Chronic Fructose and Sucrose Intake and 24-Hour Urine Composition

Key Points

Higher dietary intakes of fructose and sucrose are associated with lower 24-hour urine calcium. Higher dietary intakes of fructose and sucrose are associated with other modest changes in 24-hour urine composition.

Background

Consumption of sugar, including fructose and sucrose, is associated with higher risk of kidney stones. The association is believed to be because of an acute rise in urine calcium after sugar intake. However, the association between chronic sugar intake and urine composition is not known.

Methods

We conducted a cross-sectional analysis of dietary intake from a food frequency questionnaire and 24-hour urine collections from 6457 kidney stone- and non–stone-former participants from the Nurses' Health Study I (1,297), Nurses' Health Study II (4,053), and Health Professionals Follow-up Study (1,107). We used multivariate adjusted linear regression to examine the association between long-term intake of free fructose, total fructose, and sucrose and 24-hour urine composition.

Results

Higher free and total fructose and sucrose intakes were each associated with lower 24-hour urine calcium. Comparing the highest versus lowest quintiles, mean urine calcium was 23 (31–15) mg/d lower for free fructose (P -trend <0.001), 26 (34–18) mg/d for total fructose (P -trend <0.001), and 8 (17–1) mg/d for sucrose (P -trend 0.03). Higher total fructose intake was associated with slightly higher calcium phosphate supersaturation (P -trend 0.002), and higher sucrose intake was associated with higher calcium oxalate (P -trend 0.03) and calcium phosphate (P -trend <0.001) supersaturations. Differences in 24-hour urine calcium were similar between kidney stone- and non–stone-former participants.

Conclusions

In contrast to the acute rise in urine calcium previously seen in short-term studies, higher long-term intake of free and total fructose and sucrose was associated with lower 24-hour urine calcium excretion in those with and without a history of kidney stones. Other modest differences in urine composition were noted for each sugar. Future studies should test potential mechanisms for the observed lower 24-hour urine calcium with chronic sugar intake.

Trends in Patient Complexity, Practice Setting, and Surgeon Reimbursement for Urolithiasis: Do Rural Urologists Pay the Price?

OBJECTIVE

To evaluate the relationship between patient complexity, practice setting, and surgeon reimbursement for ureteroscopy and percutaneous nephrolithotomy (PCNL).

METHODS

The "2021 Medicare Physician and Other Provider" file was used to collect Rural-Urban Commuting Area (RUCA) codes and hierarchical condition category (HCC) scores of urologists. Higher HCC score corresponds to higher medical complexity and higher RUCA code corresponds to a more rural area. Medicare reimbursement for ureteroscopy and PCNL were collected. Linear regressions were performed to predict change in reimbursement based on RUCA and HCC scores.

RESULTS

In 2021, 52,816 procedures under Current Procedural Terminology (CPT) code 52356 (ureteroscopy) and 1649 procedures under 50080 or 50081 (PCNL) were billed to Medicare. Mean reimbursement was $338.24 for ureteroscopy and $957.89 for PCNL. For ureteroscopy, higher HCC score predicted lower reimbursement (P <.001). Higher HCC score predicted higher reimbursement for PCNL (P <.01). Average RUCA for ureteroscopy was higher than for PCNL (P = .02). Rural location predicted lower reimbursement for ureteroscopy (P <.001), however, there was no association for PCNL.

CONCLUSION

For ureteroscopy, higher-risk patients are associated with lower reimbursement while the opposite holds true for PCNL. Rural practices were associated with lower reimbursement for ureteroscopy, but there was no association between location and PCNL reimbursement. Together, these findings suggest practice pattern variation between ureteroscopy and PCNL and highlight gaps in reimbursement policy. Risk-adjusted reimbursement should be considered to incentivize urologists to treat complex patients within their practice scope.

[Renal colic]

INTRODUCTION

Renal colic accounts for 5-10% of all emergency department visits, making it a common condition in acute medicine. The typical clinical presentation is an early indication of urolithiasis.

DIAGNOSIS

Diagnostic measures include laboratory tests, ultrasound, and low-dose noncontrast computed tomography (CT) scans. Kidney, ureter, bladder (KUB) plain film radiography has been widely replaced by low-dose noncontrast CT with similar radiation dosage. In special patient groups such as children or pregnant women, ionizing radiation should be avoided if possible.

TREATMENT

General measures involve pain management (non-steroidal anti-inflammatory agents, opioids) and empirical antibiotic treatment for suspected bacterial infection. Depending on the location/size of the stone, pharmacological stone expulsion therapy may be considered. In cases of obstructive pyelonephritis or acute renal insufficiency, early urinary drainage (JJ stent/nephrostomy) is recommended. Definitive stone removal may be performed primarily in some cases (rather small and rather distal ureterolithiasis). It is common to schedule stone removal as a secondary intervention.

The impact of kidney stone disease on quality of life in high-risk stone formers

OBJECTIVE

To assess the impact of kidney stone disease (KSD) and its treatment on the health-related quality of life (HRQOL) of high-risk stone formers with hyperparathyroidism, renal tubular acidosis, malabsorptive disease, and medullary sponge kidney.

PATIENTS AND METHODS

The Wisconsin Stone Quality of Life questionnaire was used to evaluate HRQOL in 3301 patients with a history of KSD from 16 institutions in North America between 2014 and 2020. Baseline characteristics and medical history were collected from patients, while active KSD was confirmed through radiological imaging. The high-risk group was compared to the remaining patients (control group) using the Wilcoxon rank-sum test.

RESULTS

Of 1499 patients with active KSD included in the study, the high-risk group included 120 patients. The high-risk group had significantly lower HRQOL scores compared to the control group (P < 0.01). In the multivariable analyses, medullary sponge kidney disease and renal tubular acidosis were independent predictors of poorer HRQOL, while alkali therapy was an independent predictor of better HRQOL (all P < 0.01).

CONCLUSIONS

Among patients with active KSD, high-risk stone formers had impaired HRQOL with medullary sponge kidney disease and renal tubular acidosis being independent predictors of poorer HRQOL. Clinicians should seek to identify these patients earlier as they would benefit from prompt treatment and prevention.

Contrasting Response of Urine Stone Risk to Medical Treatment in Calcium Oxalate versus Calcium Phosphate Stone Formers

Key Points

Thiazide treatment successfully lowered urine calcium and both calcium oxalate and calcium phosphate supersaturations in both types of stone formers (SFs). Alkali therapy may not confer the same benefits on calcium phosphate SFs as it does on calcium oxalate SFs.

Background

Randomized controlled trials have shown that both thiazide diuretics and potassium citrate (K-Cit) can prevent calcium stone recurrence, but most participants formed calcium oxalate (CaOx) stones. While thiazides are expected to lower risk of calcium phosphate (CaP) stone formation, the effect of K-Cit on risk of CaP stone formation is unclear.

Methods

To study the effect of common calcium stone treatments, we analyzed the 24-hour urines of CaOx and CaP stone formers (SFs) by four treatment types: Lifestyle, K-Cit, Thiazide, or Both medications.

Results

Patients treated with thiazides reduced urine calcium in both CaOx (M =−74.4, SD =94.6 mg/d) and CaP (M =−102, SD =99.7 mg/d) SFs while those on K-Cit had no change in urine calcium. Among CaOx SFs, urine citrate rose in patients administered K-Cit with or without thiazide, but citrate did not rise significantly in CaP SFs. Urine pH rose in all CaOx SFs, but among CaP SFs, only rose in patients receiving K-Cit. CaOx supersaturation (SS) decreased in all patients who received Thiazide, and decreased among CaOx SFs treated with K-Cit. CaP SS decreased in both CaOx SFs (M =−0.46, SD =0.86) and CaP SFs (M =−0.76, SD =0.85) treated with Thiazide, except CaOx SFs who received Both. Patients treated with K-Cit alone increased CaP SS in CaOx SFs (M =0.25, SD =0.79).

Conclusions

Patients treated with Thiazide lowered urine calcium and SS in both stone groups. Patients treated with K-Cit had no significant changes in urine calcium and had a decrease in CaOx SS in CaOx SFs. The study raises questions about the best preventive treatment for patients with CaP stones and suggests that K-Cit may not confer the same benefits on CaP SFs as it does on CaOx SFs.

Computed tomographic characterization of urinary stones in patients with urolithiasis from Southeast Mexico

Urolithiasis (UL) is a severe public health concern in southeastern Mexico. Computed tomography (CT) is the first-line diagnostic method for patients with suspected UL. The present study aimed to characterize stones in the entire urinary system using CT and to contribute to personalized treatment in patients with UL. Patients >18 years of age with suspected UL were enrolled. Characteristics of UL included stone size, location (kidney, ureters, and bladder), composition of the stone in Hounsfield units (HU), presence of staghorn stone(s), and obstructive uropathy. Patients were stratified according to sex and age to determine whether stone size and HU were dependent on hormonal factors in females and on prostatic hyperplasia in males. The Mann-Whitney U test was used to compare median values. Frequencies are expressed as percentages and were analyzed using the Mantel-Haenszel chi-squared test. A total of 1150 patients were included in this study, of whom 744 (64.7 %) had UL in only 1 anatomical location in the urinary system, and 406 (35.3 %) had stones in ≥2 anatomical locations. Localization and stone size differed between males and females (p < 0.05). Additionally, males exhibited differences in HU (p = 0.024) and frequency of obstructive uropathy (p = 0.10) when stratified according to age (≤50 and > 50 years). In addition, females exhibited statistical differences in HU (p = 0.010) and kidney stone size (p = 0.047) dependent on age (≤47 and > 47 years). In conclusion, findings suggest that HU and stone size differ in different anatomical structures of the urinary system. In addition, differences in stone size and composition may be associated with age and sex.

Endoscopic Stone Composition Identification: Is Accuracy Improved by Stone Appearance During Laser Lithotripsy?

OBJECTIVE

To evaluate if videos during laser lithotripsy increase accuracy and confidence of stone identification by urologists compared to still pictures.

METHODS

We obtained representative pictures and videos of 4 major stone types from 8 different patients during ureteroscopy with holmium laser lithotripsy. A REDCap survey was created and emailed to members of the Endourological Society. The survey included a picture followed by the corresponding video of each stone undergoing laser lithotripsy and additional clinical information. Each picture and video included multiple-choice questions about stone composition and response confidence level. Accuracy, confidence levels, and rates of rectification (change from incorrect to correct answer) or confounding (correct to incorrect) after watching videos were analyzed.

RESULTS

One hundred eighty-seven urologists responded to the survey. The accuracy rate of stone identification with pictures was 43.8% vs 46.1% with videos (P = .27). Accuracy for individual stones was low and highly variable. Video only improved accuracy for 1 cystine stone. After viewing videos, participants were more likely to rectify vs confound their answers. Urologists were more likely to be confident with videos than pictures alone (65.4% vs 53.7%, respectively; P <.001); however, confident answers were not more likely to yield accurate predictions with videos vs still pictures.

CONCLUSION

Stone identification by urologists is marginally improved with videos vs pictures alone. Overall, accuracy in stone identification is low irrespective of confidence level, picture, and lithotripsy video visualization. Urologists should be cautious in using endoscopic stone appearance to direct metabolic management.

Association between novel anthropometric indices and prevalence of kidney stones in US adults

BACKGROUND

Our aim is to evaluate the relationship between prevalence of kidney stones (KS) and novel anthropometric indices (AHIs).

METHODS

Participants who participated in the KS questionnaire was extracted from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2018.A series of covariates were also obtained. The novel AHIs include a body shape index (ABSI) and body roundness index (BRI). Weighted multivariable-adjusted logistic regression was performed to investigate the association of KS with AHIs.

RESULTS

After relative covariates were adjusted, a greater risk of KS for each z score increase in ABSI (OR = 1.13, 95%CI 1.05-1.22), and the risk of KS augmented by 19% for every 1 BRI z score added (OR = 1.19, 95%CI 1.11-1.27). The results from subgroup analysis showed that among adults aged 20-39 (OR = 1.31, 95%CI 1.04-1.65), male (OR = 1.14, 95%CI 1.02-1.28), the risk of KS is higher with the increase of each ABSI z score. Raising each BRI z score in those who were male aged 20-39 and 40-59 resulted in a higher risk of KS (aged 20-39: OR = 1.34, 95%CI 1.06-1.69; aged 40-59: OR = 1.29, 95%CI 1.09-1.53). In female aged 40-59, increasing each BRI z score led to a higher risk of KS (OR = 1.23, 95%CI 1.07-1.41). A linear association of ABSI z score with the risk of KS and a non-linear relationship between BRI z score and the risk of KS were discovered.

CONCLUSION

This study found that the novel AHIs was related to the risk of kidney stones, and can be used as important indicators to evaluate the risk of KS.

Photonic Lithotripsy: Near-Infrared Laser Activated Nanomaterials for Kidney Stone Comminution

Near-infrared activated nanomaterials have been reported for biomedical applications ranging from photothermal tumor destruction to biofilm eradication and energy-gated drug delivery. However, the focus so far has been on soft tissues, and little is known about energy delivery to hard tissues, which have thousand-fold higher mechanical strength. We present photonic lithotripsy with carbon and gold nanomaterials for fragmenting human kidney stones. The efficacy of stone comminution is dependent on the size and photonic properties of the nanomaterials. Surface restructuring and decomposition of calcium oxalate to calcium carbonate support the contribution of photothermal energy to stone failure. Photonic lithotripsy has several advantages over current laser lithotripsy, including low operating power, noncontact laser operation (distances of at least 10 mm), and ability to break all common stones. Our observations can inspire the development of rapid, minimally invasive techniques for kidney stone treatment and extrapolate to other hard tissues such as enamel and bone.

Prevalence of Stone Disease and Procedure Trends in the United States

OBJECTIVE

To evaluate the prevalence of stone disease and procedure trends among US commercial and Medicare populations.

METHODS

Retrospective analyses for a US commercial population and Medicare population were conducted using the Merative MarketScan Commercial Database and Medicare Standard Analytic File (5% sample), respectively. Patients aged 18+ were included if they had an encounter in any setting with a primary stone diagnosis or stone procedure (ureteroscopy [URS], percutaneous nephrolithotomy (PCNL), or shockwave lithotripsy [SWL]) between 2011 and 2019. Analyses were conducted at the patient level.

RESULTS

Over the study time horizon, the prevalence of stone disease showed a small yet statistically significant decrease in the commercial population (1.04%-1.01%; P.ß<.ß0.0001) and a statistically significant increase in the Medicare population (1.84%-2.34%; P.ß<.ß0.0001). URS.ßprocedure volumes increased by 22.6% (P.ß<.ß0.0001) in the commercial population and by 56.6% (P.ß<.ß0.0001) in the Medicare population over the study period. Similarly, PCNL.ßprocedure volumes increased by 17.4% (P.ß<.ß0.0001) in the commercial population and 27.5% (P.ß<.ß0.0001) in the Medicare population. Procedure volumes for SWL decreased by 26.9% in the commercial population (P.ß<.ß0.0001) and by 3.8% in the Medicare population although the results were not statistically significant.

CONCLUSION

The prevalence of stone disease showed a small decrease in the US commercial population and an increase in the Medicare population over the study time horizon. In both populations, increasing procedure volumes were observed for URS and PCNL while decreasing volumes were observed for SWL.

Does Moses technology enhance the efficiency and outcomes of regular holmium laser lithotripsy? Results of a pooled analysis of comparative studies

Holmium laser lithotripsy is currently the optimum standard for surgical treatment of upper urinary calculi. This study aims to evaluate the clinical efficacy and safety of Moses compared with conventional holmium laser lithotripsy for the treatment of patients with upper urinary calculi. We conducted a systematic search using multiple databases (PubMed/Medline, Scopus, Web of Science, and ClinicalTrials.gov) until June 2022. Clinical trials comparing Moses and conventional holmium laser lithotripsy were included. Analysis was performed using RevMan version 5.4.4 software. Four studies with 892 patients were included. There were no significant differences regarding stone-free rate (mean difference [MD] 1.19, 95% CI 0.54, 2.64, p = 0.66), operative time (MD - 9.31, 95% CI - 21.11, 2.48, p = 0.12), fragmentation time (MD - 1.71, 95% CI - 11.81, 8.38, p = 0.74), total energy used (MD 1.23, 95% CI - 0.44, 2.90, p = 0.15), auxiliary procedures (MD 0.38, 95% CI 0.08, 1.90, p = 0.24), and overall complications (odds ratio [OR] 0.70, 95% CI 0.30, 1.66, p = 0.42) between the groups. However, the laser working time (MD - 0.94, 95% CI - 1.20, - 0.67, p < 0.001) of Moses technology was shorter than that of conventional technology. Moses technology has similar outcomes to regular technology in terms of safety and efficacy. Given the higher operating costs of the Moses technology, further study is required to determine whether there are benefits to this new technology.

Epidemiology of Kidney Stones

In the past two decades, major breakthroughs that improve our understanding of the pathophysiology and therapy of kidney stones (KS) have been lacking. The disease continues to be challenging for patients, physicians, and healthcare systems alike. In this context, epidemiological studies are striving to elucidate the worldwide changes in the patterns and the burden of the disease and identify modifiable risk factors that contribute to the development of kidney stones. Our expanding knowledge of the epidemiology of kidney stones is of paramount importance and largely upgrades the modern management of the disease. In this paper, we review the variables affecting prevalence and incidence, including age, gender, race, ethnicity, occupation, climate, geography, systemic diseases, diabetes, vascular disease, chronic kidney disease, and dietary risk factors relevant to kidney stones.

Trends and patterns of initial percutaneous nephrolithotomy and subsequent procedures among commercially-insured US adults with urinary system stone disease: a 10-year population-based study

PURPOSE

To describe trends and patterns of initial percutaneous nephrolithotomy (PCNL) and subsequent procedures from 2010 to 2019 among commercially-insured US adults with urinary system stone disease (USSD).

METHODS

Retrospective study of administrative data from the IBM® MarketScan^® Database. Eligible patients were aged 18-64 years and underwent PCNL between 1/1/2010 and 12/31/2019. Measures of interest for analysis of trends and patterns included the setting of initial PCNL (inpatient vs. outpatient), percutaneous access (1 vs. 2-step), and the incidence, time course, and type of subsequent procedures (extracorporeal shockwave lithotripsy [SWL], ureteroscopy [URS], and/or PCNL) performed up-to 3 years after initial PCNL.

RESULTS

A total of 8,348 patients met the study eligibility criteria. During the study period, there was a substantial shift in the setting of initial PCNL, from 59.9% being inpatient in 2010 to 85.3% being outpatient by 2019 (P < 0.001). The proportion of 1 vs. 2-step initial PCNL fluctuated over time, with a low of 15.1% in 2016 and a high of 22.0% in 2019 but showed no consistent yearly trend (P = 0.137). The Kaplan-Meier estimated probability of subsequent procedures following initial PCNL was 20% at 30 days, 28% at 90 days, and 50% at 3 years, with slight fluctuations by initial PCNL year. From 2010 to 2019, the proportion of subsequent procedures accounted for by URS increased substantially (from 30.8 to 51.8%), whereas SWL decreased substantially (from 39.5 to 14.7%) (P < 0.001).

CONCLUSIONS

From 2010 to 2019, PCNL procedures largely shifted to the outpatient setting. Subsequent procedures after initial PCNL were common, with most occurring within 90 days. URS has become the most commonly-used subsequent procedure type.

Association of Height and Prevalence of Kidney Stones

Introduction and objectives Nephrolithiasis is universally understood to be a multifactorial disease resulting from genetic and environmental factors including gender, diet, calcium, and uric acid excretion. Notably, several of these factors may be related to body habitus. Because men are more likely to develop kidney stones and on average have a larger body size, height may be an important risk factor for stone formation. Several studies have demonstrated that short adult stature is associated with numerous conditions such as hypertension, hypercholesterolemia, and cardiovascular diseases. However, other studies have demonstrated otherwise. Additionally, stones have been shown to be correlated with a high body mass index (BMI). This is likely due to dietary factors. Although height is a component of BMI, there is minimal literature regarding the relationship of height to stone prevalence adjusting for weight.  Methods We aimed to examine whether short adult height is associated with the development of kidney stones using a population-based cohort of the National Center for Health Statistics. Data was gathered from National Health and Nutrition Examination Surveys (NHANES) "Kidney Conditions - Urology" and "Weight History" questionnaire datasets from March 2017 to March 2020 along with demographic data. Logistic regression analysis was used to determine an association between current self-reported height (inches) and if the participant has ever had kidney stones, controlling for weight, gender, age, race, educational level, and marital status.  Results We found that those who were shorter had higher odds of reporting a history of stones (OR: 1.017; 95%CI: 1.005-1.028). This association was found after controlling for covariates such as age, gender, race, education, and weight. In addition, the male gender and Hispanic race had higher odds of reporting a history of stones (OR: 1.43 and 1.073, respectively).  Conclusion Our results suggest that short height is related to the prevalence of kidney stones independent of weight, age, gender, and race. This supports previous literature indicating height to be a component of renal disease.

Vantera Mediated Quantification of Urine Citrate and Creatinine: A New Technology to Assess Risk of Nephrolithiasis

Urine citrate is often used to identify patients at risk of recurrent nephrolithiasis or kidney stones. A high-throughput assay was developed to measure urine citrate and creatinine on the Vantera® Clinical Analyzer, a nuclear magnetic resonance (NMR) instrument designed for the clinical laboratory. Assay performance was evaluated and comparisons between the NMR and chemistry results were conducted. Linearity was demonstrated over a wide range of concentrations for citrate (6 and 2040 mg/L) and creatinine (2.8 and 1308 mg/dL). Intra-and inter-assay precision (%CV) ranged from 0.9 to 3.7% for citrate and 0.4 to 2.1% for creatinine. The correlation coefficients for the comparison between NMR and chemistry results were 0.98 (Y = 1.00X + 5.0) for citrate and 0.96 (Y = 0.968X + 0.97) for creatinine. The reference intervals for both analytes were confirmed. Ten endogenous and exogenous substances were tested and none were found to interfere with the assay results. In conclusion, the newly developed high-throughput NMR assay exhibited robust performance and generated results comparable to the currently utilized chemistry tests, thereby providing an alternative means to simultaneously quantify urine citrate and creatinine for clinical and research use. Furthermore, the NMR assay does not exhibit the same interference limitations as the chemistry tests and it enables multiplexing with other urine metabolite assays which saves time and costs.

Estimating 24-hour urinary excretion using spot urine measurements in kidney stone formers

BACKGROUND

One limitation of the use of 24-hour collection is impracticality. We analysed the performance of spot urine measurements to estimate 24-hour excretion in patients with kidney stones.

METHODS

A total of 74 adult patients from two centres performed a 24-hour urine collection. A sample of the last micturition was sent for spot urine analysis. Twenty patients were asked to collect two additional spot urine samples, one before dinner and the other after dinner. Urinary concentrations of creatinine, calcium, oxalate, uric acid, citrate and magnesium were measured in the 24-hour and each of the spot urine samples. Four approaches were used to estimate 24-hour urinary excretion, multiplying the ratio of the spot urinary analyte to creatinine concentration by (i) measured 24-hour urinary creatinine excretion (Prediction 1), (ii) estimated 24-hour urinary creatinine excretion (Prediction 2), (iii) assumed 1-g 24-hour urinary creatinine excretion (Prediction 3) or (iv) assumed 1.5-g 24-hour urinary creatinine excretion (Prediction 4). For each parameter we computed Lin's concordance correlation coefficients (CCCs), Bland-Altman plots and 95% limits of agreement.

RESULTS

The performance of estimates obtained with Prediction 1 and Prediction 2 was similar, except for citrate and uric acid, for which Prediction 2 performed worse. Both approaches performed moderately well: citrate CCC {0.82 [95% confidence interval (CI) 0.75-0.90]}, oxalate [0.66 (95% CI 0.55-0.78)], magnesium [0.66 (95% CI 0.54-0.77)], calcium [0.63 (95% CI 0.50-0.75)] and uric acid [0.52 (95% CI 0.36-0.68)]. The performance of Predictions 3 and 4 was worse.

CONCLUSIONS

Although spot urine samples may hold promise for clinical and population-based research, at present they have limited utility in clinical practice. Measuring or estimating 24-hour creatinine, rather than assuming a given creatinine excretion, will be necessary in future studies of spot urine samples.

Loss of Ecrg4 improves calcium oxalate nephropathy

Kidney stone is one of the most frequent urinary tract diseases, affecting 10% of the population and displaying a high recurrence rate. Kidney stones are the result of salt supersaturation, including calcium and oxalate. We have previously identified Esophageal cancer-related gene 4 (Ecrg4) as being modulated by hypercalciuria. Ecrg4 was initially described as a tumor suppressor gene in the esophagus. Lately, it was shown to be involved as well in apoptosis, cell senescence, cell migration, inflammation and cell responsiveness to chemotherapy. To the best of our knowledge, nothing is known about ECRG4's function in the renal tissue and its relationship with calciuria. We hypothesized that the increased expression of Ecrg4 mRNA is triggered by hypercalciuria and might modulate intratubular calcium-oxalate precipitation. In this study, we have first (i) validated the increased Ecrg4 mRNA in several types of hypercalciuric mouse models, then (ii) described the Ecrg4 mRNA expression along the nephron and (iii) assessed ECRG4's putative role in calcium oxalate nephropathy. For this, Ecrg4 KO mice were challenged with a kidney stone-inducing diet, rich in calcium and oxalate precursor. Taken together, our study demonstrates that Ecrg4's expression is restricted mainly to the distal part of the nephron and that the Ecrg4 KO mice develop less signs of tubular obstruction and less calcium-oxalate deposits. This promotes Ecrg4 as a modulator of renal crystallization and may open the way to new therapeutic possibilities against calcium oxalate nephropathy.

[Urolithiasis-Therapy and recurrence prevention taking into account gender-specific aspects]

The prevalence of urolithiasis is steadily increasing worldwide in both genders. Diet and lifestyle, such as the rising prevalence of obesity and other metabolic syndrome traits, are considered key factors in this trend. Gender differences as a result of interventional therapy for urolithiasis have not been observed. However, iatrogenic injury to the male urethra is considered the most common reason for urethral strictures after endourologic (stone) therapy. In contrast, sepsis, as the major cause of urinary stone-related mortality, is more frequently reported in women after ureterorenoscopy and percutaneous nephrolithotomy. There are also differences in the frequency of various types of stones between men and women. Calcium oxalate and uric acid stones are more commonly observed in men, while carbonate apatite and struvite are diagnosed more often in women. Urinary stone analysis is therefore paramount for successful recurrence prevention. Diagnosis is based on the assignment of patients to the low-risk or high-risk group. The medical nutrition and pharmacological measures for the therapy of the respective type of stone are based on the risk factors in 24 h urine samples. A personalized approach that accounts for gender differences could further improve treatment, and recurrence prevention decisions for urinary stones.

Impact of COVID-19 on the management and outcomes of ureteric stones in the UK: a multicentre retrospective study

OBJECTIVES

To determine if management of ureteric stones in the UK changed during the coronavirus disease 2019 (COVID-19) pandemic and whether this affected patient outcomes.

PATIENTS AND METHODS

We conducted a multicentre retrospective study of adults with computed tomography-confirmed ureteric stone disease at 39 UK hospitals during a pre-pandemic period (23/3/2019-22/6/2019) and a period during the pandemic (the 3-month period after the first severe acute respiratory syndrome coronavirus-2 case at individual sites). The primary outcome was success of primary treatment modality, defined as no further treatment required for the index ureteric stone. Our study protocol was published prior to data collection.

RESULTS

A total of 3735 patients were included (pre-pandemic 1956 patients; pandemic 1779 patients). Stone size was similar between groups (P > 0.05). During the pandemic, patients had lower hospital admission rates (pre-pandemic 54.0% vs pandemic 46.5%, P < 0.001), shorter mean length of stay (4.1 vs 3.3 days, P = 0.02), and higher rates of use of medical expulsive therapy (17.4% vs 25.4%, P < 0.001). In patients who received interventional management (pre-pandemic 787 vs pandemic 685), rates of extracorporeal shockwave lithotripsy (22.7% vs 34.1%, P < 0.001) and nephrostomy were higher (7.1% vs 10.5%, P = 0.03); and rates of ureteroscopy (57.2% vs 47.5%, P < 0.001), stent insertion (68.4% vs 54.6%, P < 0.001), and general anaesthetic (92.2% vs 76.2%, P < 0.001) were lower. There was no difference in success of primary treatment modality between patient cohorts (pre-pandemic 73.8% vs pandemic 76.1%, P = 0.11), nor when patients were stratified by treatment modality or stone size. Rates of operative complications, 30-day mortality, and re-admission and renal function at 6 months did not differ between the data collection periods.

CONCLUSIONS

During the COVID-19 pandemic, there were lower admission rates and fewer invasive procedures performed. Despite this, there were no differences in treatment success or outcomes. Our findings indicate that clinicians can safely adopt management strategies developed during the pandemic to treat more patients conservatively and in the community.

ALARA in Urology: Steps to Minimise Radiation Exposure During All Parts of the Endourological Journey

Purpose of the Review

The global burden of kidney stone disease (KSD) and its management relies on ionising radiation. This includes the diagnosis, treatment and follow-up of KSD patients. The concept ‘As Low As Reasonably Achievable’ (ALARA) developed in response to the radiation risks and the key principles include optimisation, justification and limitation of radiation. This article provides an overview of the topic including background to the risks and steps that can be taken during all stages of endourological management.

Recent Findings

Our review suggests that ionising radiation is an invaluable tool in delineating the anatomy, localising disease, guiding manoeuvres and monitoring treatment in patients with KSD. It therefore plays an integral role in many stages of patient care; preoperatively, intraoperatively and postoperatively.

The reduction of radiation pre- and post-surgical intervention relies on the use of low-radiation CT scan and ultrasound scan. It can also be achieved through various intraoperative techniques or fluoroless techniques in selected patients/procedures, customised to the patients and procedural complexity.

Summary

There are many parts of the patient journey where exposure to radiation can take place. Urologists must be diligent to minimise and mitigate this wherever possible as they too face exposure risks. Implementation of strategies such as teaching programmes, fluoroscopy checklists and judicious use of CT imaging among other things is a step towards improving practice in this area.

The health effects of soy: A reference guide for health professionals

Soy is a hotly debated and widely discussed topic in the field of nutrition. However, health practitioners may be ill-equipped to counsel clients and patients about the use of soyfoods because of the enormous, and often contradictory, amount of research that has been published over the past 30 years. As interest in plant-based diets increases, there will be increased pressure for practitioners to gain a working knowledge of this area. The purpose of this review is to provide concise literature summaries (400-500 words) along with a short perspective on the current state of knowledge of a wide range of topics related to soy, from the cholesterol-lowering effects of soy protein to the impact of isoflavones on breast cancer risk. In addition to the literature summaries, general background information on soyfoods, soy protein, and isoflavones is provided. This analysis can serve as a tool for health professionals to be used when discussing soyfoods with their clients and patients.

Advances in Ureteroscopy: New technologies and current innovations in the era of Tailored Endourological Stone Treatment (TEST)

Ureteroscopy has undergone many advances in recent decades. As a result, it is able to treat an increasing range of patient groups including special populations such as pregnancy, anomalous kidneys and extremes of age. Such advances include Holmium laser, high-power systems and pulse modulation. Thulium fibre laser is a more recent introduction to clinical practice. Ureteroscopes have also been improved alongside vision and optics. This article provides an up-to-date guide to these topics as well as disposable scopes, pressure control and developments in operating planning and patient aftercare. These advances allow for a custom strategy to be applied to the individual patient in what we describe using a new term: Tailored endourological stone treatment (TEST).

Level of evidence: 5

Assessing kidney stone composition using smartphone microscopy and deep neural networks

Objectives

To propose a point-of-care image recognition system for kidney stone composition classification using smartphone microscopy and deep convolutional neural networks.

Materials and methods

A total of 37 surgically extracted human kidney stones consisting of calcium oxalate (CaOx), cystine, uric acid (UA) and struvite stones were included in the study. All of the stones were fragmented from percutaneous nephrolithotomy (PCNL). The stones were classified using Fourier transform infrared spectroscopy (FTIR) analysis before obtaining smartphone microscope images. The size of the stones ranged from 5 to 10 mm in diameter. Nurugo 400× smartphone microscope (Nurugo, Seoul, Republic of Korea) was functionalized to acquire microscopic images (magnification = 25×) of dry kidney stones using iPhone 6s+ (Apple, Cupertino, CA, USA). Each kidney stone was imaged in six different locations. In total, 222 images were captured from 37 stones. A novel convolutional neural network architecture was built for classification, and the model was assessed using accuracy, positive predictive value, sensitivity and F1 scores.

Results

We achieved an overall and weighted accuracy of 88% and 87%, respectively, with an average F1 score of 0.84. The positive predictive value, sensitivity and F1 score for each stone type were respectively reported as follows: CaOx (0.82, 0.83, 0.82), cystine (0.80, 0.88, 0.84), UA (0.92, 0.77, 0.85) and struvite (0.86, 0.84, 0.85).

Conclusion

We demonstrate a rapid and accurate point of care diagnostics method for classifying the four types of kidney stones. In the future, diagnostic tools that combine smartphone microscopy with artificial intelligence (AI) can provide accessible health care that can support physicians in their decision-making process.

The duration of stone disease and the impact of a stone event on patients' quality of life

INTRODUCTION

With a 5-year stone recurrence rate of 30-50%, kidney stone formers are subject to significant morbidity which negatively impacts their Health Related Quality of Life (HRQOL). We sought to determine the impact of age of kidney stone onset, duration of stone disease, and kidney stone event (surgery or stone passage) on patients' individual HRQOL by querying the validated and prospectively collected Wisconsin Stone Quality of Life (WISQOL) database.

MATERIALS AND METHODS

Cross-sectional data were obtained from a total of 2,438 kidney stone formers from 14 institutions in North America who completed the WISQOL questionnaire from 2014 to 2019. The 28-question survey has a 1-5 point scale for each item (total score range 0-140). Multivariable linear regression models assessed the impact of age of kidney stone onset, duration of stone disease and time since most recent surgery or stone passage on HRQOL.

RESULTS

Of 2,438 patients, older age at kidney stone onset and longer duration of disease were both independent predictors of better WISQOL (β=0.33 points/year; CI 0.17-0.49; p<0.001 and β=0.50 points/year; CI 0.32-0.68; p<0.001, respectively). Of 1,376 patients with surgery between 2010-2019, increased time since most recent surgery was an independent predictor of better WISQOL scores (β = 2.28 points/year; CI: 1.47-3.10; p=<0.001). Of 1,027 patients with spontaneous stone passage between 2010-2019, increased time since most recent stone passage was an independent predictor of better WISQOL scores (β = 1.59 points/year; CI: 0.59-2.59; p=<0.05).

CONCLUSION

Our study demonstrates that older age of onset, longer duration of disease, increase time from most recent surgery or stone passage were independent predictors of better HRQOL in kidney stone formers. Results of future studies that focus on optimizing stone related modifiable risk factors to decrease the amount of recurrent stone episodes and thus the need for recurrent surgeries will be essential.

Perception of Dietary Influences on Renal Stone Formation Among the General Population

Introduction

Urolithiasis is a common disorder worldwide with an increasing prevalence and high recurrence rate. This makes preventive measures like dietary modification an essential part of patient care. This study focuses on gauging the perception of dietary habits favoring kidney stone formation.

Materials and methods

A cross-sectional questionnaire-based study was conducted at Aga Khan University, Karachi, Pakistan. For nine food items and 14 beverages, respondents chose one of four options with regards to their relationship with stone formation, i.e. “increasing”, “decreasing”, “no effect”, and “do not know”. Responses were matched against evidence from the literature to generate correct and incorrect responses, thereby gauging perception for individual items. 

Results

Seven hundred and three participants including 69 (9.6%) with a prior history of kidney stones, were recruited for the study. Participants with a personal history of kidney stone disease were older (odds ratio {OR}: 1.042 CI 1.020-1.064) with a significantly higher family history of stones (OR: 2.151 CI: 1.472-3.144). The majority were managed medically (87%) but never received dietary counseling (57%). Water, soft drinks, and tomatoes were the only three items out of 23 that were correctly identified by >50% of the participants with regards to their effect on stone formation. Responses did not differ significantly between those with stone disease and those without.

Conclusion

There is a lack of awareness among the general population, including individuals with a prior history of kidney stones regarding dietary prevention of kidney stone disease. This demonstrates a lack of existing dietary counseling thus necessitating the need for incorporating it at a mass level.

Cavitation Plays a Vital Role in Stone Dusting During Short Pulse Holmium:YAG Laser Lithotripsy

Objective: To investigate the mechanism of stone dusting in Holmium (Ho): YAG laser lithotripsy (LL). Materials and Methods: Cylindrical BegoStone samples (6 × 6 mm, H × D) were treated in water using a clinical Ho:YAG laser lithotripter in dusting mode (0.2-0.4 J with 70-78 μs in pulse duration, 20 Hz) at various fiber tip to stone standoff distances (SD = 0, 0.5, and 1 mm). Stone damage craters were quantified by optical coherence tomography and bubble dynamics were captured by high-speed video imaging. To differentiate the contribution of cavitation vs thermal ablation to stone damage, three additional experiments were performed. First, presoaked wet stones were treated in air to assess stone damage without cavitation. Second, the laser fiber was advanced at various offset distances (OSD = 0.25, 1, 2, 3, and 10 mm) from the tip of a flexible ureteroscope to alter the dynamics of bubble collapse. Third, stones were treated with parallel fiber to minimize photothermal damage while isolating the contribution of cavitation to stone damage. Results: Treatment in water resulted in 2.5- to 90-fold increase in stone damage compared with those produced in air where thermal ablation dominates. With the fiber tip placed at OSD = 0.25 mm, the collapse of the bubble was distracted away from the stone surface by the ureteroscope tip, leading to significantly reduced stone damage compared with treatment without the scope or with scope at large OSD of 3-10 mm. The average crater volume produced by parallel fiber orientation at 0.2 J after 100 pulses, where cavitation is the dominant mechanism of stone damage, was comparable with those produced by using perpendicular fiber orientation within SD = 0.25-1 mm. Conclusion: Cavitation plays a dominant role over photothermal ablation in stone dusting during short pulse Ho:YAG LL when 10 or more pulses are delivered to the same location.

A Machine Learning Approach to Predict the Outcome of Urinary Calculi Treatment Using Shock Wave Lithotripsy: Model Development and Validation Study

Background

Shock wave lithotripsy (SWL), ureteroscopy, and percutaneous nephrolithotomy are established treatments for renal stones. Historically, SWL has been a predominant and commonly used procedure for treating upper tract renal stones smaller than 20 mm in diameter due to its noninvasive nature. However, the reported failure rate of SWL after one treatment session ranges from 30% to 89%. The failure rate can be reduced by identifying candidates likely to benefit from SWL and manage patients who are likely to fail SWL with other treatment modalities. This would enhance and optimize treatment results for SWL candidates.

Objective

We proposed to develop a machine learning model that can predict SWL outcomes to assist practitioners in the decision-making process when considering patients for stone treatment.

Methods

A data set including 58,349 SWL procedures performed during 31,569 patient visits for SWL to a single hospital between 1990 and 2016 was used to construct and validate the predictive model. The AdaBoost algorithm was applied to a data set with 17 predictive attributes related to patient demographics and stone characteristics, with success or failure as an outcome. The AdaBoost algorithm was also applied to a training data set. The generated model’s performance was compared to that of 5 other machine learning algorithms, namely C4.5 decision tree, naïve Bayes, Bayesian network, K-nearest neighbors, and multilayer perceptron.

Results

The developed model was validated with a testing data set and performed significantly better than the models generated by the other 5 predictive algorithms. The sensitivity and specificity of the model were 0.875 and 0.653, respectively, while its positive predictive value was 0.7159 and negative predictive value was 0.839. The C-statistics of the receiver operating characteristic (ROC) analysis was 0.843, which reflects an excellent test.

Conclusions

 We have developed a rigorous machine learning model to assist physicians and decision-makers to choose patients with renal stones who are most likely to have successful SWL treatment based on their demographics and stone characteristics. The proposed machine learning model can assist physicians and decision-makers in planning for SWL treatment and allow for more effective use of limited health care resources and improve patient prognoses.

Sex Differences and the Risk of Kidney Stones

A significant increase in the prevalence of kidney stones has been observed worldwide. In the past decades, this expansion was more pronounced among women than men. The precise mechanisms involved in the differences in the risk profile of stone disease between men and women have not been fully elucidated. Diet and lifestyle only partially can explain the differences, and the combination of factors such as the influence of sex hormones, genetics, and disorders in acid-base handling and urine pH, as well as differences in calcium tubular reabsorption and stone composition in men and women, may contribute to differences in the risk profile. In this review, we summarize the sex differences in the pathophysiologic basis of kidney stones, which may contribute to a more focused approach.

Factors associated with sex differences in the risk of kidney stones

BACKGROUND

Men are at higher risk of developing stones compared with women; however, recent data suggest a changing epidemiology, with women being relatively more affected than before.

METHODS

To estimate the proportion of excess risk among men, we analysed data from large cohorts (Health Professionals Follow-up Study and Nurses' Health Study I and II). Kidney stone incidence rates were computed and hazard ratios (HRs) and 95% confidence intervals (CIs) generated with age-adjusted Cox proportional regression models. Mediation analysis estimated the excess risk for men explained by risk factors, including waist circumference, high blood pressure, diabetes, use of thiazides and dietary intake. The 24-h urine composition was also examined.

RESULTS

The analysis included 268 553 participants, contributing 5 872 249 person-years of follow-up. A total of 10 302 incident stones were confirmed and the overall incidence rate was 271 and 159 per 100 000 person-years for men and women, respectively. The age-adjusted HR was 2.32 (95% CI 2.20, 2.45) and the risk of stones was consistently higher across categories of age (HRs ranging from 2.02 to 2.76) for men compared with women. The risk remained higher among men, but tended to decrease over time (48.1%), while it increased among women. Urine supersaturations for calcium oxalate and uric acid were higher among men, primarily because of higher oxalate (26.3%), uric acid (16.3%), phosphate (23.5%) and lower pH.

CONCLUSIONS

The risk of kidney stones is higher among men and this difference is only partly explained by lifestyle risk factors; differences in urine chemistries explain a substantial fraction of the excess risk.

Urinary Metabolic Disturbances During Topiramate Use and their Reversibility Following Drug Cessation

OBJECTIVE

To understand the metabolic disturbances of stone formers currently taking topiramate and to examine the reversibility of these disturbances with cessation of the medication.

MATERIALS AND METHODS

All progress notes written by 5 endourologists from a single academic center were retrospectively reviewed from January 2010 to July 2020 containing the words "topiramate" or "topamax." Inclusion criteria were age > 18 and presence of either a 24-hour urine sample or stone analysis while on topiramate. In addition, a subgroup of 18 patients with 24-hour urine samples before and after stopping topiramate were identified.

RESULTS

A total of 93 patients were identified and included for final analysis. Twenty-four hour urine samples were available in 67 patients and showed mean citrate excretion of 331 ± 322 mg/day, mean pH of 6.6 ± 0.5, and mean calcium phosphate supersaturation of 1.9 ± 1.1. In the subgroup analysis urinary citrate excretion increased from 225 mg/day to 614 mg/day (p<0.01), pH decreased from 6.59 ± 0.54 to 6.33 ± 0.47 (p = 0.06). In addition, 114 stone events occurred in 73 distinct patients, with 50% of stones either pure or majority (≥ 50%) calcium phosphate by composition.

CONCLUSIONS

Hypocitraturia and elevated pH is seen during topiramate use with resultant higher rate of calcium phosphate stone formation compared to the general population. Stopping topiramate leads to significant increase in citrate excretion and normalization of pH. These metabolic disturbances appear to be reversible with medication cessation.

Ureteroscopy with thulium fiber laser lithotripsy results in shorter operating times and large cost savings

PURPOSE

Prolonged ureteroscopy (URS) is associated with complications including ureteral perforation, stricture, and urosepsis. As laser lithotripsy is one of the most common urologic procedures, small cost savings per case can have a large financial impact. This retrospective study was designed to determine if Thulium fiber laser (TFL) lithotripsy decreases operative time and costs compared to standard Holmium:YAG (Ho:YAG) lithotripsy without pulse modulation.

METHODS

A retrospective review of URS with laser lithotripsy was conducted for 152 cases performed from August 2020 to January 2021. Variables including cumulative stone size, location, chemical composition, prior ureteral stenting, and ureteral access sheath use were recorded for each case. A cost benefit analysis was performed to show projected cost savings due to potentially decreased operative times.

RESULTS

Compared to Ho:YAG, use of TFL resulted in an average decrease of 12.9 min per case (p = .021, 95% CI [2.03-23.85]). In subgroup analysis of cases with cumulative stone diameter less than 15 mm, the difference was 14.0 min (p = .007, CI [3.95-23.95]). For cases less than 10 mm, the mean difference was 17.3 min in favor of TFL (p = .002, 95% CI [6.89-27.62]). This ~ 13 min reduction in operative time resulted in saving $440/case in direct operating room costs giving our institution a range of $294,000 to $381,900 savings per year.

CONCLUSIONS

TFL has a significantly shorter operative time and decreased cost when compared to the standard Ho:YAG for equivalent kidney stone and patient characteristics. Longer term follow up is needed to see if recurrence rates are affected.

Oxalate Flux Across the Intestine: Contributions from Membrane Transporters

Epithelial oxalate transport is fundamental to the role occupied by the gastrointestinal (GI) tract in oxalate homeostasis. The absorption of dietary oxalate, together with its secretion into the intestine, and degradation by the gut microbiota, can all influence the excretion of this nonfunctional terminal metabolite in the urine. Knowledge of the transport mechanisms is relevant to understanding the pathophysiology of hyperoxaluria, a risk factor in kidney stone formation, for which the intestine also offers a potential means of treatment. The following discussion presents an expansive review of intestinal oxalate transport. We begin with an overview of the fate of oxalate, focusing on the sources, rates, and locations of absorption and secretion along the GI tract. We then consider the mechanisms and pathways of transport across the epithelial barrier, discussing the transcellular, and paracellular components. There is an emphasis on the membrane-bound anion transporters, in particular, those belonging to the large multifunctional Slc26 gene family, many of which are expressed throughout the GI tract, and we summarize what is currently known about their participation in oxalate transport. In the final section, we examine the physiological stimuli proposed to be involved in regulating some of these pathways, encompassing intestinal adaptations in response to chronic kidney disease, metabolic acid-base disorders, obesity, and following gastric bypass surgery. There is also an update on research into the probiotic, Oxalobacter formigenes, and the basis of its unique interaction with the gut epithelium. © 2021 American Physiological Society. Compr Physiol 11:1-41, 2021.

On the protein content of kidney stones: an explorative study

OBJECTIVES

Kidney stone formation is complex; urinary protein inhibitors play a major role in natural defense against stone formation. Using attenuated total-reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy of kidney stones, proteins are usually not quantified and often reported as 'organic matrix', for which there is little attention: treatment of urolithiasis is based on the nature of the major organic/inorganic stone compound. Literature no longer regards urinary proteins as innocent bystander, but highlights the role of proteins as urolithiasis modulators. We explored the potential significance of the protein content of kidney stones.

METHODS

800 stones were analyzed using ATR-FTIR spectroscopy; spectra were corrected for protein content. The ratio of the amide I peak (1655 cm^-1) divided by the maximum peak was calculated. A subgroup of stones (n = 43) was weighed; protein concentration was assayed. Kidney stone composition was taken into account when calculating protein concentration. Electrophoresis was implemented to investigate the protein bands. Multiple regression analysis was carried out to study the influence of various demographic variables (age, gender, stone type) on protein concentration.

RESULTS

Protein concentration showed a marked variation according to the stone composition. High relative protein content (>0.4% stone mass) was found in mixed calcium apatite/calcium oxalate dihydrate stones, mixed calcium oxalate dihydrate/calcium oxalate monohydrate/calcium apatite stones, and mixed calcium oxalate monohydrate/brushite stones, whereas lower protein percentages were found in cystine, urate, and calcium oxalate monohydrate stones. Protein concentration was dependent of the patient's age.

CONCLUSION

ATR-FTIR is a practical way for assessing protein concentration in kidney stones.

LIST OF ABBREVIATIONS

A: absorbance; as, asymmetric vibrations; ATR-FTIR, attenuated total-reflectance Fourier-transform infrared; β, standardized regression coefficient; CAP, calcium apatite; COD, calcium oxalate dihydrate; COM, calcium oxalate monohydrate; CV, coefficient of variation; δ, bending vibrations; ELISA, enzyme-linked immunosorbent assay; IQR, interquartile range; IR, infrared; LOD, limit of detection; LOQ, limit of quantification; MIR, mid-infrared; N or n, amount; r, correlation; r², coefficient of determination; s, symmetric vibrations; SD, standard deviation; SE, standard error; THP, Tamm-Horsfall protein; UA, uric acid; V, stretching vibrations; VIF: variance inflation factor; ZnSe, zinc selenide.

The controversial association of gut and urinary microbiota with kidney stone formation

Nephrolithiasis (kidney stones) is one of the most common chronic kidney diseases that are typically more common among adult men comparing to adult women. The prevalence of this disease is increasing which is influenced by genetic and environmental factors. Kidney stones are mainly composed of calcium oxalate and urinary oxalate which is considered a dangerous factor in their formation. Besides diverse leading reasons in the progression of nephrolithiasis, the gut and urinary microbiome has been recognized as a major player in the development or prevention of it. These microbes produce metabolites that have diverse effects on host biological functions. Therefore, Changes in the composition and structure of the microbiome (dysbiosis) have been implicated in various diseases. The present review focuses on the roles of gut and urinary in kidney stone formation.

Gender Differences in Kidney Stone Disease (KSD): Findings from a Systematic Review

PURPOSE OF REVIEW

The prevalence of kidney stones is rising and historically carries a preponderance for males. However, recent evidence has questioned whether this gender gap is closing. The aim of this systematic review was to examine this further as well as evaluate possible underlying causes.

RECENT FINDINGS

Recent evidence confirms the disparity in kidney stone disease between genders is closing. In the modern era, the rise in prevalence among females has been greater, especially in adolescence. Quality of life is also more adversely affected by kidney stone events among females who are also more likely to develop sepsis after endourological surgery. Males, however, are more likely to present with stone events during periods of high ambient temperatures Recent literature demonstrates a temporal change in the disease burden of KSD among men and women. The latter, especially adolescent females, are more likely to develop KSD in their lifetime compared to previous eras. Determining causation is complex and continued research is warranted.

Increased Nephrolithiasis Prevalence in People with Disabilities: A National Health and Nutrition Survey Analysis

OBJECTIVES

To estimate the prevalence of nephrolithiasis in people with disabilities (PWD), while accounting for known kidney stone disease risk factors.

METHODS

We used answers to the disability and kidney disease questionnaires from the 2013-2016 cycles of the National Health and Nutrition Examination Survey (NHANES), a nationally representative cross-sectional survey by the Centers for Disease Control, to calculate nephrolithiasis prevalence by functional disability type. We additionally estimated the total US population of stone formers with disabilities and compared disability prevalence between stone formers and non-stone formers. Multivariate logistic regression models were built using known correlates of nephrolithiasis.

RESULTS

34.7% (CI: 30.5-39.1%) of United States stone-formers are PWD. The prevalence of nephrolithiasis in PWD is 16.1% (CI: 14.4-18.0) in comparison to 9.2% (CI: 8.3-10.3) in people without disabilities. PWD have significantly elevated odds of nephrolithiasis (un-adjusted OR: 1.91 CI: 1.55-2.36). Adjusting for age, gender, race, diabetes, hypertension, and obesity, odds of nephrolithiasis remains elevated in PWD overall (adjusted OR: 1.46 95% CI: 1.17-1.83) and in all disability domains.

CONCLUSIONS

One in 3 people with nephrolithiasis are PWD. Odds of nephrolithiasis are increased in PWD even after adjustment for multiple known risk factors in all disability domains. PWD are known to be a unique population that can face significant health disparities, but there is a dearth of studies that estimate urologic disease prevalence within this group. Future urologic research should incorporate disability status to explore potential disparities.

Assessing causal associations of obesity and diabetes with kidney stones using Mendelian randomization analysis

BACKGROUND

Obesity and type 2 diabetes have been associated with an increased risk of kidney stones in observational studies, but the causality of these associations remains unestablished. We conducted a Mendelian randomization study to determine these associations.

METHODS

Independent single nucleotide polymorphisms at the genome-wide significance threshold (p < 5 × 10^-8) were selected as instrumental variables and were identified from meta-analyses of genome-wide association studies on body mass index (up to 806,834 individuals) and type 2 diabetes (228,499 cases and 1,178,783 non-cases). Summary-level data for the associations of exposure-associated SNPs with kidney stones were obtained from the UK Biobank study (3540 cases and 357,654 non-cases) and the FinnGen consortium (3856 cases and 172,757 non-cases). Causal estimates from two sources were combined using the meta-analysis method.

RESULTS

Higher genetically predicted body mass index and genetic liability to type 2 diabetes were associated with an increased risk of kidney stones in both the UK Biobank study and FinnGen consortium. In the meta-analysis of results from the two data sources, the odds ratios of kidney stones were 1.33 (95% confidence interval, 1.17, 1.51; p < 0.001) per one standard deviation increase in genetically predicted body mass index (~4.8 kg/m²) and 1.15 (95% confidence interval, 1.10, 1.20; p < 0.001) for one unit increase in genetically predicted log-transformed odds of type 2 diabetes.

INTERPRETATION

This study based on genetic data suggests that a high body mass index and type 2 diabetes may be causal risk factors for kidney stone formation.

Do organic substances act as a degradable binding matrix in calcium oxalate kidney stones?

BACKGROUND

Calcium oxalate (CaOx) stones are considered to be highly resistant to chemolysis. While significant organic matter has been identified within these stones, which is presumed to bind (inorganic) CaOx particles and aggregates, most chemolysis efforts have focused on methods to attack the CaOx components of a stone. We examine the feasibility of inducing chemolysis of CaOx kidney stones, within hours, by specifically attacking the organic matrix present in these stones.

METHODS

In contrast to previous studies, we focused on the possible "brick and mortar" stone configuration. We systematically tested, via in vitro experiments, the ability of an extensive range of 26 potential chemolysis agents to induce relatively fast disintegration (and/or dissolution) of a large set of natural CaOx stone fragments, extracted during endourological procedures, without regard to immediate clinical application. Each stone fragment was monitored for reduction in weight and other changes over 72 h.

RESULTS

We find that agents known to attack organic material have little, if any, effect on stone chemolysis. Similarly, protein and enzymatic agents, and oral additive medical treatments, have little immediate effect.

CONCLUSIONS

These findings suggest that the organic and inorganic constituents present in CaOx stones are not structured as "brick and mortar" configurations in terms of inorganic and organic components.

Trends in the prevalence of kidney stones in the United States from 2007 to 2016

The overall prevalence of kidney stones (KS) in the US rose from 3.2% in 1980 to 10.1% in 2016, but the trends in important subgroups have not been reported. We examined the prevalence trends of KS in subgroups of age, sex and race in the US and identified relevant laboratory factors associated with a history of KS using National Health and Nutrition Examination Survey (NHANES) data. We conducted a cross-sectional study among 28,209 US adults aged ≥ 20 years old in the NHANES from 2007 to 2016. We calculated the prevalence of a self-reported history of KS by using weights and standardized to the 2010 US Census population. We also compared relevant laboratory values according to the history of KS. The prevalence of KS decreased from 8.7% in 2007-2008 to 7.2% in 2011-2012 but then increased to 9.0% in 2013-2014 and 10.1% in 2015-2016. However, the overall prevalence of KS increased over 2007-2016 (p-trend = 0.02). Prevalence of KS among men was higher than women. Among men aged 20-79, there were significant quadratic trends in the prevalence of KS. Whereas, the prevalence of KS increased as a linear trend among women aged 20-59 years over 2007-2016. There were no consistent trends in the prevalence of KS by race. The prevalence trend of KS among non-Hispanic whites was 9.8% from 2007 to 2010 then dropped to 7.9% in 2011-2012 and increased to 10.6% in 2013-2014 and 12.1% in 2015-2016. A similar trend was also observed among non-Hispanic blacks. Among Hispanic, the prevalence of KS was 7.6% in 2007-2008 and 7.4% in 2009-2010 and then fluctuated over the next several time periods. For non-Hispanic Asians, the range was 4.4-4.6%. Regarding relevant laboratory factors, after adjusting for sex, race, age, BMI, smoking status, alcohol drinking, history of diabetes and gout, urine albumin-creatinine ratio and serum osmolality were independently associated with the history of KS in women and men. In conclusion, there was substantial variability in KS prevalence across individual 2-year time periods. This variation of period-specific prevalence values emphasizes the importance of looking at long-term trends and using more than a single 2-year cycle in analyses to increase the precision of the estimate. However, there was an overall increase in the prevalence of KS over 2007-2016.

Association of urinary sex steroid hormones with urinary calcium, oxalate and citrate excretion in kidney stone formers

BACKGROUND

Sex-specific differences in nephrolithiasis with respect to both distribution of prevalence and stone composition are widely described and may be influenced by sex hormones.

METHODS

We conducted a cross-sectional analysis of the relationship between 24-hour urinary sex hormone metabolites measured by gas chromatography-mass spectrometry with urinary calcium, oxalate and citrate excretion in a cohort of 628 kidney stone formers from a tertiary care hospital in Switzerland, taking demographic characteristics, kidney function and dietary factors into account.

RESULTS

We observed a positive association of urinary calcium with urinary testosterone and 17β-estradiol. Positive associations of urinary calcium with dehydroepiandrosterone, 5α-DH-testosterone, etiocholanolone, androsterone, and estriol were modified by net gastrointestinal alkali absorption or urinary sulfate excretion. As the only sex hormone, dehydroepiandrosterone was inversely associated with urinary oxalate excretion in adjusted analyses. Urinary citrate correlated positively with urinary testosterone. Associations of urinary citrate with urinary androsterone, 17β-estradiol and estriol were modified by urinary sulfate or sodium, or by sex.

CONCLUSIONS

Urinary androgens and estrogens are significantly associated with urinary calcium and citrate excretion, and associations are in part modified by diet. Our data furthermore reveal dehydroepiandrosterone as a novel factor associated with urinary oxalate excretion in humans.

Early Surgical Intervention for Symptomatic Renal and Ureteral Stones is Associated With Reduced Narcotic Requirement Relative to Trial of Passage

OBJECTIVES

To evaluate if trial of passage (TOP) or initial surgical intervention resulted in less narcotic analgesia utilization in patients with acute renal colic due to stone disease.

METHODS

We retrospectively evaluated 135 patients with acute renal colic due to nephroureterolithiasis managed by a single surgeon. Patients were standardly offered TOP or surgical intervention with ureteroscopy (URS). A subset of patients were stented with delayed URS due to presence of infection, pain, or a nonaccommodating ureter. Our standard practice is narcotic-free URS, prescribing a stent cocktail including non-steroidal anti-inflammatories. We compared rates of narcotic prescription over the entire treatment course for patients electing TOP vs surgery (primary or delayed URS). We secondarily analyzed rates of surgical intervention among initial TOP.

RESULTS

We included 135 patients, with 69 (51.1%) TOP as initial treatment, 39 (28.9%) stent with delayed URS, and 27 (20.0%) primary URS. Thirty-nine (56.5%) TOP patients underwent URS at a median time of 18 days (IQR 6-31 days) from diagnosis. More TOP patients required a narcotic prescription (60.9% vs 35.9% vs 33.3%, respectively; P = .010) compared to patients undergoing initial stent or URS. However, when an opioid prescription was provided, the total morphine milligram equivalents prescribed among each group was not statistically significant.

CONCLUSION

Patients electing initial treatment with TOP for renal colic due to stone disease were more likely to require narcotic prescriptions than patients electing initial surgical intervention.

Normocalcemic Hyperparathyroidism: A Heterogeneous Disorder Often Misdiagnosed?

Normocalcemic primary hyperparathyroidism (NHPT) was first described over 10 years ago, but uncertainties still remain about its definition, prevalence, and rates of complications. As a result, consensus management guidelines for this condition have not yet been published. Several hypotheses have been proposed for the pathophysiology of NHPT, but it may be a heterogeneous disorder with multiple causes, rather than a single etiology that explains this biochemical phenotype. A common clinical concern is whether NHPT should be treated surgically when complications are already present at first recognition of the disorder, rather than following patients clinically over time. The literature on NHPT is based mostly on larger studies of population‐based cohorts and smaller studies from referral centers. Lack of rigorous diagnostic criteria and selection bias inherent in populations seen at tertiary referral centers may explain the heterogeneity of reported rates of bone and renal complications in relation to consistently mild laboratory alterations. Unresolved questions remain about the significance of NHPT when it is diagnosed biochemically without evident bone or kidney complications. Moreover, its natural history remains to be elucidated because a proportion of what is classified as NHPT may revert to normal spontaneously, thus revealing previously unrecognized secondary hyperparathyroidism. These issues indicate that caution should be used in recommending surgery for NHPT. This review will focus on recent issues regarding the pathophysiology, evaluation, and management of NHPT. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Predictive Factors for Kidney Stone Recurrence in Type 2 Diabetes Mellitus

OBJECTIVE

To determine the predictive factors for kidney stone recurrence in type 2 diabetic patients.

METHODS

A retrospective cohort study was conducted from 2013 to 2019 by using the database of diabetic patients diagnosed with kidney stone disease. The patients were divided into 2 groups according to stone disease status: recurrent stone and nonrecurrent stone. Baseline characteristics were compared and logistic regression was done to assess which variables could predict a stone recurrence.

RESULTS

There were 1617 type 2 diabetic patients with kidney stone disease, 1244 (77%) did not have a stone recurrence and 373 (23%) had a stone recurrence. Of these patients with recurrent stone, 40% had asymptomatic stones, 43% visited emergency department, and 45% required a surgical intervention. Median time to recurrence was 64 months. Multivariable analysis revealed that body mass index (odds ratios [OR] 1.032, 95% confidence interval [CI] 1.016-1.047), urine pH (OR 0.500, CI 0.043-0.581), HbA1c (OR 1.186, CI 1.012-1.277), diabetic neuropathy (OR 1.839, CI 1.413-2.392), diabetic retinopathy (OR 1.690, CI 1.122-2.546), insulin as well as potassium citrate therapy (OR 0.611, CI 0.426-0.87), and stone with calcium oxalate and uric acid composition (OR 1.955, CI 1.420-2.691 and OR 2.221, CI 1.249-3.949, respectively) are significant predictors for stone recurrence.

CONCLUSION

The severity of diabetes and stone composition are strong predictors for stone recurrence in type 2 diabetic patients, while HbA1c and urine pH are important modifiable factors.