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

The Swiss Kidney Stone Cohort: A Longitudinal, Multicentric, Observational Cohort to Study Course and Causes of Kidney Stone Disease in Switzerland

BACKGROUND

Kidney stone disease has a high prevalence worldwide of approximately 10% of the population and is characterized by a high recurrence rate. Kidney stone disease results from a combination of genetic, environmental, and lifestyle risk factors, and the dissection of these factors is complex.

METHODS

The Swiss Kidney Stone Cohort (SKSC) is an investigator-initiated prospective, multicentric longitudinal, observational study in patients with kidney stones followed with regular visits over a period of 3 years after inclusion. Ongoing follow-ups by biannual telephone interviews will provide long-term outcome data. SKSC comprises 782 adult patients (age >18 years) with either recurrent stones or a single stone event with at least one risk factor for recurrence. In addition, a control cohort of 207 individuals without kidney stone history and absence of kidney stones on a low-dose CT scan at enrolment has also been recruited. SKSC includes extensive collections of clinical data, biochemical data in blood and 24-h urine samples, and genetic data. Biosamples are stored at a dedicated biobank. Information on diet and dietary habits was collected through food frequency questionnaires and standardized recall interviews by trained dieticians with the Globodiet software.

CONCLUSION

SKSC provides a unique opportunity and resource to further study cause and course of kidney disease in a large population with data and samples collected of a homogeneous collective of patients throughout the whole Swiss population.

Potential of Unenhanced Ultra-Low-Dose Abdominal Photon-Counting CT with Tin Filtration: A Cadaveric Study

OBJECTIVES

This study investigated the feasibility and image quality of ultra-low-dose unenhanced abdominal CT using photon-counting detector technology and tin prefiltration.

MATERIALS AND METHODS

Employing a first-generation photon-counting CT scanner, eight cadaveric specimens were examined both with tin prefiltration (Sn 100 kVp) and polychromatic (120 kVp) scan protocols matched for radiation dose at three different levels: standard-dose (3 mGy), low-dose (1 mGy) and ultra-low-dose (0.5 mGy). Image quality was evaluated quantitatively by means of contrast-to-noise-ratios (CNR) with regions of interest placed in the renal cortex and subcutaneous fat. Additionally, three independent radiologists performed subjective evaluation of image quality. The intraclass correlation coefficient was calculated as a measure of interrater reliability.

RESULTS

Irrespective of scan mode, CNR in the renal cortex decreased with lower radiation dose. Despite similar mean energy of the applied x-ray spectrum, CNR was superior for Sn 100 kVp over 120 kVp at standard-dose (17.75 ± 3.51 vs. 14.13 ± 4.02), low-dose (13.99 ± 2.6 vs. 10.68 ± 2.17) and ultra-low-dose levels (8.88 ± 2.01 vs. 11.06 ± 1.74) (all p ≤ 0.05). Subjective image quality was highest for both standard-dose protocols (score 5; interquartile range 5-5). While no difference was ascertained between Sn 100 kVp and 120 kVp examinations at standard and low-dose levels, the subjective image quality of tin-filtered scans was superior to 120 kVp with ultra-low radiation dose (p < 0.05). An intraclass correlation coefficient of 0.844 (95% confidence interval 0.763-0.906; p < 0.001) indicated good interrater reliability.

CONCLUSIONS

Photon-counting detector CT permits excellent image quality in unenhanced abdominal CT with very low radiation dose. Employment of tin prefiltration at 100 kVp instead of polychromatic imaging at 120 kVp increases the image quality even further in the ultra-low-dose range of 0.5 mGy.

Quantification of outflow resistance for ureteral drainage devices used during ureteroscopy

PURPOSE

Since renal pelvis pressure is directly related to irrigation flowrate and outflow resistance, knowledge of outflow resistance associated with commonly used drainage devices could help guide the selection of the type and size of ureteral access sheath or catheter for individual ureteroscopic cases. This study aims to quantitatively measure outflow resistance for different drainage devices utilized during ureteroscopy.

METHODS

With measured irrigation flowrate and renal pelvis pressure, outflow resistance was calculated using a hydrodynamic formula. After placement of a drainage device into a silicone kidney-ureter model, a disposable ureteroscope with a 9.5-Fr outer diameter was inserted with its tip positioned at the renal pelvis. Irrigation was delivered through the ureteroscope from varying heights above the renal pelvis. Renal pelvis pressure was measured directly from the port of the kidney model using a pressure sensor (Opsens, Canada). Outflow resistance was determined by plotting flowrate versus renal pelvis pressure. All trials were performed in triplicate for each drainage device inserted.

RESULTS

Flowrate was linearly dependent on renal pelvis pressure for all drainage devices tested. Outflow resistance values were 0.2, 1.1, 1.4, 3.9, and 6.5 cmH₂O/[ml/min] for UAS 13/15 Fr, UAS 11/13 Fr, UAC 6 Fr, UAC 4.8 Fr, and UAC 4.0 Fr, respectively, across the range of commonly used irrigation flowrates.

CONCLUSIONS

In this study, outflow resistance of different ureteral drainage devices was quantitatively measured. This knowledge can be useful when selecting which type and size of drainage device to insert to maintain safe renal pelvis pressure during ureteroscopy.

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.

Ureteroscopy and Shock Wave Lithotripsy Trends from 2012 to 2019 Within the US Medicare Dataset: Sharp Growth in Ureteroscopy Utilization

Introduction and Objective: Both ureteroscopy (URS) and shock wave lithotripsy (SWL) are cornerstones in the surgical management of urolithiasis in the United States. We hypothesized that URS utilization outpaced SWL utilization in recent years and quantified the magnitude of change over time for caseloads of URS and SWL among urologists from a national Medicare database. Methods: Using the public "Medicare Physician & Other Practitioners" database (https://data.cms.gov), we determined case numbers of SWL (current procedural terminology [CPT] 50590) and URS (CPT 52356 or 52353) from 2012 to 2019. In a subanalysis, we identified "high-volume stone urologists" as those in the upper quartile of case numbers for both SWL and URS in baseline years of either 2012 or 2013 and trended their caseload from 2012 to 2019. Linear estimation models assessed annual rates of change and their statistical significance. Results: In 2012, urologists performed 41,135 SWL procedures vs 21,184 URS. URS overtook SWL in 2017 and by 2019 was the dominant modality (60,063 URS vs 43,635 SWL). Between 2012 and 2019, total URS cases annually increased by 5700 (15%/year, p < 0.001), while the number of SWL cases peaked in 2015 and has since declined on average -1.6%/year (p = 0.020). The number of urologists performing URS steadily rose from 1147 in 2012 to 2809 in 2019, reflecting an additional 246 urologists (21%/year) performing URS annually. The caseload of high-volume stone urologists showed similar trends with average URS cases increasing by 2.9/year/urologist (9.8%/year, p < 0.001) and average SWL cases declining by 0.9/year/urologist (-1.7%/year, p = 0.023). Conclusions: URS utilization has increased dramatically and outpaced SWL utilization from 2012 to 2019 within the Medicare population. URS was increasingly used by both the general urologist population and high-volume stone urologists while SWL utilization has begun to decline.

The microbiome of kidney stones and urine of patients with nephrolithiasis

The incidence of nephrolithiasis is rising worldwide. Although it is a multifactorial disease, lifestyle plays a major role in its etiology. Another considerable factor could be an aberrant microbiome. In our observational single-center study, we aimed to investigate the composition of bacteria in kidney stones and urine focusing on patients with features of metabolic syndrome. Catheterized urine and kidney stones were collected prospectively from 100 consecutive patients undergoing endoscopic nephrolithotomy between 2020 and 2021 at our clinic. Microbiome composition was analyzed via 16S rRNA gene amplicon sequencing. Detection of bacteria was successful in 24% of the analyzed kidney stones. These patients had a prolonged length of stay compared to patients without verifiable bacteria in their stones (2.9 vs 1.5 days). Patients with features of metabolic syndrome were characterized by kidney stones colonized with classical gastrointestinal bacteria and displayed a significant enrichment of Enterococcaceae and Enterobacteriaceae. Stones of patients without features of metabolic syndrome characterized by Ureaplasma and Staphylococcaceae. Patients with bacteria in their kidney stones exhibit a longer length of stay, possibly due to more complex care. Patients presenting with features of metabolic syndrome displayed a distinct stone microbiome compared to metabolically fit patients. Understanding the role of bacteria in stone formation could enable targeted therapy, prevention of post-operative complications and new therapeutic strategies.

Deep Learning Model for Computer-Aided Diagnosis of Urolithiasis Detection from Kidney-Ureter-Bladder Images

Kidney-ureter-bladder (KUB) imaging is a radiological examination with a low cost, low radiation, and convenience. Although emergency room clinicians can arrange KUB images easily as a first-line examination for patients with suspicious urolithiasis, interpreting the KUB images correctly is difficult for inexperienced clinicians. Obtaining a formal radiology report immediately after a KUB imaging examination can also be challenging. Recently, artificial-intelligence-based computer-aided diagnosis (CAD) systems have been developed to help clinicians who are not experts make correct diagnoses for further treatment more effectively. Therefore, in this study, we proposed a CAD system for KUB imaging based on a deep learning model designed to help first-line emergency room clinicians diagnose urolithiasis accurately. A total of 355 KUB images were retrospectively collected from 104 patients who were diagnosed with urolithiasis at Kaohsiung Chang Gung Memorial Hospital. Then, we trained a deep learning model with a ResNet architecture to classify KUB images in terms of the presence or absence of kidney stones with this dataset of pre-processed images. Finally, we tuned the parameters and tested the model experimentally. The results show that the accuracy, sensitivity, specificity, and F1-measure of the model were 0.977, 0.953, 1, and 0.976 on the validation set and 0.982, 0.964, 1, and 0.982 on the testing set, respectively. Moreover, the results demonstrate that the proposed model performed well compared to the existing CNN-based methods and was able to detect urolithiasis in KUB images successfully. We expect the proposed approach to help emergency room clinicians make accurate diagnoses and reduce unnecessary radiation exposure from computed tomography (CT) scans, along with the associated medical costs.

Theranostic roles of machine learning in clinical management of kidney stone disease

Kidney stone disease (KSD) is a common illness caused by deposition of solid minerals formed inside the kidney. The disease prevalence varies, based on sociodemographic, lifestyle, dietary, genetic, gender, age, environmental and climatic factors, but has been continuously increasing worldwide. KSD is a highly recurrent disease, and the recurrence rate is about 11% within two years after the stone removal. Recently, machine learning has been widely used for KSD detection, stone type prediction, determination of appropriate treatment modality and prediction of therapeutic outcome. This review provides a brief overview of KSD and discusses how machine learning can be applied to diagnostics, therapeutics and prognostics in clinical management of KSD for better therapeutic outcome.

Economic burden of complicated ureteral stent removal in patients with kidney stone disease in the USA

Aim: To examine the medical costs of simple versus complicated ureteral stent removal. Materials & methods: We included adults with kidney stones undergoing simple or complicated cystoscopy-based stent removal (CBSR) post ureteroscopy from the 2014 to 2018 Merative™ MarketScan^® Commercial Database. The medical costs of patients with complicated and simple CBSR were compared. Results: Among 16,682 patients, 2.8% had complicated CBSR. Medical costs for patients with complicated CBSR were higher than for simple CBSR ($2182 [USD] vs $1162; p < 0.0001). Increased stenting time, increased age, southern US geography and encrusted stent diagnoses were significantly associated with complicated CBSR. Conclusion: Complicated ureteral stent removal doubled the medical costs associated with CBSR. Ureteral stents with anti-encrustation qualities may reduce the need for complicated CBSR and associated costs.

Comparison of Surgical Outcomes between Single-Use and Reusable Flexible Ureteroscopes for Renal Stone Management: A Systematic Review and Meta-Analysis

Background and Objectives: Disposable flexible ureteroscopes have been widely used because of their cost-effectiveness and higher sterility potential compared with reusable flexible ureteroscopes. This study aimed to compare the surgical outcomes and complication rates in patients who undergo reusable or disposable flexible ureteroscopic stone surgeries (fURS) for urinary stone disease. Materials and Methods: A systematic review and meta-analysis were conducted under the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. This systematic review was registered with PROSPERO (CRD42022331291). Clinical trials comparing reusable and disposable fURS for stone disease were found from PubMed, EMBASE, Cochrane Library, and the Web of Science up to March 2022. Participants were patients with upper urinary tract stones; the interventions were reusable or disposable fURS. Outcomes, including stone-free rate, operation time, length of hospital stay, and complication rate, were compared for analysis. Results: Overall, 111 studies were identified, but after removing duplicate studies, 75 studies remained. Thirty-two of these studies were excluded. Of the 43 screened studies, 11 met the eligibility criteria. There was no difference in the stone-free rate (SFR) between disposable and reusable fURS (p = 0.14; OR = 1.36; 95% CI, 0.9 to 2.04). For operation time, no difference was identified between reusable and disposable fURS groups (p = 0.12; MD = -5.31; 95% CI, -12.08 to 1.46). For hospital stay, there was also no difference between the two groups (p = 0.61; MD = -0.03; 95% CI, -0.17 to 0.10). There was no significant difference in complication rate between the two groups (p = 0.85; OR = 0.95; 95% CI, 0.56 to 1.61). Conclusions: There were no differences in the SFR, operation time, length of hospital stay, and complication rate between reusable and disposable fURS. Disposable fURS may be a comparable alternative to reusable fURS.

Dietary Risk Factors for Incident and Recurrent Symptomatic Kidney Stones

OBJECTIVE

To compare dietary factors between incident symptomatic stone formers and controls, and among the incident stone formers, to determine whether dietary factors were predictive of symptomatic recurrence.

PATIENTS AND METHODS

We prospectively recruited 411 local incident symptomatic kidney stone formers (medical record validated) and 384 controls who were seen at Mayo Clinic in Minnesota or Florida between January 1, 2009, and August 31, 2018. Dietary factors were based on a Viocare, Inc, food frequency questionnaire administered during a baseline in-person study visit. Logistic regression compared dietary risk factors between incident symptomatic stone formers and controls. Incident stone formers were followed up for validated symptomatic recurrence in the medical record. Cox proportional hazards models estimated risk of symptomatic recurrence with dietary factors. Analyses adjusted for fluid intake, energy intake, and nondietary risk factors.

RESULTS

In fully adjusted analyses, lower dietary calcium, potassium, caffeine, phytate, and fluid intake were all associated with a higher odds of an incident symptomatic kidney stone. Among incident stone formers, 73 experienced symptomatic recurrence during a median 4.1 years of follow-up. Adjusting for body mass index, fluid intake, and energy intake, lower dietary calcium and lower potassium intake were predictive of symptomatic kidney stone recurrence. With further adjustment for nondietary risk factors, lower dietary calcium intake remained a predictor of recurrence, but lower potassium intake only remained a predictor of recurrence among those not taking thiazide diuretics or calcium supplements.

CONCLUSION

Enriching diets in stone formers with foods high in calcium and potassium may help prevent recurrent symptomatic kidney stones.

Roles of heat-shock protein 90 and its four domains (N, LR, M and C) in calcium oxalate stone-forming processes

Human heat-shock protein 90 (HSP90) has four functional domains, including NH₂-terminal (N), charged linker region (LR), middle (M) and COOH-terminal (C) domains. In kidney stone disease (or nephrolithiasis/urolithiasis), HSP90 serves as a receptor for calcium oxalate monohydrate (COM), which is the most common crystal to form kidney stones. Nevertheless, roles of HSP90 and its four domains in kidney stone formation remained unclear and under-investigated. We thus examined and compared their effects on COM crystals during physical (crystallization, growth and aggregation) and biological (crystal–cell adhesion and crystal invasion through extracellular matrix (ECM)) pathogenic processes of kidney stone formation. The analyses revealed that full-length (FL) HSP90 obviously increased COM crystal size and abundance during crystallization and markedly promoted crystal growth, aggregation, adhesion onto renal cells and ECM invasion. Comparing among four individual domains, N and C domains exhibited the strongest promoting effects, whereas LR domain had the weakest promoting effects on COM crystals. In summary, our findings indicate that FL-HSP90 and its four domains (N, LR, M and C) promote COM crystallization, crystal growth, aggregation, adhesion onto renal cells and invasion through the ECM, all of which are the important physical and biological pathogenic processes of kidney stone formation.

Predictors and Healthcare Utilization of Sepsis Post-Ureteroscopy in a US-Based Population : Results from the Endourological Society TOWER Collaborative

Purpose To investigate the incidence, predictive factors, and healthcare utilization of sepsis post-ureteroscopy (URS) in patients enrolled in commercial insurance plans. Materials and Methods A retrospective claims analysis was conducted using the IBM® MarketScan® commercial database. Patients ≥18 years were included if they had URS between January 2015-October 2019 and developed sepsis within 30 days of URS. Multivariate logistic regression was used to identify various clinical and demographic predictors of sepsis post-URS. All-cause healthcare utilization (i.e., inpatient admissions and intensive care unit stays) and all-cause healthcare costs up to 1 month post-septic event were measured. Results Among the 104,100 URS patients meeting the inclusion criteria, 5.5% developed sepsis. Patients with diabetes (OR=1.52; p<0.0001), older age (age 55-64 versus 18-34; OR=1.35; p<0.0001), baseline sepsis (OR=3.51; p<0.0001), baseline inpatient visits (OR=1.17; p=0.0012), and higher Elixhauser comorbidity scores (OR=1.09; p<0.0001) had a significantly higher likelihood of developing sepsis post-URS. In septic patients, 94.8% required inpatient care and 35% were admitted to the ICU. Mean hospital stay for septic patients was 6.86 days. Average all-cause healthcare cost per patient at 1 month in the septic cohort was $49,625 versus $17,782 in the non-septic cohort indicating an incremental all-cause cost of $31,843 (p<0.0001). Conclusions A total of 5.5% of commercially insured patients undergoing URS developed sepsis post-URS. Diabetes, older age, baseline sepsis, baseline inpatient visit, and higher comorbidity score were all found to be independent predictors of post-URS sepsis. Patients with sepsis post-URS had higher healthcare utilization and costs indicating that sepsis is both a significant clinical and economic event.

Vascular Calcification Is Associated with Fetuin-A and Cortical Bone Porosity in Stone Formers

Background: Nephrolithiasis has been associated with bone loss and vascular calcification (VC), reflecting abnormal extraosseous calcium deposition. Fetuin-A (Fet-A) acts as a potent inhibitor of ectopic mineralization. The aim of the present study was to evaluate the prevalence of VC in stone formers (SF) and non-stone formers (NSF) and to investigate potential determinants of VC among SF, including circulating levels of Fet-A and bone microarchitecture parameters. Methods: Abdominal aortic calcification (AAC) was assessed using available computed tomography in SF and in age-, sex-, and BMI-matched NSF (potential living kidney donors). Serum Fet-A was measured in stored blood samples from SF. Bone microarchitecture parameters were obtained as a post hoc analysis of a cross-sectional cohort from young SF evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT). Results: A total of 62 SF (38.0 [28.0−45.3] years old) and 80 NSF (40.0 [37.0−45.8] years old) were included. There was no significant difference in AAC scores between SF and NSF. However, when dividing SF according to mean AAC score, below <5.8% (n = 33) or above ≥5.8% (n = 29), SF with higher AAC presented significantly higher BMI and tibial cortical porosity (Ct.Po) and significantly lower serum HDL, klotho, Fet-A, and eGFR. Urinary calcium did not differ between groups, but fractional excretion of phosphate was higher in the former. Upon multivariate regression, BMI, serum Fet-A, and tibial Ct.Po remained independently associated with AAC. Conclusions: This study suggests an association between reduced circulating Fet-A levels and increased bone Ct.Po with VC in SF.

Prevalence and trends of urolithiasis among adults

PURPOSE OF REVIEW

The purpose of this article is to review and synthesize the current literature on the epidemiology of urolithiasis.

RECENT FINDINGS

The global patterns of urolithiasis are changing, as the prevalence of urolithiasis appears to be increasing across the world. Geographical variation in the prevalence of urolithiasis is noted across countries and within each country. Although urolithiasis is more common among men and white race, recent data suggests a more prominent rise in the prevalence among women and African Americans. Yet, no conclusive explanations for these phenomena are reported so far.

SUMMARY

Urolithiasis is a highly prevalent condition with an increasing prevalence among women as compared with men closing the gender gap in urolithiasis. Further studies are needed to identify the potential causes for this observation.

Imaging in stone diagnosis and surgical planning

PURPOSE OF REVIEW

Radiological imaging techniques and applications are constantly advancing. This review will examine modern imaging techniques in the diagnosis of urolithiasis and applications for surgical planning.

RECENT FINDINGS

The diagnosis of urolithiasis may be done via plain film X-ray, ultrasound (US), or contrast tomography (CT) scan. US should be applied in the workup of flank pain in emergency rooms and may reduce unnecessary radiation exposure. Low dose and ultra-low-dose CT remain the diagnostic standard for most populations but remain underutilized. Single and dual-energy CT provide three-dimensional imaging that can predict stone-specific parameters that help clinicians predict stone passage likelihood, identify ideal management techniques, and possibly reduce complications. Machine learning has been increasingly applied to 3-D imaging to support clinicians in these prognostications and treatment selection.

SUMMARY

The diagnosis and management of urolithiasis are increasingly personalized. Patient and stone characteristics will support clinicians in treatment decision, surgical planning, and counseling.

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.

Urinary stone composition in Germany: results from 45,783 stone analyses

Purpose

Stone composition can provide valuable information for the diagnosis, treatment and recurrence prevention of urolithiasis. The aim of this study was to evaluate the distribution of urinary stone components and the impact of different crystal forms according to gender and age of patients in Germany.

Methods

A total of 45,783 urinary stones submitted from 32,512 men and 13,271 women between January 2007 and December 2020 were analyzed by infrared spectroscopy. Only the first calculus obtained per patient was included in the analysis.

Results

The most common main stone component was calcium oxalate (CaOx) (71.4%), followed by carbonate apatite (CA) (10.2%) and uric acid (UA) (8.3%). Struvite (2.1%), brushite (1.3%), protein (0.5%) and cystine (0.4%) stones were only rarely diagnosed. CaOx (75%) and UA stones (81%) were more frequently obtained from men than women (p < 0.001). Weddellite (COD) and uric acid dihydrate (UAD) were more common in younger ages than whewellite (COM) and anhydrous uric acid (UAA), respectively, in both men and women. The ratios of COM-to-COD and UAA-to-UAD calculi were approximately 4:1 and 8:1, respectively. The peak of stone occurrence was between the ages of 40 and 59 years.

Conclusion

Stone composition is strongly associated with gender and age. The peak incidence of calculi in both women and men was in the most active phase of their working life. The distinction between different crystal forms could provide clues to the activity and mechanisms of lithogenesis. Further research is needed in understanding the causative factors and the process of stone formation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00345-022-04060-w.

Effects of metabolic syndrome on renal stone progression

PURPOSE

Studies on howmetabolic syndrome affects renal stone progression in untreated asymptomatic patients are lacking. Therefore, we investigated the effect of metabolic syndrome on changes in renal stone size.

MATERIALS AND METHODS

We retrospectively analyzed 820 patients with renal stones incidentally detected on CT during regular health examinations and who underwent follow-up CT evaluations for > 1 year. The patients were divided into two groups according to the presence of metabolic syndrome. Changes in stone size during the follow-up were assessed, and differences were compared according to various factors. Predictors of stone size change on CT were assessed using linear regression analysis.

RESULTS

Overall, 820 asymptomatic patients without a history of stone treatments and with a mean follow-up of 52.4 months were included. Of these, 104 (12.7%) had metabolic syndrome and 335 (40.9%) showed stone size increase during the follow-up. The stone size at diagnosis was not significantly different between patients with and without metabolic syndrome (225.3 ± 332.6 vs. 183.9 ± 310.2 mm³, p = 0.159); however, a significant difference was observed in the change in stone size at follow-up (148.5 ± 352.0 vs. 81.5 ± 222.4 mm³, p = 0.001). Multivariable analysis showed that age (β = - 0.11; - 5.92 to -0.69; p = 0.013), fasting glucose level ≥ 100 mg/dl (β = 0.11; 9.78-99.73; p = 0.017), and metabolic syndrome (β = 0.10; 9.78-99.73; p = 0.017) were factors predictive of stone size changes.

CONCLUSION

Metabolic syndrome, fasting glucose level ≥ 100 mg/dl and young age are positively related to renal stone size changes. Therefore, periodic follow-up and metabolic syndrome management are required in asymptomatic patients with renal stones, especially in young age.

Risk factors for kidney stone disease recurrence: a comprehensive meta-analysis

Background

Kidney stone disease (KSD) is a common illness that causes an economic burden globally. It is easy for patients to relapse once they have suffered from this disease. The reported recurrence rate of KSD ranged from 6.1% to 66.9%. We performed this meta-analysis to identify various potential risk factors for the recurrence of KSD.

Methods

The PubMed, Embase and Web of Science databases were searched using suitable keywords from inception to Mar 2022. A total of 2,663 records were collected initially. After screening the literature according to the inclusion and exclusion criteria, 53 articles (40 retrospective studies; 13 prospective studies) including 488,130 patients were enrolled. The study protocol was registered with PROSPERO (No. CRD42020171771).

Results

The pooled results indicated that 12 risk factors including younger age (n = 18), higher BMI (n = 16), family history of kidney stones (n = 12), personal history of kidney stones (n = 11), hypertension (n = 5), uric acid stone (n = 4), race of Caucasian (n = 3), suspected kidney stone episode before the first confirmed stone episode (n = 3), surgery (n = 3), any concurrent asymptomatic (nonobstructing) stone (n = 2), pelvic or lower pole kidney stone (n = 2), and 24 h urine test completion (n = 2) were identified to be associated with KSD recurrence. In the subgroup analysis, patients with higher BMI (OR = 1.062), personal history of nephrolithiasis (OR = 1.402), or surgery (OR = 3.178) had a higher risk of radiographic KSD recurrence.

Conclusions

We identified 12 risk factors related to the recurrence of KSD. The results of this analysis could serve to construct recurrence prediction models. It could also supply a basis for preventing the recurrence of KSD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-022-01017-4.

Comparison of Ultra-Mini Percutaneous Nephrolithotomy and Retrograde Intrarenal Surgery for Renal Stones: A Systematic Review and Meta-Analysis from the KSER Update Series

Miniaturized percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS) for renal stones have been developed to overcome the invasive disadvantages of PCNL. We aimed to compare the therapeutic effect and safety of ultra-mini percutaneous nephrolithotomy (UMPCNL) and RIRS for renal stones using an updated systematic review and meta-analysis. We searched clinical trials comparing UMPCNL and RIRS for renal stones using the PubMed, EMBASE, Cochrane Library, and Google Scholar databases up to October 2021. Seven studies were included in the current study. The renal stone size was 10–20 mm in three studies, 10–25 mm in one study, 10–35 mm in two studies, and not specified in one study. The stone-free rate of UMPCNL was higher than that of RIRS (p = 0.02; odds ratio (OR) = 2.01; 95% confidence interval (CI) = 1.12, 3.61). The complication rate showed no significant difference between UMPCNL and RIRS (p = 0.48; OR = 1.20; 95% CI = 0.73, 1.98). Regarding the operative time, UMPCNL was shorter than RIRS (p = 0.005; weighted mean difference (WMD) = −15.63; 95% CI = −26.60, −4.67). The hospital stay of UMPCNL was longer than that of RIRS (p = 0.0004; WMD = 1.48; 95% CI = 0.66, 2.31). UMPCNL showed higher efficacy than RIRS and similar safety to RIRS. UMPCNL may be a useful therapeutic option for moderate-sized renal stones.

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.

Association between body fat distribution and kidney stones: Evidence from a US population

OBJECTIVES

We aimed to evaluate the relationship between the proportion of Android to Gynoid ratio and the incidence of kidney stones among US adults.

METHODS

Participants aged 20-59 years from the 2011-2018 National Health and Nutrition Examination Survey (NHANES) database were selected to assess the association between Android to Gynoid ratio and kidney stone prevalence using logistic regression analysis, subgroup analysis and calculation of dose-response curves.

RESULTS

This study ultimately included 10858 participants, of whom 859 self-reported a history of kidney stones. And after adjusting for all confounders, an increased Android to Gynoid ratio was associated with an increased prevalence of kidney stones (OR=2.75, 95% CI:1.62-4.88). And subgroup analysis showed an increased prevalence of kidney stones in women (OR=3.55, 95% CI: 1.54-8.22), non-diabetic (OR=2.59, 95% CI: 1.45-4.60), 60 > age ≥ 40 years (OR=3.51, 95% CI: 1.83-6.71), Mexican-American (OR=4.35, 95% CI: 1.40- 13.53) and white (OR=3.86, 95% CI: 1.82-8.18) groups, there was a significant positive association between A/G ratio and kidney stones. In contrast, in the hypertensive subgroup, the A/G ratio was associated with kidney stones in all groups.

CONCLUSIONS

Higher Android to Gynoid ratio is associated with a high prevalence of kidney stone disease.

Application of Clavien-Dindo Classification System for Complications of Minimally Invasive Percutaneous Nephrolithotomy

Objective

To investigate the clinical applications of the Clavien-Dindo classification system (CDCS) in the assessment of perioperative complications in minimally invasive percutaneous nephrolithotomy (MPCNL).

Methods

Totally, 390 patients with renal stones in our hospital from March 2015 to March 2020 were included for this study and then were divided into observation group (complication group, 78 cases) and control group (noncomplication group, 312 cases) according to the incidence of perioperative complications in CDCS. Single factor analysis and multivariate logistic regression analysis were used to analyze the risk factors of the perioperative complications of MPCNL.

Results

The total incidence of complication in the 390 cases with MPCNL was 20.00% (78 cases) according to CDCS, among which the incidence of complications at grades I, II, III, IV, and V was 6.92% (27 cases), 8.21% (32 cases), 2.82% (11 cases), 1.79% (7 cases), and 0.26% (1 case), respectively. The proportion of patients, that aged >60 years, complicated with comorbidities, sophisticated calculi, the preoperative albumin level (<35 g/L), the operation time (>180 minutes), intraoperative bleeding volume (>300 mL), and hospitalization time (>7 days) in the observation group was significantly higher than that in the control group ((75.64% vs. 61.86%, 38.46% vs. 24.36%, 83.33% vs. 69.55%, 83.33% vs. 69.55%, 70.51% vs. 30.76%, 53.85% vs. 36.54%, and 60.26% vs. 43.27%), all P < 0.05). Multivariate logistic regression analysis showed that gender, associated comorbidities, preoperative albumin level, calculus complexity, operation time, and intraoperative bleeding volume (>300 mL) were correlated with the occurrence of complications (P ≤ 0.001, 0.001, 0.001, 0.001, 0.003, and 0.001 respectively).

Conclusion

The CDCS can give standard and more comparative criteria for the assessment of perioperative complications, which will provide reference data for reducing complications and ensuring safety profiles in these high-risk patients.

Effect of Black Tea Consumption on Urinary Risk Factors for Kidney Stone Formation

Copious fluid intake is the most essential nutritional measure in the treatment of urolithiasis, and is suggested to be a protective factor in the primary prevention of urinary stone formation. Although the intake of black tea contributes to daily fluid intake, the high oxalate content could outweigh the beneficial effect of urine dilution. The present study investigated the effect of black tea consumption on urinary risk factors for kidney stone formation. Ten healthy men received a standardized diet for a period of ten days. Subjects consumed 1.5 L/day of fruit tea (0 mg/day oxalate) during the 5-day control phase, which was replaced by 1.5 L/day of black tea (86 mg/day oxalate) during the 5-day test phase. Fractional and 24-h urines were obtained. The intake of black tea did not significantly alter 24-h urinary oxalate excretion. Urinary citrate, an important inhibitor of calcium stone formation, increased significantly, while the relative supersaturation of calcium oxalate, uric acid, and struvite remained unchanged. No significantly increased risk for kidney stone formation could be derived from the ingestion of black tea in normal subjects. Further research is needed to evaluate the impact of black tea consumption in kidney stone patients with intestinal hyperabsorption of oxalate.

Outcomes for Geriatric Urolithiasis Patients aged ≥80 Years Compared to Patients in Their Seventies

BACKGROUND

Demographic changes are leading to an increase in geriatric urolithiasis patients aged ≥70 yr. Published data regarding their management remain sparse. In particular, for the subgroup of patients aged ≥80 yr there is a lack of evidence supporting the hypothesis that stone-removing treatment is effective, safe, and beneficial.

OBJECTIVE

To examine the efficiency and safety of stone-removing treatment in geriatric urolithiasis patients aged ≥80 yr compared to their younger geriatric counterparts aged 70-79 yr against the background of their respective life expectancy.

DESIGN, SETTING, AND PARTICIPANTS

Data for the study cohort were extracted from an institutional review board-approved retrospective database with 325 patients aged ≥70 yr (70-79 yr: n = 241; ≥80 yr: n = 84) consecutively admitted to hospital because of symptomatic urolithiasis from 2013 to 2018.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Baseline characteristics, outcome and follow-up data, and survival were compared using Wilcoxon-Mann-Whitney U tests, χ² tests, Kaplan-Meier estimation, log-rank tests, and Cox regression.

RESULTS AND LIMITATIONS

At baseline, the incidence of infected hydronephrosis was greater among patients aged ≥80 yr (p < 0.05), whereas the median stone burden and Charlson comorbidity index did not differ between the groups. Outcome analysis revealed no significant differences in terms of complication, stone-free, and 6-mo readmission rates (p > 0.05). Survival analysis for the two groups demonstrated a 2-yr overall survival (OS) rate of 0.91 (95% confidence interval [CI] 0.75-1) for patients aged ≥80 yr and 0.97 (95% CI 0.88-1), for those aged 70-79 yr (p < 0.01). Multivariable Cox analysis revealed age ≥80 yr (hazard ratio [HR] 3.3, 95% CI 1.3-8.5) and infected hydronephrosis (HR 2.8, 95% CI 1.0-7.8) as predictors of all-cause mortality (p < 0.05). The study is limited by its retrospective design.

CONCLUSIONS

Stone-removing treatment for patients aged ≥80 yr proved to be as effective and safe as for patients in their seventies. Although characterized by shorter remaining life expectancy, excellent 2-yr OS for patients aged ≥80 yr supports the hypothesis of equal benefit from stone-removing treatment when compared to septuagenarians.

PATIENT SUMMARY

There is a lack of evidence supporting the benefit of urinary stone-removing treatment for patients older than 80 yr. Our study included geriatric patients older than 70 yr with symptomatic urinary stone disease for which urinary drainage or stone removal is indicated. We compared treatment outcomes and survival between two age groups: patients aged 70-79 yr and those aged 80 yr or older. We found equivalent outcomes for the two groups and excellent 2-yr overall survival of 91% for those older than 80 yr. The study strengthens the evidence that active stone-removing therapy is safe and beneficial for these patients.

Use of extracorporeal physical vibration lithecbole through greater sciatic foramen for treatment of distal ureteral calculi

Introduction To evaluate the efficacy and safety of preforming extracorporeal physical vibration lithecbole(EVPL)through greater sciatic foramen(GSF)for distal ureteral calculi(DUC) treatment. Materials and methods All patients with a diagnosis of DUC (6 - 10 mm in diameter) were enrolled in this study from October 2018 to May 2020. Patients were randomly divided into three groups receiving EPVL through GSF (Group A, n = 58), or abdominal (Group B, n = 60), or combined with oral use of tamsulosin at 0.4 mg daily (Group C, n = 63). Results There was no significant difference observed in terms of demographic characteristics or size of stones among the three groups (p >0.05). Compared with the group B and C, patients of the group A displayed a significantly higher score of comfort but with significantly decreased number of renal colic attacks or analgesics required (p < 0.01). The stone-free rate also significantly increased after one and two weeks of treatment (p < 0.01), despite such a significant difference among these groups vanished after four weeks of treatment. Conclusion Extracorporeal physical vibrational lithecbole in the prone position use the greater sciatic foramen as the path is the safe and effective approach to treat the distal ureter calculi.

Nutrition and Kidney Stone Disease

The prevalence of kidney stone disease is increasing worldwide. The recurrence rate of urinary stones is estimated to be up to 50%. Nephrolithiasis is associated with increased risk of chronic and end stage kidney disease. Diet composition is considered to play a crucial role in urinary stone formation. There is strong evidence that an inadequate fluid intake is the major dietary risk factor for urolithiasis. While the benefit of high fluid intake has been confirmed, the effect of different beverages, such as tap water, mineral water, fruit juices, soft drinks, tea and coffee, are debated. Other nutritional factors, including dietary protein, carbohydrates, oxalate, calcium and sodium chloride can also modulate the urinary risk profile and contribute to the risk of kidney stone formation. The assessment of nutritional risk factors is an essential component in the specific dietary therapy of kidney stone patients. An appropriate dietary intervention can contribute to the effective prevention of recurrent stones and reduce the burden of invasive surgical procedures for the treatment of urinary stone disease. This narrative review has intended to provide a comprehensive and updated overview on the role of nutrition and diet in kidney stone disease.

Standardization of microbiome studies for urolithiasis: an international consensus agreement

Numerous metagenome-wide association studies (MWAS) for urolithiasis have been published, leading to the discovery of potential interactions between the microbiome and urolithiasis. However, questions remain about the reproducibility, applicability and physiological relevance of these data owing to discrepancies in experimental technique and a lack of standardization in the field. One barrier to interpreting MWAS is that experimental biases can be introduced at every step of the experimental pipeline, including sample collection, preservation, storage, processing, sequencing, data analysis and validation. Thus, the introduction of standardized protocols that maintain the flexibility to achieve study-specific objectives is urgently required. To address this need, the first international consortium for microbiome in urinary stone disease - MICROCOSM - was created and consensus panel members were asked to participate in a consensus meeting to develop standardized protocols for microbiome studies if they had published an MWAS on urolithiasis. Study-specific protocols were revised until a consensus was reached. This consensus group generated standardized protocols, which are publicly available via a secure online server, for each step in the typical clinical microbiome-urolithiasis study pipeline. This standardization creates the benchmark for future studies to facilitate consistent interpretation of results and, collectively, to lead to effective interventions to prevent the onset of urolithiasis, and will also be useful for investigators interested in microbiome research in other urological diseases.

Risk of Metabolic Syndrome in Kidney Stone Formers: A Comparative Cohort Study with a Median Follow-Up of 19 Years

Background: Kidney stone formers (SF) are more likely to develop diabetes mellitus (DM), but there is no study examining risk of metabolic syndrome (MetS) in this population. We aimed to describe the risk of MetS in SF compared to non-SF. Methods and Materials: SF referred to a tertiary referral metabolic centre in Southern England from 1990 to 2007, comparator patients were age, sex, and period (first stone) matched with 3:1 ratio from the same primary care database. SF with no documentation or previous MetS were excluded. Ethical approval was obtained and MetS was defined using the modified Association of American Clinical Endocrinologists (AACE) criteria. Analysis with cox proportional hazard regression. Results: In total, 828 SF were included after 1000 records were screened for inclusion, with 2484 age and sex matched non-SF comparators. Median follow-up was 19 years (interquartile range—IQR: 15–22) for both stone formers and stone-free comparators. SF were at significantly increased risk of developing MetS (hazard ratio—HR: 1.77; 95% confidence interval—CI: 1.55–2.03, p < 0.001). This effect was robust to adjustment for pre-existing components (HR: 1.91; 95% CI: 1.66–2.19, p < 0.001). Conclusions: Kidney stone formers are at increased risk of developing metabolic syndrome. Given the pathophysiological mechanism, the stone is likely a ‘symptom’ of an underlying metabolic abnormality, whether covert or overt. This has implications the risk of further stone events and cardiovascular disease.

The effect of shock wave lithotripsy and retrograde intrarenal surgery on health-related quality of life in 10-20 mm renal stones: a prospective randomized pilot study

The effects of treatment modalities such as retrograde intrarenal surgery (RIRS) and shock wave lithotripsy (SWL) on health-related quality of life (HRQoL) were determined in patients with renal stones between 10 and 20 mm. A total of 120 patients were included in the study and prospectively randomized to RIRS or SWL group. A total of 39 patients experienced treatment failure and finally 81 patients (45 patients in the RIRS group, 36 patients in the SWL group) were analyzed for HRQoL. SF-36 survey was used to determine HRQoL pre-operatively, post-operative day 1 and 1 month. The patient and stone characteristics such as age, gender, stone size, grade of hydronephrosis and body mass index were similar between the two groups. At post-operative day 1, the RIRS group was associated with lower scores of role functioning/physical (p = 0.008), role functioning/emotional (p = 0.047) energy/fatigue (p = 0.011), social functioning (p = 0.003) and pain (p = 0.003) when compared to the SWL group. At post-operative 1 month, only pain and emotional well-being scores (p = 0.012 and p = 0.011, respectively) in the RIRS group were statistically lower according to the SWL group. In our study, patients in the SWL group showed more favorable HRQoL scores when compared to the patients in the RIRS group in short-term follow-up.