Medical management of kidney stones: AUA guideline

Spectrophotometric and chromatographic analysis of creatine:creatinine crystals in urine

Creatinine is the end product of the catabolism of creatine and creatine phosphate. Creatine phosphate serves as a reservoir of high-energy phosphate, especially in skeletal and cardiac muscle. Besides typical known changes in serum and urinary creatinine concentrations, rare cases associated with changes in serum and urinary creatine levels have been described in the literature in humans. These cases are mostly linked to an excessive intake of creatine ethyl ester or creatine monohydrate, often resulting in increased urine creatinine concentrations. In addition, it is known that at such elevated creatinine concentrations, creatinine crystallisation may occur in the urine. Analysis of crystals and urinary concrements, often of heterogenous chemical composition, may provide diagnostic and therapeutic hints to the benefit of the patient. The aim of the present work was to analyze urine crystals of unclear composition with microscopic and spectroscopic techniques. On routine microscopic analysis of urine, a preliminary suspicion of uric acid or creatinine crystals was expressed. The crystals were of a cuboid shape and showed polarization effects in microscopy. The dried urine sample was whitish-orange in colour, odourless and dissolved well in water. Protein concentration in dry weight (DW) urine was about 0.3 mg/mg. The measured zinc content in the studied sample was approximately 660 µg/g DW sample and copper content was approximately 64 µg/g DW sample. A lead signal of around 10 µg/g DW sample was also observed. UV-Vis analysis showed a maximum creatine peak around 220 nm, compatible with the spectrum of creatinine with a maximum peak of 230 nm. Using HPLC technique, an extreme high ratio of creatine to creatinine of about 38 was measured, which led to the conclusion of the occurrence of rare creatine crystals in urine.

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.

Diagnosis and management of primary hyperoxalurias: best practices

The primary hyperoxalurias (PH 1, 2, and 3) are rare autosomal recessive disorders of glyoxylate metabolism resulting in hepatic overproduction of oxalate. Clinical presentations that should prompt consideration of PH include kidney stones, nephrocalcinosis, and kidney failure of unknown etiology, especially with echogenic kidneys on ultrasound. PH1 is the most common and severe of the primary hyperoxalurias with a high incidence of kidney failure as early as infancy. Until the recent availability of a novel RNA interference (RNAi) agent, PH care was largely supportive of eventual need for kidney/liver transplantation in PH1 and PH2. Together with the Oxalosis and Hyperoxaluria Foundation, the authors developed a diagnostic algorithm for PH1 and in this report outline best clinical practices related to its early diagnosis, supportive treatment, and long-term management, including the use of the novel RNAi. PH1-focused approaches to dialysis and kidney/liver transplantation for PH patients with progression to chronic kidney disease/kidney failure and systemic oxalosis are suggested. Therapeutic advances for this devastating disease heighten the importance of early diagnosis and informed treatment.

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.

Proteome-wide mendelian randomization identifies therapeutic targets for nephrolithiasis

Kidney Stone Disease (KSD) constitutes a multifaceted disorder, emerging from a confluence of environmental and genetic determinants, and is characterized by a high frequency of occurrence and recurrence. Our objective is to elucidate potential causative proteins and identify prospective pharmacological targets within the context of KSD. This investigation harnessed the unparalleled breadth of plasma protein and KSD pooled genome-wide association study (GWAS) data, sourced from the United Kingdom Biobank Pharma Proteomics Project (UKBPPP) and the FinnGen database version R10. Through Mendelian randomization analysis, proteins exhibiting a causal influence on KSD were pinpointed. Subsequent co-localization analyses affirmed the stability of these findings, while enrichment analyses evaluated their potential for pharmacological intervention. Culminating the study, a phenome-wide association study (PheWAS) was executed, encompassing all phenotypes (2408 phenotypes) catalogued in the FinnGen database version R10. Our MR analysis identified a significant association between elevated plasma levels of proteins FKBPL, ITIH3, and SERPINC1 and increased risk of KSD based on genetic predictors. Conversely, proteins CACYBP, DAG1, ITIH1, and SEMA6C showed a protective effect against KSD, documented with statistical significance (PFDR<0.05). Co-localization analysis confirmed these seven proteins share genetic variants with KSD, signaling a shared genetic basis (PPH3 + PPH4 > 0.8). Enrichment analysis revealed key pathways including hyaluronan metabolism, collagen-rich extracellular matrix, and serine-type endopeptidase inhibition. Additionally, our PheWAS connected the associated proteins with 356 distinct diseases (PFDR<0.05), highlighting intricate disease interrelations. In conclusion, our research elucidated a causal nexus between seven plasma proteins and KSD, enriching our grasp of prospective therapeutic targets.

Evaluation and Long-Term Follow-Up of Living Kidney Donors

The evaluation of living kidney donor candidates is a complex and lengthy process. Donor candidates face geographic and socioeconomic barriers to completing donor evaluation. Inequities in access to living donations persist. With a growing demand for kidney transplants and a shortage of living donors, transplant centers are more permissive of accepting less-than-ideal donor candidates. Donors have an increased lifetime risk of kidney failure, but the absolute risk increase is small. Efforts are needed to support donor candidates to complete donor nephrectomy safely and efficiently and receive optimal follow-up care to prevent risk factors for kidney disease and detect complications early. In this article, the authors address key elements of donor kidney evaluation, including current living donation policy requirements and transplant center practices. The authors present a simplified comprehensive practical approach to help guide providers in completing donor evaluation and follow-up care with best outcomes possible.

Evaluation of a urinary filtration device for kidney stone retrieval: Pi-Box®

INTRODUCTION

There is an unmet need to offer a proper urinary straining device for patients in whom spontaneous expulsion of stones is expected. The objective of this study was to assess the efficacity, duration and ease of use of a new filtration device: the Pi-Box®.

MATERIAL AND METHODS

This was a single-institution, non-randomized open-label study. Consecutive male patients with at least one stone that was susceptible of spontaneous passage, or after shockwave lithotripsy were included. The first 30 consecutive patients (Group 1) used the usual recommended techniques, and the 30 following consecutive patients (Group 2) were given the Pi-Box®. The patients completed a questionnaire when seen at 1-month follow-up.

RESULTS

Sixty men were included between January 2023 and May 2023. Thirteen (43%) patients retrieved a stone in each group (P=1). Filtration was performed for a median of 5 days in Group 1 and 10 days in Group 2 (P=0.03). Fourteen (46%) patients were satisfied or very satisfied with their filtration technique without the device versus 18 (60%) with the Pi-Box® (P=0.3). Eighteen (60%) and 21 patients (70%) would recommend their straining technique to a relative in groups 1 and 2, respectively (P=0.42).

CONCLUSIONS

The number of straining days was twice longer with the Pi-Box® device and is in favor of a better observance. The device did not increase the number of stones retrieved by urine filtration, which was high in this pilot study and may have been due to a participation bias.

LEVEL OF EVIDENCE

2B.

Low daily water intake profile-is it a contributor to disease?

Few previous review articles have focused on the associations between inadequate daily water intake (LOW) or urinary biomarkers of dehydration (UD; low urine volume or high urine osmolality) and multiple diseases. Accordingly, we conducted manual online searches (47 key words) of the PubMed, Embase, and Google Scholar databases with these inclusion criteria: English language, full-text, peer reviewed, no restriction on research design, and three publications minimum. Initially, 3,903 articles were identified based on their titles and abstracts. Evaluations of full length .pdf versions identified 96 studies that were acceptable for inclusion. We concluded that the evidence is insufficient or conflicting for seven disorders or diseases (i.e. suggesting the need for additional clarifying research) and it is lacking for all-cause mortality. Differential characterizations among women and men have been reported in the results of nine studies involving five diseases. Finally, the evidence for associations of LOW or UD is strong for both kidney stones and type 2 diabetes with hyperglycemia. This suggests that great public health value (i.e. reduced disease risk) may result from increased daily water intake-a simple and cost-effective dietary modification.

Investigation and quantification of composition variability in urinary stone analysis

PURPOSE

To investigate the variability in urinary stone composition analysis due to sampling and suggest potential solutions.

MATERIALS AND METHODS

We collected 1,135 stone fragments from 149 instances that had undergone a stone removal at Hanoi Medical University Hospital from January 2022 to August 2022. Each fragment was ground into fine powder and divided into separate specimens if the amount was abundant. For composition analyzing every specimen, Fourier transform infrared spectroscopy was performed. The composition of a given fragment was the average of its belonging specimens. The variability in composition was assessed on the fragment level (i.e., between fragments of an instance). We defined an instance as "significantly variable" if the maximum difference in any composition across its belonging fragments was equal to or greater than a given threshold.

RESULTS

On average, there were 7.6±3.3 stone fragments per instance and 2.3±0.5 specimens per fragment. We found that the variability could be substantial on the fragment level. Eighty-nine (69.5%) and 70 (54.7%) out of 128 multiple-component instances were significantly variable if the threshold was set at 20% and 30%, respectively. The variability of an instance on the fragment level was correlated with the size of fragment and the number of components.

CONCLUSIONS

Our study demonstrated the significant variability in urinary stone composition and showed that it correlated with the size and the impurity of samples. Mapping denotation while sampling and analyzing as well as reporting the composition of individual fragments could be valuable to reduce potential variability.

Plant-based diets, animal agriculture, and the connection with urological and planetary health

PURPOSE OF REVIEW

We summarize the latest evidence regarding the impact of plant-based diets on urological and planetary health to facilitate patient counseling and research regarding dietary intervention.

RECENT FINDINGS

Studies have highlighted the association of plant-based diets with a lower risk of multiple urological conditions including prostate cancer, erectile dysfunction, benign prostatic hyperplasia, and nephrolithiasis, as well as benefits for planetary health.

SUMMARY

Plant-based diets are associated with numerous benefits that co-promote urological and planetary health.

Prevalence and characteristics of genetic disease in adult kidney stone formers

BACKGROUND

Molecular mechanisms of kidney stone formation remain unknown in most patients. Previous studies have shown a high heritability of nephrolithiasis, but data on the prevalence and characteristics of genetic disease in unselected adults with nephrolithiasis are lacking. This study was conducted to fill this important knowledge gap.

METHODS

We performed whole exome sequencing in 787 participants in the Bern Kidney Stone Registry, an unselected cohort of adults with one or more past kidney stone episodes [kidney stone formers (KSFs)] and 114 non-kidney stone formers (NKSFs). An exome-based panel of 34 established nephrolithiasis genes was analysed and variants assessed according to American College of Medical Genetics and Genomics criteria. Pathogenic (P) or likely pathogenic (LP) variants were considered diagnostic.

RESULTS

The mean age of KSFs was 47 ± 15 years and 18% were first-time KSFs. A Mendelian kidney stone disease was present in 2.9% (23/787) of KSFs. The most common genetic diagnoses were cystinuria (SLC3A1, SLC7A9; n = 13), vitamin D-24 hydroxylase deficiency (CYP24A1; n = 5) and primary hyperoxaluria (AGXT, GRHPR, HOGA1; n = 3). Of the KSFs, 8.1% (64/787) were monoallelic for LP/P variants predisposing to nephrolithiasis, most frequently in SLC34A1/A3 or SLC9A3R1 (n = 37), CLDN16 (n = 8) and CYP24A1 (n = 8). KSFs with Mendelian disease had a lower age at the first stone event (30 ± 14 versus 36 ± 14 years; P = .003), were more likely to have cystine stones (23.4% versus 1.4%) and less likely to have calcium oxalate monohydrates stones (31.9% versus 52.5%) compared with KSFs without a genetic diagnosis. The phenotype of KSFs with variants predisposing to nephrolithiasis was subtle and showed significant overlap with KSFs without diagnostic variants. In NKSFs, no Mendelian disease was detected and LP/P variants were significantly less prevalent compared with KSFs (1.8% versus 8.1%).

CONCLUSION

Mendelian disease is uncommon in unselected adult KSFs, yet variants predisposing to nephrolithiasis are significantly enriched in adult KSFs.

Oral supplementation with probiotics, potassium citrate, and magnesium in reducing crystalluria in stone formers: A phase II study

INTRODUCTION

Crystalluria is an important indicator of renal stone recurrence. Mechanisms underlying urinary stone formation are still not fully understood and raising interests has been giving to intestinal commensal bacteria for their contribute in maintaining urinary solutes equilibrium. The aim of our phase II study was to examine the administration of potassium citrate, magnesium and probiotics in order to reduce crystalluria.

MATERIALS AND METHODS

Since May 2021, we enrolled 23 patients candidates for ureterorenolithotripsy for calcium oxalate kidney stones with crystalluria and a normal metabolic profile. The analysis was validated by the Institution's Ethical Committee (no. approval STS CE Lazio 1/N-823). At discharge, patients were provided with daily food supplementation for 20 days of 1 billion Lactobacillus paracasei LPC09, 1 billion Lactobacillus plantarum LP01, 1 billion Bifidobacterium breve BR03, potassium (520 mg), citrate (1400 mg), and magnesium (80 mg). Crystalluria was re-assessed at 1, 3, 6, and 12-months follow-up by polarized light microscopy.

RESULTS

After one month from the oral supplementation, no patient reported crystalluria; at 3 months, among the 20 participants available for re-evaluation, still no patient reported crystalluria. Instead, crystalluria was reported in three patients (15%) at 6 months, and in five patients (25%) at 12 months follow-up.

CONCLUSIONS

The oral supplementation with Lactobacillus spp. and Bifidobacterium spp. was found able to reduce the prevalence of crystalluria in a cohort of patients with diagnosis of calcium oxalate kidney stones with crystalluria candidate to ureterorenolithotripsy.

MOF-818 Nanozyme Suppresses Calcium Oxalate Kidney Stones by Alleviating Oxidative Stress and Inflammatory Injury

There remains a lack of effective drugs to alleviate the kidney stones caused by oxidative stress and inflammatory damage. The MOF-818 nanozyme is utilized to lessen the generation of reactive oxygen species (ROS) effectively, restore the membrane potential of mitochondria, regulate the cell cycle, decrease cell death, hinder the recruitment of macrophages, and mitigate the release of inflammatory factors in macrophages. These effects are attributed to the nanozyme's ability to mimic the enzyme properties of catalase (CAT) and superoxide dismutase (SOD). It is demonstrated that this nanozyme can reduce kidney calcium oxalate crystal deposition by reducing the renal injury caused by high concentration oxalate, upregulate the expression levels of SOD and CAT in tissues, downregulate adhesion proteins and inflammatory factor IL-6 and TNF-α, and promote the polarization of macrophages from M1 to M2 phenotype in the rat model induced by ethylene glycol. Overall, MOF-818 has the potential to effectively suppress oxidative stress and inflammatory harm caused by high levels of oxalate, hence lowering the likelihood of stone formation. MOF-818 nanozyme is also expected to be used as an alternative drug for the treatment of calcium oxalate kidney stones and provide an experimental theoretical basis for the development of new nanomedicines.

A novel infrared spectroscopy marker for assessing the postoperative infection risk in patients with upper urinary tract calculus

The aim of this study is to evaluate the ability of infrared wavenumber of calculus to predict postoperative infection in patients with upper urinary tract calculus (UUTC), and to establish a predictive model based on this. From March 2018 to March 2023, 480 UUTC patients from Fujian Provincial Hospital were included in this study. The infrared-wavenumbers related infection score (IR-infection score) was constructed by univariate analysis, multicollinearity screening, and Lasso analysis to predict postoperative infection. Continually, the Delong test was used to compare the predictive power between the IR-infection score and traditional indicators. Afterward, we performed urine metagene sequencing and stone culture to prove the correlation between calculus toxicity and IR-infection score. Finally, logistic regression was used to build a nomogram. IR-infection score composed of four independent wavenumbers could precisely predict postoperative infection (AUCvalidation cohort = 0.707) and sepsis (AUCvalidation cohort = 0.824). IR-infection score had better predictive ability than commonly used clinical indicators. Moreover, metagenomics sequencing and calculus culture confirmed the correlation between IR-infection score and calculus toxicity (all P < 0.05). The nomogram based on the IR-infection score had high predictive power (all AUCs > 0.803). Our study first developed a novel infrared spectroscopy marker and nomogram, which can help urologists better predict postoperative infection in UUTC patients.

Consensus statement addressing controversies and guidelines on pediatric urolithiasis

PURPOSE

We aimed to investigate controversial pediatric urolithiasis issues systematically, integrating expert consensus and comprehensive guidelines reviews.

METHODS

Two semi-structured online focus group meetings were conducted to discuss the study's need and content, review current literature, and prepare the initial survey. Data were collected through surveys and focus group discussions. Existing guidelines were reviewed, and a second survey was conducted using the Delphi method to validate findings and facilitate consensus. The primary outcome measures investigated controversial issues, integrating expert consensus and guideline reviews.

RESULTS

Experts from 15 countries participated, including 20 with 16+ years of experience, 2 with 11-15 years, and 4 with 6-10 years. The initial survey identified nine main themes, emphasizing the need for standardized diagnostic and treatment protocols and tailored treatments. Inter-rater reliability was high, with controversies in treatment approaches (score 4.6, 92% agreement), follow-up protocols (score 4.8, 100% agreement), and diagnostic criteria (score 4.6, 92% agreement). The second survey underscored the critical need for consensus on identification, diagnostic criteria (score 4.6, 92% agreement), and standardized follow-up protocols (score 4.8, 100% agreement).

CONCLUSION

The importance of personalized treatment in pediatric urolithiasis is clear. Prioritizing low-radiation diagnostic tools, effectively managing residual stone fragments, and standardized follow-up protocols are crucial for improving patient outcomes. Integrating new technologies while ensuring safety and reliability is also essential. Harmonizing guidelines across regions can provide consistent and effective management. Future efforts should focus on collaborative research, specialized training, and the integration of new technologies in treatment protocols.

Artificial Intelligence in Urology: Application of a Machine Learning Model to Predict the Risk of Urolithiasis in a General Population

This research presents our application of artificial intelligence (AI) in predicting urolithiasis risk. Previous applications, including AI for stone disease, have focused on stone composition and aiding diagnostic imaging. AI applications centered around patient-specific characteristics, lifestyle considerations, and diet have been limited. Our study comprised a robust sample size of 976 Chilean participants, with meticulously analyzed demographic, lifestyle, and health data through a comprehensive questionnaire. We developed a predictive model using various classifiers, including logistic regression, decision trees, random forests, and extra trees, reaching high accuracy (88%) in identifying individuals at risk of kidney stone formation. Key protective factors highlighted by the algorithm include the pivotal role of hydration, physical activity, and dietary patterns that played a crucial role, emphasizing the protective nature of higher fruit and vegetable intake, balanced dairy consumption, and the nuanced impact of specific protein sources on kidney stone risk. In contrast, identified risk factors encompassed gender disparities with males found to be 2.31 times more likely to develop kidney stones than females. Thirst and self-perceived dark urine color emerged as strong predictors, with a significant increase in the likelihood of stone formation. The development of predictive tools with AI, in urolithiasis management signifies a paradigm shift toward more precise and personalized health care. The algorithm's ability to process extensive datasets, including dietary habits, heralds a new era of data-driven medical practice. This research underscores the transformative impact of AI in medical diagnostics and prevention, paving the way for a future where health care interventions are not only more effective but also tailored to individual patient needs. In this case, AI is an important tool that can help patients stay healthy, prevent diseases, and make informed decisions about their overall well-being.

Development of UroSAM: A Machine Learning Model to Automatically Identify Kidney Stone Composition from Endoscopic Video

Introduction: Chemical composition analysis is important in prevention counseling for kidney stone disease. Advances in laser technology have made dusting techniques more prevalent, but this offers no consistent way to collect enough material to send for chemical analysis, leading many to forgo this test. We developed a novel machine learning (ML) model to effectively assess stone composition based on intraoperative endoscopic video data. Methods: Two endourologists performed ureteroscopy for kidney stones ≥ 10 mm. Representative videos were recorded intraoperatively. Individual frames were extracted from the videos, and the stone was outlined by human tracing. An ML model, UroSAM, was built and trained to automatically identify kidney stones in the images and predict the majority stone composition as follows: calcium oxalate monohydrate (COM), dihydrate (COD), calcium phosphate (CAP), or uric acid (UA). UroSAM was built on top of the publicly available Segment Anything Model (SAM) and incorporated a U-Net convolutional neural network (CNN). Discussion: A total of 78 ureteroscopy videos were collected; 50 were used for the model after exclusions (32 COM, 8 COD, 8 CAP, 2 UA). The ML model segmented the images with 94.77% precision. Dice coefficient (0.9135) and Intersection over Union (0.8496) confirmed good segmentation performance of the ML model. A video-wise evaluation demonstrated 60% correct classification of stone composition. Subgroup analysis showed correct classification in 84.4% of COM videos. A post hoc adaptive threshold technique was used to mitigate biasing of the model toward COM because of data imbalance; this improved the overall correct classification to 62% while improving the classification of COD, CAP, and UA videos. Conclusions: This study demonstrates the effective development of UroSAM, an ML model that precisely identifies kidney stones from natural endoscopic video data. More high-quality video data will improve the performance of the model in classifying the majority stone composition.

Using ChatGPT-4 to Analyze 24-Hour Urine Results and Generate Custom Dietary Recommendations for Nephrolithiasis

Purpose: The increasing incidence of nephrolithiasis underscores the need for effective, accessible tools to aid urologists in preventing recurrence. Despite dietary modification's crucial role in prevention, targeted dietary counseling using 24-hour urine collections is underutilized. This study evaluates ChatGPT-4, a multimodal large language model, in analyzing urine collection results and providing custom dietary advice, exploring the potential for artificial intelligence-assisted analysis and counseling. Materials and Methods: Eleven unique prompts with synthesized 24-hour urine collection results were submitted to ChatGPT-4. The model was instructed to provide five dietary recommendations in response to the results. One prompt contained all "normal" values, with subsequent prompts introducing one abnormality each. Generated responses were assessed for accuracy, completeness, and appropriateness by two urologists, a nephrologist, and a clinical dietitian. Results: ChatGPT-4 achieved average scores of 5.2/6 for accuracy, 2.4/3 for completeness, and 2.6/3 for appropriateness. It correctly identified all "normal" values but had difficulty consistently detecting abnormalities and formulating appropriate recommendations. The model performed particularly poorly in response to calcium and citrate abnormalities and failed to address 3/10 abnormalities entirely. Conclusions: ChatGPT-4 exhibits potential in the dietary management of nephrolithiasis but requires further refinement for dependable performance. The model demonstrated the ability to generate personalized recommendations that were often accurate and complete but displayed inconsistencies in identifying and addressing urine abnormalities. Despite these limitations, with precise prompt design, physician oversight, and continued training, ChatGPT-4 can serve as a foundation for personalized medicine while also reducing administrative burden, indicating its promising role in improving the management of conditions such as nephrolithiasis.

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.

Quality of Information About Kidney Stones from Artificial Intelligence Chatbots

Introduction: Kidney stones are common and morbid conditions in the general population with a rising incidence globally. Previous studies show substantial limitations of online sources of information regarding prevention and treatment. The objective of this study was to examine the quality of information on kidney stones from artificial intelligence (AI) chatbots. Methods: The most common online searches about kidney stones from Google Trends and headers from the National Institute of Diabetes and Digestive and Kidney Diseases website were used as inputs to four AI chatbots (ChatGPT version 3.5, Perplexity, Chat Sonic, and Bing AI). Validated instruments were used to assess the quality (DISCERN instrument from 1 low to 5 high), understandability, and actionability (PEMAT, from 0% to 100%) of the chatbot outputs. In addition, we examined the reading level of the information and whether there was misinformation compared with guidelines (5 point Likert scale). Results: AI chatbots generally provided high-quality consumer health information (median DISCERN 4 out of 5) and did not include misinformation (median 1 out of 5). The median understandability was moderate (median 69.6%), and actionability was moderate to poor (median 40%). Responses were presented at an advanced reading level (11th grade; median Flesch-Kincaid score 11.3). Conclusions: AI chatbots provide generally accurate information on kidney stones and lack misinformation; however, it is not easily actionable and is presented above the recommended reading level for consumer health information.

A Machine Learning (ML) Predictive Model for Ureteroscopy lasertripsy (URSL) Outcomes in a Paediatric Population - Results from a large Endourology Tertiary Centre

INTRODUCTION

We aimed to develop machine learning (ML) algorithms for the automated prediction of post operative ureteroscopy outcomes for paediatric kidney stones based on pre-operative characteristics.

MATERIAL AND METHODS

Data from paediatric patients who underwent ureteroscopy for stone treatment by a single experienced surgeon, between 2010 and 2023 in Southampton General Hospital, were retrospectively collected. 15 ML classification algorithms were used to investigate correlations between preoperative characteristics and postoperative outcomes: primary stone free status (SFS, defined as stone fragments <2mm at the end of the procedure confirmed endoscopically and no evidence of stone fragments >2mm at XR KUB or US KUB at 3 months follow up) and complications. For the task of complication and stone status, ensemble model was made out of bagging classifier, extra trees classifier and LDA. Also, a multi-task neural network was constructed for the simultaneous prediction of all post-operative characteristics. Finally, Explainable AI techniques were used to explain the prediction made by the best models.

RESULTS

The ensemble model produced the highest accuracy (90%) in predicting SFS, finding correlation with overall stone size (-0.205), presence of multiple stones (-0.127) and preoperative stenting (-0.102). Complications were predicted by SMOTE oversampled dataset (93.3% accuracy) with relation to preoperative positive urine culture (-0.060) and SFS (0.003). Training the ML for the multi task model, accuracies of 83.3% and 80% were respectively reached.

CONCLUSION

ML has a great potential of assisting healthcare research, with possibilities to investigate dataset at a higher level. With the aid of this intelligent tool, urologists can implement their practice and develop new strategies for outcome prediction and patient counselling and informed shared decision making. Our model reached an excellent accuracy in predicting SFS and complications in the paediatric population, leading the way to the validation of patient-specific predictive tools.

Comparison of automated kidney stone size measurement and volumetry in photon counting CT compared to 3rd generation dual energy CT and physically measurements - an ex vivo study

PURPOSE

This ex vivo study aimed to compare a newly developed dual-source photon-counting CT (PCCT) with a 3rd generation dual-source dual-energy CT (DECT) for the detection and measurement (stone lengths and volumetrics) of urinary stones.

METHODS

143 urinary stones with a known geometry were physically measured and defined as reference values. Next, urinary stones were placed in an anthropomorphic abdomen-model and were scanned with DECT and PCCT. Images were read by two experienced examiners and automatically evaluated using a specific software.

RESULTS

DECT and PCCT showed a high sensitivity for manual stone detection of 97.9% and 94.4%, and for automatic detection of 93.0% and 87.4%, respectively. Compared to that uric acid and xanthine stones were recognized slightly worse by DECT and PCCT with manual stone detection (93.3% and 82.2%), and with automatic detection (77.8% and 60.0%). All other stone entities were completely recognized. By comparing the maximum diameter of the reference value and DECT, Pearson-correlation was 0.96 (p < 0.001) for manual and 0.97 (p < 0.001) for automatic measurement, and for PCCT it was 0.94 (p < 0.001) for manual and 0.97 (p < 0.001) for automatic measurements. DECT and PCCT can also reliably determine volume manually and automatically with a Pearson-correlation of 0.99 (p < 0.001), respectively.

CONCLUSION

Both CTs showed comparable results in stone detection, length measurement and volumetry compared to the reference values. Automatic measurement tends to underestimate the maximum diameter. DECT proved to be slightly superior in the recognition of xanthine and uric acid stones.

The Use of Genetic Testing in Nephrolithiasis Evaluation: A Retrospective Review From a Multidisciplinary Kidney Stone Clinic

OBJECTIVE

To describe genetic and clinical characteristics for patients undergoing genetic testing at our multidisciplinary kidney stone clinic.

METHODS

A retrospective review was performed on patients evaluated in our stone clinic and referred to genetics between 2018 and 2022. Patient demographic, clinical, stone, and genetic data were included. We assessed the specific variants identified in our cohort, both those with a pathogenic association and variants of unknown significance.

RESULTS

Of 825 patients seen in our stone clinic from 2018-2022, 50 patients were referred to genetics. Among these patients, 33/50 (66%) underwent genetic testing and were included in the analysis. Of those who underwent genetic testing, a variant was identified in 19/33 (58%) patients, and 9/33 (27%) of these were a known pathogenic variant. Among patients with a pathogenic variant identified, the majority had a family history of stones (55.6%), calcium-based stones (77.8%), had their first stone prior to age 18 (66.7%), were recurrent stone formers (100%), and had been managed medically (88.9%) or surgically (88.9%) prior to testing. When comparing patients with a pathogenic variant, variants of unknown significance, and no variant, there were no significant differences in demographic or clinical parameters.

CONCLUSION

In our stone practice, more than half of patients who underwent genetic testing were found to have a variant. However, the majority of these variants were of unknown significance. Further evaluation regarding how genetic testing can impact nephrolithiasis management is needed.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Dietary Sodium and Potassium Intakes and Kidney Stone Prevalence: The National Health and Nutrition Examination Survey 2011-2018

The associations between dietary sodium intake (DSI), dietary potassium intake (DPI), and kidney stone disease (KSD) are not clear. We examined The National Health and Nutrition Examination Survey 2011-2018 to determine the independent associations between daily DSI, DPI, DSI/DPI, and KSD prevalence. In total, 19,405 participants were included for analysis, of which 1,895 had KSD. Higher DSI was not associated with increased odds of KSD in regression analysis when DSI was modeled as a continuous variable (OR = 0.99, 95% CI: 0.99-1.00, p = 0.2), or when comparing highest quartile of DSI to lowest quartile (OR = 0.84, 95% CI: 0.68-1.04, p = 0.1). Unlike DSI, higher DPI was strongly associated with reduced odds of KSD in regression analysis when DPI was modeled as a continuous variable (OR = 0.99, 95% CI: 0.99-0.99, p = 0.02), or when comparing highest quartile of DPI to lowest quartile (OR = 0.75, 95% CI: 0.60-0.94, p = 0.01). Lastly, higher DSI/DPI was also strongly associated with increased odds of KSD in regression analysis when DSI/DPI was modeled as a continuous variable (OR = 1.1, 95% CI: 1.01-1.20, p = 0.03), or when comparing highest quartile of DPI to lowest quartile (OR = 1.30, 95% CI: 1.10-1.70, p = 0.008). All the observed relationships were independent of total calorie intake. In conclusion, both lower DPI and higher DSI/DPI are associated with an increased risk of KSD. Future prospective studies are needed to clarify these causal relationships.

Effects of thiazides and new findings on kidney stones and dysglycemic side effects

Thiazide and thiazide-like diuretics (thiazides) belong to the most frequently prescribed drugs worldwide. By virtue of their natriuretic and vasodilating properties, thiazides effectively lower blood pressure and prevent adverse cardiovascular outcomes. In addition, through their unique characteristic of reducing urine calcium, thiazides are also widely employed for the prevention of kidney stone recurrence and reduction of bone fracture risk. Since their introduction into clinical medicine in the early 1960s, thiazides have been recognized for their association with metabolic side effects, particularly impaired glucose tolerance, and new-onset diabetes mellitus. Numerous hypotheses have been advanced to explain thiazide-induced glucose intolerance, yet underlying mechanisms remain poorly defined. Regrettably, the lack of understanding and unpredictability of these side effects has prompted numerous physicians to refrain from prescribing these effective, inexpensive, and widely accessible drugs. In this review, we outline the pharmacology and mechanism of action of thiazides, highlight recent advances in the understanding of thiazide-induced glucose intolerance, and provide an up-to-date discussion on the role of thiazides in kidney stone prevention.

Thiazides for kidney stone recurrence prevention

PURPOSE OF REVIEW

Kidney stones are the most common condition affecting the kidney, and characterized by a high rate of recurrence. Thiazide and thiazide-like diuretics (thiazides) are commonly prescribed to prevent the recurrence of kidney stones. This review offers a comprehensive up-to-date assessment of the evidence supporting the use of thiazides for kidney stone recurrence prevention, highlights potential harms associated with treatment, and identifies areas of knowledge that require further investigation.

RECENT FINDINGS

The clinical routine to prescribe thiazides for kidney stone prevention has recently been challenged by the findings of the large NOSTONE trial that failed to show superiority of hydrochlorothiazide at doses up to 50 mg daily over placebo in preventing a composite of clinical or radiological recurrence in patients at high risk of recurrence. Yet, adverse events such as new onset diabetes mellitus and gout were more common in patients receiving hydrochlorothiazide compared to placebo. As demonstrated by a novel meta-analysis presented in this review encompassing all randomized placebo-controlled trials with thiazide monotherapy, current trial evidence does not indicate that thiazide monotherapy is significantly better than placebo in preventing kidney stone recurrence.

SUMMARY

Given the limited efficacy and possible adverse effects, we advocate for a restrictive use of thiazides for kidney stone recurrence prevention. Clearly, there remains a high unmet medical need for effective, targeted therapies to prevent recurrence of kidney stones.

Real-World Effectiveness of Preventive Pharmacological Therapy in Patients With Urolithiasis: A Retrospective Cohort Study

RATIONALE & OBJECTIVE

Data supporting the efficacy of preventive pharmacological therapy (PPT) to reduce urolithiasis recurrence are based on clinical trials with composite outcomes that incorporate imaging findings and have uncertain clinical significance. This study evaluated whether the use of PPT leads to fewer symptomatic stone events.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Medicare enrollees with urolithiasis who completed 24-hour urine collections that revealed hypercalciuria, hypocitraturia, low urine pH, or hyperuricosuria.

EXPOSURE

PPT (thiazide diuretics for hypercalciuria, alkali for hypocitraturia or low urine pH, or uric acid lowering drugs for hyperuricosuria) categorized as (1) adherent to guideline-concordant PPT, (2) nonadherent to guideline-concordant PPT, or (3) untreated.

OUTCOME

Symptomatic stone event occurrence (emergency department [ED] visit or hospitalization for urolithiasis or stone-directed surgery).

ANALYTICAL APPROACH

Cox proportional hazards regression.

RESULTS

Among 13,942 patients, 31.0% were prescribed PPT. Compared with no treatment, concordant/adherent PPT use was associated with a significantly lower hazard of symptomatic stone events for patients with hypercalciuria (HR, 0.736 [95% CI, 0.593-0.915]) and low urine pH (HR, 0.804 [95% CI, 0.650-0.996]) but not for patients with hypocitraturia or hyperuricosuria. These associations were largely driven by significantly lower rates of ED visits after initiating PPT among the concordant/adherent group versus untreated patients. Patients with hypercalciuria had adjusted 2-year predicted probabilities of a visit of 3.8% [95% CI, 2.5%-5.2%%] and 6.9% [95% CI, 6.0%-7.7%] for the concordant/adherent PPT and no-treatment groups, respectively. Among patients with low urine pH, these probabilities were 4.3% (95% CI, 2.9%-5.7%) and 7.3% (95% CI, 6.5%-8.0%) for the concordant/adherent PPT and no-treatment groups, respectively.

LIMITATIONS

Potential bias from the possibility that patients prescribed PPT had more severe disease than untreated patients.

CONCLUSIONS

Patients with urolithiasis and hypercalciuria who were adherent to treatment with thiazide diuretics as well as those with low urine pH adherent to prescribed alkali therapy had fewer symptomatic stone events than untreated patients.

PLAIN-LANGUAGE SUMMARY

Despite multiple clinical trials demonstrating the efficacy of thiazide diuretics and alkali for secondary prevention of kidney stones, they are infrequently prescribed due in part to a lack of data about their effectiveness in real-world settings. We analyzed medical claims from older adults with kidney stones for whom urine chemistry data were available. We found that patients who took prescribed thiazide diuretics for elevated urine calcium levels or alkali for low urinary pH were less likely to experience symptomatic stone recurrences than untreated patients. This benefit was expressed as lower rates of emergency department visits after initiating therapy. Our findings should inform the prescription of and adherence to treatment with thiazide diuretics and alkali for the prevention of recurrent kidney stones.

Management of urinary stones: state of the art and future perspectives by experts in stone disease

AIM

To present state of the art on the management of urinary stones from a panel of globally recognized urolithiasis experts who met during the Experts in Stone Disease Congress in Valencia in January 2024. Options of treatment: The surgical treatment modalities of renal and ureteral stones are well defined by the guidelines of international societies, although for some index cases more alternative options are possible. For 1.5 cm renal stones, both m-PCNL and RIRS have proven to be valid treatment alternatives with comparable stone-free rates. The m-PCNL has proven to be more cost effective and requires a shorter operative time, while the RIRS has demonstrated lower morbidity in terms of blood loss and shorter recovery times. SWL has proven to be less effective at least for lower calyceal stones but has the highest safety profile. For a 6mm obstructing stone of the pelviureteric junction (PUJ) stone, SWL should be the first choice for a stone less than 1 cm, due to less invasiveness and lower risk of complications although it has a lower stone free-rate. RIRS has advantages in certain conditions such as anticoagulant treatment, obesity, or body deformity. Technical issues of the surgical procedures for stone removal: In patients receiving antithrombotic therapy, SWL, PCN and open surgery are at elevated risk of hemorrhage or perinephric hematoma. URS, is associated with less morbidity in these cases. An individualized combined evaluation of risks of bleeding and thromboembolism should determine the perioperative thromboprophylactic strategy. Pre-interventional urine culture and antibiotic therapy are mandatory although UTI treatment is becoming more challenging due to increasing resistance to routinely applied antibiotics. The use of an intrarenal urine culture and stone culture is recommended to adapt antibiotic therapy in case of postoperative infectious complications. Measurements of temperature and pressure during RIRS are vital for ensuring patient safety and optimizing surgical outcomes although techniques of measurements and methods for data analysis are still to be refined. Ureteral stents were improved by the development of new biomaterials, new coatings, and new stent designs. Topics of current research are the development of drug eluting and bioresorbable stents. Complications of endoscopic treatment: PCNL is considered the most invasive surgical option. Fever and sepsis were observed in 11 and 0.5% and need for transfusion and embolization for bleeding in 7 and 0.4%. Major complications, as colonic, splenic, liver, gall bladder and bowel injuries are quite rare but are associated with significant morbidity. Ureteroscopy causes less complications, although some of them can be severe. They depend on high pressure in the urinary tract (sepsis or renal bleeding) or application of excessive force to the urinary tract (ureteral avulsion or stricture). Diagnostic work up:  Genetic testing consents the diagnosis of monogenetic conditions causing stones. It should be carried out in children and in selected adults. In adults, monogenetic diseases can be diagnosed by systematic genetic testing in no more than 4%, when cystinuria, APRT deficiency, and xanthinuria are excluded. A reliable stone analysis by infrared spectroscopy or X-ray diffraction is mandatory and should be associated to examination of the stone under a stereomicroscope. The analysis of digital images of stones by deep convolutional neural networks in dry laboratory or during endoscopic examination could allow the classification of stones based on their color and texture. Scanning electron microscopy (SEM) in association with energy dispersive spectrometry (EDS) is another fundamental research tool for the study of kidney stones. The combination of metagenomic analysis using Next Generation Sequencing (NGS) techniques and the enhanced quantitative urine culture (EQUC) protocol can be used to evaluate the urobiome of renal stone formers. Twenty-four hour urine analysis has a place during patient evaluation together with repeated measurements of urinary pH with a digital pH meter. Urinary supersaturation is the most comprehensive physicochemical risk factor employed in urolithiasis research. Urinary macromolecules can act as both promoters or inhibitors of stone formation depending on the chemical composition of urine in which they are operating. At the moment, there are no clinical applications of macromolecules in stone management or prophylaxis. Patients should be evaluated for the association with systemic pathologies.

PROPHYLAXIS

Personalized medicine and public health interventions are complementary to prevent stone recurrence. Personalized medicine addresses a small part of stone patients with a high risk of recurrence and systemic complications requiring specific dietary and pharmacological treatment to prevent stone recurrence and complications of associated systemic diseases. The more numerous subjects who form one or a few stones during their entire lifespan should be treated by modifications of diet and lifestyle. Primary prevention by public health interventions is advisable to reduce prevalence of stones in the general population. Renal stone formers at "high-risk" for recurrence need early diagnosis to start specific treatment. Stone analysis allows the identification of most "high-risk" patients forming non-calcium stones: infection stones (struvite), uric acid and urates, cystine and other rare stones (dihydroxyadenine, xanthine). Patients at "high-risk" forming calcium stones require a more difficult diagnosis by clinical and laboratory evaluation. Particularly, patients with cystinuria and primary hyperoxaluria should be actively searched.

FUTURE RESEARCH

Application of Artificial Intelligence are promising for automated identification of ureteral stones on CT imaging, prediction of stone composition and 24-hour urinary risk factors by demographics and clinical parameters, assessment of stone composition by evaluation of endoscopic images and prediction of outcomes of stone treatments. The synergy between urologists, nephrologists, and scientists in basic kidney stone research will enhance the depth and breadth of investigations, leading to a more comprehensive understanding of kidney stone formation.

Urinary stone analysis and clinical characteristics of 496 patients in Taiwan

Evaluate urinary stone components' epidemiological features in urolithiasis individuals and explore potential correlations between stone components and patients' clinical characteristics. A retrospective analysis of urinary stone compositions in 496 patients from a northern Taiwan medical center (February 2006 to October 2021) was conducted. We investigated associations between sex, age, body mass index (BMI), hypertension, diabetes mellitus (DM), hyperlipidemia (HLP), gout, coronary artery disease (CAD), cerebral vascular accident (CVA), chronic kidney disease (CKD), habits, urine pH, and three main stone groups: calcium oxalate (CaOx), calcium phosphate (CaP), and uric acid (UA). Males accounted for 66.5% of cases, with a male-to-female ratio of 1.99:1. Males were negatively associated with CaP stones (OR 0.313, p < 0.001) and positively with UA stones (OR 2.456, p = 0.009). Age showed a negative correlation with CaOx stones (OR 0.987, p = 0.040) and a positive correlation with UA stones (OR 1.023, p < 0.001). DM had a protective effect against CaP stones (OR 0.316, p = 0.004). Gout had a positive association with UA stones (OR 2.085, p = 0.035). Smoking was adversely associated with UA stones (OR 0.350, p = 0.018). Higher urine pH was a risk factor for CaP stones (OR 1.641, p = 0.001) and a protective factor against UA stones (OR 0.296, p < 0.001). These results may provide insights into the pathogenesis of urinary stones and the development of preventative strategies for high-risk populations. Further research is required to confirm and expand upon these findings.

The Multidisciplinary Approach in the Management of Patients with Kidney Stone Disease-A State-of-the-Art Review

Kidney stone disease has a multifactorial etiology, and evolving dietary habits necessitate continuous updates on the impact of dietary components on lithogenesis. The relationship between diseases influenced by lifestyle, such as obesity and diabetes, and kidney stone risk underscores the need for comprehensive lifestyle analysis. Effective management of kidney stones requires a multidisciplinary approach, involving collaboration among nutritionists, urologists, nephrologists, and other healthcare professionals to address the complex interactions between diet, lifestyle, and individual susceptibility. Personalized dietary therapy, based on each patient's unique biochemical and dietary profile, is essential and necessitates comprehensive nutritional assessments. Accurate dietary intake evaluation is best achieved through seven-day, real-time dietary records. Key factors influencing urinary risk include fluid intake, dietary protein, carbohydrates, oxalate, calcium, and sodium chloride. Personalized interventions, such as customized dietary changes based on gut microbiota, may improve stone prevention and recurrence. Current research suggests individualized guidance on alcohol intake and indicates that tea and coffee consumption might protect against urolithiasis. There is potential evidence linking tobacco use and secondhand smoke to increased kidney stone risk. The effects of vitamins and physical activity on kidney stone risk remain unresolved due to mixed evidence. For diseases influenced by lifestyle, conclusive evidence on targeted interventions for nephrolithiasis prevention is lacking, though preliminary research suggests potential benefits. Management strategies emphasize lifestyle modifications to reduce recurrence risks, support rapid recovery, and identify predisposing conditions, highlighting the importance of these changes despite inconclusive data.

Can Machine Learning Correctly Predict Outcomes of Flexible Ureteroscopy with Laser Lithotripsy for Kidney Stone Disease? Results from a Large Endourology University Centre

Background and objective

The integration of machine learning (ML) in health care has garnered significant attention because of its unprecedented opportunities to enhance patient care and outcomes. In this study, we trained ML algorithms for automated prediction of outcomes of ureteroscopic laser lithotripsy (URSL) on the basis of preoperative characteristics.

Methods

Data were retrieved for patients treated with ureteroscopy for urolithiasis by a single experienced surgeon over a 7-yr period. Sixteen ML classification algorithms were trained to investigate correlation between preoperative characteristics and postoperative outcomes. The outcomes assessed were primary stone-free status (SFS, defined as the presence of only stone fragments <2 mm on endoscopic visualisation and at 3-mo imaging) and postoperative complications. An ensemble model was constructed from the best-performing algorithms for prediction of complications and for prediction of SFS. Simultaneous prediction of postoperative characteristics was then investigated using a multitask neural network, and explainable artificial intelligence (AI) was used to demonstrate the predictive power of the best models.

Key findings and limitations

An ensemble ML model achieved accuracy of 93% and precision of 87% for prediction of SFS. Complications were mainly associated with a preoperative positive urine culture (1.44). Logistic regression revealed that SFS was impacted by the total stone burden (0.34), the presence of a preoperative stent (0.106), a positive preoperative urine culture (0.14), and stone location (0.09). Explainable AI results emphasised the key features and their contributions to the output.

Conclusions and clinical implications

Technological advances are helping urologists to overcome the classic limits of ureteroscopy, namely stone size and the risk of complications. ML represents an excellent aid for correct prediction of outcomes after training on pre-existing data sets. Our ML model achieved accuracy of >90% for prediction of SFS and complications, and represents a basis for the development of an accessible predictive model for endourologists and patients in the URSL setting.

Patient summary

We tested the ability of artificial intelligence to predict treatment outcomes for patients with kidney stones. We trained 16 different machine learning tools with data before surgery, such as patient age and the stone characteristics. Our final model was >90% accurate in predicting stone-free status after surgery and the occurrence of complications.

Pharmacists' perspectives and perceived barriers to counselling patients with kidney stones

BACKGROUND

The global increase in kidney stone incidence and its complications emphasise the need for effective management. While pharmacists can play a significant role in counselling and guiding patients, their practices in managing patients with kidney stones remain unclear.

OBJECTIVE(S)

To explore counselling practices and experiences of pharmacists when dealing with patients with kidney stones and to identify the barriers they face while providing counselling.

METHODS

A qualitative study was performed using semi-structured phone interviews with pharmacists practising in Jordan. Pharmacists were selected using quota sampling from those who took part in a previous study focused on pharmacists' knowledge of kidney stone aetiology and treatment. The COM-B Model of Behaviour Change was used to develop the interview guide and the analytical framework. Interviews were transcribed verbatim and analysed using a deductive thematic approach based on the pre-specified analytical framework.

RESULTS

Seven pharmacists (85.7% female; 57.1% working in community pharmacies) were interviewed. Counselling practices of patients with kidney stones were categorised into five themes: (1) Pharmacists' beliefs about patient counselling: perceived importance and desire to improve health through counselling; (2) Most priority patients: Types of patients mostly counselled; (3) Content of kidney stones-specific counselling: patient assessment and recommendations about kidney stones management; (4) Duration of the counselling sessions: time offered and influencing factors; (5) Barriers to patient counselling: patient-related, and pharmacist- and doctor-related challenges.

CONCLUSIONS

Pharmacists recognise the crucial role of kidney stones counselling but face gaps in their practices, including incomplete dietary education, limited knowledge of medication prescriptions, inconsistent patient-specific approaches, and potential communication challenges. These gaps can be overcome by enhancing training, standardising protocols of kidney stone treatment, promoting interprofessional communication, and improving communication strategies. Future research, including quantitative assessments, is needed to inform strategies that optimise patient counselling practices and facilitate improved outcomes.

Comparison of 24-hour urine composition prior to and after stone removal in nephrolithiasis: a prospective observational study

BACKGROUND

To evaluate 24-hour urine composition prior to and after complete stone removal in nephrolithiasis patients to determine potential relationship between kidney stones and patient metabolic status.

METHODS

A prospective observational study was performed with patient enrollment from March 2019 to August 2020. 24-hour urine samples were collected prior to stone removal and 4 weeks after double-J stent removal, and examined the following urinary parameters: volume, creatinine, sodium, calcium, uric acid, citrate, oxalate, potassium, phosphorous, magnesium, and pH value. For each parameter, pairwise t test was performed to compare samples prior to and after stone removal. The number of cases that changed from normal to abnormal or vice versa was also evaluated for each parameter. The study was registered at http://clinicaltrials.gov/ (NCT03846011).

RESULTS

A total of 109 patients completed 24-hour urine collections prior to and after stone removal. The urinary calcium and phosphate levels increased significantly after stone removal, showing a mean difference of 0.55 mmol (P=0.015) and 2.35 mmol (P=0.001) respectively. None of the other urinary parameters demonstrated a statistically significant difference when means were compared. The percentage differences for all urinary parameters ranged from 5.4% to 14.1%. The percentages of patients that presented clinically significant changes in urinary parameter values from normal to abnormal or vice versa ranged from 4.6% to 20.1%.

CONCLUSIONS

Ideally, evaluation of 24-hour urine compositions should be undertaken after total stone removal, especially for patients with calcium stones. For patients who cannot achieve total stone removal, 24-hour urine samples should be thoroughly interpreted as urinary calcium and phosphate levels might be depleted in the presence of urinary stones.

Engineered microorganisms: A new direction in kidney stone prevention and treatment

Numerous studies have shown that intestinal and urinary tract flora are closely related to the formation of kidney stones. The removal of probiotics represented by lactic acid bacteria and the colonization of pathogenic bacteria can directly or indirectly promote the occurrence of kidney stones. However, currently existing natural probiotics have limitations. Synthetic biology is an emerging discipline in which cells or living organisms are genetically designed and modified to have biological functions that meet human needs, or even create new biological systems, and has now become a research hotspot in various fields. Using synthetic biology approaches of microbial engineering and biological redesign to enable probiotic bacteria to acquire new phenotypes or heterologous protein expression capabilities is an important part of synthetic biology research. Synthetic biology modification of microorganisms in the gut and urinary tract can effectively inhibit the development of kidney stones by a range of means, including direct degradation of metabolites that promote stone production or indirect regulation of flora homeostasis. This article reviews the research status of engineered microorganisms in the prevention and treatment of kidney stones, to provide a new and effective idea for the prevention and treatment of kidney stones.

Development of a radiomics model to discriminate ammonium urate stones from uric acid stones in vivo : A remedy for the diagnostic pitfall of dual-energy computed tomography

BACKGROUND

Dual-energy computed tomography (DECT) is purported to accurately distinguish uric acid stones from non-uric acid stones. However, whether DECT can accurately discriminate ammonium urate stones from uric acid stones remains unknown. Therefore, we aimed to explore whether they can be accurately identified by DECT and to develop a radiomics model to assist in distinguishing them.

METHODS

This research included two steps. For the first purpose to evaluate the accuracy of DECT in the diagnosis of uric acid stones, 178 urolithiasis patients who underwent preoperative DECT between September 2016 and December 2019 were enrolled. For model construction, 93, 40, and 109 eligible urolithiasis patients treated between February 2013 and October 2022 were assigned to the training, internal validation, and external validation sets, respectively. Radiomics features were extracted from non-contrast CT images, and the least absolute shrinkage and selection operator (LASSO) algorithm was used to develop a radiomics signature. Then, a radiomics model incorporating the radiomics signature and clinical predictors was constructed. The performance of the model (discrimination, calibration, and clinical usefulness) was evaluated.

RESULTS

When patients with ammonium urate stones were included in the analysis, the accuracy of DECT in the diagnosis of uric acid stones was significantly decreased. Sixty-two percent of ammonium urate stones were mistakenly diagnosed as uric acid stones by DECT. A radiomics model incorporating the radiomics signature, urine pH value, and urine white blood cell count was constructed. The model achieved good calibration and discrimination {area under the receiver operating characteristic curve (AUC; 95% confidence interval [CI]), 0.944 (0.899-0.989)}, which was internally and externally validated with AUCs of 0.895 (95% CI, 0.796-0.995) and 0.870 (95% CI, 0.769-0.972), respectively. Decision curve analysis revealed the clinical usefulness of the model.

CONCLUSIONS

DECT cannot accurately differentiate ammonium urate stones from uric acid stones. Our proposed radiomics model can serve as a complementary diagnostic tool for distinguishing them in vivo .

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

OBJECTIVE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Prevention, diagnosis, and treatment of urolithiasis in geriatric patients - differences, similarities and caveats in comparison to the general population

PURPOSE OF REVIEW

Purpose of the review is to address management and prevention of urolithiasis in elderly patients examining the dynamic interplay between general measures, dietary adjustments, lifestyle modifications, and targeted pharmacological and/ or surgical interventions. The goal is to provide understanding of the evolving strategies required for effective urolithiasis prevention in the geriatric population.

RECENT FINDINGS

Age-specific diagnostic considerations are necessary because urolithiasis in the elderly population is characterized by bigger stones, greater peri-operative risks, and heightened symptom severity. When comorbidities are present, conservative treatments - especially analgesia - provide difficulties. Surgical procedures prove to be safe and effective, with complication rates and practical application comparable to younger cohorts. Prevention approaches that include lifestyle changes and the investigation of novel pharmaceutical options such as sodium-dependent glucose co-transporter 2 (SGLT-2)-inhibitors are promising in the management of urolithiasis in the elderly population.

SUMMARY

Our review offers a thorough investigation of urolithiasis in the elderly population, elucidating distinct clinical manifestations, complex diagnostic issues, and treatment implications. The safety and effectiveness of ureteroscopy in older patients, as well as the possible prophylactic function of SGLT-2-I, offer crucial insights for clinicians. Subsequent studies are necessary to enhance age-specific therapies, addressing the distinct obstacles presented by urolithiasis in the elderly population within this rapidly growing demographic.

Beneficial roles of gastrointestinal and urinary microbiomes in kidney stone prevention via their oxalate-degrading ability and beyond

Formation of calcium oxalate (CaOx) crystal, the most common composition in kidney stones, occurs following supersaturation of calcium and oxalate ions in the urine. In addition to endogenous source, another main source of calcium and oxalate ions is dietary intake. In the intestinal lumen, calcium can bind with oxalate to form precipitates to be eliminated with feces. High intake of oxalate-rich foods, inappropriate amount of daily calcium intake, defective intestinal transporters for oxalate secretion and absorption, and gastrointestinal (GI) malabsorption (i.e., from gastric bypass surgery) can enhance intestinal oxalate absorption, thereby increasing urinary oxalate level and risk of kidney stone disease (KSD). The GI microbiome rich with oxalate-degrading bacteria can reduce intestinal oxalate absorption and urinary oxalate level. In addition to the oxalate-degrading ability, the GI microbiome also affects expression of oxalate transporters and net intestinal oxalate transport, cholesterol level, and short-chain fatty acids (SCFAs) production, leading to lower KSD risk. Recent evidence also shows beneficial effects of urinary microbiome in KSD prevention. This review summarizes the current knowledge on the aforementioned aspects. Potential benefits of the GI and urinary microbiomes as probiotics for KSD prevention are emphasized. Finally, challenges and future perspectives of probiotic treatment in KSD are discussed.

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.

Pathophysiology and management of enteric hyperoxaluria

Enteric hyperoxaluria is a metabolic disorder resulting from conditions associated with fatty acid malabsorption and characterized by an increased urinary output of oxalate. Oxalate is excessively absorbed in the gut and then excreted in urine where it forms calcium oxalate crystals, inducing kidney stones formation and crystalline nephropathies. Enteric hyperoxaluria is probably underdiagnosed and may silently damage kidney function of patients affected by bowel diseases. Moreover, the prevalence of enteric hyperoxaluria has increased because of the development of bariatric surgical procedures. Therapeutic options are based on the treatment of the underlying disease, limitation of oxalate intakes, increase in calcium salts intakes but also increase in urine volume and correction of hypocitraturia. There are few data regarding the natural evolution of kidney stone events and chronic kidney disease in these patients, and there is a need for new treatments limiting kidney injury by calcium oxalate crystallization.

Prospective Evaluation of Extracorporeal Shockwave Lithotripsy in Renal and Upper Ureteric Stone Treatment: Clinical Assessment and Results

INTRODUCTION

Extracorporeal shockwave lithotripsy (ESWL) is a widely accepted non-invasive treatment for renal and upper ureteric stones smaller than 2 cm due to its safety and efficacy. Despite advancements in minimally invasive techniques, extracorporeal shockwave lithotripsy remains an important modality.

AIMS AND OBJECTIVE

This prospective observational study aimed to evaluate the outcomes of ESWL in managing renal and upper ureteric stones measuring less than 2 cm in terms of stone clearance.

MATERIAL AND METHODS

In a study conducted at a university-affiliated tertiary care hospital, 119 patients with renal and upper ureteric stones underwent extracorporeal shockwave lithotripsy over a 12-month period. Data on patient demographics, stone characteristics, treatment procedures, and complications were collected. Follow-up assessments were performed at two-week intervals for up to two months post-treatment.

RESULTS

The mean age of patients was 39.78 years, with a mean stone size of 1.2 cm. Right kidney stones were more prevalent (61.3% [n=76]). Complications included fever (19.3% [n=23]), gross haematuria (24.3% [n=29]), and steinstrasse (21.8% [n=26]). The success rate of extracorporeal shockwave lithotripsy was 81.5% (n=97), with 18.5% (n=22) of patients requiring surgical intervention due to incomplete fragmentation or residual fragments >4 mm. Stone size and density played significant roles in treatment success.

CONCLUSION

Despite advancements in minimally invasive techniques, ESWL retains its significance as a noninvasive and effective treatment option for renal and upper ureteric stones smaller than 2 cm. Its success depends on various factors, including the stone site, size, and composition. ESWL offers advantages such as minimal morbidity, shorter hospital stays, and better patient compliance. Complications such as steinstrasse are manageable with conservative measures or ancillary procedures. While ESWL may be losing ground in some cases, its noninvasive nature and favourable outcomes make it a valuable option in the armamentarium for stone management.

Surgeon, and Institution Characteristics Associated Surgical Preferences in the Pediatric KIDney Stone Care Improvement Network

OBJECTIVE

To reveal barriers and opportunities to implement evidence for the management of pediatric kidney stone disease, we determined surgeon and institutional factors associated with preferences for the type of surgical intervention for kidney and ureteral stones.

METHODS

We conducted a cross-sectional study of urologists participating in the Pediatric KIDney Stone Care Improvement Network (PKIDS) trial. Questionnaires ascertained strengths of urologists' preferences for types of surgery as well as characteristics of participating urologists and institutions. The outcome was the strength of preferences for ureteroscopy, shockwave lithotripsy, and percutaneous nephrolithotomy for four scenarios for which two alternative procedures are recommended by the AUA guidelines: (1) 2 cm kidney stone, (2) 9 mm proximal ureteral stone, (3) 1.5 cm lower pole kidney stone, (4) 1 cm nonlower pole kidney stone. Principal component analysis was performed to identify unique clusters of factors that explain surgical preferences.

RESULTS

One hundred forty-eight urologists at 29 sites completed surveys. Stated preferences were highly skewed except for the choice between ureteroscopy and percutaneous nephrolithotomy for a 1.5 cm kidney stone. Shockwave lithotripsy ownership and local practice patterns most frequently associated with the strength of surgeons' preferences for the type of surgery. Principal component analysis revealed that three clusters of stone, patient, and heterogenous characteristics explained 30% of the variance in preferences.

CONCLUSION

There is wide variation in the strengths of preferences for surgical interventions supported by current guidelines that are partially explained by surgeon and institutional characteristics. These results reveal opportunities to develop strategies for guidelines that consider real-world drivers of care.

Higher oxidative balance score is associated with lower kidney stone disease in US adults: a population-based cross-sectional study

PURPOSE

Oxidative balance stress (OBS) was an important indicator for assessing exposure to oxidative stress related to diet and lifestyle. The purpose of this study was to explore the relationship between OBS and kidney stone disease (KSD).

METHODS

Secondary dataset analysis was performed by the study from six survey cycles (2007-2018) in the National Health and Nutrition Examination Survey (NHANES). OBS was the exposure factor and ever had kidney stone (yes or no) was the outcome. Weighted univariate or multivariate logistic regression models were used to estimate the associations.

RESULTS

The prevalence of KSD among participants was 8.6%. OBS showed a significant negative correlation with KSD (OR: 0.98, 95% CI 0.96-0.999), 35% reduction in KSD in the highest OBS quartile compared to the lowest OBS quartile. Dietary OBS was significantly negatively correlated with KSD (OR: 0.98, 95% CI 0.96-0.9998), but not with lifestyle OBS. In addition, OBS had a negative correlation with KSD in females (OR: 0.97, 95% CI 0.94-0.996), non-diabetic participants (OR: 0.98, 95% CI 0.96-0.99), and hypertensive participants (OR: 0.96, 95% CI 0.93-0.99), but OBS was not observed to be associated with KSD in gout participants. Interestingly, this relationship existed in participants aged 30-60 years and a ratio of family income to poverty (PIR) of 1.3-3.5 (all P value < 0.05).

CONCLUSION

Our study revealed that OBS was negative associated with KSD, and high OBS might be a protective factor in KSD. Targeting one of the components of OBS might be beneficial.

Medical management of urolithiasis: Great efforts and limited progress

Objective

To provide a comprehensive review on the existing literature on medical management of urolithiasis.

Methods

A thorough literature review was performed using Medline, PubMed/PMC, Embase, and the Cochrane Database of Systematic Reviews up to December 2022 to identify publications on the medical management of urolithiasis. Studies that assessed dietary and pharmacologic management of urolithiasis were reviewed; studies on medical expulsive therapy were not included in this review.

Results

Medical management of urolithiasis ranges from the prophylactic management of kidney stone disease to dissolution therapies. While most treatment concepts have been long established, large randomized controlled trials are scarce. Dietary modification and increased fluid intake remain cornerstones in the conservative management of urolithiasis. A major limitation for medical management of urolithiasis is poor patient compliance.

Conclusion

Medical management of urolithiasis is more important in patients with recurrent urolithiasis and patients with metabolic abnormalities putting them at higher risk of developing stones. Although medical management can be effective in limiting stone recurrence, medical interventions often fail due to poor compliance.