Outcomes of alpha-blockers as medical expulsive therapy following shockwave lithotripsy: a systematic review and meta-analysis.

OBJECTIVES: To determine stone-free rate following shockwave lithotripsy (SWL) with/without alpha-blockers as well as complication rates (individual and classified using the Clavien-Dindo system). MATERIALS AND METHODS: We performed a systematic review of all randomized controlled trials that included more than 20 patients (age > 18 years) and examined the use of alpha-blockers after SWL. Meta-analysis was performed using 'metafor' in R. We report risk ratios (RRs) with 95% confidence intervals (95% CIs). The PROSPERO ID for the trial was: CRD42021248108. RESULTS: We assessed 158 full-text articles and included a total of 21 studies in our review. There were 1445 patients receiving alpha-blockers and 1478 control patients. Those receiving alpha-blockers were significantly more likely to be stone-free (RR 1.12, 95% CI 1.07-1.16; P < 0.001). This effect was robust to 'trim-and-fill' adjustment. In those taking alpha-blockers there was a significant reduction in Clavien III-V complications and, on trim-and-fill adjustment, a significant reduction in Clavien I-II complications. There were also significant reduction in rates of steinstrasse, pain and requirement for auxiliary procedures. There was no significant difference in retreatment rates. These effects were robust to trim-and-fill adjustment. CONCLUSIONS: There is a modest increase in stone-free rates in those receiving alpha-blockers following SWL, with a reciprocal modest risk reduction for steinstrasse, pain and auxiliary procedures. However, alpha-blockers do not reduce the risk of requiring retreatment.

Does pre-stenting influence outcomes of shockwave lithotripsy? A systematic review and meta-analysis.

OBJECTIVE: To determine whether preoperative use of JJ stents in patients undergoing shockwave lithotripsy (SWL) impacts on stone clearance and the rate of postoperative complications. PATIENTS AND METHODS: We screened multiple databases from inception to January 2021, using the relevant search terms for SWL in patients with a preoperative stent. Inclusion criteria were randomised controlled trials of ≥20 patients aged >18 years who had had SWL with a JJ stent. This review has been registered in the International Prospective Register of Systematic Reviews (PROSPERO; registration number CRD42023443195). Statistical analysis was performed using 'meta' in R. RESULTS: There were seven eligible studies (403 patients receiving JJ stents and 394 controls). There was no significant difference in the stone-free rate (SFR) following SWL with a JJ stent compared to SWL alone. When considering the complication rates, there was a significantly reduced risk of steinstrasse in patients with a JJ stent. However, there was no significant difference in the risk of other complications including pain, fever, and haematuria, and no significant difference in the likelihood of requiring auxiliary procedures or re-treatment. CONCLUSIONS: There was a reduced risk of steinstrasse in patients undergoing SWL with a JJ stent compared to SWL alone. However, there was no significant difference in the risk of other postoperative complications. Use of a JJ stent had no effect on the efficacy of SWL, with no significant difference in the SFR.

Natural history of small asymptomatic kidney and residual stones over a long-term follow-up: systematic review over 25 years.

OBJECTIVE: To systematically review the natural history of small asymptomatic kidney and residual stones, as the incidental identification of small, asymptomatic renal calculi has risen with increasing use of high-resolution imaging. MATERIALS AND METHODS: We reviewed the natural history of small asymptomatic kidney and residual stones using the Cochrane and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. We searched MEDLINE, Scopus, EMBASE, EBSCO, Cochrane library and Clinicaltrials.gov using themes of 'asymptomatic', 'nephrolithiasis', 'observation', 'symptoms', 'admission', 'intervention' and similar allied terms for all English language articles from 1996 to 2020 (25 years). Inclusion criteria were studies with ≥50 patients, stones ≤10 mm, and a mean follow-up of ≥24 months. Primary outcomes were occurrence of symptoms, emergency admission, and interventions. RESULTS: Our literature search returned 2247 results of which 10 papers were included in the final review. Risk of symptomatic episodes ranged from 0% to 59.4%. Meta-analysis did not identify any significant difference in the likelihood of developing symptoms when comparing stones <5 mm to those >5 mm, nor those <10 mm to those >10 mm. Risk of admission varied from 14% to 19% and the risk of intervention from 12% to 35%. Meta-analysis showed a significantly decreased likelihood of intervention for stones <5 vs >5 mm and <10 vs >10 mm. Studies had variable risk of bias due to heterogeneous reporting of outcome measures with significant likelihood that observed differences in results were compatible with chance alone (Symptoms: I2 =0%, Cochran's Q = 3.09, P = 0.69; Intervention: I2 =0%, Cochran's Q = 1.76, P = 0.88). CONCLUSIONS: The present systematic review indicates that stone size is not a reliable predictor of symptoms; however, risk of intervention is greater for stones >5mm vs <5 mm and >10 vs <10 mm. This review will inform urologists as they discuss management strategies with patients who have asymptomatic renal stones and offer insight to committees during the development of evidence-based guidelines.

Changes in Urine Composition and Risk of Kidney Stone Disease Following Bariatric Surgery: A Systematic Review over Last 2 Decades.

PURPOSE OF REVIEW: The association of kidney stone disease (KSD) and gastrointestinal (GI) surgery has been well established. With a rising obesity crisis, we wanted to see the correlation of urinary composition in patients undergoing bariatric surgery and their risk of KSD. The objective of this paper is to perform a systematic review and meta-analysis of literature to evaluate the changes in urinary composition and risk of KSD following bariatric surgery. RECENT FINDINGS: A total of seven studies (2498 patients) underwent bariatric surgery with a mean age of 46.7 years and a male:female ratio of 1:3. The most popular bariatric surgery was the Roux-en-Y procedure. Meta-analysis of the studies showed that significant decrease in urinary calcium, citrate, and urate, and increase in urinary oxalate. There was also a nonsignificant volume reduction in the post-operative cohort. The decrease in urinary citrate and increase in urinary oxalate are both predisposing factors of stone formation. There is strong evidence that bariatric surgery results in significant changes in urine composition in keeping with the increased risk of developing KSD. This identifies useful therapeutic targets in the prophylactic management of patients who have undergone bariatric surgery.

Natural History of Post-Treatment Kidney Stone Fragments: A Systematic Review and Meta-Analysis.

PURPOSE: We assessed the literature around post-treatment asymptomatic residual stone fragments and performed a meta-analysis. The main outcomes were intervention rate and disease progression. MATERIALS AND METHODS: We searched Ovid®, MEDLINE®, Embase™, the Cochrane Library and ClinicalTrials.gov using search terms: "asymptomatic", "nephrolithiasis", "ESWL", "PCNL", "URS" and "intervention." Inclusion criteria were all studies with residual renal fragments following treatment (shock wave lithotripsy, ureteroscopy or percutaneous nephrolithotomy). Analysis was performed using 'metafor' in R and bias determined using Newcastle-Ottawa scale. RESULTS: From 273 articles, 18 papers (2,096 patients) had details of intervention rate for residual fragments. Aggregate intervention rates for ≤4 mm fragments rose from 19% (20 months) to 22% (50 months), while >4 mm fragments rose from 22% to 47%. Aggregate disease progression rates for ≤4 mm rose from 25% to 47% and >4 mm rose from 26% to 88%. However, there was substantial difference in definition of "disease progression." Meta-analysis comparing >4 mm against ≤4 mm fragments: intervention rate for >4 mm (vs ≤4 mm): OR=1.50 (95% CI 0.70-2.30), p <0.001, I2=67.6%, tau2=0.48, Cochran's Q=11.4 (p=0.02) and Egger's regression: z=3.11, p=0.002. Disease progression rate for >4 mm: OR=0.06 (95% CI -0.98-1.10), p=0.91, I2=53.0%, tau2=0.57, Cochran's Q=7.11 (p=0.07) and Egger's regression: z=-0.75, p=0.45. Bias analysis demonstrated a moderate risk. CONCLUSIONS: Larger post-treatment residual fragments are significantly more likely to require further intervention especially in the long term. Smaller fragments, although less likely to require further intervention, still carry that risk. Notably, there is no significant difference in disease progression between fragment sizes. Patients with residual fragments should be appropriately counselled and informed decision-making regarding further management should be done.

Risk of UTI in kidney stone formers: a matched-cohort study over a median follow-up of 19 years.

PURPOSE: To describe risk of UTI in Stone formers comparing to non-stone formers. METHODS: Retrospective cohort study using electronic records for patients across southern England. Stone formers referred to a tertiary referral centre in Southern England, comparator patients were age and sex matched with 3:1 ratio from same database. Those with no documentation were excluded. UTI defined using ICD-10 codes. Risk of UTI presented as hazard ratio with 95% confidence interval, generated using cox regression. Sample size calculated using 80% power and significance set at 0.05. RESULTS: Eight hundred and nineteen stone formers were included after 1000 records were screened for inclusion, with 2477 age and sex matched non-stone formers extracted from the same database. Sample size was calculated at 287 per group. Stone formers were at significantly increased risk of developing a UTI (HR 5.67; 95% CI 4.52-7.18, p < 0.001). Median follow-up was 19 years (IQR: 15-22). CONCLUSIONS: Kidney stone formers are at increased risk of developing urinary tract infections.

Evaluation of the economic burden of kidney stone disease in the UK: a retrospective cohort study with a mean follow-up of 19 years.

OBJECTIVE: To estimate the cost of kidney stone disease (KSD) in England. PATIENTS AND METHODS: We conducted a retrospective cohort study of patients with KSD, referred to a metabolic stone clinic between 1990 and 2007 using electronic records of patients with KSD in a tertiary referral centre, to determine cost using UK National Health Service (NHS) tariff, with subsequent extrapolation to the entire England population. Those with no documentation and <5 years follow-up were excluded. The outcome measure was calculation of cost (as per 2018 NHS tariff) presented as lower and higher estimates for: per episode; total within the cohort; and estimation of initial, 5-,10- and 15-year costs for the cohort and total population in England. Linear regression was used to examine for significant predictors of per episode and total cost. RESULTS: A total of 781 patients were included in the study after 1000 records were screened for inclusion, with a mean follow-up of 19 years. The mean (SD) overall costs per episode were between £1277 (1724) and £2887 (2492). Total initial costs for the cohort were between £950 842 and £2 336 442, rising to between £1.43 million and £3.02 million at 15 years of follow-up. Estimated cost in 2010 in England alone was between £190 million and £324 million. CONCLUSION: KSD is a costly disease, comparable to the combined cost of prostate and bladder cancer in UK.

Simultaneous Bilateral Endoscopic Surgery (SBES) for Bilateral Urolithiasis: the Future? Evidence from a Systematic Review.

PURPOSE OF REVIEW: Urolithiasis is a disease of prevalence across the world and up to a quarter of patients present with multiple stones. Most procedures carried out in this scenario are staged; however, there is a growing body of evidence to suggest bilateral simultaneous (BS) procedures are safe. We performed a systematic review to investigate and evaluate the evidence for these procedures. RECENT FINDINGS: A systematic review was conducted according to Cochrane and PRISMA checklist for all English-language articles from January 1996 to January 2018 using Medline, CINAHL, Scopus, EMBASE, Cochrane library, Clinicaltrials.gov and Google Scholar. All studies (a minimum of 10 patients) with bilateral simultaneous percutaneous nephrolithotomy (BS-PCNL) or bilateral simultaneous ureteroscopy (BS-URS) and ipsilateral URS with contralateral simultaneous PCNL were included. Data was extracted for patient and stone demographics, outcomes and stone-free rate (SFR) and the level of evidence (using the GRADE assessment tool). Overall, 32 studies (1966 patients) were included in the review after the identification of 302 articles in the search. This included 16 studies (1073 patients) with BS-URS, 13 studies (750 patients) with BS-PCNL and 3 studies (143 patients) with URS and simultaneous contralateral PCNL. Of these, 8 were comparative studies and compared bilateral simultaneous procedure to either a unilateral or staged comparator. The mean operating time, SFR, the Clavien I-II and the Clavien ≥ III were 75 min, 91%, 22% and 1.4% for BS-URS; 157 min, 92%, 27% and 6.4% for BS-PCNL; 151 min, 76% and 5.6% for URS with contralateral PCNL. In comparison to staged procedures, although the SFR and complication rates were similar, there was a significantly reduced operative time and hospital stay with simultaneous procedures (p < 0.001). Although evidence for bilateral simultaneous endourological procedures is limited, results from available studies show that outcomes are at least equivalent to staged procedures. Key advantages seem to be reduced operative times, cost and hospital stay which will lead to an increased uptake of these procedures in the future.

Nephrolithiasis in the Obese Patient.

PURPOSE OF REVIEW: The link between metabolic syndrome (MetS)/obesity and kidney stone disease (KSD) has gained importance over recent years due to the increasing prevalence and healthcare burden worldwide. This review analyses the literature exploring the link between MetS/obesity and KSD and the impact that obesity has on KSD management. RECENT FINDINGS: Metabolic syndrome has been shown to increase an individual's risk of developing kidney stone disease, with insulin resistance forming a core component of the pathophysiology. The body habitus of an individual also influences the type of intervention that is most appropriate, with flexible ureteroscopy increasingly being the preferred option in obese patients. It is important for urologists to consider the features of metabolic syndrome to effectively manage episodes of KSD in obese patients. In addition, better quality evidence is required to effectively compare different treatment options in this group of patients.

Ureteroscopy is more cost effective than shock wave lithotripsy for stone treatment: systematic review and meta-analysis.

INTRODUCTION: A rising incidence of kidney stone disease has led to an increase in ureteroscopy (URS) and shock wave lithotripsy (SWL). Our aim was to compare the cost of URS and SWL for treatment of stones. METHODS: A systematic review and meta-analysis based on Cochrane and PRISMA standards was conducted for all studies reporting on comparative cost of treatment between URS and SWL. The cost calculation was based on factual data presented in the individual studies as reported by the authors. English language articles from January 2001 to December 2017 using Medline, PubMed, EMBASE, CINAHL, Cochrane library and Google Scholar were selected. Our study was registered with PROSPERO (International prospective register of systematic reviews)-registration number CRD 42017080350. RESULTS: A total of 12 studies involving 2012 patients (SWL-1243, URS-769) were included after initial identification and screening of 725 studies with further assessment of 27 papers. The mean stone size was 10 and 11 mm for SWL and URS, respectively, with stone location in the proximal ureter (n = 8 studies), distal ureter (n = 1), all locations in the ureter (n = 1) and in the kidney (n = 2). Stone free rates (84 vs. 60%) were favourable for URS compared to SWL (p < 0.001). Complication rates (23 vs. 30%) were non-significantly in favor of SWL (p = 0.11) whereas re-treatment rates (11 vs. 27%) were non-significantly in favor of URS (p = 0.29). Mean overall cost was significantly lower for URS ($2801) compared to SWL ($3627) (p = 0.03). The included studies had high risk of bias overall. On sub-analysis, URS was significantly cost-effective for both stones < 10 and ≥ 10 mm and for proximal ureteric stones. CONCLUSION: There is limited evidence to suggest that URS is less expensive than SWL. However, due to lack of standardization, studies seem to be contradictory and further randomized studies are needed to address this issue.

Evidence for plical support of the patella.

There is a consensus that there is no overt anterior joint capsule in the knee. However, other anterior structures act in lieu of a joint capsule: the quadriceps tendon and patellar retinacular fibres. In the absence of a capsule, the synovium forms the suprapatellar pouch. Other synovial structures, the plicae, are more controversial. They are often described as embryonic remnants with no function, despite surrounding the patella. We aimed to identify plical anatomy and histology on cadaveric dissection and to examine their embryology using the human virtual embryo website. Plicae were identified by two independent observers. Plical histology was examined using a panel of stains: H&E, Ab H&E, EVG and MSB trichrome. Embryonic knees were examined from Carnegie stages 20-23. Each knee had a suprapatellar plica and mediopatellar plica (MPP). The lateropatellar plica (LPP) appeared as a band in 5/10 cadavers, and as a ridge in the remainder. The overall impression, consistent across all specimens, was that the plicae formed a continuous band of synovial tissue around the proximal three-quarters of the patella. The infrapatellar fat pad (IFP) surrounded the remainder. Histologically, the plicae and IFP consisted of three layers (in order): a synovial layer, an undulated collagenous layer, and an adipose or areoloadipose layer. The subsynovial collagenisation is normally associated with the synovio-capsular boundary. Embryologically, plicae were not seen in either knee at any level for any given Carnegie stage. We suggest that plicae, along with the dynamic IFP, provide internal support to the patella mirroring the external support of retinacular fibres. Thus, the plicae complete the tissue complex acting in lieu of an anterior joint capsule. Evidence of plical functionality lends credence to the theory that the plicae are anatomical structures not functionless embryonic remnants.

Bilateral Simultaneous Ureteroscopic (BS-URS) Approach in the Management of Bilateral Urolithiasis Is a Safe and Effective Strategy in the Contemporary Era-Evidence from a Systematic Review.

PURPOSE OF REVIEW: Ureteroscopic treatment of urolithiasis has become safer and more effective in the modern era. With a rise in the incidence of bilateral urolithiasis, management dilemma of staged single-side ureteroscopy versus bilateral simultaneous ureteroscopy (BS-URS) is often debatable. This review evaluates the current evidence base for bilateral simultaneous ureteroscopic approach in the modern era. RECENT FINDINGS: A systematic review was conducted from 1990 to June 2016 including all English language articles reporting on outcomes of BS-URS for urolithiasis. Data was split into two periods: period 1: 2003-2012 and period 2: 2013-2016, and analysed using SPSS version 21. A total of 11 studies (491 patients) were identified from a literature search of 148 studies with mean age of 45 years and a male: female ratio of 2:1 and a mean operative time of 69 min (SD = ±15). The initial and final stone-free rate (SFR) was 87 and 93%, respectively. Post-operative stents were placed in 89% of patients with a mean hospital stay of 1.6 days (SD = ±0.5). Overall, there was a significant negative association between case volume (procedures per month) and complication rate (p = 0.045). Mean hospital stay was significantly longer in period 1 (1.9 days, SD = ±0.5) than period 2 (1.3 days, SD = ±0.3) and complications were also significantly higher in period 1 (47%) compared to period 2 (12%) (p < 0.001). There were six studies examining holmium laser (HL) lithotripsy and three examining pneumatic lithotripsy (PL). There were significantly more complications after PL than HL; however, their SFR was similar. Our review shows that the complication rates and hospital stay are significantly reduced in the contemporary data suggesting an improving trend in outcomes following BS-URS. Simultaneous bilateral ureteroscopic treatment of urolithiasis is safe and effective in the modern era. Safety is increased in centers with increased number of procedures performed and with laser lithotripsy.

Use of Temporally Validated Machine Learning Models To Predict Outcomes of Percutaneous Nephrolithotomy Using Data from the British Association of Urological Surgeons Percutaneous Nephrolithotomy Audit.

BACKGROUND AND OBJECTIVE: Machine learning (ML) is a subset of artificial intelligence that uses data to build algorithms to predict specific outcomes. Few ML studies have examined percutaneous nephrolithotomy (PCNL) outcomes. Our objective was to build, streamline, temporally validate, and use ML models for prediction of PCNL outcomes (intensive care admission, postoperative infection, transfusion, adjuvant treatment, postoperative complications, visceral injury, and stone-free status at follow-up) using a comprehensive national database (British Association of Urological Surgeons PCNL). METHODS: This was an ML study using data from a prospective national database. Extreme gradient boosting (XGB), deep neural network (DNN), and logistic regression (LR) models were built for each outcome of interest using complete cases only, imputed, and oversampled and imputed/oversampled data sets. All validation was performed with complete cases only. Temporal validation was performed with 2019 data only. A second round used a composite of the most important 11 variables in each model to build the final model for inclusion in the shiny application. We report statistics for prognostic accuracy. KEY FINDINGS AND LIMITATIONS: The database contains 12 810 patients. The final variables included were age, Charlson comorbidity index, preoperative haemoglobin, Guy's stone score, stone location, size of outer sheath, preoperative midstream urine result, primary puncture site, preoperative dimercapto-succinic acid scan, stone size, and image guidance (https://endourology.shinyapps.io/PCNL_Demographics/). The areas under the receiver operating characteristic curve was >0.6 in all cases. CONCLUSIONS AND CLINICAL IMPLICATIONS: This is the largest ML study on PCNL outcomes to date. The models are temporally valid and therefore can be implemented in clinical practice for patient-specific risk profiling. Further work will be conducted to externally validate the models. PATIENT SUMMARY: We applied artificial intelligence to data for patients who underwent a keyhole surgery to remove kidney stones and developed a model to predict outcomes for this procedure. Doctors could use this tool to advise patients about their risk of complications and the outcomes they can expect after this surgery.

Use of whole genome sequencing to determine the genetic basis of visceral myopathies including Prune Belly syndrome.

Objectives/aims: The visceral myopathies (VM) are a group of disorders characterised by poorly contractile or acontractile smooth muscle. They manifest in both the GI and GU tracts, ranging from megacystis to Prune Belly syndrome. We aimed to apply a bespoke virtual genetic panel and describe novel variants associated with this condition using whole genome sequencing data within the Genomics England 100,000 Genomes Project. Methods: We screened the Genomics England 100,000 Genomes Project rare diseases database for patients with VM-related phenotypes. These patients were screened for sequence variants and copy number variants (CNV) in ACTG2, ACTA2, MYH11, MYLK, LMOD1, CHRM3, MYL9, FLNA and KNCMA1 by analysing whole genome sequencing data. The identified variants were analysed using variant effect predictor online tool, and any possible segregation in other family members and novel missense mutations was modelled using in silico tools. The VM cohort was also used to perform a genome-wide variant burden test in order to identify confirm gene associations in this cohort. Results: We identified 76 patients with phenotypes consistent with a diagnosis of VM. The range of presentations included megacystis/microcolon hypoperistalsis syndrome, Prune Belly syndrome and chronic intestinal pseudo-obstruction. Of the patients in whom we identified heterozygous ACTG2 variants, 7 had likely pathogenic variants including 1 novel likely pathogenic allele. There were 4 patients in whom we identified a heterozygous MYH11 variant of uncertain significance which leads to a frameshift and a predicted protein elongation. We identified one family in whom we found a heterozygous variant of uncertain significance in KCNMA1 which in silico models predicted to be disease causing and may explain the VM phenotype seen. We did not find any CNV changes in known genes leading to VM-related disease phenotypes. In this phenotype selected cohort, ACTG2 is the largest monogenic cause of VM-related disease accounting for 9% of the cohort, supported by a variant burden test approach, which identified ACTG2 variants as the largest contributor to VM-related phenotypes. Conclusions: VM are a group of disorders that are not easily classified and may be given different diagnostic labels depending on their phenotype. Molecular genetic analysis of these patients is valuable as it allows precise diagnosis and aids understanding of the underlying disease manifestations. We identified ACTG2 as the most frequent genetic cause of VM. We recommend a nomenclature change to 'autosomal dominant ACTG2 visceral myopathy' for patients with pathogenic variants in ACTG2 and associated VM phenotypes. Supplementary Information: The online version contains supplementary material available at 10.1007/s44162-023-00012-z.

Best Practice in Interventional Management of Urolithiasis: An Update from the European Association of Urology Guidelines Panel for Urolithiasis 2022.

PURPOSE: The European Association of Urology (EAU) has updated its guidelines on clinical best practice in urolithiasis for 2021. We therefore aimed to present a summary of best clinical practice in surgical intervention for patients with upper tract urolithiasis. MATERIALS AND METHODS: The panel performed a comprehensive literature review of novel data up to May 2021. The guidelines were updated and a strength rating was given for each recommendation, graded using the modified Grading of Recommendations, Assessment, Development, and Evaluations methodology. RESULTS: The choice of surgical intervention depends on stone characteristics, patient anatomy, comorbidities, and choice. For shockwave lithotripsy (SWL), the optimal shock frequency is 1.0-1.5 Hz. For ureteroscopy (URS), a postoperative stent is not needed in uncomplicated cases. Flexible URS is an alternative if percutaneous nephrolithotomy (PCNL) or SWL is contraindicated, even for stones >2 cm. For PCNL, prone and supine approaches are equally safe. For uncomplicated PCNL cases, a nephrostomy tube after PCNL is not necessary. Radiation exposure for endourological procedures should follow the as low as reasonably achievable principles. CONCLUSIONS: This is a summary of the EAU urolithiasis guidelines on best clinical practice in interventional management of urolithiasis. The full guideline is available at https://uroweb.org/guidelines/urolithiasis. PATIENT SUMMARY: The European Association of Urology has produced guidelines on the best management of kidney stones, which are summarised in this paper. Kidney stone disease is a common condition; computed tomography (CT) is increasingly used to diagnose it. The guidelines aim to decrease radiation exposure to patients by minimising the use of x-rays and CT scans. We detail specific advice around the common operations for kidney stones.

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.

Post-Ureteroscopy Infections Are Linked to Pre-Operative Stent Dwell Time over Two Months: Outcomes of Three European Endourology Centres.

BACKGROUND: The aim of this study is to investigate outcomes of pre-operative stent dwell time on infectious complications following ureteroscopy and stone treatment to identify a time cut-off. MATERIAL AND METHODS: Three tertiary referral centres in Europe retrospectively collected outcomes of ureteroscopy and laser fragmentation (URSL) for all patients with pre-operative indwelling ureteric stents over a period of up to 5 years. Data was collected on patient details, stone demographics, stent dwell time, complications and stone free rate (SFR). Matching for age, sex, operative time, stone size and post-operative stent insertion. To examine for a threshold effect, monthly cut-offs were used to compare post-ureteroscopic febrile UTIs. Binomial logistic regression was used (SPSS v.24) with a significance level set at 0.0036. The risk ratio (RR) with a 95% confidence interval (CI) and the number needed to harm (NNH) are reported. RESULTS: There were 467 patients with a pre-operative stent for analysis. These patients (n = 315) were matched to non-stented controls after excluding 152 patients to achieve adequate matching. There was a significant difference in rates of post-ureteroscopic febrile UTI between stented vs non-stented patients (RR = 2.67, 95% CI: 1.10-6.48, p = 0.03). On adjustment, a dwell time of more than two months was associated with an increased risk of post-ureteroscopic febrile UTI (RR = 3.94, 95% CI: 1.30-12.01, p = 0.02), this increased risk rose with longer dwell time. At stent time longer than four months was associated with a significantly increased risk of post-ureteroscopic febrile UTI (5% vs. 15%, RR = 3.09, 95% CI: 1.56-6.10, p = 0.001), with the number needed to harm at 10. CONCLUSIONS: Overall infectious complication rates from URSL are low. The risk of post-operative UTI after four months of dwell time is nearly tripled compared to less than four months.

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

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