Economic Considerations in the Management of Nephrolithiasis

Two distinct phenotypes of calcium oxalate stone formers could imply different long-term risks for renal function

Endoscopic and biopsy findings have identified two distinct phenotypes among individuals with calcium oxalate (CaOx) kidney stones. The first type has normal renal papillae but shows interstitial mineral deposition, known as Randall's plaque. The other phenotype presents with collecting duct plugging and a higher incidence of loss of papilla tissue mass. With Randall's plaque, renal papilla injury involves the loss of small patches of calcified tissue (Randall's plaque detaching with the stone), which likely results in damage to only a few nephrons. In contrast, collecting duct mineral plugs are very large, causing obstruction to tubular flow. Since each terminal collecting duct drains thousands of nephrons, ductal plugs could lead to the degeneration of many nephrons and a significant loss of renal glomeruli. New visualization techniques for immune cells in papillary biopsies have revealed that the Randall's plaque phenotype is marked by the accumulation of macrophages around the plaque regions. In contrast, preliminary data on the plugging phenotype shows collecting duct damage with mineral plugs and increased T-lymphocytes throughout the papilla. These regions also show tubulitis, i.e., T-cell infiltration into nearby collecting duct epithelium. This suggests that while some CaOx stone formers may have some papillary inflammation but with minimal damage to nephrons, others suffer from obstruction to flow for many nephrons that may also include destructive inflammation in the renal tissue. We propose that CaOx stone formers with the plugging phenotype will have a higher long-term risk for loss of renal function.

Two distinct phenotypes of calcium oxalate stone formers could imply different long-term risks for renal function

Endoscopic and biopsy findings have identified two distinct phenotypes among individuals with calcium oxalate (CaOx) kidney stones. One phenotype exhibits normal renal papillae but shows interstitial mineral deposition, known as Randall's plaque. The other phenotype presents with collecting duct plugging and a higher incidence of loss of papilla tissue mass. With Randall's plaque, renal papilla injury involves the loss of small patches of calcified tissue (Randall's plaque detaching with the stone), which likely results in damage to only a few nephrons. In contrast, collecting duct mineral plugs are very large, causing obstruction to tubular flow. Since each terminal collecting duct drains thousands of nephrons, ductal plugs could lead to the degeneration of many nephrons and a significant loss of renal glomeruli. New visualization techniques for immune cells in papillary biopsies have revealed that the Randall's plaque phenotype is marked by the accumulation of macrophages around the plaque regions. In contrast, preliminary data on the plugging phenotype shows collecting duct damage with mineral plugs, increased T-lymphocytes throughout the papilla, and tubulitis, characterized by T-cell infiltration into nearby collecting duct epithelium. This suggests that while some CaOx stone formers may have some papillary inflammation but with minimal damage to nephrons, others suffer from obstruction to flow for many nephrons that may also include destructive inflammation in the renal tissue. We propose that the long-term risks for loss of renal function will be greater for CaOx stone formers with the plugging phenotype.

Association between the oxidative balance score and kidney stones in adults

OBJECTIVES

This study was to investigate the correlation between oxidative balance score (OBS) and the prevalence of kidney stones in the general adult population.

MATERIALS AND METHODS

We conducted an analysis using data from the 2007-2018 National Health and Nutrition Examination Survey (NHANES) project, including 17,988 participants. The OBS was computed based on previous research, combining 16 dietary factors and 4 lifestyle factors. Multiple logistic regressions and restricted cubic spline (RCS) regressions were utilized to explore the associations between OBS and kidney stone prevalence.

RESULTS

Our analysis included 1,622 adults with kidney stones and 16,366 adults without kidney stones. The average age of participants was 46.86 ± 0.27 years, with 50.72% being male. The median OBS was 22.00 (17.00, 27.00). After adjusting for all covariates, each one-unit increase in OBS was associated with a 3% decrease in kidney stone prevalence (odds ratio [OR] = 0.97 [0.96-0.98], P < 0.001). Moreover, compared to the first quartile, the fourth quartile of OBS (OR = 0.65 [0.50-0.84], P = 0.001) exhibited a negative association with kidney stone prevalence after adjusting for multiple variables. Furthermore, we observed a non-linear negative relationship between OBS and kidney stone prevalence, with inflection points at 18.2 (P for nonlinearity = 0.048). Stratified analysis did not identify any variables significantly affecting the results.

CONCLUSION

Our findings indicate that a higher OBS is associated with a decreased prevalence of kidney stones in the general adult population.

Exploring the economic landscape of ureteric stones: impact of age and gender on direct healthcare costs

OBJECTIVES

To assess whether age or gender affects ureteric stone management costs, in patients presenting to the Emergency Department (ED) with CT proven ureteric stones.

PATIENTS AND METHODS

A retrospective examination was conducted on patients admitted to the ED who were diagnosed with a ureteric stone through CT scans. Data encompassing clinical, laboratory, and imaging parameters were gathered, alongside information on admissions, ED readmissions, surgical procedures, and the overall treatment cost. Comparative analyses were performed on various cost rates in relation to different stone parameters, patient clinical presentations, laboratory results, and personal histories of urolithiasis.

RESULTS

From January 2018 to January 2020, 805 patients underwent abdominal CT scans at a single institution's ED and were diagnosed with ureteric stones. Among them, 773 patients met the inclusion criteria, with 78% (609) being males and 22% (169) females. The mean ages for males and females were 49.4 (SD 14.4) and 51.6 (SD 15.7), respectively (p = 0.08). Treatment costs exhibited a direct relationship with age, amounting to 4,025, 5,116, 6,058, and 9,225 US dollars (USD) in the 18-30, 31-50, 51-70, and over 70 age groups, respectively. Female gender was associated with higher treatment costs, averaging 6,831 USD, compared to 5,450 USD in males (p = 0.03). However, there were no significant differences between genders in terms of the type of surgical procedure (p = 0.4) or hospital stay duration (p = 0.1).

CONCLUSIONS

Age and gender exerted a significant impact on treatment costs, revealing that advanced age and female gender were both correlated with higher direct treatment costs in the care of ureteric stones.

Gaps in kidney stone disease management: From clinical theory to patient reality

With nephrolithiasis projected to affect 25% of the global population in the next three decades, there is an urgent call for innovative management strategies to prevent and reduce stone recurrence. This study aims to explore the evolving management needs in nephrolithiasis from both patient and healthcare provider perspectives. An expert-collaborative online survey comprising 10 targeted questions on kidney stone management was developed and disseminated. This survey was designed to gather comprehensive insights from patients, physicians and dietician and other person in the field of nephrolithiasis. Analysis of responses from 120 participants, including 45 nephrologists, 38 dieticians, 11 urologists, and 14 kidney stones patients followed in our hospital, revealed critical insights. A significant 97.5% emphasized the necessity of optimizing daily water intake, and 94.1% recognized the need for practical dietary modifications. Additionally, 88.3% of respondents found timely hydration reminders beneficial. Notably, monitoring urine color and pH was valued by 85% and 84.3% of the participants, respectively. A striking disparity emerged in the perception of fatigue and wellness monitoring, with 65% of patients prioritizing fatigue monitoring, a view less shared by healthcare professionals. Similarly, 71% of patients deemed wellness monitoring essential, highlighting a gap in understanding between patients and their caregivers. This study underscores the critical need for more tailored guidance on hydration strategies and the promise of remote urine parameters monitoring in nephrolithiasis management. The findings strongly advocate for a patient-centered approach, aligning medical recommendations with patient lifestyles and experiences, to enhance the effectiveness of nephrolithiasis management.

Prevention of complications in endourological management of stones: What are the basic measures needed before, during, and after interventions?

Objective

This narrative review aims to describe measures to minimise the risk of complications during percutaneous nephrolithotomy (PCNL), ureteroscopy, and retrograde intrarenal surgery.

Methods

A literature search was conducted from the PubMed/PMC database for papers published within the last 10 years (January 2012 to December 2022). Search terms included "ureteroscopy", "retrograde intrarenal surgery", "PCNL", "percutaneous nephrolithotomy", "complications", "sepsis", "infection", "bleed", "haemorrhage", and "hemorrhage". Key papers were identified and included meta-analyses, systematic reviews, guidelines, and primary research. The references of these papers were searched to identify any further relevant papers not included above.

Results

The evidence is assimilated with the opinions of the authors to provide recommendations. Best practice pathways for patient care in the pre-operative, intra-operative, and post-operative periods are described, including the identification and management of residual stones. Key complications (sepsis and stent issues) that are relevant for any endourological procedure are then be discussed. Operation-specific considerations are then explored. Key measures for PCNL include optimising access to minimise the chance of bleeding or visceral injury. The role of endoscopic combined intrarenal surgery in this regard is discussed. Key measures for ureteroscopy and retrograde intrarenal surgery include planning and technique to minimise the risk of ureteric injury. The role of anaesthetic assessment is discussed. The importance of specific comorbidities on each step of the pathway is highlighted as examples.

Conclusion

This review demonstrates that the principles of meticulous planning, interdisciplinary teamworking, and good operative technique can minimise the risk of complications in endourology.

Occupational hazard in urolithiasis patients in Qatar: A single-center cross-sectional study

BACKGROUND

Urolithiasis is one of the most prevalent urological diseases and is associated with a substantial economic burden. Its prevalence varies according to geographical location. Qatar is a Middle Eastern country located in the Afro-Asian Stone Belt. It has a dry and hot climate, which may predispose individuals working in these environments to form kidney stones (KSs).

METHODS

A population sample of 4204 patients was categorized into five occupational classes. The frequencies and correlations of these occupations with KS formation were calculated.

RESULTS

Among the total cases, 2000 presented with KSs, with the majority being of Asian descent (49%), followed by individuals of Middle Eastern descent (35.1%). Technicians accounted for 35.15% of KS cases followed by clerks (29.2%) and executives (14.6%). Among KS cases, 44% had a single stone, 30% had multiple stones, and 26% had two stones. In comparing both KS and non-KS groups, age, gender, occupation, and race were significantly associated with KS formation (p<0.05), while BMI did not show any significant correlation (p>0.05). Asian males aged 31-40, working as technicians, were significantly more prone to urolithiasis. In comparing age, BMI, and gender with stone characteristics, only age was found significantly associated with stone size (p<0.05). Occupation showed an impact on all studied stone characteristics. Clerks and technicians presented more frequently with stones within the 11-15 mm range, while executives more frequently presented with smaller stones (p<0.001). Stone density was more frequently <500 HU in workers, technicians and housewives and >500 HU in executives and clerks (p<0.001).

CONCLUSIONS

Our findings revealed an elevated risk of urolithiasis among certain occupational groups, particularly technicians, who frequently work outdoors in high-temperature environments. Alternatively, the sedentary nature of clerical and executive positions can also contribute to the risk of urolithiasis.

Comparison of endoscopic versus CT assessment of stone-free status after percutaneous nephrolithotomy (PCNL)

This study is aimed to determine whether postoperative low dose computed tomography (LDCT) imaging is necessary after percutaneous nephrolithotomy (PCNL), or the surgeon's intraoperative assessment of residual fragments (RF) is sufficient and avoidance of postoperative imaging with reduction of radiation exposure can be achieved. Data of all 610 patients who underwent PCNL in prone position in our institution from February 2009 to September 2020 was collected. Parameters such as age, gender, BMI, ASA-Classification, stone related parameters and the surgeon's assessment of stone-free status were analyzed. The LDCT performed postoperatively was compared to the intraoperative assessment of the surgeon regarding RF. The mean age of patients was 52.82 years; the mean BMI was 28.18 kg/m2. In 418 cases, the surgeon made a clear statement about the presence of RF and postoperative LDCT was carried out. The discrepancy between the two methods (surgeon´s assessment vs. LDCT) was significant at p < 0.0001. The sensitivity, specificity, positive and negative predictive value of the surgeon when assessing RF were 24.05%, 99.45%, 98.28% and 50%. Stone free rate (SFR) after primary PCNL was 45.57%. The overall SFR at discharge was 96.23%. Although the surgeon´s assessment of RF was reliable, postoperative LDCT imaging should still be performed if endoscopic stone clearance is suspected due to the high false negative rate and the low negative predictive value. The optimal timing of postoperative imaging following PCNL remains unclear.

Prospective Randomized Trial of Single-Use vs Reusable Cystoscope for Ureteral Stent Removal

Background: Reusable cystoscopes are associated with risks of cross-contamination, need for chemical reprocessing, mechanical breakdown, maintenance costs, and labor for cleaning. A sterile, single-use cystoscope may reduce or eliminate the source of these infections while also decreasing exposure to reprocessing chemical agents. In this multicenter, randomized trial, we sought to compare single use with reusable endoscopes for ureteral stent removal. Methods: A three-center, randomized, dual-arm postmarket clinical trial was performed to compare the single-use cystoscope (Ambu A/S) with standard-of-care flexible reusable cystoscopes for outpatient ureteral stent removal. A total of 102 patients were randomized and evaluated from baseline through day 10 postprocedure. Primary endpoint was successful stent removal. Secondary endpoints were time from preparation to disposal/reprocessing, adverse events (AEs), and clinician satisfaction. Results: A total of 102 subjects were randomized in a 1:1 manner. The successful stent removal rate was 51/51 (reusable) and 50/51 (single use). One patient required the conversion to reusable cystoscope owing to grasper passage issue. Median time from prep for the procedure to disposal/prep for reprocessing was 10.2 minutes for the single use and 18.4 minutes for the reusable (p < 0.001). There was no difference in clinician satisfaction between both arms. There was no difference in AEs between arms and no device causal attribution for any AE reports. There was one serious AE necessitating hospitalization for infection in the reusable arm. Conclusion: The randomized-controlled trial of single-use cystoscopes vs reusables showed comparable device success with significant time savings for single use and equivalent clinician satisfaction. The study was registered on clinicaltrials.gov database (NCT04829461) on April 2, 2021.

Pediatric Stone Disease: Current Trends and Future Directions

Pediatric nephrolithiasis is less common in children than in adults but the incidence has been rising rapidly, and it is now a public health and economic burden in the United States. There are challenges unique to children that should be taken into consideration when evaluating and managing pediatric stone disease. In this review, we present the current research on risk factors, emerging new technologies for treatment of stones and recent investigations on prevention of stones in this population.

Metformin ameliorates calcium oxalate crystallization and stone formation by activating the Nrf2/HO-1 signaling pathway: Two birds with one stone

Deposition of calcium oxalate (CaOx) crystals and oxidative stress-induced injury of renal tubular epithelial cell are the primary pathogenic factors of nephrolithiasis. In this study we investigated the beneficial effects of metformin hydrochloride (MH) against nephrolithiasis and explored the underlying molecular mechanism. Our results demonstrated that MH inhibited the formation of CaOx crystals and promoted the transformation of thermodynamically stable CaOx monohydrate (COM) to more unstable CaOx dihydrate (COD). MH treatment effectively ameliorated oxalate-induced oxidative injury and mitochondrial damage in renal tubular cells and reduced CaOx crystal deposition in rat kidneys. MH also attenuated oxidative stress by lowering MDA level and enhancing SOD activity in HK-2 and NRK-52E cells and in a rat model of nephrolithiasis. In both HK-2 and NRK-52E cells, COM exposure significantlylowered the expressions of HO-1 and Nrf2, which was rescued by MH treatment even in the presence of Nrf2 and HO-1 inhibitors. In rats with nephrolithiasis, MH treatment significantly rescued the down-regulation of the mRNA and protein expression of Nrf2 and HO-1 in the kidneys. These results demonstrate that MH can alleviate CaOx crystal deposition and kidney tissue injury in rats with nephrolithiasis by suppressing oxidative stress and activating the Nrf2/HO-1 signaling pathway, suggesting the potential value of MH in the treatment of nephrolithiasis.

Role of microbiome in kidney stone disease

PURPOSE OF REVIEW

The process of renal stone formation is complex, multifactorial, and variable depending on the type of stone. The microbiome, whether by direct or indirect action, is a factor that both promotes the formation and protects from developing of renal stones. It is a highly variable factor due to the great interindividual and intraindividual variability that it presents. In recent years, with the incorporation of nonculture-based techniques such as the high-throughput sequencing of 16S rRNA bacterian gene, both intestinal and urinary microbiota have been deeply studied in various diseases such as the kidney stone disease.

RECENT FINDINGS

This review has examined the new insights on the influence of the intestinal and urinary microbiome in nephrolithiasis disease and its usefulness as a diagnostic and prognostic tool, highlighting its contribution to the pathogenesis, its ability to modulate it and to influence disease development.

SUMMARY

The incidence of urolithiasis has been increasing considerably. These patients represent a significant expense for national health systems. With the knowledge of the influence of the urobiome and intestinal microbiota on the urolithiasis, it could be possible to modulate it to interrupt its development.

The Role of Urinary Modulators in the Development of Infectious Kidney Stones

Introduction: The pathogenesis of infectious kidney stones is poorly understood. Bacteria have been implicated in promoting infectious stones via urease production; however, there is mounting evidence indicating the relationship is more complex. The aim of our study was to characterize suspected biotic and abiotic extrinsic factors that may modulate the formation of infectious stones. Materials and Methods: A high-throughput experimental model with Griffith's artificial urine was used to test a wide variety of urinary modulators and cytoplasmic enzymes present in crude cell-free extracts (CFEs) from bacterial strains to investigate how they impact struvite and calcium (Ca) phosphate crystal production. Crystal formation was evaluated with spectrophotometry and growth curve analysis. Light microscopy and scanning electron microscopy/X-ray diffraction was used for crystal structure and composition identification. Results: The acidic urinary modulators used in this study prevented crystal formation, whereas osteopontin had a significant inhibitory effect. Addition of CFEs from Proteus mirabilis 175A and 177A resulted in Ca phosphate and struvite crystals. Of interest, Klebsiella pneumoniae and Klebsiella oxytoca produced crystals including Ca phosphate and Ca oxalate, respectively. Pseudomonas aeruginosa had no urease production detected and produced Ca phosphate crystals. Discussion: Urinary modulators can have a wide variety of effects on infectious stone formation and the role of pH is important but does not guarantee robust crystal formation. Bacterial strains can produce Ca oxalate, Ca phosphate, and struvite stones with and without urease activity. Conclusion: Various urinary modulators appear to influence the process and are worthy of further evaluation as a potential therapeutic strategy to prevent infection-related urinary stone formation. Stones formed from urinary tract infections may be a result of multiple encoded metabolic pathways and discovering these would improve our understanding of the stone-bacterial relationship.

National Utilization, Reimbursement, and Urban Versus Rural Trends of Extracorporeal Shockwave Lithotripsy and Ureteroscopic Laser Lithotripsy

OBJECTIVE

To describe temporal utilization and reimbursement trends of extracorporeal shockwave lithotripsy (ESWL) and ureteroscopy (URS) with laser lithotripsy.

METHODS

The Medicare Provider Utilization and Payment Database was queried for all ESWL and URS performed between 2013 and 2020 using Current Procedural Terminology codes: ESWL - 50590; URS - 52352, 52353, 52356. Cases that lacked rural or urban identification codes were excluded. A total of 347,174 ESWL and 401,899 URS cases were identified. Linear regression was performed with statistical significance set to 95% confidence intervals.

RESULTS

There was a significant upward trend for URS utilization over the study period (R² = 0.91, P <.001), but there was not a significant trend for ESWL utilization. In 2013, ESWL was used more frequently than URS, but by 2016, URS was used more frequently than ESWL. From 2013 to 2019, URS utilization increased by 241% and 168% by urban and rural urologists, respectively. URS was also associated with a slight increase in physician reimbursement over time (R² = 0.87, P <.001), whereas there was no association between ESWL and physician reimbursement. For URS, rural and urban urologists were reimbursed an average of $312.07 (standard deviation [SD] $14.03) and $404.86 (SD $21.96), respectively. For ESWL, rural and urban urologists were reimbursed an average of $456.22 (SD $5.74) and $562.66 (SD $16.68), respectively.

CONCLUSION

According to the Medicare database, URS has surpassed ESWL in utilization, especially by urban urologists. Physician reimbursement for ESWL remained higher than URS reimbursement, though URS reimbursement increased slightly in recent years.

Microdamage analysis of single-use flexible ureteroscope immediately after lithotripsy use

This prospective ex vivo study investigated microdamage to single-use flexible ureteroscopes (fURS) after ureteroscopy and endoscopic combined intrarenal surgery (ECIRS). The performance of 30 WiScope devices (OTU Medical, San Jose, CA, USA) was examined immediately after use, dividing them into three equal groups: ureteroscopy and ECIRS in the prone and supine positions. The overall scope of microdamage assessment included the scope deflection, bending radius, resolution, and water flow rate. Additionally, we analyzed the association between scope status and surgical parameters. The deflection, bending radius, and resolution remained similarly above the thresholds in all groups. However, the water flow rate was below the threshold in seven scopes (70%) in the ureteroscopy group and none in the ECIRS groups (P = 0.001). Univariate and multivariable logistic regression analyses demonstrated that basket wire catheter use was associated with an increased risk for overall scope microdamage (odds ratio [OR], 22.70; P = 0.006 and OR, 22.40; P = 0.019, respectively). Stone size, total laser energy, and surgical position were not associated with a risk for scope microdamage. In conclusion, ureteroscopy was more closely associated with scope damage than ECIRS, and basket wire catheter use seemed to inflict more damage to the fURS.

Financial Toxicity of Nephrolithiasis: The First Assessment of the Economic Stresses of Kidney Stone Treatment

OBJECTIVE

To investigate the financial toxicity (FT) related to kidney stone treatment.

METHODS

We performed a cross-sectional cohort study with multi-institutional in-person and online cohorts of stone formers.  Participants were surveyed using the validated COST tool (COmprehensive Score for financial Toxicity). The maximum score is 44 and lower scores indicate increased FT. "Moderate FT" was defined by COST scores between 25-14 points and "severe FT" for scores <14. Descriptive statistics, X² tests, T tests, Spearman correlation, and logistic regression were performed using SPSS v28.

RESULTS

241 participants were surveyed, including 126 in-person participants and 115 online. 60% of participants reported at least moderate FT (COST score <26) and 26% reported severe FT (COST score <14). Patients who reported moderate to severe FT were younger than those with low FT by a median difference of 8 years (95%CI = 4, 12). There was a significant correlation between out-of-pocket expense and COST scores, such that as out-of-pocket expenses increased, COST scores decreased, (Spearman's rho =-0.406, p = <0.001). Participants with moderate to severe FT tended to miss more workdays (p = 0.002), and their caretakers tended to miss more workdays (p = 0.007) due to their stone disease.

CONCLUSIONS

Most participants reported moderate to severe FT. As prior studies have shown that patients with "moderate FT" employ cost-coping strategies (i.e., medication rationing) and those with "severe FT" have worse health outcomes, urologists need to be sensitive to the financial burdens of treatment experienced by such patients undergoing kidney stone treatment.

Hybrid flexible ureteroscopy strategy in the management of renal stones - a narrative review

The introduction of single-use flexible ureteroscopes (suFURSs) in daily practice tends to overcome the main limitations of reusable ureteroscopes (reFURSs), in terms of high acquisition costs, maintenance, breakages and repairing costs, reprocessing and sterilization, as retrograde intrarenal surgery (RIRS) is promoted as first-line treatment of renal stones in most cases. A hybrid strategy implies having both instruments in the armamentarium of endourology and choosing the best strategy for cost-efficiency and protecting expensive reusable instruments in selected high-risk for breakage cases such as large stones of the inferior calyx, a steep infundibulopelvic angle or narrow infundibulum, or abnormal anatomy as in horseshoe and ectopic kidney. In terms of safety and efficiency, data present suFURSs as a safe alternative considering operating time, stone-free, and complication rates. An important aspect is highlighted by several authors about reusable instrument disinfection as various pathogens are still detected after proper sterilization. This comprehensive narrative review aims to analyze available data comparing suFURSs and reFURSs, considering economic, technical, and operative aspects of the two types of instruments, as well as the strategy of adopting a hybrid approach to selecting the most appropriate flexible ureteroscope in each case.

Imaging in stone diagnosis and surgical planning

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Prediction of the Uric Acid Component in Nephrolithiasis Using Simple Clinical Information about Metabolic Disorder and Obesity: A Machine Learning-Based Model

There is a great need for a diagnostic tool using simple clinical information collected from patients to diagnose uric acid (UA) stones in nephrolithiasis. We built a predictive model making use of machine learning (ML) methodologies entering simple parameters easily obtained at the initial clinical visit. Socio-demographic, health, and clinical data from two cohorts (A and B), both diagnosed with nephrolithiasis, one between 2012 and 2016 and the other between June and December 2020, were collected before nephrolithiasis treatment. A ML-based model for predicting UA stones in nephrolithiasis was developed using eight simple parameters-sex, age, gout, diabetes mellitus, body mass index, estimated glomerular filtration rate, bacteriuria, and urine pH. Data from Cohort A were used for model training and validation (ratio 3:2), while data from Cohort B were used only for validation. One hundred and forty-six (13.3%) out of 1098 patients in Cohort A and 3 (4.23%) out of 71 patients in Cohort B had pure UA stones. For Cohort A, our model achieved a validation AUC (area under ROC curve) of 0.842, with 0.8475 sensitivity and 0.748 specificity. For Cohort B, our model achieved 0.936 AUC, with 1.0 sensitivity, and 0.912 specificity. This ML-based model provides a convenient and reliable method for diagnosing urolithiasis. Using only eight readily available clinical parameters, including information about metabolic disorder and obesity, it distinguished pure uric acid stones from other stones before treatment.

Clinical Evaluation of Single-Use, Fiber-Optic, and Digital Ureterorenoscopes in the Treatment of Kidney Stones

<b><i>Introduction:</i></b> Indication of ureteroscopy for the treatment of urolithiasis has expanded immensely over the last decade. Fiber-optic and digital reusable instruments present the standard in clinical practice, but various newly available single-use devices might offer an exciting alternative. To date, the evidence is limited to clinical evaluation and efficacy of single-use ureteroscopes (URS) compared to standard instruments. Therefore, we evaluate a single-use instrument’s clinical characteristics and efficacy in direct comparison with a fiber-optic and digital device. <b><i>Methods:</i></b> A prospective study was conducted for patients undergoing endoscopic therapy for urolithiasis at a tertiary care center. We evaluated the different instruments’ clinical performance in categories of visibility, the stability of visibility, irrigation flow, and surgeon’s satisfaction. Statistical analyses were performed by SPSS using the Chi-Quadrat and Kruskal-Wallis test. A <i>p</i> value of <i>p</i> ≤ 0.05 was defined as statistically significant. <b><i>Results:</i></b> A total number of 77 patients were included and distributed as follows: 35 (46.7%) single-use, 19 (25.3%) digital, and 23 (28%) fiber-optic URS. Patients’ characteristics were homogenous over the three cohorts in sex, stone amount, and localization. The stone-free rate was equal in all three cohorts (<i>p</i> = 0.31). We identify stability of visibility, irrigation flow, and satisfaction were equal in all cohorts (<i>p</i> = 0.73; <i>p</i> = 0.20; <i>p</i> = 0.20). We report a significant difference in visibility, with 100% rated excellent in the digital URS group (<i>p</i> = 0.028). <b><i>Discussion/Conclusions:</i></b> Single-use URS achieve comparable clinical outcomes with equal stone-free rates in direct comparison with fiber-optic and digital reusable instruments. Accordingly, single-use devices present an adequate alternative for endoscopic therapy of urolithiasis.

Predictors and Cost Comparison of Subsequent Urinary Stone Care at Index versus Non-Index Hospitals

OBJECTIVE

To examine the effects of care fragmentation, or the engagement of different health care systems along the continuum of care, on patients with urinary stone disease.

METHODS

All-payer data from the 2016 Healthcare Cost and Utilization Project (HCUP) State Databases from Florida (FL) and New York (NY) were used to identify a cohort of adult patients with an emergency department visit for a diagnosis of urolithiasis, who subsequently re-presented to an index or non-index hospital for renal colic and/or urological intervention. Patient demographics, regional data, and procedural information were collected and 30-day episode-based costs were calculated. Multivariable logistic and gamma generalized linear regression were utilized to identify predictors of receiving subsequent care at an index hospital and associated costs, respectively.

RESULTS

Of the 33,863 patients who experienced a subsequent encounter related to nephrolithiasis, 9,593 (28.3%) received care at a non-index hospital. Receiving subsequent care at the index hospital was associated with fewer acute care encounters prior to surgery (2.5 vs. 2.7; p <0.001) and less days to surgery (29 vs. 42; p < 0.001). Total episode-based costs were higher in the non-index setting, with a mean difference of $783 (Non-index: $13,672, 95% CI $13,292 - $14,053; Index: $12,889, 95% CI $12,677 - $13,102; p < 0.001).

CONCLUSIONS

Re-presentation to a unique healthcare facility following an initial diagnosis of urolithiasis is associated with a greater number of episode-related health encounters, longer time to definitive surgery, and increased costs.

Medical management for the prevention of kidney stones

The alarming fact is that approximately one out of every 10 of us will have a kidney stone during our lifetime. The increasing prevalence and associated costs of kidney stones have resulted in it being one of the most commonly encountered and impactful medical conditions. Contributing factors include, but are not limited to, diet, climate, genetics, medications, activity and underlying medical conditions. Symptoms generally parallel stone size. Treatment varies from supportive to procedural (invasive and non-invasive). Prevention remains the best way to avoid this condition especially given the high recurrence rate. First time stone formers require counselling regarding dietary adjustments. Certain risk factors ultimately require a more in-depth metabolic investigation, especially if stones are recurrent. Ultimately, management is defined by stone composition. Where appropriate, we review both pharmacologic and non-pharmacologic options. Pivotal to successful prevention is patient education and the encouragement of compliance with the appropriate regimen.

Kidney stone proteomics: an update and perspectives

INTRODUCTION

Main problems of kidney stone disease are its increasing prevalence and high recurrence rate after calculi removal in almost all areas around the globe. Despite enormous efforts in the past, its pathogenic mechanisms remain unclear and need further elucidations. Proteomics has thus become an essential tool to unravel such sophisticated disease mechanisms at cellular, subcellular, molecular, tissue, and whole organism levels.

AREAS COVERED

This review provides abrief overview of kidney stone disease followed by updates on proteomics for investigating urinary stone modulators, matrix proteins, cellular responses to different types/doses of calcium oxalate (CaOx) crystals, sex hormones and other stimuli, crystal-cell interactions, crystal receptors, secretome, and extracellular vesicles (EVs), all of which lead to better understanding of the disease mechanisms. Finally, the future challenges and translation of these obtained data to the clinic are discussed.

EXPERT OPINION

Knowledge from urinary proteomics for exploring the important stone modulators (either inhibitors or promoters) will be helpful for early detection of asymptomatic cases for prompt prevention of symptoms, complications, and new stone formation. Moreover, these modulators may serve as the new therapeutic targets in the future for successful treatment and prevention of kidney stone disease by medications or other means of intervention.

Risk of Postpartum Urinary Stone Disease in Women with History of Urinary Stone Disease During Pregnancy

OBJECTIVE

To determine the risk of postpartum urinary stone disease in women with a history of stone disease during pregnancy.

METHODS

Using the Optum® de-identified Clinformatics® Datamart we identified pregnant women with urinary stone disease in the United States between January 2003 to December 2017 by standardized ICD-9, ICD-10, and CPT code criteria. We limited the cohort to include women without evidence of urinary stone disease prior to pregnancy. We abstracted patient demographic characteristics, clinical risk factors for stone disease, and data for urinary stone disease encounters and related procedures after pregnancy. Encounters occurring within 1 year of pregnancy were excluded. Cox proportional hazard models were used to analyze for significance.

RESULTS

We identified a total of 1,395,783 pregnant women with a median postpartum follow-up of 4.0 years, including 5,971 (0.4%) women diagnosed with a urinary stone during pregnancy. Of these, 736 (12.3%) had an additional urinary stone diagnosis claim after pregnancy, compared with 13,275 (0.95%) women without a history of stone disease during pregnancy (p < 0.0001). In multivariable proportional hazards models urinary stone disease during pregnancy (HR 12.8, 95% CI [11.8 - 13.8]) was independently associated with a higher hazard of urinary stone disease after pregnancy.

CONCLUSION

Women urinary stone disease during pregnancy were more likely to present with recurrent urinary stone disease after pregnancy. Given the 1 in 8 chance of needing further care, women with history of stone disease during pregnancy may benefit from risk counseling, surveillance, or secondary prevention efforts in the postpartum period.

Comparison of scoring systems for predicting stone-free status and complications after retrograde ıntrarenal surgery

PURPOSE

To compare the effectiveness of scoring systems in predicting stone-free rates (SFR) and complications following retrograde intrarenal surgery (RIRS).

MATERIALS AND METHODS

We retrospectively analyzed 280 patients who underwent RIRS for kidney stones between 2016 and 2019. The Resorlu-Unsal Stone score (RUSS), Modified Seoul National University Renal Stone Complexity (S-ReSC) score, and R.I.R.S. scoring system score were calculated for each patient who was enrolled in the study. Subsequently, stone scoring systems were compared as to their predictive capability for SFR using receiver-operating characteristic curves. Furthermore, multivariate analysis was done to determine whether the scoring systems associated with SFR and complications.

RESULTS

The median patient age was 44 (35--56). The median RUSS, S-ReSC, and R.I.R.S scores were 0 (0-1), 1(1-2), and 6 (5-7), respectively. The overall SFR was 76.7%. The R.I.R.S. scoring system was found to have a higher predictive value in predicting postoperative SFR than the other two scoring systems (p < 0.001, AUC = 0,816). RUSS, R.I.R.S. score, and stone size were found to be independent predictive factors for SFR (p = 0.049, p = 0.024, p = 0.033, respectively). Complications were observed in 3.2%(9/280) of patients. Stone scoring systems were not statistically associated with complications. Operation duration was the only independent risk factor for complications (p = 0.010).

CONCLUSIONS

The R.I.R.S. scoring system was found to have a higher predictive value than RUSS and S-ReSC to predict SFR following RIRS in our study. However, none of the stone scoring systems was directly proportional to complications of RIRS.

Relevance of Adopting a Hybrid Strategy Mixing Single-Use and Reusable Ureteroscopes for Stones Management: An Economic Study to Support the Best Strategy

Endoscopic procedures such as ureteroscopy (URS) have seen a recent increase in single-use devices. Despite all the advantages provided by disposable ureteroscopes (sURSs), their cost effectiveness remains questionable, leading most teams to use a hybrid strategy combining reusable (rURS) and disposable devices. Our study aimed to create an economic model that estimated the cut-off value of rURS procedures needed to support the profitability of a hybrid strategy (HS) for ureteroscopy. We used a budget impact analysis (BIA) model that estimated the financial impact of an HS compared to 100% sURS use. The model included hospital volume, sterilization costs and the private or public status of the institution. Although the hybrid strategy generally remains the best economic and clinical option, a predictive BIA model is recommended for the decision-making. We found that the minimal optimal proportion of rURS procedures in an HS was mainly impacted by the activity volume and overall number of sterilization procedures. Private and public institutions must consider these variables and models in order to adapt their HS and remain profitable.

Macrophage Function in Calcium Oxalate Kidney Stone Formation: A Systematic Review of Literature

Background

The global prevalence and recurrence rate of kidney stones is very high. Recent studies of Randall plaques and urinary components in vivo, and in vitro including gene manipulation, have attempted to reveal the pathogenesis of kidney stones. However, the evidence remains insufficient to facilitate the development of novel curative therapies. The involvement of renal and peripheral macrophages in inflammatory processes offers promise that might lead to the development of therapeutic targets. The present systematic literature review aimed to determine current consensus about the functions of macrophages in renal crystal development and suppression, and to synthesize evidence to provide a basis for future immunotherapy.

Methods

We systematically reviewed the literature during February 2021 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Articles investigating the relationship between macrophages and urolithiasis, particularly calcium oxalate (CaOx) stones, were extracted from PubMed, MEDLINE, Embase, and Scopus. Study subjects, languages, and publication dates were unrestricted. Two authors searched and screened the publications.

Results

Although several studies have applied mixed modalities, we selected 10, 12, and seven (total, n = 29) of 380 articles that respectively described cultured cells, animal models, and human samples.

The investigative trend has shifted to macrophage phenotypes and signaling pathways, including micro (m)-RNAs since the discovery of macrophage involvement in kidney stones in 1999. Earlier studies of mice-associated macrophages with the acceleration and suppression of renal crystal formation. Later studies found that pro-inflammatory M1- and anti-inflammatory M2-macrophages are involved. Studies of human-derived and other macrophages in vitro and ex vivo showed that M2-macrophages (stimulated by CSF-1, IL-4, and IL-13) can phagocytose CaOx crystals, which suppresses stone development. The signaling mechanisms that promote M2-like macrophage polarization toward CaOx nephrocalcinosis, include the NLRP3, PPARγ-miR-23-Irf1/Pknox1, miR-93-TLR4/IRF1, and miR-185-5p/CSF1 pathways.

Proteomic findings have indicated that patients who form kidney stones mainly express M1-like macrophage-related proteins, which might be due to CaOx stimulation of the macrophage exosomal pathway.

Conclusions

This systematic review provides an update regarding the current status of macrophage involvement in CaOx nephrolithiasis. Targeting M2-like macrophage function might offer a therapeutic strategy with which to prevent stones via crystal phagocytosis.

Current and emerging pharmacological targets for medical expulsive therapy

The primary goals of medical expulsive therapy are to increase the rate of stone expulsion along the ureter to avoid ureteral obstruction and reduce ureteral colic and thus avoid the need for surgical and more invasive interventions. This review focussed on the findings from in vivo and in vitro animal and human studies that have investigated the pharmacological mechanisms controlling ureteral motility and their translation to current and potentially new clinically used drugs for increasing the rate of stone expulsion along the ureter. The complicated contractility profile of the ureter, which alters with age, tissue segment region, orientation and species contributes to the difficulty of interpreting studies on ureteral pharmacology, which translates to the complexity of discovering ideal drug targets for medical expulsive therapy. Nevertheless, the current drug classes clinically used for patients with stone lodgement include α₁ -adrenoceptor antagonists, calcium channel blockers and NSAIDS, whilst there are promising targets for drug development that require further clinical investigations including the phosphodiesterase type 5 enzyme, β-adrenoceptors and 5-HT receptors.

Spontaneous ureteral stone passage: a novel and comprehensive nomogram

BACKGROUND

Ureteral stones pose a high economic and medical burden among Emergency Department (ED) admissions. Management strategies vary from expectant therapy to surgical interventions. Since predictors of ureteral spontaneous stone passage (SSP) are still not well understood, we sought to create a novel nomogram to guide management decisions.

METHODS

Charts were retrospectively reviewed for patients who presented to our institution's ED with non-febrile renal colic and received a radiological diagnosis of ureteral stone ≤10 mm. Demographic, clinical, laboratory, and non-contrast CT data were collected. This novel nomogram incorporates the serum neutrophil-to-lymphocyte ratio (NLR) as a potential predictor of SSP. The model was derived from a multivariate logistic regression and was validated on a different cohort. A receiver operator characteristic (ROC) curve was constructed and the area under the curve (AUC) was computed.

RESULTS

A total of 1186 patients presented to our ED between January 2010 and October 2018. We randomly divided our population into a derivation and validation cohort in one to five ratio. A stone size ≥7 mm was the strongest predictor of SSP failure; OR=9.47; 95% CI: 6.03-14.88. Similarly, a NLR≥3.14 had 2.17; (1.58-2.98) the odds of retained stone. SSP failure was also correlated with proximal position, severe hydronephrosis, and leukocyte esterase ≥75, P=0.02, P=0.05, and P=0.006, respectively. The model had an AUC of 0.804 (0.776-0.832). The nomogram was also used to compute the risk of SSP failure (AUC 0.769 [0.709-0.829]).

CONCLUSIONS

Our novel nomogram can be used as a predictor for SSP and can be used clinically in decision making.

Switching to Single-use Flexible Ureteroscopes for Stones Management: Financial Impact and Solutions to Reduce the Cost Over a 5-Year Period

OBJECTIVES

To assess the financial impact of switching to single-use ureteroscopes (sURS) in urolithiasis management for a hospital, over a 5-year period, and to identify possible solutions to contain or reduce it.

METHODS

A Budget Impact (BI) model was designed for a public hospital performing around 200 ureteroscopies or extracorporeal shockwave lithotripsies per year. The BI was estimated as the difference between financial balances (between costs and revenues) of 2 environments (with and without sURS). The population was defined as adults treated for urolithiasis. The BI model was based on assumptions about the expected progression in the incidence of urolithiasis, and the expected change in clinical practices due to the availability of sURS. We considered the costs and revenues of hospital stays, the purchase price of sURS and the costs of digital or fiberoptic reusable ureteroscopes (rURS). Univariate and multivariate sensitivity analyses were performed.

RESULTS

The cumulative 5-year financial impact of switching completely to sURS was €807,824 and €649,677 in comparison with fiberoptic and digital rURS respectively. This impact could be reduced by half or more if the health-care facility were to adopt different solutions, including negotiating the purchase price of sURS, developing outpatient activity and reducing production costs for ureteroscopy procedures.

CONCLUSION

The BI model gives decision-makers a more accurate picture of the financial impact of switching to sURS and highlights ways to reduce the expected additional cost.