The ROKS nomogram for predicting a second symptomatic stone episode

Mesenchymal stem cells attenuate hyperoxaluria-induced kidney injury and crystal depositions via inhibiting the activation of NLRP3 inflammasome

AIMS

Calcium oxalate (CaOx) is the predominant form of kidney stones, associated with significant morbidity and recurrence rates. Mesenchymal stem cells (MSCs) have shown promise in treating renal injury, but their impact on CaOx stone formation remains unclear.

MATERIALS AND METHODS

We established a hyperoxaluria-induced AKI model in mice through intraperitoneal injection of glyoxylate. Two types of MSCs, bone marrow-derived MSCs (BMSCs) and umbilical cord-derived mesenchymal stem cells (UMSCs), were injected through tail vein injection. Histological evaluations and blood biochemical tests were performed to assess crystal deposition and kidney function. The inflammatory response and NLRP3 inflammasome activation were assessed using immunofluorescence, immunohistochemistry, TUNEL staining, and qPCR. In vitro, macrophages were cocultured in the presence of MSCs. ELISA was used to measure IL-1β and IL-18 release. MTS assays assessed renal epithelial cell protection. Western blotting evaluated NLRP3 inflammasome activation in macrophages.

KEY FINDINGS

Both BMSCs and UMSCs significantly inhibited CaOx crystal deposition and kidney injury by inhibiting NLRP3 inflammasome activation. In vitro, both MSC types suppressed NLRP3 inflammasome activation in macrophages through the NF-κB signaling pathway, leading to decreased release of IL-1β and IL-18 and enhanced protection of renal epithelial cells. This attenuation of renal tubular cell injury is a critical factor in preventing CaOx stone formation.

SIGNIFICANCE

Our findings reveal that Both BMSCs and UMSCs effectively attenuate hyperoxaluria-induced kidney injury and crystal deposition by inhibiting NLRP3 inflammasome activation. This discovery is helpful for developing new effective therapeutic means for nephrolithiasis.

Risk stratification for repeat stone surgery: the role of stone composition

PURPOSE

Kidney stones have a recurrence risk of 30-50% within five years, with surgical recurrence often being the most clinically significant and burdensome. Stone composition results obtained after surgery are readily available and typically precede metabolic evaluation. However, only few, relatively small studies, correlated stone composition with surgical reccurence. This study aims to determine whether stone composition alone can reliably predict recurrent stone surgery, offering insights into personalized management strategies.

METHODS

A retrospective analysis of surgically treated patients with an available stone composition analysis performed between 2013 and 2020 in a large healthcare provider database. Data were analyzed for up to 5 years from the initial surgery.

RESULTS

8,561 patients underwent surgical procedures for stones and 2,097 (24.5%) had repeat surgery within 5 years. Compared to calcium oxalate stone formers, individuals forming uric acid, calcium phosphate, infection, brushite, and cystine stones were 1.5, 1.5, 1.87, 2.64, and 2.71 times more likely, respectively, to undergo a second stone surgery (p < 0.001). The median time for repeat stone surgery in cystine and infection stone formers was significantly shorter compared to calcium oxalate (p < 0.01).

CONCLUSIONS

Stone composition significantly affects the 5-year surgical recurrence rates and the median time to recurrence, with non-calcium oxalate stone formers at a higher risk for recurrence. Sharing this information with patients may improve compliance with preventive strategies, including comprehensive metabolic evaluation and adherence to preventive therapy. Emphasizing this risk may help prioritize proactive management in high-risk patients.

Re-defining the interpretation of 24-h urine studies for stone formers

OBJECTIVES

To identify associations between 24-h urine abnormalities and clinical risk factors for recurrent stone formers.

PATIENTS AND METHODS

The Registry for Stones of the Kidney and Ureter was queried for all patients who underwent 24-h urine studies. Patients were categorised by the number of clinical risk factors for recurrent stone disease. Stone recurrence was calculated by stone events per person-year. We utilised a novel method to calculate an overall severity score for 24-h urine parameters. The stone recurrence and 24-h urinary analyte values were then compared using Student's t-tests, chi-square analysis and negative binomial regression.

RESULTS

A total of 614 stone patients met our inclusion criteria and were categorised by the number of clinical stone risk factors. On adjusted and unadjusted analysis, an escalating number of clinical risk factors predicted increased stone recurrence risk. However, there were no differences in mean 24-h urine analyte values amongst these groups aside from higher urinary calcium. However, after calculation of a 24-h urine severity score there was a significantly higher mean severity as the number of clinical risk factors increased. This severity score also independently predicted stone recurrence on adjusted negative binomial regression.

CONCLUSIONS

Utilising a novel 24-h urine scoring system, we showed that higher-risk stone patients have more severe 24-h urine characteristics, which was not apparent using conventional analysis. Both the severity score and clinical characteristics independently identified those at risk of stone recurrence.

Brazilian Guidelines on evaluation and clinical management of Nephrolithiasis: Brazilian Society of Nephrology

The prevalence of nephrolithiasis has been increasing in recent years, affecting appro-ximately 10% and 15% of the population. Kidney stone disease is associated with syste-mic comorbidities such as cardiovascular dis-ease, diabetes mellitus, and obesity. The first Nephrolithiasis Guideline by the Brazilian Society of Nephrology was published in 2002, and since then, the accumulation of new clinical studies and guidelines has justified a review of the subject. This updated document, prepared by the Nephrolithiasis Committee of the Brazilian Society of Nephrology, reflects the advances in the management of patients with kidney stones. The guideline aims to provide recommendations for the diagnosis, prevention, and treatment of nephrolithiasis, based on the best available evidence. Topics covered include clinical evaluation, laboratory and imaging tests, as well as dietary and pharmacological interventions, and follow-up strategies.

Simultaneous Bilateral Percutaneous Nephrolithotomy: Is It Cost-Effective?

OBJECTIVE

To compare the cost-effectiveness of simultaneous vs staged percutaneous nephrolithotomy (PCNL) during treatment of patients with large, bilateral stone burden.

METHODS

A decision-analytic Markov model was used to assess the cost-effectiveness of simultaneous and staged PCNL for large, bilateral stone burden. Model probabilities and outcomes for index procedures were drawn from a large-volume, single-center cohort. Primary outcomes included costs from a Medicare standpoint with the addition of operative time, length-of-stay costs, effectiveness (quality adjusted life years, QALYs), and incremental cost-effectiveness ratios with a willingness-to-pay threshold of $100,000/QALY.

RESULTS

At 1year following the index procedure, costs per patient were $52,585 and $61,687 for simultaneous and staged PCNL, respectively. In addition to being less costly, simultaneous PCNL resulted in slightly higher QALYs (0.982) compared to staged PCNL (0.977). On one-way sensitivity analyses, staged PCNL became cost-effective if the stone-free rate increased from 56% to 88% (40% greater per renal unit relative to simultaneous PCNL) or the cost of unilateral PCNL decreased approximately 50% to $4699 ($16,266 less than simultaneous PCNL).

CONCLUSION

Even when assuming a modest reduction in stone-free rate and slightly higher major and minor complication rates at index procedure, simultaneous bilateral PCNL was both less costly and more effective at 1year follow up relative to staged bilateral PCNL. This offers further support of simultaneous bilateral PCNL in the proper clinical setting.

Age-stratified analysis of the BMI-kidney stone relationship: findings from a national cross-sectional study

Background

The association between body mass index (BMI) and kidney stone formation may vary across different age groups and follow nonlinear patterns.

Methods

This study analyzed data from NHANES 2009-2018, including 14,880 participants aged ≥20 years, to evaluate the association between BMI and the risk of kidney stones. BMI was categorized as normal weight (<25.0 kg/m2), overweight (25.0-29.9 kg/m2), and obesity (≥30.0 kg/m2). Weighted logistic regression models were employed to adjust for multiple confounders, including sex, age, race/ethnicity, education level, smoking history, alcohol consumption, coronary heart disease, diabetes mellitus, hypertension, and physical activity. Interaction effects between BMI and key variables such as sex, race/ethnicity and other factors were also analyzed. Age-stratified analyses were performed for the groups aged 20-39 years, 40-59 years, and ≥ 60 years. A restricted cubic spline model was used to explore the non-linear relationship between BMI and the risk of kidney stones.

Results

After adjusting for confounders, participants with a BMI ≥30 kg/m2 had a significantly higher risk of kidney stones compared to those with a BMI <25 kg/m2 (adjusted OR [aOR]: 1.86; 95% CI: 1.48-2.34; p < 0.001), with the association being most pronounced in the 40-59-year age group (aOR: 2.02; 95% CI: 1.36-3.02; p < 0.001). The interaction analysis did not reveal significant interactions between BMI and sex or other factors. Non-linear analysis indicated that the relationship between BMI and kidney stone risk differed across age groups. In the 40-59-year group, the risk of kidney stones peaked and then plateaued as BMI increased beyond a certain threshold. In the ≥60-year age group, risk initially increased with BMI but then slightly declined. This non-linear relationship suggests that the impact of BMI on kidney stone risk varies by age and should be considered in clinical strategies.

Conclusion

High BMI is significantly associated with an increased risk of kidney stones, particularly among middle-aged and older adults. The relationship between BMI and kidney stones is non-linear, highlighting the need to develop age-specific BMI management strategies to reduce the occurrence of kidney stones.

Kidney failure from kidney stones: an ANZDATA study

BACKGROUND

Kidney stones are common, with an increasing trend over time, and have been well studied in the general population. However, the incidence and outcomes of kidney stones leading to kidney failure (KF) and the receipt of kidney replacement therapy (KRT) are poorly examined. We examined the incidence of KF due to kidney stones and compared outcomes with KRT patients due to other causes.

METHODS

We studied adult patients who started KRT (January 1981-December 2020) and are included in the Australia and New Zealand Dialysis and Transplant (ANZDATA) registry. Exposure was KRT patients due to kidney stones, comparing them with patients with other causes. We examined incidence, prevalence, patient survival (KRT and transplant) and graft survival (transplant). Cox regression models were fitted to compare patient survival between the kidney stones and non-kidney stones groups, overall KRT, dialysis and patient and graft survival after kidney transplant.

RESULTS

A total of 834 (1.1%) patients commenced KRT due to kidney stones. The incidence was 1.17 per million population per year and remained stable during the study period (annual change -0.3% [95% confidence interval (CI) -1.5-0.9]. Survival was higher in kidney stone patients receiving dialysis compared with the non-kidney stone group [hazard ratio (HR) 0.89 (95% CI 0.82-0.96)], with similar estimates in a matched cohort. In kidney transplant patients, time to transplant was longer for patients with kidney stones compared with non-kidney stone patients (2.5 versus 1.7 years; P = .001). There was no difference in mortality [HR 1.02 (95% CI 0.82-1.28)] or graft loss [HR 1.07 (95% CI 0.79-1.45)] between the kidney stones and non-kidney stones patients in the kidney transplant group.

CONCLUSION

The incidence of KF due to kidney stones was unchanged over the study period. Survival of patients with kidney stones who require KRT was better compared with patients with other causes. For the kidney transplant group, survival and risk of graft failure were similar.

Risk of Nephrolithiasis Associated With SGLT2 Inhibitors Versus DPP4 Inhibitors Among Patients With Type 2 Diabetes: A Target Trial Emulation Study

OBJECTIVE

We aim to compare the risk of nephrolithiasis among type 2 diabetes patients who initiated sodium-glucose cotransporter 2 inhibitors (SGLT2is) versus dipeptidyl peptidase 4 inhibitors (DPP4is), individually within stone never- and ever-formers.

RESEARCH DESIGN AND METHODS

Using the 2010-2021 Korea National Health Insurance Service database, we conducted a population-based cohort study, comparing initiators of SGLT2is versus DPP4is. The primary outcome was incident nephrolithiasis. Osteoarthritis encounters served as a negative control outcome. After 1:1 propensity score (PS) matching in stone never- and ever-formers, pooled and individual hazard ratios (HRs), incidence rate difference (IRD), and 95% CIs were reported. Subgroup analyses by sex, age, thiazide co-use, and baseline cardiovascular risk were done.

RESULTS

The 17,006 PS-matched pairs of SGLT2i and DPP4i initiators were pooled from stone never-formers (105,378 pairs) and ever-formers (11,628 pairs). Over a mean of 654 days, the risk of nephrolithiasis was lower in SGLT2i initiators than in DPP4i initiators: 0.65 vs. 1.12 events per 100 person-years, HR 0.54 (95% CI, 0.50-0.57), IRD -0.46 (95% CI, -0.21 to -0.52). Among never-formers, the HR was 0.43 (95% CI, 0.39-0.48) and IRD was -0.32 (95% CI, -0.27 to -0.36). Among ever-formers, the HR was 0.64 (95% CI, 0.59-0.69) and IRD was -2.26 (95% CI, -1.77 to -2.76). Near-null associations were found for osteoarthritis encounters. Results were consistent across subgroups.

CONCLUSIONS

We found a lower risk of nephrolithiasis associated with SGLT2is versus DPP4is in stone never- and ever-formers. Despite a greater relative risk reduction in the former, the absolute risk reduction was greater in the latter.

Long-Term Risks of Living Kidney Donation: State of the Evidence and Strategies to Resolve Knowledge Gaps

Living-donor kidney transplantation is the preferred treatment for kidney failure. In the United States, rates of living kidney donation have been stagnant, which is partly related to concerns over medical and financial risks. Recent research has better characterized the risks of living kidney donation, although the field is limited by a lack of robust registries. Available evidence supports small increases in the risks of end-stage kidney disease and hypertensive disorders of pregnancy in living donors. For most donors, the 15-year risk of kidney failure is less than 1%, but for certain populations this risk may be higher. New tools such as genetic kidney disease panels may assist with risk stratification. Living kidney donors generally have similar or improved psychosocial health following donation compared to prior to donation and nondonor experience. Postdonation care allows for preventative care measures to mitigate risk as well as ongoing surveillance of donor outcomes. Continuing efforts to capture and report outcomes of living donation are necessary to safely expand living donation worldwide.

Role of Genetic Testing in Kidney Stone Disease: A Narrative Review

PURPOSE OF REVIEW

Kidney stone disease (KSD) is a common and potentially life-threatening condition, and half of patients experience a repeat kidney stone episode within 5-10 years. Despite the ~50% estimate heritability of KSD, international guidelines have not kept up with the pace of discovery of genetic causes of KSD. The European Association of Urology guidelines lists 7 genetic causes of KSD as 'high risk'.

RECENT FINDINGS

There are currently 46 known monogenic (single gene) causes of kidney stone disease, with evidence of association in a further 23 genes. There is also evidence for polygenic risk of developing KSD. Evidence is lacking for recurrent disease, and only one genome wide association study has investigated this phenomenon, identifying two associated genes (SLC34A1 and TRPV5). However, in the absence of other evidence, patients with genetic predisposition to KSD should be treated as 'high risk'. Further studies are needed to characterize both monogenic and polygenic associations with recurrent disease, to allow for appropriate risk stratification. Durability of test result must be balanced against cost. This would enable retrospective analysis if no genetic cause was found initially. We recommend genetic testing using a gene panel for all children, adults < 25 years, and older patients who have factors associated with high risk disease within the context of a wider metabolic evaluation. Those with a genetic predisposition should be managed via a multi-disciplinary team approach including urologists, radiologists, nephrologists, clinical geneticists and chemical pathologists. This will enable appropriate follow-up, counselling and potentially prophylaxis.

Adjudication of Self-reported Symptomatic Stone Recurrence in the Prevention of Urinary Stones With Hydration Trial

OBJECTIVE

To assess accuracy of self-reported stone events in a large clinical trial by adjudication against the weight of documentation for spontaneous stone passage or surgical intervention.

METHODS

Participants in the Prevention of Urinary Stones with Hydration (PUSH) trial were randomized to a multi-component behavioral intervention or control arm to increase and maintain high fluid intake. The primary endpoint was urinary stone events including symptomatic stone passage or procedural intervention. An independent adjudication committee blinded to randomization assignments reviewed all events. Confirmed clinical stone events required typical stone symptoms and documentation of stone passage (eg, via photograph, clinical record) and/or surgical intervention. Events with typical symptoms and self-described stone passage but without objective documentation of passage were also considered as meeting the primary endpoint and classified separately as patient-reported passage. Non-events did not meet either criteria.

RESULTS

At time of this blinded analysis, a total of 1658 participants were randomized and had a median follow-up of 19 months. Self-reported stone events (n = 217) were adjudicated by the committee as either confirmed clinical events (134; 61.8%), patient-reported passage (71; 32.7%), or non-events (12; 5.5%). Confirmed clinical events consisted of stone passage in 66/134 and procedural interventions in 68/134 (53 for symptoms and 15 without symptoms).

CONCLUSION

Rigorous adjudication revealed that self-reported stone events in the PUSH trial overwhelmingly represented clinically documented passage, surgical intervention, and patient-reported passage outside healthcare settings, with only 5.5% failing to satisfy adjudication criteria. Similar adjudication and classification processes warrant consideration for implementation in future stone trials.

CLINICAL TRIALS REGISTRATION

NCT03244189.

Incidence of and Risk Factors for Urinary Stones Among Patients with Spinal Cord Injury: A Systematic Review with Meta-analysis

Background and objective

Urinary stones are a significant and common complication among patients with spinal cord injury (SCI), but epidemiological data are scarce and the evidence regarding risk factors remains unclear. Our aim was to investigate the incidence of and risk factors for urinary stones in SCI patients to provide evidence for better prevention and treatment strategies.

Methods

Relevant studies were identified from the PubMed, Web of Science, Cochrane, Embase, and Scopus databases. Literature screening, information extraction, and quality evaluation were conducted in accordance with established standards. Data analysis was performed using the metaprop and metan commands in Stata 16.0.

Key findings and limitations

A total of 65 studies involving 64 059 patients were included in the analysis. Meta-analysis using a random-effects model revealed that the overall incidence of urinary stones after SCI was 16.6% (95% confidence interval 14.1-19.3%). Over time, the incidence rate has stabilized between 15% and 20%, although annual rates varied significantly, ranging from 2.2% to 68.7%. The highest incidence was observed for bladder stones, with lower incidence rates for kidney and ureteral stones. Among the 13 factors assessed, male sex, a complete injury, and the use of intermittent, indwelling, and condom catheters were identified as independent risk factors for urinary stones.

Conclusions and clinical implications

The incidence of urinary stones after SCI is high, with a number of risk factors identified. However, further high-quality research is needed to explore additional potential risk factors.

Patient summary

We reviewed the results of previous studies on urinary stones in patients with a spinal cord injury. We found a high rate of urinary stones of about 17% for this patient group. Males are more prone to urinary stones and use of a catheter is a risk factor. More research is needed to identify other risk factors.

Suppression of renal crystal formation, inflammation, and fibrosis by blocking oncostatin M receptor β signaling

Oncostatin M (OSM) has pleiotropic effects on various inflammatory diseases, including kidney stone disease. The prevalence of kidney stones has increased worldwide, despite recent therapeutic advances, due to its high recurrence rate, suggesting the importance of prevention of repeated recurrence in the treatment of kidney stone disease. Using a mouse model of renal crystal formation, we investigated the preventive effects of blockade of OSM receptor β (OSMRβ) signaling on the development of kidney stone disease by treatment with a monoclonal anti-OSMRβ antibody that we generated. The anti-OSMRβ antibody abrogated OSM-induced phosphorylation of STAT3 and expression of crystal-binding molecules (Opn, Anxa1, Anxa2) and inflammation/fibrosis-associated molecules (Tnfa, Tgfb, Col1a2) in renal tubular epithelial cells and fibroblasts. In glyoxylate-injected mice, a mouse model of renal crystal formation, there was significant suppression of crystal deposits and expression of crystal-binding molecules (Opn, Anxa1, Anxa2), a tubular injury marker (Kim-1), and inflammation/fibrosis-associated molecules (Tnfa, Il1b, Mcp-1, Tgfb, Col1a2) in the kidneys of the anti-OSMRβ antibody-treated mice, compared with those in vehicle- or isotype control antibody-treated mice. In addition, treatment with the anti-OSMRβ antibody significantly decreased infiltrating macrophages and fibrosis in the kidneys. These findings suggest that anti-OSMRβ antibody-treatment may be effective in preventing kidney stone disease.

Predicting urinary stone recurrence: a joint model analysis of repeated 24-hour urine collections from the MSTONE database

To address the limitations in existing urinary stone recurrence (USR) models, including failure to account for changes in 24-hour urine (24U) parameters over time and ignoring multiplicity of stone recurrences, we presented a novel statistical method to jointly model temporal trends in 24U parameters and multiple recurrent stone events. The MSTONE database spanning May 2001 to April 2015 was analyzed. A joint recurrent model was employed, combining a linear mixed-effects model for longitudinal 24U parameters and a recurrent event model with a dynamic first-order Autoregressive (AR(1)) structure. A mixture cure component was included to handle patient heterogeneity. Comparisons were made with existing methods, multivariable Cox regression and conditional Prentice-Williams-Peterson regression, both applied to established nomograms. Among 396 patients (median follow-up of 2.93 years; IQR, 1.53-4.36 years), 34.6% remained free of stone recurrence throughout the study period, 30.0% experienced a single recurrence, and 35.4% had multiple recurrences. The joint recurrent model with a mixture cure component identified significant associations between 24U parameters - including urine pH (adjusted HR = 1.991; 95% CI 1.490-2.660; p < 0.001), total volume (adjusted HR = 0.700; 95% CI 0.501-0.977; p = 0.036), potassium (adjusted HR = 0.983; 95% CI 0.974-0.991; p < 0.001), uric acid (adjusted HR = 1.528; 95% CI 1.105-2.113, p = 0.010), calcium (adjusted HR = 1.164; 95% CI 1.052-1.289; p = 0.003), and citrate (adjusted HR = 0.796; 95% CI 0.706-0.897; p < 0.001), and USR, achieving better predictive performance compared to existing methods. 24U parameters play an important role in prevention of USR, and therefore, patients with a history of stones are recommended to closely monitor for future recurrence by regularly conducting 24U tests.

Urinary Stone Composition Analysis of 1465 Patients: The First Series from Azerbaijan

BACKGROUND

Urinary stone disease is a prevalent health issue worldwide, with varying incidence influenced by multiple factors. This study aims to provide the first comprehensive analysis of urinary stone composition in Azerbaijan.

METHODS

A retrospective study was conducted on 1465 patients, aged 1‒83 years, who underwent biochemical urinary stone analysis at the Department of Renal Diseases and Organ Transplantation, Azerbaijan State Security Service Military Hospital, between April 2015 and December 2023. Stone samples were analyzed using Fourier transform infrared (FTIR) spectroscopy. Statistical analyses were performed using the IBM® SPSS software version 29.0.

RESULTS

The cohort had a median age of 45 years, with a male-to-female ratio of 1.65:1. Calcium oxalate stones were the most common (56.2%), followed by uric acid (33.7%), struvite (5.3%), cystine (2.5%), calcium phosphate (1.9%), and xanthine (0.1%) stones. Men had a higher prevalence of calcium oxalate and uric acid stones, while women had more struvite stones. Mixed stones were common, particularly among uric acid and struvite stones. Significant differences in stone composition were observed between age groups and genders, with uric acid stones found predominantly in older individuals.

CONCLUSION

This study highlights the predominance of calcium oxalate stones and the elevated prevalence of uric acid stones in Azerbaijan, emphasizing the need for tailored diagnostic and therapeutic approaches. The high prevalence of mixed stones underscores the complexity of urinary stone disease and the need for comprehensive metabolic evaluation and individualized preventive strategies.

Bidirectional Impact of Varying Severity of Acute Kidney Injury on Calcium Oxalate Stone Formation

INTRODUCTION

Acute kidney injury (AKI) is a prevalent renal disorder. The occurrence of AKI may promote the formation of renal calcium oxalate stones by exerting continuous effects on renal tubular epithelial cells (TECs). We aimed to delineate the molecular interplay between AKI and nephrolithiasis.

METHODS

A mild (20 min) and severe (30 min) renal ischemia-reperfusion injury model was established in mice. Seven days after injury, calcium oxalate stones were induced using glyoxylate (Gly) to evaluate the impact of AKI on the formation of kidney stones. Transcriptome sequencing was performed on TECs to elucidate the relationship between AKI severity and kidney stones. Key transcription factors (TFs) regulating differential gene transcription levels were identified using motif analysis, and pioglitazone, ginkgetin, and fludarabine were used for targeted therapy to validate key TFs as potential targets for kidney stone treatment.

RESULTS

Severe AKI led to increased deposition of calcium oxalate crystals in renal, impaired kidney function, and upregulation of kidney stone-related gene expression. In contrast, mild AKI was associated with decreased crystal deposition, preserved kidney function, and downregulation of similar gene expression. Transcriptomic analysis revealed that genes associated with inflammation and cell adhesion pathways were significantly upregulated after severe AKI, while genes related to energy metabolism pathways were significantly upregulated after mild AKI. An integrative bioinformatic analysis uncovered a TF regulatory network within TECs, pinpointing that PKNOX1 was involved in the upregulation of inflammation-related genes after severe AKI, and inhibiting PKNOX1 function with pioglitazone could simultaneously reduce the increase of calcium oxalate crystals after severe AKI in kidney. On the other hand, motif analysis also revealed the protective role of STAT1 in the kidneys after mild AKI, enhancing the function of STAT1 with ginkgetin could reduce kidney stone formation, while the specific inhibitor of STAT1, fludarabine, could eliminate the therapeutic effects of mild AKI on kidney stones.

CONCLUSION

Inadequate repair of TECs after severe AKI increases the risk of kidney stone formation, with the upregulation of inflammation-related genes regulated by PKNOX1 playing a role in this process. Inhibiting PKNOX1 function can reduce kidney stone formation. Conversely, after mild AKI, effective cell repair through upregulation of STAT1 expression can protect TEC function and reduce stone formation, and activating STAT1 function can also achieve the goal of treating kidney stones.

Effects of multiple fluid intake on Urolithiasis by mendelian randomization study

Urolithiasis, a common and recurrent condition, imposes a significant global health burden. This study investigates the causal relationship between various types of fluid intake and urolithiasis using univariable and multivariable Mendelian randomization (MR) approaches. Genetic data for urolithiasis were obtained from the FinnGen Consortium (n = 400,681), while genetic measures for nine fluid types were sourced from meta-analyses of genome-wide association studies (GWAS). The analysis revealed that genetically predicted coffee intake (OR: 0.571, 95% confidence interval (CI): 0.341-0.958, p = 0.034) and ground coffee intake (OR: 0.219, 95% CI: 0.005-0.923, p = 0.038) were protective factors for upper urinary calculi. Additionally, a standard deviation (SD) increase in tea intake was associated with a 53% reduction in risk (OR: 0.473, 95% CI: 0.320-0.700, p < 0.001). Conversely, milk intake (OR: 1.072, 95% CI: 1.018-1.130) and alcohol intakefrequency (OR: 1.304, 95% CI: 1.083-1.570, p = 0.005) increased the risk of upper urinary calculi. These findings highlight the association of tea with reduced risk of urolithiasis, instead for milk and alcohol intake, in formulating prevention strategies for urolithiasis.

Inflammatory cytokines and their potential role in kidney stone disease: a Mendelian randomization study

PURPOSE

Previous studies have reported a complex relationship between inflammatory cytokines and kidney stone disease (KSD). The purpose of this paper is to investigate the potential causal impact of inflammatory cytokines on KSD by Mendelian randomization (MR) analysis.

METHODS

In our study, a thorough two-sample Mendelian randomization (MR) analysis was performed by us to determine the potential causal relationship between inflammatory cytokines and kidney stone disease. Utilizing GWAS summary data of inflammatory cytokines and KSD, we performed the first two-sample MR analysis. Genetic variants in GWASs related to inflammatory cytokines were employed as instrumental variables (IVs). The data on cytokines were derived from 14,824 participants and analyzed by utilizing the Olink Target-96 Inflammation Panel. GWAS summary data related to KSD (9713 cases and 366,693 controls) were obtained from the FinnGen consortium. The primary MR analysis method was Inverse variance weighted. Reverse MR analysis, Cochran's Q test, MR Egger, and MR-Pleiotropy RESidual Sum and Outlier (MR-PRESSO) were used to assess the stability of the results.

RESULTS

91 cytokines were enrolled in the MR analysis after strict quality control of IV. The IVW analysis revealed 2 cytokines as risk factors for KSD: Cystatin D (OR 1.06, 95% CI 1.01-1.11), Fibroblast growth factor 5 (OR 1.06, 95% CI 1.00-1.12), suggesting they are positively associated with the occurrence of kidney stones. We also found 3 protective associations between cytokines and KSD: Artemin (OR 0.86, 95% CI 0.78-0.96), T-cell surface glycoprotein CD6 isoform (OR 0.92, 95% CI 0.88-0.98), STAM-binding protein (OR 0.83, 95% CI 0.69-0.99). There was no horizontal pleiotropy or significant heterogeneity in our MR analysis, as determined by the p-value results of our MR Egger's intercept test, Cochrane Q-test, and MR-PRESSO, which were all > 0.05.

CONCLUSIONS

Our study explored a variety of inflammatory cytokines related to KSD through MR analysis, which validated several previous findings and provided some new potential biomarkers for KSD. However, the findings require further investigation to validate their exact functions in the pathogenesis and evolution of KSD.

Ureteric wall thickness as a novel predictor for failed retrograde ureteric stent placement

INTRODUCTION

We sought to identify predictors of failed retrograde ureteric stent (FRS) placement in the setting of obstructing ureteric calculi. In addition to patient- and stone-specific characteristics, we also considered computed tomography (CT) measures of ureteric wall thickness (UWT), as it has shown clinical potential in predicting outcomes of shockwave lithotripsy, ureteroscopy, and spontaneous stone passage.

METHODS

We performed a retrospective, case-control study comparing patients who had successful retrograde stent (SRS) insertions with those who failed stent placement and ultimately required nephrostomy tube (NT) insertion (2013-2019). Patients were identified using administrative data from a shared electronic medical record (capturing all urology patients in our geographic area) and a prospective database capturing all institutional interventional radiology procedures. Patient demographics, as well as clinical and stone characteristics, were then collected, and imaging manually reviewed. Statistical analysis was performed using univariate and multivariate logistic regression analysis in collaboration with a statistician.

RESULTS

A total of 109 patients met inclusion for analysis (34 FRS, 75 SRS). The most common indication for stent insertion included sepsis (79%). On multivariate analysis, both acute kidney injury as primary indication for stent insertion (odds ratio [OR ] 9.16, 95% confidence interval [CI] 1.91-44.00, p=0.006) and UWT (OR 0.34, 95% CI 0.15-0.74, p=0.007) were found to be significantly associated with FRS placement. A receiver operator characteristic curve analysis demonstrates an optimal UWT cutoff of 3.2 mm (sensitivity 60.6%, specificity 83.3%).

CONCLUSIONS

Elevated UWT and acute kidney injury as an indication for urgent urinary decompression in the setting of obstructing ureteric stones are predictive of FRS placement. These patients may benefit from upfront nephrostomy tube insertion.

Metabolic Evaluation and Recurrence Prevention for Urinary Stone Patients: An EAU Guidelines Update

BACKGROUND AND OBJECTIVE

The aim of this review was to define patients who are at high risk of recurrence of urolithiasis, to delineate diagnostic and therapeutic algorithms for each type of stone, and to clarify general guidelines and recommendations for prevention of recurrence.

METHODS

A professional research librarian carried out literature searches for all sections of the urolithiasis guidelines, covering the timeframe between 1976 and June 2023.

KEY FINDINGS AND LIMITATIONS

For every patient with urolithiasis, an attempt should be made to analyse the stone. Patients should be given general instructions on how to prevent recurrence, including adequate fluid and calcium intake, and low consumption of sodium and protein. Identifying and correcting the causative factors is a cornerstone in preventing the recurrence of urolithiasis. Diagnostic and therapeutic algorithms by stone composition are available. Every patient should undergo baseline metabolic screening, while patients with calcium stones, who are at high risk of relapse and complications, should undergo extensive metabolic screening with two 24-h urine collections and should receive targeted therapy. Patients with uric acid, infection, or cystine stones are at high risk of relapse. All patients at high risk of recurrence should be closely monitored, especially those not complying with therapy in the long term.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Metabolic stone evaluation and patient follow-up are highly recommended to prevent urolithiasis recurrence.

Association and risk of metabolic syndrome and kidney stone disease: outcomes from a systematic review and meta-analysis

PURPOSE OF REVIEW

Metabolic syndrome (MetS) has emerged as a potential contributor to the development of kidney stone disease (KSD). This study aims to conduct a systematic review of the literature, and meta-analysis of the association between MetS and KSD.

RECENT FINDINGS

Systematic review revealed Fifteen articles (433 201 patients) were eligible for analysis. Meta-analysis of 11 studies identified a statistically significant association between MetS and KSD with unadjusted odds ratio of 2.02 [95% confidence interval (CI) 1.96-2.08, P < 0.001], and pooled adjusted odds ratio of 1.22 [95% CI 1.09-1.37, P < 0.001]. Of the different MetS traits, hypertension and impaired glucose tolerance were the most significantly associated with KSD.

SUMMARY

This study confirms a significant association between MetS and KSD. Despite variations in MetS definitions across different studies analysed, consistent associations were observed across studies. This may have clinical implications in that guidelines do not currently recommend routine MetS screening in KSD patients.

Bacteria-mediated resistance of neutrophil extracellular traps to enzymatic degradation drives the formation of dental calculi

Dental calculi can cause gingival bleeding and periodontitis, yet the mechanism underlying the formation of such mineral build-ups, and in particular the role of the local microenvironment, are unclear. Here we show that the formation of dental calculi involves bacteria in local mature biofilms converting the DNA in neutrophil extracellular traps (NETs) from being degradable by the enzyme DNase I to being degradation resistant, promoting the nucleation and growth of apatite. DNase I inhibited NET-induced mineralization in vitro and ex vivo, yet plasma DNases were ineffective at inhibiting ectopic mineralization in the oral cavity in rodents. The topical application of the DNA-intercalating agent chloroquine in rodents fed with a dental calculogenic diet reverted NET DNA to its degradable form, inhibiting the formation of calculi. Our findings may motivate therapeutic strategies for the reduction of the prevalence of the deposition of bacteria-driven calculi in the oral cavity.

A Novel Machine-Learning Algorithm to Predict Stone Recurrence with 24-Hour Urine Data

Objectives: The absence of predictive markers for kidney stone recurrence poses a challenge for the clinical management of stone disease. The unpredictability of stone events is also a significant limitation for clinical trials, where many patients must be enrolled to obtain sufficient stone events for analysis. In this study, we sought to use machine learning methods to identify a novel algorithm to predict stone recurrence. Subjects/Patients and Methods: Patients enrolled in the Registry for Stones of the Kidney and Ureter (ReSKU), a registry of nephrolithiasis patients collected between 2015-2020, with at least one prospectively collected 24-hour urine test (Litholink 24-hour urine test; Labcorp) were included in the training set. A validation set was obtained from chart review of stone patients not enrolled in ReSKU with 24-hour urine data. Stone events were defined as either an office visit where a patient reports symptomatic passage of stones or a surgical procedure for stone removal. Seven prediction classification methods were evaluated. Predictive analyses and receiver operator characteristics (ROC) curve generation were performed in R. Results: A training set of 423 kidney stone patients with stone event data and 24-hour urine samples were trained using the prediction classification methods. The highest performing prediction model was a Logistic Regression with ElasticNet machine learning model (area under curve [AUC] = 0.65). Restricting analysis to high confidence predictions significantly improved model accuracy (AUC = 0.82). The prediction model was validated on a validation set of 172 stone patients with stone event data and 24-hour urine samples. Prediction accuracy in the validation set demonstrated moderate discriminative ability (AUC = 0.64). Repeat modeling was performed with four of the highest scoring features, and ROC analyses demonstrated minimal loss in accuracy (AUC = 0.63). Conclusion: Machine-learning models based on 24-hour urine data can predict stone recurrences with a moderate degree of accuracy.

The immune factors have complex causal regulation effects on kidney stone disease: a mendelian randomization study

PURPOSE

Previous studies have reported the potential impact of immune cells on kidney stone disease (KSD), but definitive causal relationships have yet to be established. The purpose of this paper is to elucidate the potential causal association between immune cells and KSD by Mendelian randomization (MR) analysis.

METHODS

In our study, a thorough two-sample Mendelian randomization (MR) analysis was performed by us to determine the potential causal relationship between immune cell traits and kidney stone disease. We included a total of four immune traits (median fluorescence intensity (MFI), relative cellular (RC), absolute cellular (AC), and morphological parameters (MP)), which are publicly available data. GWAS summary data related to KSD (9713 cases and 366,693 controls) were obtained from the FinnGen consortium. The primary MR analysis method was Inverse variance weighted. Cochran's Q test, MR Egger, and MR-Pleiotropy RESidual Sum and Outlier (MR-PRESSO) were used to assess the stability of the results.

RESULTS

After FDR correction, the CD8 on HLA DR + CD8br (OR = 0.95, 95% CI = 0.93-0.98, p-value = 7.20 × 10- 4, q-value = 0.088) was determined to be distinctly associated with KSD, and we also found other 25 suggestive associations between immune cells and KSD, of which 13 associations were suggested as protective factors and 12 associations were suggested as risk factors. There was no horizontal pleiotropy or significant heterogeneity in our MR analysis, as determined by the p-value results of our Cochrane Q-test, MR Egger's intercept test, and MR-PRESSO, which were all > 0.05.

CONCLUSIONS

Our study has explored the potential causal connection between immune cells and KSD by Mendelian randomization analysis, thus providing some insights for future clinical studies.

Recurrent Urinary Stone Formers: Imaging Assessment and Endoscopic Treatment Strategies: A Systematic Search and Review

Background/Objectives: Nephrolithiasis is a heterogeneous disease with a high prevalence and recurrence rate. Although there has been much progress regarding the surgical treatment of stones, a standardized follow-up, especially in recurrent stone formers (SFs), has yet to be decided. This fact leads to the overuse of computed tomography (CT) scans and many reoperations in patients, thus increasing their morbidity and the financial burden on the health systems. This review systematically searched the literature for original articles regarding imaging strategies and endoscopic treatment for patients with recurrent urolithiasis, aiming to identify optimal strategies to deal with these patients. Methods: We systematically searched the Medline database (accessed on 1 April 2024) for articles regarding imaging modalities and endoscopic treatment for patients with recurrent urinary tract lithiasis. Results: No specific follow-up or endoscopic treatment strategy exists for patients with recurrent urolithiasis. CT scan was the imaging modality most used in the studies, followed by X-ray, ultrasonography, and digital tomosynthesis. A transparent algorithm could not be identified. Percutaneous nephrolithotomy (PCNL), retrograde intrarenal surgery (RIRS), and ureteroscopy (URS) were used in the studies for endoscopic treatment. PCNL showed the best stone-free (SFr) rate and lowest hazard ratio (HR) for reoperation. RIRS showed superiority over extracorporeal shockwave lithotripsy for recurrent SFs, but fragments over 4 mm increased the recurrent rate. URS has an increased HR for reoperation for bilateral stones. Conclusions: The heterogeneity of urolithiasis leaves urologists without a standardized plan for recurrent SFs. Thus, each patient's follow-up should be planned individually and holistically. Pre-stenting is not to be avoided, especially in high-risk patients, and SFr status needs to be the aim. Finally, CT scans should not be generally overused but should be part of a patient's treatment plan. Prospective studies are required to define SFr status, the size of significant residual fragments, and the modalities of intervention and follow-up.

Higher Risk of Repeat Stone Surgery in Stone Formers With Concomitant Bowel Disease: Single-Center Long-Term Analysis

OBJECTIVE

To identify the need for repeat stone surgery in patients with and without bowel disease. Few studies have compared risks between different types of bowel disease and whether their need for repeat stone surgery differs.

METHODS

From our IRB-approved study, we identified patients with and without bowel disease. We categorized patients' bowel disease into 4 categories: inflammatory bowel disease (IBD), bypass procedures, bowel resection, and bowel disease not otherwise specified (eg, irritable bowel syndrome, celiac disease). Differences between patient demographics, stone disease, and recurrent stone events for patients with and without bowel disease were compared using univariate and multivariate survival analyses (SPSS 25).

RESULTS

Of all surgical stone patients (2011), 484 (24%) had some type of bowel disease. Compared to patients without bowel disease, patients with bowel disease presented with stones at an older age (62.2 ± 14.5 vs 58.4 ± 15.3 years; P <.001) and were more likely to be female (56 vs 46%; P <.001). Patients with bowel disease required more repeat stone surgery than those without bowel disease (31% vs 23%, P <.001). In multivariate analysis, patients with bypass and bowel resection were associated with more repeat surgery than patients without bowel disease (P <.001, P = .002, respectively). Patients with IBD and bowel disease not otherwise specified did not have higher risk for repeat surgery than patients without bowel disease.

CONCLUSION

Surgical stone patients with bowel disease, specifically those with prior bowel resection and bypass, had a higher risk of repeat stone surgery over time than stone formers without bowel disease.

DATA AVAILABILITY

The data sets generated and analyzed during the current study are available from the corresponding author on reasonable request.

Preventive Pharmacological Therapy and Risk of Recurrent Urinary Stone Disease

BACKGROUND

Urinary stone disease is a prevalent condition associated with a high recurrence risk. Preventive pharmacological therapy has been proposed to reduce recurrent stone episodes. However, limited evidence exists regarding its effectiveness, contributing to its underutilization by physicians. This study aimed to evaluate the association between preventive pharmacological therapy (thiazide diuretics, alkali therapy, and uric acid-lowering medications) and clinically significant urinary stone disease recurrence.

METHODS

Using data from the Veterans Health Administration, adults with an index episode of urinary stone disease from 2012 through 2019 and at least one urinary abnormality (hypercalciuria, hypocitraturia, or hyperuricosuria) on 24-hour urine collection were included. The primary outcome was a composite variable representing recurrent stone events that resulted in emergency department visits, hospitalizations, or surgery for urinary stone disease. Cox proportional hazards regression was performed to estimate the association between preventive pharmacological therapy use and recurrent urinary stone disease while adjusting for relevant baseline patient characteristics.

RESULTS

Among the cohort of patients with urinary abnormalities ( n =5637), treatment with preventive pharmacological therapy was associated with a significant 19% lower risk of recurrent urinary stone disease during the 12-36-month period after the initial urine collection (hazard ratio, 0.81; 95% confidence interval, 0.65 to 1.00; P = 0.0496). However, the effectiveness of preventive pharmacological therapy diminished over longer follow-up periods (12-48 and 12-60 months after the urine collection) and did not reach statistical significance. When examining specific urinary abnormalities, only alkali therapy for hypocitraturia was associated with a significant 26% lower recurrence risk within the 12-36-month timeframe (hazard ratio, 0.74; 95% confidence interval, 0.56 to 0.97; P = 0.03).

CONCLUSIONS

When considering all urinary abnormalities together, this study demonstrates that the use of preventive pharmacological therapy is associated with a lower risk of clinically significant recurrent episodes of urinary stone disease in the 12-36 month timeframe after urine collection, although only the association with the use of alkali therapy for hypocitraturia was significant when individual abnormalities were examined.

The Analgesic Effects of the Thoracic Paravertebral Block on Post-percutaneous Nephrolithotripsy: A Retrospective Study

INTRODUCTION

Percutaneous nephrolithotripsy (PCNL) is a minimally invasive procedure for treating large and complex kidney stones, often resulting in significant post-operative pain and increased opioid use. This study aims to compare pain scores between patients undergoing PCNL who did and did not receive a preoperative single-shot thoracic paravertebral block (PVB) at the post-anesthesia care unit (PACU) as the primary outcome. Secondary outcomes were patient-controlled analgesia (PCA) usage on post-operative day 1 (POD 1), total opioid consumption on PACU and POD 1, and post-operative nausea and vomiting (PONV).

METHODS

A retrospective cohort study was conducted on the medical records of 341 patients who underwent PCNL from July 2014 to April 2016 in a single major academic center. PVB was administered at thoracic levels T7-9 using a volume of 20 cc of bupivacaine, ranging from 0.25% to 0.5%, to achieve the desired analgesic effect.

RESULTS

After excluding 34 patients, the study included 123 in the no block (NB) group and 149 in the regional anesthesia (RA) group. There were no differences in demographics, including age, sex, weight and height, BMI, and indication for PCNL. The results revealed that the RA group experienced a statistically significant reduction in PCA usage in both crude and adjusted models (adjusted logistic regression analysis: OR = 0.19, 95% CI = 0.05-0.60; p = 0.008). However, there were no significant changes in total opioid consumption, pain scores, or incidents of PONV.

CONCLUSION

The retrospective analysis did not reveal any discernible advantage in pain management associated with the use of PVB for post-PCNL analgesia, except for reducing the percentage of PCA narcotics used. Future investigations with larger sample sizes and meticulous control for surgical indications and complexity are imperative to accurately assess the efficacy of this block in the context of post-PCNL surgery.

Predictors of Recurrent Urolithiasis in Iran: Findings from a Nationwide Study

BACKGROUND

Prevention of urinary stone recurrence is the ultimate goal in urolithiasis patients. In this study, we aimed to investigate the national prevalence rate and possible determinants of increased urolithiasis recurrence risk in a nationwide study in Iran.

METHODS

All data regarding stone occurrence and recurrence episodes were extracted from the cross-sectional Iran National Stone Survey (INSS) study, and the possible determinants of recurrence were evaluated in the subset of 2913 patients who had a positive history of at least one episode of urolithiasis.

RESULTS

The national prevalence rate of recurrent urolithiasis was 2.6% (95% CI: 2.5, 2.8) in Iran. Moreover, the relative ratio of recurrent stone formers to all stone formers was 39.8% (95% CI: 38.0, 41.6). Our univariable truncated negative binomial regressions suggested that a positive history of urolithiasis in the patient's father (prevalence ratio [PR] [95% CI]=1.83 [1.39, 2.41], P<0.001), mother (PR [95% CI]=1.92 [1.39, 2.66], P<0.001) or brother (PR [95% CI]=1.32 [1.03, 1.69], P=0.026); and residence in urban areas (PR [95% CI]=1.27 [1.04, 1.55], P=0.016) were significant predictors of repetitive recurrence episodes. However, when incorporated into a multivariable truncated negative binomial regression model, the only significant predictors of more frequent recurrence episodes were a positive history in father (PR [95% CI]=1.66 [1.24, 2.22], P<0.001) and mother (PR [95% CI]=1.68 [1.20, 2.36], P=0.002); and urban residence (PR [95% CI]=1.24 [1.01, 1.51], P=0.031).

CONCLUSION

Our results indicate that a positive family history of urolithiasis in mother and father and residence in urban areas are the significant predictors of recurrence risk in urolithiasis patients in Iran.

Surgical procedure and recurrence of upper urinary tract stone: a national-wide study based on hospitalized patients

PURPOSE

This study aimed to investigate the influence of surgical intervention on recurrence risk of upper urinary tract stone and compare the medical burden of various surgical procedures.

METHODS

This study analyzed data from patients with upper urinary tract stone extracted from a national database of hospitalized patients in China, from January 2013 to December 2018. Surgical recurrence was defined as patients experience surgical procedures for upper urinary tract stone again with a time interval over 90 days. Associations of surgical procedures with surgical recurrence were evaluated by Cox regression.

RESULTS

In total, 556,217 patients with upper urinary tract stone were included in the present analysis. The mean age of the population was 49.9 ± 13.1 years and 64.1% were men. During a median follow-up of 2.7 years (IQR 1.5-4.0 years), 23,012 patients (4.1%) had surgical recurrence with an incidence rate of 14.9 per 1000 person-years. Compared to patients receiving open surgery, ESWL (HR, 1.59; 95% CI 1.49-1.70), URS (HR, 1.38; 95% CI 1.31-1.45), and PCNL (HR, 1.11; 95% CI 1.06-1.18) showed a greater risk for surgical recurrence. Patients receiving ESWL had the shortest hospital stay length and the lowest cost among the 4 procedures.

CONCLUSIONS

Compared with open surgery, ESWL, URS, and PCNL are associated with higher risks of surgical recurrence for upper urinary tract stone, while ESWL showed the least medical burden including both expenditure and hospital stay length. How to keep balance of intervention efficacy and medical expenditure is an important issue to be weighed cautiously in clinic practice and studied more in the future.

Pathophysiology and Main Molecular Mechanisms of Urinary Stone Formation and Recurrence

Kidney stone disease (KSD) is one of the most common urological diseases. The incidence of kidney stones has increased dramatically in the last few decades. Kidney stones are mineral deposits in the calyces or the pelvis, free or attached to the renal papillae. They contain crystals and organic components, and they are made when urine is supersaturated with minerals. Calcium-containing stones are the most common, with calcium oxalate as the main component of most stones. However, many of these form on a calcium phosphate matrix called Randall's plaque, which is found on the surface of the kidney papilla. The etiology is multifactorial, and the recurrence rate is as high as 50% within 5 years after the first stone onset. There is a great need for recurrence prevention that requires a better understanding of the mechanisms involved in stone formation to facilitate the development of more effective drugs. This review aims to understand the pathophysiology and the main molecular mechanisms known to date to prevent recurrences, which requires behavioral and nutritional interventions, as well as pharmacological treatments that are specific to the type of stone.

Advancements in stone classification: unveiling the beauty of urolithiasis

PURPOSE

Urolithiasis has become increasingly prevalent, leading to higher disability-adjusted life years and deaths. Various stone classification systems have been developed to enhance the understanding of lithogenesis, aid urologists in treatment decisions, and predict recurrence risk. The aim of this manuscript is to provide an overview of different stone classification criteria.

METHODS

Two authors conducted a review of literature on studies relating to the classification of urolithiasis. A narrative synthesis for analysis of the studies was used.

RESULTS

Stones can be categorized based on anatomical position, size, medical imaging features, risk of recurrence, etiology, composition, and morphoconstitutional analysis. The first three mentioned offer a straightforward approach to stone classification, directly influencing treatment recommendations. With the routine use of CT imaging before treatment, precise details like anatomical location, stone dimensions, and Hounsfield Units can be easily determined, aiding treatment planning. In contrast, classifying stones based on risk of recurrence and etiology is more complex due to dependencies on multiple variables, including stone composition and morphology. A classification system based on morphoconstitutional analysis, which combines morphological stone appearance and chemical composition, has demonstrated its value. It allows for the rapid identification of crystalline phase principles, the detection of crystalline conversion processes, the determination of etiopathogenesis, the recognition of lithogenic processes, the assessment of crystal formation speed, related recurrence rates, and guidance for selecting appropriate treatment modalities.

CONCLUSIONS

Recognizing that no single classification system can comprehensively cover all aspects, the integration of all classification approaches is essential for tailoring urolithiasis patient-specific management.

Study from the United States: increased prevalence of kidney stones in patients with high weight-adjusted waist index

Objective

Using data from NHANES 2007-2018, to examine the association between WWI (weight-adjusted waist index) index and prevalence of kidney stones.

Methods

Using multiple logistic regression analysis of the National Health and Nutrition Examination Survey (NHANES) 2007-2018, we evaluated the association between WWI index and the prevalence of kidney stones, followed by subgroup analysis of sensitive populations. Smooth curve fitting was used to determine whether there was a non-linear relationship between the WWI index and kidney stone prevalence, and threshold effect analysis was used to test this relationship.

Results

Among 29,280 participants, 2,760 self-reported renal calculi. After adjustment for all confounders, there was a positive association between WWI and kidney stone prevalence (OR = 1.20, 95% CI: 1.12, 1.28), and this positive association was stronger with increasing WWI (and P = 0.01 for trend). Our results indicate a non-linear positive correlation between WWI index and kidney stones, with the saturation threshold effect analysis and the most important threshold value at 11.02. According to subgroup analysis, WWI showed the strongest association with kidney stone prevalence in participants aged 20-39 years, males, other US ethnic groups, and participants without hypertension and diabetes.

Conclusion

Increased WWI is positively associated with increased incidence of kidney stones, and increased WWI is a high risk for kidney stones that should be treated with caution. This association should be more pronounced in people between the ages of 20 and 39 years, in men, in other US ethnic populations, and in participants who do not have hypertension or diabetes.

Comparison of Class-Specific Side Effects Across Preventative Pharmacologic Therapies for Kidney Stone Disease

INTRODUCTION

Clinical guidelines recommend monitoring for metabolic derangements while on preventive pharmacologic therapy for kidney stone disease. The study objective was to compare the frequency of side effects among patients receiving alkali citrate, thiazides, and allopurinol.

METHODS

Using claims data from working-age adults with kidney stone disease (2008-2019), we identified those with a new prescription for alkali citrate, thiazide, or allopurinol within 12 months after their index stone-related diagnosis or procedure. We fit multivariable logistic regression models, adjusting for cohort characteristics like comorbid illness and medication adherence, to estimate 2-year measured frequencies of claims-based outcomes of acute kidney injury, falls/hip fracture, gastritis, abnormal liver function tests/hepatitis, hypercalcemia, hyperglycemia/diabetes, hyperkalemia, hypokalemia, hyponatremia, and hypotension.

RESULTS

Our cohort consisted of 1776 (34%), 2767 (53%), and 677 (13%) patients prescribed alkali citrate, thiazides, or allopurinol, respectively. Comparing unadjusted rates of incident diagnoses, thiazides compared to alkali citrate and allopurinol were associated with the highest rates of hypercalcemia (2.3% vs 1.5% and 1.0%, respectively, P = .04), hypokalemia (6% vs 3% and 2%, respectively, P < .01), and hyperglycemia/diabetes (17% vs 11% and 16%, respectively, P < .01). No other differences with the other outcomes were significant. In adjusted analyses, compared to alkali citrate, thiazides were associated with a higher odds of hypokalemia (OR=2.01, 95% CI 1.44-2.81) and hyperglycemia/diabetes (OR=1.52, 95% CI 1.26-1.83), while allopurinol was associated with a higher odds of hyperglycemia/diabetes (OR=1.34, 95% CI 1.02-1.75).

CONCLUSIONS

These data provide evidence to support clinical guidelines that recommend periodic serum testing to assess for adverse effects from preventive pharmacologic therapy.

Routine Urinary Biochemistry Does Not Accurately Predict Stone Type Nor Recurrence in Kidney Stone Formers: A Multicentre, Multimodel, Externally Validated Machine-Learning Study

Objectives: Urinary biochemistry is used to detect and monitor conditions associated with recurrent kidney stones. There are no predictive machine learning (ML) tools for kidney stone type or recurrence. We therefore aimed to build and validate ML models for these outcomes using age, gender, 24-hour urine biochemistry, and stone composition. Materials and Methods: Data from three cohorts were used, Southampton, United Kingdom (n = 3013), Newcastle, United Kingdom (n = 5984), and Bern, Switzerland (n = 794). Of these 3130 had available 24-hour urine biochemistry measurements (calcium, oxalate, urate [Ur], pH, volume), and 1684 had clinical data on kidney stone recurrence. Predictive ML models were built for stone type (n = 5 models) and recurrence (n = 7 models) using the UK data, and externally validated with the Swiss data. Three sets of models were built using complete cases, multiple imputation, and oversampling techniques. Results: For kidney stone type one model (extreme gradient boosting [XGBoost] built using oversampled data) was able to effectively discriminate between calcium oxalate, calcium phosphate, and Ur on both internal and external validation. For stone recurrence, none of the models were able to discriminate between recurrent and nonrecurrent stone formers. Conclusions: Kidney stone recurrence cannot be accurately predicted using modeling tools built using specific 24-hour urinary biochemistry values alone. A single model was able to differentiate between stone types. Further studies to delineate accurate predictive tools should be undertaken using both known and novel risk factors, including radiomics and genomics.

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.

POCUS-first for nephrolithiasis: A Monte Carlo simulation illustrating cost savings, LOS reduction, and preventable radiation

OBJECTIVES

Non-contrast computed tomography (NCCT) is the gold standard for nephrolithiasis evaluation in the emergency department (ED). However, Choosing Wisely guidelines recommend against ordering NCCT for patients with suspected nephrolithiasis who are <50 years old with a history of kidney stones. Our primary objective was to estimate the national annual cost savings from using a point-of-care ultrasound (POCUS)-first approach for patients with suspected nephrolithiasis meeting Choosing Wisely criteria. Our secondary objectives were to estimate reductions in ED length of stay (LOS) and preventable radiation exposure.

METHODS

We created a Monte Carlo simulation using available estimates for the frequency of ED visits for nephrolithiasis and eligibility for a POCUS-first approach. The study population included all ED patients diagnosed with nephrolithiasis. Based on 1000 trials of our simulation, we estimated national cost savings in averted advanced imaging from this strategy. We applied the same model to estimate the reduction in ED LOS and preventable radiation exposure.

RESULTS

Using this model, we estimate a POCUS-first approach for evaluating nephrolithiasis meeting Choosing Wisely guidelines to save a mean (±SD) of $16.5 million (±$2.1 million) by avoiding 159,000 (±18,000) NCCT scans annually. This resulted in a national cumulative decrease of 166,000 (±165,000) annual bed-hours in ED LOS. Additionally, this resulted in a national cumulative reduction in radiation exposure of 1.9 million person-mSv, which could potentially prevent 232 (±81) excess cancer cases and 118 (±43) excess cancer deaths annually.

CONCLUSION

If adopted widely, a POCUS-first approach for suspected nephrolithiasis in patients meeting Choosing Wisely criteria could yield significant national cost savings and a reduction in ED LOS and preventable radiation exposure. Further research is needed to explore the barriers to widespread adoption of this clinical workflow as well as the benefits of a POCUS-first approach in other patient populations.

Underdiagnosis of Hyperparathyroidism in Patients With Nephrolithiasis in a Community Setting

Objective Untreated primary hyperparathyroidism (PHPT) has wide-ranging multisystemic effects. Recent studies based in the US have shown a less than 25% screening rate for PHPT. Our study aims to detect whether similar deficiencies exist in our community healthcare system while quantifying the prevalence of PHPT underdiagnosis and inadequate surgical referrals. Study design This retrospective quantitative study enrolled patients aged ≥18 years with imaged-confirmed nephrolithiasis at our healthcare facilities from 2017 to the present (n=2021). Patients with documented calcium levels and kidney/ureter stones were included. Descriptive and univariate analyses were performed. Results A total of 2021 subjects met the criteria to be enrolled in the study. 26.6% (n=537) of patients with nephrolithiasis had elevated calcium levels on record. 13.6% (n=73) of hypercalcemic patients were screened for PHPT with an intact parathyroid hormone (PTH). A majority (63%, n=46) of patients with intact PTH had PHPT defined as PTH levels >55 pg/mL. Ultimately, only 19.6% (n=9) of patients with PHPT were referred for surgical intervention, and there was no significant difference in referral rate between patients with PHPT and those without (p=0.913). Conclusions PHPT is underdiagnosed in our community, leading to a significantly low rate of surgical referral and delay in management. Implementation of hospital protocols to aid in improving diagnosis and interventions could improve outcomes for PHPT patients.

Predictive value of single-nucleotide polymorphism signature for nephrolithiasis recurrence: a 5-year prospective study

Background

Genetic variations are linked to kidney stone formation. However, the association of single nucleotide polymorphism (SNPs) and stone recurrence has not been well studied. This study aims to identify genetic variants associated with kidney stone recurrences and to construct a predictive nomogram model using SNPs and clinical features to predict the recurrence risk of kidney stones.

Methods

We genotyped 49 SNPs in 1001 patients who received surgical stone removal between Jan 1 and Dec 31 of 2012. All patients were confirmed stone-free by CT scan and then received follow-up at least 5 years. SNP associations with stone recurrence were analyzed by Cox proportion hazard model. A predictive nomogram model using SNPs and clinical features to predict the recurrence risk of kidney stones was developed by use of LASSO Cox regression.

Results

The recurrence rate at 3, 5, 7 years were 46.8%, 71.2%, and 78.4%, respectively. 5 SNPs were identified that had association with kidney stone recurrence risk. We used computer-generated random numbers to assign 500 of these patients to the training cohort and 501 patients to the validation cohort. A nomogram that combined the 14-SNPs-based classifier with the clinical risk factors was constructed. The areas under the curve (AUCs) at 3, 5 and 7 years of this nomogram was 0.645, 0.723, and 0.75 in training cohort, and was 0.631, 0.708, and 0.727 in validation cohort, respectively. Results show that the nomogram presented a higher predictive accuracy than those of the SNP classifier or clinical factors alone.

Conclusion

SNPs are significantly associated with kidney stone recurrence and should add prognostic value to the traditional clinical risk factors used to assess the kidney stone recurrence. A nomogram using clinical and genetic variables to predict kidney stone recurrence has revealed its potential in the future as an assessment tool during the follow-up of kidney stone patients.

Vitamins as regulators of calcium-containing kidney stones - new perspectives on the role of the gut microbiome

Calcium-based kidney stone disease is a highly prevalent and morbid condition, with an often complicated and multifactorial aetiology. An abundance of research on the role of specific vitamins (B6, C and D) in stone formation exists, but no consensus has been reached on how these vitamins influence stone disease. As a consequence of emerging research on the role of the gut microbiota in urolithiasis, previous notions on the contribution of these vitamins to urolithiasis are being reconsidered in the field, and investigation into previously overlooked vitamins (A, E and K) was expanded. Understanding how the microbiota influences host vitamin regulation could help to determine the role of vitamins in stone disease.

Nomogram to predict the risk of adverse outcomes in patients with residual stones following percutaneous nephrolithotomy

PURPOSE

To investigate the risk factors associated with adverse outcomes in patients with residual stones after percutaneous nephrolithotomy (PCNL) and to establish a nomogram to predict the probability of adverse outcomes based on these risk factors.

METHODS

We conducted a retrospective review of 233 patients who underwent PCNL for upper urinary tract calculi and had postoperative residual stones. The patients were divided into two groups according to whether adverse outcomes occurred, and the risk factors for adverse outcomes were explored by univariate and multivariate analyses. Finally, we created a nomogram for predicting the risk of adverse outcomes in patients with residual stones after PCNL.

RESULTS

In this study, adverse outcomes occurred in 125 (53.6%) patients. Multivariate logistic regression analysis indicated that the independent risk factors for adverse outcomes were the diameter of the postoperative residual stones (P < 0.001), a positive urine culture (P = 0.022), and previous stone surgery (P = 0.004). The above independent risk factors were used as variables to construct the nomogram. The nomogram model was internally validated. The calculated concordance index was 0.772. The Hosmer-Lemeshow goodness-of-fit test was performed (P > 0.05). The area under the ROC curve of this model was 0.772.

CONCLUSIONS

Larger diameter of residual stones, positive urine culture, and previous stone surgery were significant predictors associated with adverse outcomes in patients with residual stones after PCNL. Our nomogram could help to assess the risk of adverse outcomes quickly and effectively in patients with residual stones after PCNL.

Causal relationship of genetically predicted circulating micronutrients levels with the risk of kidney stone disease: a Mendelian randomization study

Background

Current studies have reported conflicting associations between circulating micronutrient levels and kidney stone disease (KSD). We aimed to elucidate the causal relationship between circulating micronutrient levels and KSD by a two-sample Mendelian randomization (MR) analysis.

Methods

Total of 36 single nucleotide polymorphisms (SNPs) from published genome-wide association studies (GWAS) significantly associated with eight micronutrients (vitamin B12, folic acid, magnesium, iron, phosphorus, copper, zinc, and selenium) were used as instrumental variables. The GWAS summary data associated with KSD (8,060 cases and 301,094 controls) were obtained from the FinnGen consortium. Inverse variance weighted was the main MR analysis method. MR-Pleiotropy RESidual Sum and Outlier (MR-PRESSO), weighted median and MR-Egger were used to assess pleiotropy and heterogeneity.

Results

Genetically predicted circulating vitamin B12 and zinc levels were causally associated with the risk of KSD (vitamin B12: OR: 1.17, 95% CI: 1.04-1.32, p = 0.008; zinc: OR: 1.15, 95% CI: 1.03-1.28, p = 0.015). We found no evidence that other circulating micronutrients were associated with risk of KSD. p-value for Cochrane Q test, MR Egger intercept test, and MR-PRESSO were >0.05, indicating no significant heterogeneity or horizontal pleiotropy in this MR analysis.

Conclusion

Increasing circulating zinc levels may increase the risk of KSD. More studies are needed to provide evidence on whether genetically predicted circulating vitamin B12 and zinc levels are a risk factor for KSD.

Treatment of donors' asymptomatic small kidney stones and post-transplant outcomes: a meta-analysis

Kidney donors with asymptomatic small kidney stones were increasingly accepted in kidney transplantation (KT) due to organ shortage and advances in endoscopic urology. However, recipients' clinical outcomes using these donors remained unclear. We conducted a meta-analysis to summarize transplant outcomes using these donors with asymptomatic small kidney stones. Finally, 15 retrospective studies were included. The prevalence of asymptomatic small kidney stones was 5.3% (95%CI 3.5-7.8%). After transplantation, low incidence of urinary fistula (0%, 95%CI 0-1.0%), obstruction (0%, 95%CI 0-1.1%), relapse of kidney graft stone (0.3%, 95%CI 0-2.5%), and delayed graft function (0.6%, 95%CI 0-3.5%) was reported. Pooled serum creatinine was 1.3 (95%CI 1.2-1.5) mg/dl and 1.4 (95%CI 1.2-1.6) mg/dl at post-transplant 1 month and 1 year, respectively. Notably, we observed numerically higher relapse rate after conservative management (1.8% [0-9.2%] vs 0% [0-1.8%]) but numerically higher DGF rate after surgical removal of asymptomatic stones (1.8% [0-7.0%] vs 0% [0-1.9%]). Overall, short-term transplant outcomes using kidneys with asymptomatic small stones were acceptable. However, long-term transplant outcomes remained unexplored. Well-designed prospective studies are also needed to compare the efficacy of conservative management with surgical removal of "donors' gifted" asymptomatic kidney stones.

Application of ultrasound imaging in the treatment of urinary tract stones

Urinary tract stones are a common clinical condition that affect millions of individuals worldwide. The management of these stones has evolved significantly over the past 70 years, and ultrasound imaging has emerged as a valuable tool for diagnosis, treatment planning, and follow-up. This review aims to provide an overview of the application of ultrasound imaging in the treatment of urinary tract stones, highlighting its advantages, limitations, and current advancements in the field.

Outpatient Antibiotic Use is Not Associated with an Increased Risk of First-Time Symptomatic Kidney Stones

SIGNIFICANCE STATEMENT

Antibiotics modify human microbiomes and may contribute to kidney stone risk. In a population-based case-control study using 1247 chart-validated first-time symptomatic kidney stone formers and 4024 age- and sex-matched controls, the risk of kidney stones was transiently higher during the first year after antibiotic use. However, this risk was no longer evident after adjustment for comorbidities and excluding participants with prior urinary symptoms. Findings were consistent across antibiotic classes and the number of antibiotic courses received. This suggests that antibiotics are not important risk factors of kidney stones. Rather, kidney stones when they initially cause urinary symptoms are under-recognized, resulting in antibiotic use before a formal diagnosis of kidney stones ( i.e. , reverse causality).

BACKGROUND

Antibiotics modify gastrointestinal and urinary microbiomes, which may contribute to kidney stone formation. This study examined whether an increased risk of a first-time symptomatic kidney stone episode follows antibiotic use.

METHODS

A population-based case-control study surveyed 1247 chart-validated first-time symptomatic kidney stone formers with a documented obstructing or passed stone (cases) in Olmsted County, Minnesota, from 2008 to 2013 and 4024 age- and sex-matched controls. All prescriptions for outpatient oral antibiotic use within 5 years before the onset of symptomatic stone for the cases and their matched controls were identified. Conditional logistic regression estimated the odds ratio (OR) of a first-time symptomatic kidney stone across time after antibiotic use. Analyses were also performed after excluding cases and controls with prior urinary tract infection or hematuria because urinary symptoms resulting in antibiotic prescription could have been warranted because of undiagnosed kidney stones.

RESULTS

The risk of a symptomatic kidney stone was only increased during the 1-year period after antibiotic use (unadjusted OR, 1.31; P = 0.001), and this risk was attenuated after adjustment for comorbidities (OR, 1.16; P = 0.08). After excluding cases and controls with prior urinary symptoms, there was no increased risk of a symptomatic kidney stone during the 1-year period after antibiotic use (unadjusted OR, 1.04; P = 0.70). Findings were consistent across antibiotic classes and the number of antibiotic courses received.

CONCLUSIONS

The increased risk of a first-time symptomatic kidney stone with antibiotic use seems largely due to both comorbidities and prescription of antibiotics for urinary symptoms. Under-recognition of kidney stones that initially cause urinary symptoms resulting in antibiotic use may explain much of the perceived stone risk with antibiotics ( i.e. , reverse causality).

A critical appraisal of urolithiasis clinical practice guidelines using the AGREE II instrument

Background

The Appraisal of Guidelines for Research and Evaluation II (AGREE II) instrument was developed to improve the methodological quality of clinical practice guidelines (CPGs). High-quality guidelines can provide reliable recommendations for different clinical issues. Currently, there is no quality appraisal of CPGs for urolithiasis. This study evaluated the quality of evidence-based CPGs for urolithiasis and provided new insights into improving guideline quality on urolithiasis.

Methods

Systematic reviews were conducted to identify urolithiasis CPGs in PubMed, electronic databases, and websites of medical associations from January 2009 to July 2022. The quality of included CPGs was evaluated by four reviewers using the AGREE II instrument. Subsequently, the scores of all domains in the AGREE II instrument were calculated.

Results

A total of 19 urolithiasis CPGs were identified for review: seven from Europe, six from USA, three from international union, two from Canada, and one from Asia. The agreement among reviewers was rated good [intraclass correlation coefficient (ICC), 0.806; 95% CI: 0.779-0.831]. The domains with the highest scores were scope and purpose (69.7%, 54.2-86.1%) and clarity of presentation (76.8%, 59.7-90.3%). The domains of stakeholder involvement (44.9%, 19.4-84.7%) and applicability (48.5%, 30.2-72.9%) gained the lowest score. Only five guidelines (26.3%) were considered "strongly recommended".

Conclusions

The overall quality of the eligible CPGs was relatively high; however, future work is still needed in the domains of rigor of development, editorial independence, applicability, and stakeholder involvement.

Machine Learning Models to Predict Kidney Stone Recurrence Using 24 Hour Urine Testing and Electronic Health Record-Derived Features

Objective

To assess the accuracy of machine learning models in predicting kidney stone recurrence using variables extracted from the electronic health record (EHR).

Methods

We trained three separate machine learning (ML) models (least absolute shrinkage and selection operator regression [LASSO], random forest [RF], and gradient boosted decision tree [XGBoost] to predict 2-year and 5-year symptomatic kidney stone recurrence from electronic health-record (EHR) derived features and 24H urine data (n = 1231). ML models were compared to logistic regression [LR]. A manual, retrospective review was performed to evaluate for a symptomatic stone event, defined as pain, acute kidney injury or recurrent infections attributed to a kidney stone identified in the clinic or the emergency department, or for any stone requiring surgical treatment. We evaluated performance using area under the receiver operating curve (AUC-ROC) and identified important features for each model.

Results

The 2- and 5- year symptomatic stone recurrence rates were 25% and 31%, respectively. The LASSO model performed best for symptomatic stone recurrence prediction (2-yr AUC: 0.62, 5-yr AUC: 0.63). Other models demonstrated modest overall performance at 2- and 5-years: LR (0.585, 0.618), RF (0.570, 0.608), and XGBoost (0.580, 0.621). Patient age was the only feature in the top 5 features of every model. Additionally, the LASSO model prioritized BMI and history of gout for prediction.

Conclusions

Throughout our cohorts, ML models demonstrated comparable results to that of LR, with the LASSO model outperforming all other models. Further model testing should evaluate the utility of 24H urine features in model structure.