissue triggers various responses from the cardiovascular and gastrointestinal systems, with implications for energy and nutrient balance and uptake.

Prevention and management of urinary stone

The prevalence of urolithiasis is increasing not only in South Korea but also around the world. Urolithiasis has a high recurrence rate, therefore, reducing it is very important in the quality of life for stone formers. For this purpose, dietary modifications and drug therapy can be performed through stone analysis and 24-hour urine collection. Stone analysis is recommended for all stone formers, and the 24-hour urine collection is usually recommended for recurrent stone formers or high-risk groups. A general dietary modification for all stone formers includes a sufficient fluid intake, low levels of sodium, sugar, and animal protein, a normal calcium diet, as well as a high amount of citrate intake. Drug therapy should be performed in cases such as the recurrence of stones or increase of the existing ones, even after the application of preservation therapy, such as dietary modification. The ideal drug therapy should prevent the occurrence of urolithiasis, have no side effects, and have a suitable patientsʼ compliance. Follow-up should be performed periodically, through 24-hour urine collections and imaging studies. For follow-up imaging studies, a lowdose non-enhanced computed tomography is recommended, and it can be performed once a year if the patient is in a stable state. To control various and complex metabolic abnormalities in recurrent stone formers, multiple approaches may be required through diet modifications, drug therapy, treatment of the metabolic syndrome, and lifestyle modifications.

Changing in gender prevalence of nephrolithiasis

Although nephrolithiasis is a more common disease in men rather than women, several studies over the last decades show that the male to female ratio 3:1 is narrowing. These finding may be associated to modified risk factors for stone formation between females and males. Changes in lifestyle and increasing obesity in women may play a role in shifting of gender disparity. Furthermore, recent studies have demonstrated an increase of kidney stones in women which have necessitated emergency department visits (ED). Therefore, females show a greater percentage of mortality rate if compared to males, especially if stone disease is associated to urosepsis and requires the admission to the Intensive Care Unit (ICU). This article reviews recent insights into changing gender prevalence in urinary calculi and into identifying the relation between gender and risk factors for stone disease, that in case of severe urosepsis might also lead to mortality.

Relationship Between Body Mass Index and Kidney Stones Based on Dose-Response Analyses Using Restricted Cubic Splines Applied to NHANES 2011-2016 Data

OBJECTIVE

The objective of the study was to estimate the dose-response relationship between body mass index (BMI) and the self-reported prevalence of kidney stones based on a restricted cubic spline (RCS) method.

METHODS

This cross-sectional study analyzed 13,223 adults aged ≥20 years who had participated in the National Health and Nutrition Examination Survey performed during 2011-2016. Kidney stones were identified using a standard questionnaire, and physical examinations were used to determine BMI. Logistic regression was used to assess the relationship between BMI and the prevalence of kidney stones, with the dose-response relationship explored using RCSs.

RESULTS

The overall prevalence of kidney stones was 9.7%: 10.6% in males and 8.9% in females. After adjusting for potential confounders, compared with those with a BMI in quartile 1, the odds ratios of kidney stones among those with BMIs in quartiles 2, 3, and 4 were 1.45, 1.60, and 2.00, respectively (95% confidence interval = 1.21-1.75, 1.33-1.92, and 1.67-2.39; all P < .001). Multivariate RCS regression revealed that BMI was related to kidney stones in a nonlinear manner (P for nonlinearity <0.001). There was a significant positive relationship, with the curves being steeper when BMI was <28 kg/m².

CONCLUSION

This analysis of National Health and Nutrition Examination Survey data has demonstrated that BMI is significantly associated with the prevalence of kidney stones.

Correlation of metabolic syndrome and urolithiasis: A prospective cross-sectional study

Background:

Correlation between urolithiasis and metabolic syndrome has been demonstrated in the literature. This study assessed the association of metabolic syndrome and its components with urolithiasis in Indian patients.

Methods:

A cross-sectional prospective observation study included patients aged >18 years with urolithiasis. Demographic details, body mass index (BMI), waist circumference, blood pressure, and laboratory parameters were examined.

Results:

Total 1200 patients with urolithiasis were divided into two groups (with [n = 208] and without metabolic syndrome [n = 992]). The mean age of total population was 47.26 (14.68) years with 721 males and 479 females. The mean height, weight, BMI were significantly different between both groups (P < 0.001). Proportion of obese (BMI >25) patients, proportion of patients with hyperuricemia, waist circumference, blood pressure, triglyceride, fasting blood sugar (FBS) levels were significantly higher in patients with metabolic syndrome; however, high density lipoprotein (HDL) levels were significantly reduced in metabolic syndrome group (P < 0.001). A significantly increasing trend in mean waist circumference, triglycerides, FBS, systolic blood pressure and diastolic blood pressure and a decreasing trend in mean HDL with increase in number of metabolic components were observed (P < 0.001). Female patients were 19.6 times more likely to develop metabolic syndrome than male patients (P < 0.001). Increasing waist circumference, triglycerides, FBS, blood pressure were associated with increased risk of metabolic syndrome (P < 0.05). Decreasing HDL was associated with reduced risk of metabolic syndrome. Patients with hyperuricemia were 5.68 times more likely to exhibit metabolic syndrome (P = 0.006).

Conclusion:

This study indicates the presence of a significant association of metabolic syndrome and its components with urolithiasis.

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.

Preliminary analysis of serum electrolytes and body mass index in patients with and without urolithiasis

OBJECTIVES

To compare body mass index (BMI); serum parameters; and urine parameters between patients with and without urolithiasis.

METHODS

Data from 1164 patients admitted to our Department of Urology from January 2011 to July 2013 were retrospectively reviewed; 714 patients (age, 5-87 years; male:female ratio, 1.8:1) exhibited urolithiasis, and 450 patients (age, 12-94 years; male:female ratio, 3.8:1) did not. Blood and urine were collected from patients the morning after hospital admission. Serum and urine parameters were checked by an automatic biochemistry analyzer. Statistical analysis included the Mann-Whitney U test and binary logistic regression.

RESULTS

Serum sodium, potassium, chloride, calcium, phosphorus, and carbon dioxide combining power significantly differed between groups. In male patients, serum sodium, calcium, and phosphorus levels were higher in the urolithiasis group, whereas serum potassium and urine pH levels were lower. In female patients, serum sodium was higher in the urolithiasis group. BMI was higher in the urolithiasis group in all patients, male and female. Respective β-values of serum sodium and BMI in male patients were 0.077 and 0.084; in female patients, these values were 0.119 and 0.102.

CONCLUSIONS

Changes in serum sodium and BMI may be involved in the pathogenesis and treatment of urolithiasis.

The status and characteristics of urinary stone composition in China

OBJECTIVES

To explore characteristics of urinary stone composition in China, and determine the effects of gender, age, body mass index (BMI), stone location, and geographical region on stone composition.

PATIENTS AND METHODS

We prospectively used Fourier-transform infrared spectroscopy to analyse stones from consecutive patients presenting with new-onset urolithiasis at 46 hospitals in seven geographical areas of China, between 1 June 2010 and 31 May 2015. Chi-squared tests and logistic regression analyses were used to determine associations between stone composition and gender, age, BMI, stone location, and geographical region.

RESULTS

The most common stone constituents were: calcium oxalate (CaOx; 65.9%), carbapatite (15.6%), urate (12.4%), struvite (2.7%), and brushite (1.7%). CaOx and urate stones occurred more frequently in males, whereas carbapatite and struvite were more common in females (P < 0.01). CaOx and carbapatite were more common in those aged 30-50 and 20-40 years than in other groups. Brushite and struvite were most common amongst those aged <20 and >70 years. The detection rate of urate increased with age, whilst cystine decreased with age. Obese patients were more likely to have urate stones than carbapatite or brushite stones (P < 0.01). CaOx, carbapatite, brushite, and cystine stones were more frequently found in the kidney than other types, whereas urate and struvite were more frequent in the bladder (P < 0.01). Stone composition varied by geographical region.

CONCLUSIONS

The most common stone composition was CaOx, followed by carbapatite, urate, struvite, and brushite. Stone composition differed significantly in patients grouped by gender, age, BMI, stone location, and geographical region.

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.

The effect of the body mass index on the types of urinary tract stones

Objectives:

Urinary tract stones are a common public health problem worldwide. In addition, identifying the composition of stones is important for the further metabolic evaluation of patients. We conducted this study to further correlate the relationship between body mass index (BMI) and different compositions of urinary tract stones.

Materials and Methods:

A retrospective study of 433 patients who underwent urinary tract stone analysis via Fourier-transform infrared spectroscopy at King Khalid University Hospital in Riyadh from May 2015 to June 2017 was performed. Their BMI at the time of stone analysis was recorded.

Results:

A total of 433 stones were analyzed by the statistical data analysis software. The BMI was classified according to the WHO classification. We divided our patients into seven age groups. Most patients were between the age group of 35 and 44 years and were overweight. The incidence of calcium oxalate, carbonate apatite, and uric acid stones was higher in patients with a BMI above thirty than in patients with a lower BMI. However, cystine stones were more common in normal-weight patients.

Conclusions:

In this study, we found that the incidence of certain types of stones, such as calcium oxalate, cystine, and uric acid stones, in Saudi Arabia can be predicted by BMI measurement.

Metabolic syndrome and the composition of urinary calculi: is there any relation?

Introduction

Epidemiologic studies demonstrate that obesity and diabetes increase the prevalence of urinary lithiasis. Most of these studies did not stratify the chemical composition of calculi and the physiological mechanisms responsible for this increased risk are not well understood. This study aims to investigate the relation between the metabolic syndrome and the composition of the urinary calculi.

Material and methods

Observational and retrospective study of all urinary calculi analysis performed at the Centro Hospitalar do Tâmega e Sousa, Portugal – from January 2009 to September 2015. Calculi were analyzed by infrared spectroscopy.

Results

302 analyses of urinary calculi were identified. Metabolic syndrome was diagnosed in 20.5% of patients. A total of 7 different mineral compounds were identified: 51.6% (N = 156) contained calcium oxalate, 41% (N = 124) calcium phosphate, 37.7% (N = 114) uric acid, 22.1% (N = 67) ammonium urate, 9.6% (N = 29) ammonium magnesium phosphate, 6.3% (N = 19) sodium urate and 1.3% (N = 4) contained cystine. Patients with metabolic syndrome presented a higher proportion of uric acid calculi (66.1% vs. 0%, p <0.001) and ammonium urate calculi (38.7% vs. 17%, p = 0.001). Patients without metabolic syndrome had a higher proportion of calcium oxalate calculi (58.8% vs. 24.2%, p <0.001) and calcium phosphate (46.7% vs. 19.4%, p <0.001).

Conclusions

There is a statistically significant relation between metabolic syndrome and uric acid and ammonium urate calculi. Metabolic syndrome may be considered risk factor for this calculi and the diagnosis and treatment of this syndrome must be considered for urolithiasis prevention. Further studies are needed to better the understanding of physiological mechanisms underlying this relationship to improve our strategy of prevention of urinary lithiasis.

Predictive Factors for Achieving the Recommended AUA Daily Urine Production in Patients With Nephrolithiasis

Objective

To identify factors that predict kidney stone patient's ability to produce 2.5 L urine volume per day on metabolic evaluation.

Patients and Methods

In a retrospective chart review, the first analysis evaluated initial 24-hour urine collections with respect to those who achieved or did not achieve a urine volume of 2.5 L/day. The second analysis evaluated those who achieved or did not achieve a daily urine volume of 2.5 L on their subsequent collection. Several variables were assessed.

Results

Patients' initial collections (n=1100) that achieved 2.5 L/day (n=274) were of younger age and had a higher body mass index, increased urine sodium, phosphorus, calcium levels, increased protein catabolic rate, and decreased supersaturation of calcium oxalate. In the second analysis (n=273), decreased supersaturation of calcium oxalate, increased urine urea nitrogen level, and increased protein catabolic rate were observed in subsequent collections with a urine volume of 2.5 L/day or more. Patients with a diagnosis of hyponatremia were less likely to achieve 2.5 L/day urine volume. Collection date, other comorbidities, and diuretic use were not associated with achieving 2.5 L/day urine volume. Patients' mean creatinine per kilogram for all study cohorts were within the range of adequate collection.

Conclusion

Predictive factors for a urine volume of 2.5 L/day or more include increased fluid intake, higher salt and animal protein diet, elevated body mass index, and male sex. Patients with these factors may require interventions other than hydration recommendations to optimize their prevention of future kidney.

Rapid kVp switching dual-energy CT in the assessment of urolithiasis in patients with large body habitus: preliminary observations on image quality and stone characterization

PURPOSE

The purpose of this study was to investigate the image quality (IQ) considerations of rapid kVp switching dual-energy CT (rsDECT) in the assessment of urolithiasis in patients with large body habitus and to evaluate whether it allows stone characterization.

MATERIALS AND METHODS

In this IRB-approved, HIPAA compliant retrospective study, 93 consecutive patients (M/F = 72/21, mean age 56.9 years, range 23-83 years) with large body habitus (> 90 kg/198 lbs) who underwent dual-energy (DE) stone protocol CT on a rapid kVp switching DECT scanner between January 2013 and December 2016 were included. Scan acquisition protocol included an initial unenhanced single-energy CT (SECT) scan of KUB followed by targeted DECT in the region of stones. Two readers evaluated both CT data sets (axial 5 mm 120 kVp/140 kVp QC/70 keV monoenergetic, material density water/iodine images and coronal/sagittal 3 mm images) for the assessment of image quality (Scores: 1-4) and characterization of stone composition (reference standard: crystallography).

RESULTS

One hundred and five CT examinations were performed in 93 patients (mean body weight 105.12 ± 13.53 kg, range 91-154 kg), and a total of 321 urinary tract calculi (mean size-4.8 ± 3.2 mm, range 1.2-22 mm) were detected. Both SECT and targeted monoenergetic images were of acceptable image quality (mean IQ: 3.77 and 3.83, kappa 0.79 and 0.87 respectively). Material density water and iodine images had lower IQ scores (mean IQ: 2.97 and 3.09 respectively) with image quality deterioration due to severe photon starvation/streak artifacts in 20% (21/105) and 17% (18/105) scans, respectively. Characterization of stone composition into uric acid/non-uric acid stones was achieved in 93.14% (299/321) of calculi (mean size: 4.99 ± 3.3 mm, range 1.2-22 mm), while 7% (22/321) stones could not be characterized (mean size 3.03 ± 1.16 mm, range 1.6-6.4 mm) (p < 0.001). Most common reason for non-characterization was image quality deterioration of the material density iodine images due to severe photon starvation artifacts. On multivariate regression, stone size and patient weight were predictors of stone composition determination on DECT (p < 0.05). The transverse diameter had a weak negative correlation with stone composition determination, but it was not statistically significant. Stone characterization into uric acid vs. non-uric acid stones was accurate in 95% (n = 38/40) of stones in comparison with crystallography.

CONCLUSION

In patients with large body habitus, rsDECT allowed characterization of most calculi (93%) despite image quality deterioration due to photon starvation/streak artifacts in up to 20% of material density images. Stone size and patient weight were predictors of stone composition determination on DECT, and small calculi in very large patients may not be characterized.

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.

Fructose increases risk for kidney stones: potential role in metabolic syndrome and heat stress

Background

Fructose intake, mainly as table sugar or high fructose corn syrup, has increased in recent decades and is associated with increased risk for kidney stones. We hypothesized that fructose intake alters serum and urinary components involved in stone formation.

Methods

We analyzed a previously published randomized controlled study that included 33 healthy male adults (40–65 years of age) who ingested 200 g of fructose (supplied in a 2-L volume of 10% fructose in water) daily for 2 weeks. Participants were evaluated at the Unit of Nephrology of the Mateo Orfila Hospital in Menorca. Changes in serum levels of magnesium, calcium, uric acid, phosphorus, vitamin D, and intact PTH levels were evaluated. Urine magnesium, calcium, uric acid, phosphorus, citrate, oxalate, sodium, potassium, as well as urinary pH, were measured.

Results

Ingestion of fructose was associated with an increased serum level of uric acid (p < 0.001), a decrease in serum ionized calcium (p = 0.003) with a mild increase in PTH (p < 0.05) and a drop in urinary pH (p = 0.02), an increase in urine oxalate (p = 0.016) and decrease in urinary magnesium (p = 0.003).

Conclusions

Fructose appears to increase urinary stone formation in part via effects on urate metabolism and urinary pH, and also via effects on oxalate. Fructose may be a contributing factor for the development of kidney stones in subjects with metabolic syndrome and those suffering from heat stress.

Trial registration

ClinicalTrials.gov NCT00639756 March 20, 2008.

Renal stones

Renal stone disease is a worldwide problem which carries significant morbidity. It frequently requires specialist urology intervention. Patients with recurrent disease and those at high risk require specialist investigations and review. Certain cases benefit from medical and surgical intervention. In this review, we discuss the pathophysiology, risk assessment, specialist investigations and various interventions, their rationale and evidence base. This review aims to provide an update of the previous publication in 2001 in this journal on this topic.

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.

Metabolic syndrome and uric acid nephrolithiasis: insulin resistance in focus

Uric acid nephrolithiasis (UAN) is an increasingly common disease in ethnically diverse populations and constitutes about 10% of all kidney stones. Metabolic syndrome and diabetes mellitus are accounted among the major risk factors for UAN, together with environmental exposure, individual lifestyle habits and genetic predisposition. The development and overt manifestation of UAN appears to stem on the background of insulin resistance, which acts at the kidney level by reducing urinary pH, thus hampering the ability of the kidney to generate renal ammonium in response to an acid load. Unduly acidic urinary pH and overt UAN are both considered renal manifestations of insulin resistance. The mechanisms underlying increased endogenous acid production and/or defective ammonium excretion are yet to be completely understood. Although the development of UAN and, more in general, of kidney stones largely recognizes modifiable individual determining factors, the rising prevalence of diabetes, obesity and accompanying metabolic disorders calls for the identification of novel therapeutic approaches and intervention targets. This review aims at providing an updated picture of existing evidence on the relationship between insulin resistance and UAN in the context of metabolic syndrome and in light of the most recent advancements in our understanding of its genetic signature.

Obesity and kidney stone disease: a systematic review

INTRODUCTION

Currently, abdominal obesity has reached an epidemic stage and obesity represents an important challenge for worldwide health authorities. Epidemiologic studies have demonstrated that the stone risk incidence increases with Body Mass Index, through multiple pathways. Metabolic syndrome and diabetes are associated with an increased renal stones disease incidence. The aim of this systematic review was to investigate the prevalence, morbidity, risk factors involved in the association between obesity and urolithiasis.

EVIDENCE ACQUISITION

The search involved finding relevant studies from MEDLINE, EMBASE, Ovid, the Cochrane Central Register of Controlled Trials, CINAHL, Google Scholar, and individual urological journals between January 2001 and May 2017. The inclusion criteria were for studies written in the English language, reporting on the association between obesity and urinary stones.

EVIDENCE SYNTHESIS

The underlying pathophysiology of stone formation in obese patients is thought to be related to insulin resistance, dietary factors, and a lithogenic urinary profile. Uric acid stones and calcium oxalate stones are observed frequently in these patients. Insulin resistance is thought to alter the renal acid-base metabolism, resulting in a lower urine pH, and increasing the risk of uric acid stone disease. Obesity is also associated with excess nutritional intake of lithogenic substances and with an increase in urinary tract infection incidence. Recent studies highlighted that renal stone disease increases the risk of myocardial infarction, progression of chronic kidney disease, and diabetes. Contemporary, bariatric surgery has been shown to be associated with hyperoxaluria and oxalate nephropathy. Certainly, the many health risks of obesity, including nephrolithiasis, will add more burden on urologists and nephrologists.

CONCLUSIONS

Obesity related nephrolithiasis seems to necessitate weight loss as primary treatment, but the recognition of the associated complications is necessary to prevent induction of new and equally severe medical problems. The optimal approach to obesity control that minimizes stone risk needs to be determined in order to manage obesity-induced renal stones disease.

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.

Uric acid nephrolithiasis: An update

Uric acid nephrolithiasis appears to increase in prevalence. While a relationship between uric acid stones and low urinary pH has been for long known, additional association with various metabolic conditions and pathophysiological basis has recently been elucidated. Some conditions such as diabetes and metabolic syndrome disease, excessive dietary intake, and increased endogenous uric acid production and/or defect in ammoniagenesis are associated with low urinary pH. In addition, the phenomenon of global warming could result in an increase in areas with greater climate risk for uric acid stone formation. There are three therapeutic steps to be taken for management of uric acid stones: identification of urinary pH profiles, assessment of urinary volume status, and identification of disorders leading to excessive uric acid production. However, the most important factor for uric acid stone formation is acid urinary pH, which is a prerequisite for uric acid precipitation. This article reviews recent insights into the pathophysiology of uric acid stones and their management.

Effects of statin treatment with atorvastatin on urolithiasis-associated urinary metabolic risk factors: an experimental study

PURPOSE

To investigate whether atorvastatin has favorable effects on urinary metabolic risk factors associated with urolithiasis.

METHODS

Sixteen male Sprague-Dawley rats were randomly divided into two groups, and baseline spot and 24-h urine samples were collected. Distilled water and atorvastatin were administered to rats during 4 weeks in the control and atorvastatin groups, respectively. At the end of the experimental procedure, spot and 24-h urine samples were collected again. Citrate, oxalate, cystine, uric acid, calcium and magnesium levels were determined in 24-h urine samples. Citrate/creatinine, oxalate/creatinine, uric acid/creatinine, calcium/creatinine and magnesium/creatinine ratios were also calculated in spot urine samples. Comparison of the baseline and post-experimental levels of these parameters was made in each group.

RESULTS

The majority of the parameters were similar before and after the experimental procedure in each group. In the atorvastatin group, uric acid and calcium levels were affected. Administration of atorvastatin was significantly decreased the levels of uric acid, whereas increased the levels of calcium (P = 0.025 and P = 0.017, respectively).

CONCLUSIONS

Our study revealed that atorvastatin has decreasing effect on U_Ua levels, whereas increasing effect on U_Ca levels. We think it cannot certainly be deduced that atorvastatin could be beneficial on overall urinary metabolic risk factors. Contrarily, atorvastatin may lead to an increased risk of calcium stones, but when considering its U_Ua decreasing effect, it may help in reducing the uric acid stone recurrence.