The ROKS nomogram for predicting a second symptomatic stone episode

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

Objective

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

Methods

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

Results

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

Conclusions

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

Feasibility of stone recurrence risk stratification using the recurrence of kidney stone (ROKS) nomogram

This study seeks to evaluate the recurrence of kidney stones (ROKS) nomogram for risk stratification of recurrence in a retrospective study. To do this, we analyzed the performance of the 2018 ROKS nomogram in a case-control study of 200 patients (100 with and 100 without subsequent recurrence). All patients underwent kidney stone surgery between 2013 and 2015 and had at least 5 years of follow-up. We evaluated ROKS performance for prediction of recurrence at 2- and 5-year via area under the receiver operating curve (ROC-AUC). Specifically, we assessed the nomogram's potential for stratifying patients based on low or high risk of recurrence at: a) an optimized cutoff threshold (i.e., optimized for both sensitivity and specificity), and b) a sensitive cutoff threshold (i.e., high sensitivity (0.80) and low specificity). We found fair performance of the nomogram for recurrence prediction at 2 and 5 years (ROC-AUC of 0.67 and 0.63, respectively). At the optimized cutoff threshold, recurrence rates for the low and high-risk groups were 20 and 45% at 2 years, and 50 and 70% at 5 years, respectively. At the sensitive cutoff threshold, the corresponding recurrence rates for the low and high-risk groups were of 16 and 38% at 2 years, and 42 and 66% at 5 years, respectively. Kaplan-Meier analysis revealed a recurrence-free advantage between the groups for both cutoff thresholds (p < 0.01, Fig. 2). Therefore, we believe that the ROKS nomogram could facilitate risk stratification for stone recurrence and adherence to risk-based surveillance protocols.

Time Course and Risk Factors for Repeat Procedures After Ureteroscopy or Shockwave Lithotripsy

OBJECTIVE

To determine risk factors and time course for repeat procedures after ureteroscopy (URS) or shockwave lithotripsy (SWL) procedure using a large employer-based claims database.

METHODS

We identified all patients who underwent treatment for ureteral or renal stone with URS or SWL from January 1, 2007 to December 31, 2014 using the IBM MarketScan Commercial Database. Repeat stone procedure was evaluated after a 90-day grace period from the index procedure. Patients were followed until December 31, 2017. We performed multivariate analyses using Cox proportional hazards to determine independent risk factors for repeat procedure after the initial stone removal.

RESULTS

A total of 189,739 patients underwent a SWL or URS and were included in the study. The incidence of repeat procedure per 100 person years was 6.8, and 4.4 after SWL and URS, respectively. The median time to reoperation was 12.5 months for SWL and 14.6 months for URS. On multivariable analysis, SWL was associated with an increased risk of repeat procedure compared to URS. (HR = 1.63). Paralysis, neurogenic bladder and inflammatory bowel disease were also associated with an increased risk of repeat procedure (HR = 1.66, 1.40, and 1.36 respectively) CONCLUSION: In a large national cohort, patients with paralysis and neurogenic bladder had a significantly higher risk of repeat stone procedure. SWL was associated with higher risk of repeat procedure than URS. Urologists can use these data to identify and counsel patients at high risk for need for recurrent procedure.

Vitamin D and Calcium Supplementation and Urolithiasis: A Controversial and Multifaceted Relationship

Patients with urolithiasis, and particularly those with hypercalciuria, frequently have a marked reduction of bone mineral content up to the levels of osteoporosis, with a significant increase in bone fracture risk. For these reasons, the indication to prescribe vitamin D and/or calcium supplementations is very frequent in such patients. On the other hand, both calcium supplementation, and even more vitamin D therapy, can worsen the risk of developing urolithiasis by increasing calcium, phosphate, and oxalate urinary excretion. Despite the clinical and practical relevance of this issue, the evidence on this topic is scarce and contradictory. Therefore, some concerns exist about how and whether to prescribe such supplements to a patient with a history of kidney stones. In this narrative review, we resume some pivotal pathophysiological concepts strictly related to the dealt topic, and we draw some considerations and personal opinions on the pros and cons of such prescriptions. Finally, we share with the reader our pragmatic algorithm for handling the urolithiasis risk in patients who have strong indications to be prescribed vitamin D and calcium supplementations.

Metabolic stone workup abnormalities are not as important as stone culture in patients with recurrent stones undergoing percutaneous nephrolithotomy

To investigate the association between metabolic urinary abnormalities and urinary tract infection (UTI) and the stone recurrence status in patients undergoing percutaneous nephrolithotomy (PCNL). A prospective evaluation was performed for patients who underwent PCNL between November 2019 and November 2021 and met the inclusion criteria. Patients with previous stone interventions were classified as recurrent stone formers. Before PCNL, a 24 h metabolic stone workup and midstream urine culture (MSU-C) were done. Renal pelvis (RP-C) and stones (S-C) cultures were collected during the procedure. The association between the metabolic workup and UTI results with stone recurrence was evaluated using univariate and multivariate analyses. The study included 210 patients. UTI factors that showed significant association with stone recurrence included positive S-C [51 (60.7%) vs 23 (18.2%), p < 0.001], positive MSU-C [37 (44.1%) vs 30 (23.8%), p = 0.002], and positive RP-C [17 (20.2%) vs 12 (9.5%), p = 0.03]. Other factors were mean ± SD GFR (ml/min) (65 ± 13.1 vs 59.5 ± 13.1, p = 0.003), calcium-containing stones [47 (55.9%) vs 48 (38.1%), p = 0.01], median (IQR) urinary citrate levels (mg/day) [333 (123-512.5) vs 221.5 (120.3-412), p = 0.04], and mean ± SD urinary pH (6.1 ± 1 vs 5.6 ± 0.7, p < 0.001). On multivariate analysis, only positive S-C was the significant predictor of stone recurrence (odds ratio: 9.9, 95% confidence interval [CI] (3.8-28.6), p < 0.001). Positive S-C, and not metabolic abnormalities, was the only independent factor associated with stone recurrence. A focus on preventing UTI might prevent further stone recurrence.

Artificial Intelligence for Kidney Stone Spectra Analysis: Using Artificial Intelligence Algorithms for Quality Assurance in the Clinical Laboratory

Objective

To determine if a set of artificial intelligence (AI) algorithms could be leveraged to interpret Fourier transform infrared spectroscopy (FTIR) spectra and detect potentially erroneous stone composition results reported in the laboratory information system by the clinical laboratory.

Background

Nephrolithiasis (kidney stones) is highly prevalent, causes significant pain, and costs billions of dollars annually to treat and prevent. Currently, FTIR is considered the reference method for clinical kidney stone constituent analysis. This process, however, involves human interpretation of spectra by a qualified technologist and is susceptible to human error.

Methods

This prospective validation study was conducted from October 29, 2020, to October 28, 2021, to test if the addition of AI algorithm overreads to FTIR spectra could improve the detection rate of technologist-misclassified FTIR spectra. The preceding year was used as a control period. Disagreement between the AI overread and technician interpretation was resolved by an independent human interpretation. The rate of verified human misclassifications that resulted in revised reported results was the primary end point.

Results

Spectra of 81,517 kidney stones were reviewed over the course of 1 year. The overall clinical concordance between the technologist and algorithm was 90.0% (73,388/81,517). The report revision rate during the AI implementation period was nearly 8 times higher than that during the control period (relative risk, 7.9; 95% CI, 4.1-15.2).

Conclusion

This study demonstrated that an AI quality assurance check of human spectra interpretation resulted in the identification of a significant increase in erroneously classified spectra by clinical laboratory technologists.

Influencing factors of acute kidney injury following retrograde intrarenal surgery

PURPOSE

To investigate the influencing factors of acute kidney injury (AKI) following retrograde intrarenal surgery (RIRS).

METHODS

The data of patients who underwent RIRS for kidney stones between January 2018 and June 2022 at two tertiary centers were retrospectively analyzed. Demographic data of patients were obtained. According to kidney disease: Improving Global Outcomes (KDIGO) criteria, those with and without AKI were divided into two groups. Preoperative, intraoperative, and postoperative predictive factors of patients were investigated between the groups. In addition, the influencing factors of AKI were examined by multivariate analysis.

RESULTS

This study included 295 (35.7%) women and 532 (64.3%) men. The mean age was 50.03 ± 15.4 years (range 18-89), and mean stone size was 15.5 ± 6.1 mm (range 6-47). Overall, 672 of patients (81.3%) were stone-free after the initial treatment. According to KDIGO, 110 of patients (13.3%) had AKI during the postoperative period. Univariate analysis showed that stone size (P = .003), previous stone surgery (P = .010), renal malformations (P = .017), high operative time (P =  < .001), high preoperative creatinine value (P = .036), intraoperative complications (P = .018), and postoperative urinary tract infection (P = .003) had significant influence on the AKI after RIRS. Multivariate analysis excluded previous stone surgery, high preoperative creatinine value, renal malformations, and intraoperative complications from the logistic regression model, whereas other factors maintained their statistically significant effect on AKI, indicating that they were independent predictors.

CONCLUSIONS

Stone size, operative time, postoperative urinary tract infection, and diabetes mellitus are significant predictors of AKI. During RIRS, urologists should consider the factors that increase the risk of AKI and evaluate the treatment outcomes based on these factors.

Metabolic evaluation of high-risk stone formers: a retrospective study

Background

The purpose of this study was to assess the metabolic abnormalities in high-risk stone formers.

Methods

This was a retrospective observational study done at Tribhuvan University Teaching Hospital, Nepal, over 1-year period. High-risk stone formers were identified and were evaluated with serum chemistries and 24-h urinary chemical evaluation. Stone analysis was also included whenever available. Common metabolic abnormalities and stone analysis results were reported and compared with different studies. Continuous variables were expressed as mean ± SD. Categorical variables were expressed as percentage and proportions.

Results

During 1 year of period, sixty-five patients had undergone extensive metabolic evaluation, but complete data were available for only forty-six patients. Of the total patients (n = 46), 63% were male (n = 29) and rest (36.9%) were female. Mean age of patients was 34.4 ± 15.1 years. Common reasons for metabolic evaluation were multiple stones (40%), bilateral stones (27%), recurrent stones (17%) and others (16%). Most common stone type was mixed stone with predominant composition being calcium oxalate mono- and dihydrate (62.9%). Twenty-four-hour urinary metabolic evaluation showed hyperoxaluria (32.6%) as most common abnormalities followed by hypocitraturia (21.7%) and hypocalciuria (21.7%).

Conclusion

Hyperoxaluria and hypocitraturia are common metabolic abnormalities in our patients. These findings help in counselling dietary measures to patients.

Fluid intake recommendations in urolithiasis and general advice to patients without metabolic risk factors

Urolithiasis is a highly prevalent global disease with substantially increasing incidence in the last two decades. Data from the literature suggests that 26%-50% of patients will have a recurrence within 10 years after an initial symptomatic stone episode. Therefore, interest has been raised in preventive strategies, aiming to modify the risk factors of stone recurrence by implementing dietary and lifestyle changes and specific medical treatments for stone formers, depending on their recurrence risk factors. Certain dietary factors are thought to contribute significantly to the increased incidence of urolithiasis, particularly a diet low in fiber and high in animal protein, fat, and sodium. Fluid intake is perhaps the most important and modifiable step in the prevention of urolithiasis, irrespective of stone composition. However, the amount of fluid to be consumed and the implications of various fluid types on stone formation are still controversial. In this article, the relationship between fluid intake, beverage types and stone formation-prevention will be discussed. Moreover, general dietary recommendations for patients without metabolic risk factors will be reviewed based on the current literature.

Acute kidney injury increases risk of kidney stones-a retrospective propensity score matched cohort study

BACKGROUND

Acute kidney injury (AKI) is common. An episode of AKI may modify the risk of developing kidney stones by potential long-term effects on urine composition. We aimed to investigate the association between AKI and the risk of kidney stone presentations.

METHODS

The retrospective cohort study used patient data (1 January 2008-31 December 2017), from an Australian Local Health District, which included AKI diagnosis, demographics, comorbidities and kidney stone admissions. Time-varying Cox proportional hazards and propensity-matched analysis were used to determine the impact of AKI on the risk of kidney stones. To address possible population inhomogeneity in comparisons between no AKI and hospitalized AKI, sub-group analysis was done comparing inpatient and outpatient AKI versus no AKI, to assess consistency of association with future stones. Sensitivity analysis was undertaken to capture the impact of a known AKI status and AKI severity.

RESULTS

Out of 137 635 patients, 23 001 (17%) had an AKI diagnosis and 2295 (2%) had kidney stone presentations. In the unadjusted analysis, AKI was associated with kidney stones, with AKI used as a time-varying exposure, [hazard ratio (HR) 1.32, 95% confidence interval (CI) 1.16-1.50)]. Both inpatient-AKI (HR 1.19, 95% CI 1.01-1.39) and outpatient-AKI (HR 1.59, 95% CI 1.30-1.94) were significantly associated with future stones compared to no AKI subjects. This association persisted in the adjusted analysis (HR 1.45, 95% CI 1.26-1.66), propensity-matched dataset (HR 1.67, 95% CI 1.40-1.99) and sensitivity analysis. There was a dose-response relationship with higher stages of AKI being associated with a greater risk of kidney stones.

CONCLUSIONS

In a large cohort of patients, AKI is associated with a greater risk of kidney stones, which increases with higher stages of AKI. This association should be examined in other cohorts and populations for verification.

Influence of BMI on the Recurrence Rate of Nephrolithiasis in the Adult Population of Saudi Arabia: A Retrospective Study

Objectives Nephrolithiasis is a common disease, and Saudi Arabia is among the countries with the highest prevalence of nephrolithiasis. Obesity is one of the risk factors associated with the increased formation of renal calculi. We aimed to assess whether obesity also increases the recurrence rate of nephrolithiasis. Methods We retrospectively identified and collected data of 283 adult patients with renal stones who were managed at our hospital from November 2018 to November 2021. The demographic information, comorbidities, stone burden, and treatment methods related to them were identified, collected, and analyzed. Moreover, we performed the chi-squared test (χ2) and multivariate logistic regression analysis in order to assess the risk factors (i.e., independent predictors) of recurrence among the studied patients. Additionally, the odds ratio (OR) was calculated at a confidence interval (CI) of 95%. A p-value of less than 0.05 was considered statistically significant. Results Of the 283 adult patients we analyzed, 35 did not meet the criteria of our study and, consequently, were excluded. Therefore, we ended up with 248 patients, of whom 179 (68.1%) were males, 131 (52.8%) had a previous history of renal stones, and 90 (36.3%) had chronic illnesses. Moreover, the mean age of the studied patients was 48.91 ± 14.51 years, and the mean BMI was 29.44 ± 6.1 kg/m². It was found that most of the patients (35.5%) had only one stone, while 23.4% of them had more than 5 stones. Furthermore, the majority of the stones (35.9%) were medium size (with a stone diameter of 10-19 mm [1-1.9 cm]). We did not find a relationship between obesity and the recurrence rate of renal stones. However, there was a significant association (p < 0.05) between the recurrence rate and Saudi nationality, chronic diseases (more specifically, HTN), unilateral stones, and a stone diameter of 10-19 mm (1-1.9 cm). Additionally, we identified diabetes and the kidney as stone location factors that are associated with less recurrence. Conclusion Although obesity was reported to increase the risk of renal stone formation, we did not find it to be associated with an increased recurrent rate of the disease in the Saudi Arabian population, which is inconsistent with other studies conducted in this area in other countries. Therefore, larger studies are needed to prove this finding.

Alkali Citrate Content of Common Over-the-Counter and Medical Food Supplements

Objective: Potassium citrate effectively decreases kidney stone recurrence, but it is costly and associated with side effects. While several over-the-counter supplements and medical foods purport to provide sufficient citrate to prevent recurrent stones, corroborating data on their actual citrate content is limited. Materials and Methods: Nine common nonprescription products were purchased online. Reported citrate content was obtained from packaging, promotional materials, or ingredient labels. Using a single serving of each product, actual citrate, sodium, potassium, calcium, magnesium, and oxalate content was measured using spectrophotometry and chromatography. Total alkali citrate, cost, and amounts of each component per 10 mEq of alkali citrate were also calculated. Results: Nearly all products contained more citrate than advertised, except for Litholyte^® powder, Litholyte^® Coffee, and Horbäach^® potassium citrate. Per serving, Moonstone^® powder, LithoBalance™, and KSP tabs™ contained the most citrate (means of 63.9, 33.5, and 26.9 mEq, respectively). Moonstone and LithoBalance had the greatest discrepancy between total citrate and alkali citrate (15.7 and 11.8 mEq per serving, respectively). NOW^® potassium citrate was least expensive ($0.04/10 mEq alkali citrate). KSP tabs delivered the most daily sodium (mean 158 mg/10 mEq alkali citrate, Litholyte Coffee provided the most potassium (mean of 13 mEq/10 mEq alkali citrate), and Kidney COP^® provided the most calcium (mean 147 mg/10 mEq alkali citrate). Conclusion: Some common over-the-counter products contain sufficient alkali to potentially promote a citraturic response; Moonstone provides the most alkali citrate, but at a higher cost than other products. Sodium, potassium, and calcium from these products must also be considered in daily consumption.

Duration of Follow-up and Timing of Discharge from Imaging Follow-up, in Adult Patients with Urolithiasis After Surgical or Medical Intervention: A Systematic Review and Meta-analysis from the European Association of Urology Guideline Panel on Urolithiasis

CONTEXT

No algorithm exists for structured follow-up of urolithiasis patients.

OBJECTIVE

To provide a discharge time point during follow-up of urolithiasis patients after treatment.

EVIDENCE ACQUISITION

We performed a systematic review of PubMed/Medline, EMBASE, Cochrane Library, clinicaltrials.gov, and reference lists according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Fifty studies were eligible.

EVIDENCE SYNTHESIS

From a pooled analysis of 5467 stone-free patients, we estimated that for a safety margin of 80% for remaining stone free, patients should be followed up using imaging, for at least 2 yr (radiopaque stones) or 3 yr (radiolucent stones) before being discharged. Patients should be discharged after 5 yr of no recurrence with a safety margin of 90%. Regarding residual disease, patients with fragments ≤4 mm could be offered surveillance up to 4 yr since intervention rates range between 17% and 29%, disease progression between 9% and 34%, and spontaneous passage between 21% and 34% at 49 mo. Patients with larger residual fragments should be offered further definitive intervention since intervention rates are high (24-100%). Insufficient data exist for high-risk patients, but the current literature dictates that patients who are adherent to targeted medical treatment seem to experience less stone growth or regrowth of residual fragments, and may be discharged after 36-48 mo of nonprogressive disease on imaging.

CONCLUSIONS

This systematic review and meta-analysis indicates that stone-free patients with radiopaque or radiolucent stones should be followed up to 2 or 3 yr, respectively. In patients with residual fragments ≤4 mm, surveillance or intervention can be advised according to patient preferences and characteristics, while for those with larger residual fragments, reintervention should be scheduled.

PATIENT SUMMARY

Here, we review the literature regarding follow-up of urolithiasis patients. Patients who have no stones after treatment should be seen up to 2-3 yr, those with large fragments should be reoperated, and those with small fragments could be offered surveillance with imaging.

The effect of ALPL gene polymorphism on the development of urolithiasis in the Turkish population

Urinary system stones have a complex pathophysiology affected by environmental and genetic factors. To confirm whether ALPL gene polymorphisms are an effective universal risk factor for the development of urolithiasis, we aimed to investigate ALPL gene polymorphism in Turkish population. Our study was carried out with 187 patients with urolithiasis and 92 healthy volunteers (control group) who were not diagnosed with urolithiasis either in themselves or in their families, applied to Emergency Medicine Clinic of Health Sciences University Haydarpasa Numune Training and Research Hospital in Istanbul, Turkey between November 2021 and February 2022, prospectively. In order to evaluate the relationship between ALP gene (rs1256328) polymorphism and urolithiasis, blood samples were analyzed by quantitative Real Time PCR (qPCR) method.  Male gender (OR:3.785; 95% CI:2.118-6.763; p<0.001), increased BUN level (OR:1.082; 95% CI:1.013-1.156; p=0.019), increased NLR level (OR:1.149; 95 %CI:1.033-1.277; p=0.011) and heterozygous genotype (OR:2.353; 95% CI:1.31-4.225; p=0.004) were determined as independent risk factors for the development of urolithiasis. The presence of heterozygous (CT) genotype in the ALPL rs1256328 gene region in the Turkish population is associated with an increased risk of urolithiasis. This suggests that ALPL rs1256328 gene polymorphism can be used as a genetic marker in the Turkish population.

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

Objectives

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

Methods

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

Results

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

Conclusions

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

The Impact of Radiographic, Metabolic and Demographic Characteristics on Kidney Stone Recurrence

Urolithiasis is a frequent disease with cited rates of recurrence after initial diagnosis that vary widely and range between 35% and 50%. We assessed the radiographic recurrence rate in patients with urinary stones and its risk factors. We retrospectively identified patients who were diagnosed with urinary stones on non-contrast computed tomography from 2010 to 2011, and underwent another imaging examination at least six months afterwards. We collected patient demographic, clinical, laboratory and radiologic data and compared patients with and without urinary stone recurrence. Ultimately, 237 patients were included in the study; the mean follow-up was 6.7 years; 88 patients (37.1%) had recurrence based on our recurrence criteria. On univariate analysis, the significant parameters for recurrence were baseline serum calcium and uric acid, stone location in the kidney, surgical intervention and stone burden volume. On multivariate analysis, surgical intervention (OR 3.07, p = 0.001), baseline calcium (OR 2.56, p = 0.011), baseline uric acid (OR 1.30, p = 0.021) and stone location in the kidney (OR 2.16, p = 0.012) were associated with higher risk of recurrence. These findings may guide personalized follow-up protocols for patients with urolithiasis based on their risk factors.

The role of autophagy in calcium oxalate kidney stone: A systematic review of the literature

Background: Calcium oxalate kidney stone is one of the common diseases in the urinary system and has a high recurrence rate. Currently, the pathogenesis of kidney stone and the methods to prevent recurrence are still being investigated. Autophagy, as an event of cellular self-repair, has received attention in the field of kidney stone in recent years. In some current studies, autophagy has shown destructiveness and protectiveness in the pathogenesis of kidney stone. The inhibition or promotion of autophagy may be a key target for future kidney stone therapy. This systematic literature review discusses the function of autophagy in kidney stone pathogenesis in the context of current research and synthesizes the evidence analysis to provide a basis for new future therapies.

Method: We systematically reviewed the literature during September 2021 according to the Preferred Reporting Items for Systematic Evaluation and Meta-Analysis (PRISMA) guidelines. Articles on studying the role of autophagy in the pathogenesis of calcium oxalate kidney stone were extracted from PubMed, MEDLINE, Embase and Scopus, including in vivo versus in vitro experiments. The study topic, language and publication date were not restricted. Two authors (Li and Zhou) searched and screened the literature.

Results: We screened 18 articles from the 33 collected articles, of which 6 conducted in vitro cellular studies, four conducted animal studies, eight conducted cellular studies with animal studies, and five studied human specimens. In early studies, the literature generally concluded that autophagy is deleterious in the development of kidney stone. In 2020, the idea of the protectiveness of autophagy associated with kidney stone was first proposed and focused on targeting transcription factor EB. In addition, the interaction of autophagy with other cellular events and the regulation of signaling molecules are focused on in this paper.

Conclusion: This systematic review provides advances in research on the role of autophagy in renal calculi. The current studies suggest that both upregulation and downregulation of autophagy may ameliorate injury in kidney stone models. The authors prefer the upregulation of autophagy as a future research direction for kidney stone treatment.

Efficacy of Ficus tikoua Bur. extract in ethylene glycol-induced urolithiasis model in SD rats

The development of new herbal preparations for the treatment of urolithiasis is an urgent task of medical science. Ficus have attracted the attention of pharmacologists due to a wide range of biological properties, including antioxidant, anti-inflammatory, antibacterial and antifungal activity. We studied the effectiveness of Ficus tikoua Bur. in SD rats in which urolithiasis was induced by 6 weeks of oral administration of ethylene glycol 0.5% ad libitum instead of drinking water. Administration of the extract of Ficus tikoua Bur., as well as comparative drug Cystone® after modeling of urolithiasis lead to the restoration of diuresis and the concentration of inorganic phosphates starting from the 6th week of the experiment. The use of the Ficus tikoua Bur. extract for 6 weeks, both during the modeling of urolithiasis and during the recovery period, led to the restoration of the percentage of lymphocytes in the blood, content of sodium, chlorine and inorganic phosphates in the blood to the control level. Thus, the extract of Ficus tikoua Bur. seems to be a promising drug for effective treatment of the initial stages of the development of urolithiasis.

Diet and Stone Disease in 2022

Diet plays a central role in the development and prevention of nephrolithiasis. Although pharmacologic treatment may be required for some patients who are resistant to dietary measures alone, dietary modification may be sufficient to modulate stone risk for many patients. While there is no single specialized diet for stone prevention, several dietary principles and recommendations for stone prevention are supported by practice guidelines, including adequate fluid intake, modest calcium intake, low dietary sodium, and limited animal protein. In this review, we summarized the evidence supporting these dietary recommendations and reviewed the current literature regarding specific dietary components and comprehensive diets for stone prevention.

Dietary Risk Factors for Incident and Recurrent Symptomatic Kidney Stones

OBJECTIVE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Acidification of 24-hour urine in urolithiasis risk testing: An obsolete relic?

BACKGROUND

Recommendations on the optimal preservation of 24 h urine for the metabolic work-up in urolithiasis patients are very heterogeneous. In case two such tests with different storage condition recommendations are being analysed, multiple collections would be needed, challenging especially elderly and very young patients. We therefore aimed to evaluate the stability of urine constituents under different storage conditions.

MATERIAL AND METHODS

We collected urine samples from ten healthy volunteers and prepared aliquots to be stored either at room temperature or 4 °C. Some aliquots were preserved using hydrochloric acid prior to storage, some thereafter, some using the BD Urine preservation tube and some were not preserved at all. Storage duration was 0, 24, 48 or 72 h. In all samples calcium, magnesium, phosphorus, creatinine, oxalate, citrate and uric acid were measured and compared to the according reference sample.

RESULTS

We could not find any significant deviation for any of the analytes and preanalytical treatment conditions compared to the associated reference sample.

CONCLUSION

Preservation of 24 h urine for the metabolic evaluation in stone formers might not be necessary for sample storage up to 72 h.

Medical Treatment and Prevention of Urinary Stone Disease

The pathophysiology underlying urinary stone formation remains an area of active investigation. There are many pharmacotherapies aimed at optimizing metabolic factors and reducing urinary supersaturation of stone components that play an important role in urinary stone prevention. In addition, medical expulsive therapy for ureteral stones and medical dissolution therapy for uric acid-based urinary stones are helpful treatment tools and are used alongside surgical treatments in the management of urinary stones.

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

Background

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

Methods

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

Results

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

Conclusions

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

Supplementary Information

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

R. S, Toh CC, Sundram M, Md Yusoff NA, Nagappan P, Kamaruzaman S, Yeoh WS, Ong TA, Lim J. Cardiovascular risk factors, ethnicity and infection stone are independent factors associated with reduced renal function in renal stone formers

BACKGROUND

Recent evidence suggested the link between nephrolithiasis and renal function impairment. We aimed to determine the renal function profile and potential factors associated with reduced renal function amongst renal stone formers in multi-ethnic Asians.

METHODS

We conducted a cross-sectional study involving patients undergoing percutaneous nephrolithotomy between May 2015 and December 2019. Reduced renal function was defined as having estimated glomerular filtration rate < 60 ml/min per 1.73 m2. Renal stone samples were collected and quantified using infrared spectroscopy. Potential factors associated with reduced renal function including age, ethnicity, educational level, history of diabetes, hypertension, gout, hydronephrosis, serum uric acid level, and type of renal stone were evaluated using univariable and multivariable analyses.

RESULTS

A total of 1162 patients from a multi-ethnic population (Malays 67%, Chinese 19%, Indians 13% and indigenous people 1%) with median age of 57 years (Interquartile range 48-64) were enrolled in the study. Almost a third of patients were found with reduced renal function. Multivariable analysis showed that the odds of having reduced renal function increased with age, ethnicity, lower educational level, history of diabetes, hypertension, gout, bilateral hydronephrosis, elevated serum uric acid level and infection stone.

CONCLUSIONS

Reduced renal function varies between ethnicities and all age groups of renal stone formers. In addition to age and ethnicity, cardiovascular risk factors including diabetes and hypertension may also need to be taken into account in managing stone patients with reduced renal function.

Impact of the SGLT2 inhibitor empagliflozin on urinary supersaturations in kidney stone formers (SWEETSTONE trial): protocol for a randomised, double-blind, placebo-controlled cross-over trial

INTRODUCTION

Kidney stones are a global healthcare problem. Given high recurrence rates and the morbidity associated with symptomatic stone disease, effective medical prophylaxis is clearly an unmet need. Explanatory analyses of randomised controlled trials with sodium/glucose cotransporter isoform 2 inhibitors indicated a 30%-50% reduced rate of stone events in patients with diabetes. Underlying mechanisms remain unclear. We aim to determine the effect of empagliflozin on urinary supersaturations in non-diabetic kidney stone formers to evaluate their therapeutic potential for recurrence prevention. We will provide first clinical trial evidence on whether urinary supersaturations are affected by empagliflozin in kidney stone formers.

METHODS AND ANALYSIS

The SWEETSTONE trial is a randomised, double-blind, placebo-controlled, cross-over, exploratory study to assess the impact of empagliflozin on urinary supersaturations of calcium oxalate, calcium phosphate and uric acid in kidney stone formers. We plan to include 46 non-diabetic adults (18-74 years) with ≥1 past kidney stone event and stone composition with ≥80% of calcium or ≥80% of uric acid. Patients with secondary causes of kidney stones or chronic kidney disease will be excluded. Eligible individuals will be randomised in equal proportions to receive either a 14-day treatment with 25 mg empagliflozin followed after the 2-6 weeks wash out period by a 14-day treatment with a matching placebo or the reverse procedure. Secondary outcomes will include electrolyte concentrations, renal function, mineral metabolism and glycaemic parameters, urinary volume and safety.Results will be presented as effect measures (95% CIs) with p values and hypothesis testing for primary outcomes (significance level 0.02).

ETHICS AND DISSEMINATION

The SWEETSTONE trial was approved by the Swiss ethics committee and Swissmedic. First results are expected in the fourth quarter of 2022.

TRIAL REGISTRATION NUMBER

NCT04911660; Pre-results.

Low-Dose CT for Renal Calculi Detection Using Spectral Shaping of High Tube Voltage

PURPOSE

 To investigate reduction of radiation exposure in unenhanced CT in suspicion of renal calculi using a tin-filtered high tube voltage protocol compared to a standard low-dose protocol without spectral shaping.

MATERIALS AND METHODS

 A phantom study using 7 human renal calculi was performed to test both protocols. 120 consecutive unenhanced CT examinations performed due to suspicion of renal calculi were included in this retrospective, monocentric study. 60 examinations were included with the standard-dose protocol (SP) (100 kV/130 mAs), whereas another 60 studies were included using a low-dose protocol (LD) applying spectral shaping with tin filtration of high tube voltages (Sn150 kV/80 mAs). Image quality was assessed by two radiologists in consensus blinded to technical parameters using an equidistant Likert scale ranging from 1-5 with 5 being the highest score. Quantitative image quality was assessed using regions of interest in abdominal organs, muscles, and adipose tissue to analyze image noise and signal-to-noise ratios (SNR). Commercially available dosimetry software was used to determine and compare effective dose (ED) and size-specific dose estimates (SSDEmean).

RESULTS

 All seven renal calculi of the phantom could be detected with both protocols. There was no difference regarding calcluli size between the two protocols except for the smallest one. The smallest concretion measured 1.5 mm in LD and 1.0 mm in SP (ground truth 1.5 mm). CTDIvol was 3.36 mGy in LD (DLP: 119.3 mGycm) and 8.27 mGy in SP (DLP: 293.6 mGycm). The mean patient age in SP was 47 ± 17 years and in LD 49 ± 13 years. Ureterolithiasis was found in 33 cases in SP and 32 cases in LD. The median concretion size was 3 mm in SP and 4 mm in LD. The median ED in LD was 1.3 mSv (interquartile range (IQR) 0.3 mSv) compared to 2.3 mSv (IQR 0.9 mSv) in SP (p < 0.001). The SSDEmean of LD was also significantly lower compared to SP with 2.4 mGy (IQR 0.4 mGy) vs. 4.8 mGy (IQR 2.3 mGy) (p < 0.001). The SNR was significantly lower in LD compared to SP (p < 0.001). However, there was no significant difference between SP and LD regarding the qualitative assessment of image quality with a median of 4 (IQR 1) for both groups (p = 0.648).

CONCLUSION

Tin-filtered unenhanced abdominal CT for the detection of renal calculi using high tube voltages leads to a significant reduction of radiation exposure and yields high diagnostic image quality without a significant difference compared to the institution's standard of care low-dose protocol without tin filtration.

KEY POINTS

  · Tin-filtered CT for the detection of renal calculi significantly reduces radiation dose.. · The application of tin filtration provides comparable diagnostic image quality to that of SP protocols.. · An increase in image noise does not hamper diagnostic image quality..

CITATION FORMAT

· Gassenmaier S, Winkelmann MT, Magnus J et al. Low-Dose CT for Renal Calculi Detection Using Spectral Shaping of High Tube Voltage. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1752-0472.

Effects of medicagenic acid metabolites, originating from biotransformation of an Herniaria hirsuta extract, on calcium oxalate crystallization in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Herniaria hirsuta is traditionally used in Moroccan folk medicine for treatment of urinary stones and as a diuretic. It is rich in saponins, which are known to be deglycosylated in the colon, whereafter aglycones such as medicagenic acid are absorbed and further metabolized in the liver.

AIM OF THE STUDY

A sample of hepatic metabolites of medicagenic acid, with medicagenic acid glucuronide as the most abundant one, was evaluated for in vitro activity against urinary stones. A crystallization assay and a crystal-cell interaction assay were used to evaluate in vitro activity of hepatic metabolites of medicagenic acid on CaC₂O₄ (calciumoxalate) crystals, present in the majority of urinary stones.

MATERIALS AND METHODS

In the crystallization assay the effects on nucleation of Ca²⁺ and C₂O₄^2- and aggregation of the CaC₂O₄ crystals are studied. In the crystal-cell interaction assay crystal retention is investigated by determining the amount of Ca²⁺ bound to injured monolayers of MDCK I cells.

RESULTS

Results of the crystallization assay showed a tentative effect on crystal aggregation. The crystal-cell interaction assay showed a significant inhibition of crystal binding, which may reduce crystal retention in the urinary tract.

CONCLUSIONS

As both formation of crystals by inhibiting aggregation and retention of crystals is affected, the beneficial effect of H. hirsuta against urinary stones may at least in part be attributed to medicagenic acid metabolites, indicating that saponins containing medicagenic acid may act as prodrugs.

Association of stone surgery with patient-reported complications after spinal cord injury

AIMS

To determine if a history of urinary stone surgery in individuals with spinal cord injury (SCI) is associated with an increased incidence of SCI-related complications and lower quality of life (QOL).

METHODS

The Neurogenic Bladder Research Group (NBRG) registry is a multicenter, prospective, observational study which measures QOL after acquired SCI. Over 1.5 years, 1479 participants were enrolled and grouped according to history of stone surgery. We evaluated SCI-related complications, QOL, and associations between patient factors and prior stone surgery using multivariable regression.

RESULTS

Participants were a median of 11 years post-SCI and 189 (12.8%) reported prior bladder or kidney stone surgery; 95.8% of these occurred after the SCI. Median time between SCI and first stone was 5.6 years (IQR: 1.8-12.8). Hospitalizations were higher for those with prior stone surgery, with common reasons including UTIs, blood clots, pressure ulcers, and pneumonia (p < 0.001). During the year of observation, the incidence of stone surgery was 17% in those with a prior history of stone surgery and 2% per year in those without prior stone surgery (p < 0.001). Controlling for covariates, bladder management strategy, age, BMI, and years since SCI were associated with history of stone surgery.

CONCLUSIONS

People with SCI and a history of surgical stone disease are at high risk for episodes of recurrent stones and increased hospitalizations, particularly those with kidney stones and indwelling catheter use. Identification of high-risk patients may guide tailored surveillance for complications and stone prevention strategies.

Risk factors for subsequent stone events in pediatric nephrolithiasis: A multi-institutional analysis

INTRODUCTION

Children with nephrolithiasis have a 50% risk of recurrence 3 years following an index urinary stone event. The American Urological Association guidelines for medical management of nephrolithiasis suggest metabolic evaluations be stratified according to risk of future stone events. However, no such risk stratification exists across the pediatric population with urinary stone disease. We aim to assess the risk factors among pediatric patients for a subsequent stone event (SSE).

MATERIALS AND METHODS

A retrospective review for children <17 years of age with a diagnosis of nephrolithiasis and at least one completed follow-up at two tertiary-care children's hospitals within our state between 2012 and 2017 was performed. Children with known monogenic stone disease were excluded as well as those with follow-up less than 1 year. SSEs following initial diagnosis and treatment for nephrolithiasis were defined as follows: subsequent surgical intervention, new stone on imaging, reported stone passage, or ED evaluation for renal colic. Clinical and demographic factors were compared between patients with and without SSEs and analyzed using univariate and multivariate analyses via Cox proportional hazard models. Survival curves for significant associations for SSEs were generated and evaluated using Log-Rank and Wilcoxon comparisons.

RESULTS

A total of 200 patients with median clinical follow-up of 2.9 years were analyzed. Median age was 11.5 years (IQR: 6.0-15.5), with 109 (54.5%) males and 91 (45.5%) females, 94 (47%) of whom had a relevant comorbidity. An SSE occurred in 82 patients (41.0%). Age >12 (HR 2.21, 95%CI 1.42-3.45), reported stone event prior to enrollment encounter (i.e. personal history of nephrolithiasis) (HR 1.82, 95%CI 1.14-2.89), and family history of nephrolithiasis (HR 1.62, 95%CI 1.05-2.51) were associated with SSE on univariate analysis while age >12 (HR 2.09, 95%CI 1.33-3.27) and personal history of nephrolithiasis (HR 1.63, 1.02-2.6) retained significance on multivariable analysis. Survival analysis shows increased risk of recurrence with accumulation of risk factors (Summary Figure). Sensitivity analysis accounting for missing family history data retained significance for all three variables.

CONCLUSIONS

Adolescent age and a personal history of nephrolithiasis are independent risk factors for SSE in children. Understanding these risk factors and the nature of SSE among the pediatric population can potentially enhance counseling for further metabolic work-up and tailored clinical follow-up.

Diet-Derived Antioxidants and Risk of Kidney Stone Disease: Results From the NHANES 2007-2018 and Mendelian Randomization Study

We aimed to explore the associations between diet-derived antioxidants and kidney stone disease (KSD) risk in this study. We performed weighted multivariable-adjusted logistic regression to assess the associations between the six main diet-derived antioxidants and the risk of KSD by using data from the National Health and Nutrition Examination Survey (NHANES) 2007–2018. Then, we used the Mendelian randomization (MR) approach to verify the causal relationships between circulating antioxidants levels and KSD risk. Genetic tools were extracted from published genome-wide association studies (GWAS). Summary data for KSD was from the FinnGen study and UK biobank. Inverse variance weighted (IVW) was the primary analysis. The 26,438 participants, including 2,543 stone formers, were included for analyses. There were no significant associations between retinol, vitamin B6, vitamin C, vitamin E, and lycopene intake with the risk of KSD across all the quartile categories. Similarly, pooled odds ratio (OR) for KSD risk in genetically predicted per unit change were 1.25 (95% CI: 0.39, 4.02; p = 0.712), 1.14 (95% CI: 0.84, 1.53; p = 0.400), 0.75 (95% CI: 0.52, 1.10; p = 0.141), 1.66 (95% CI: 0.80, 3.46; p = 0.178), 1.27 (95% CI: 0.29, 5.62; p = 0.756), and 0.92 (95% CI: 0.76, 1.12; p = 0.417) for retinol, β-carotene, vitamin B6, vitamin C, α-tocopherol, and lycopene, respectively. The above estimates were replicated in the secondary analyses using UK biobank data. Our study did not support a causal association between circulating antioxidants levels and KSD risk. However, these findings should be verified in larger sample-size MR due to the pleiotropy and other limitations.

Short-Chain Fatty Acids Reduced Renal Calcium Oxalate Stones by Regulating the Expression of Intestinal Oxalate Transporter SLC26A6

Renal calcium oxalate (CaOx) stone is a common urologic disease with a high prevalence and recurrence rate. However, short-chain fatty acids (SCFAs) are less often reported in the prevention of urolithiasis. This study aimed to explore the effect of SCFAs on the renal CaOx stone formation and the underlying mechanisms. Ethylene glycol was used to induce renal CaOx crystals in rats. SCFAs (acetate, propionate, or butyrate) were added as supplements to the drinking water with or without antibiotics. Because intestinal oxalate transporters SLC26A6 and SLC26A3 regulate the excretion and absorption of oxalate in the intestine, we injected adeno-associated virus 9 (AAV9)-SLC26A6-shRNA (short hairpin RNA) and AAV9-SLC26A3 into the tail vein of rats to suppress SLC26A6 and overexpress SLC26A3 expression in the intestine, respectively, to explore the role of SLC26A3 and SLC26A6 (SLC26A3/6) in the reduction of renal CaOx crystals induced by SCFAs. Results showed that SCFAs reduced renal CaOx crystals and urinary oxalate levels but, however, increased the abundance of SCFA-producing bacteria and cecum SCFA levels. SCFA supplements still reduced renal crystals and urinary oxalate after gut microbiota depletion. Propionate and butyrate downregulated intestinal oxalate transporter SLC26A3 expression, while acetate and propionate upregulated SLC26A6 expression, both in vivo and in vitro. AAV9-SLC26A3 exerted a protective effect against renal crystals, while AAV9-SLC26A6-shRNA contributed to the renal crystal formation even though the SCFAs were supplemented. In conclusion, SCFAs could reduce urinary oxalate and renal CaOx stones through the oxalate transporter SLC26A6 in the intestine. SCFAs may be new supplements for preventing the formation of renal CaOx stones. IMPORTANCE Some studies found that the relative abundances of short-chain-fatty-acid (SCFA)-producing bacteria were lower in the gut microbiota of renal stone patients than healthy controls. Our previous study demonstrated that SCFAs could reduce the formation of renal calcium oxalate (CaOx) stones, but the mechanism is still unknown. In this study, we found that SCFAs (acetate, propionate, and butyrate) reduced the formation of renal calcium oxalate (CaOx) crystals and the level of urinary oxalate. Depleting gut microbiota increased the amount of renal crystals in model rats, and SCFA supplements reduced renal crystals and urinary oxalate after gut microbiota depletion. Intestinal oxalate transporter SLC26A6 was a direct target of SCFAs. Our findings suggested that SCFAs could reduce urinary oxalate and renal CaOx stones through the oxalate transporter SLC26A6 in the intestine. SCFAs may be new supplements for preventing the formation of renal CaOx stones.

Single-Use vs Reusable Ureteroscopes in Horseshoe Kidney Stones

Introduction: Horseshoe kidney (HSK) is one of the most frequent renal malformations which appears to present an increased risk of stone formation caused by abnormal urine drainage. This study aims to compare the results of single-use flexible ureteroscopy (SUfURS) vs reusable devices (RfURS) with holmium laser in treating stones in HSK cases. Material and method: Between February 2017 and June 2021, 29 patients diagnosed with renal stone disease and horseshoe kidney were retrospectively analyzed. Subjects were divided into two groups: Group 1 (14 patients) undergoing SUfURS and Group 2 (15 patients) operated with RfURS devices. We analyzed the mean stone burden, operation time, stone free rate and complications. The surgical equipment was represented by the SUfURS PU3022 (Zhuhai Pusen Medical Technology) and RfURS URF-V2 (Olympus). Results: The two groups had a similar mean stone burden: 22 ± 6 mm (range 15-31 mm) for Group 1 and 24 ± 7 mm (range 16-30 mm) for Group 2. The average operative time was better for Group 1 (86 ± 17 min) vs Group 2 (89 ± 20 min). The stone-free status was similar for both groups after the first session (57.14% for Group 1 vs 53.33% for Group 2) and slightly in favor of Group 1 as compared to Group 2 (85.71% vs 73.33%, respectively) after the second session. The overall complication rate (Grades I, II and III) was almost similar in both groups, with a slightly prevalence for Group 1 (no major complications Grade IV and V). Conclusion:Flexible ureteroscopy represents an effective alternative treatment technique for large stones in kidney abnormalities. single-use flexible ureteroscopy can be successfully used to treat patients with genetically renal malformations and its results may be slightly better than those provided by using RfURS devices.

Radiation risk issues in recurrent imaging

Millions of patients benefit from medical imaging every single day. However, we have entered an unprecedented era in imaging practices wherein 1 out of 125 patients can be exposed to effective dose >50 mSv from a single CT exam and 3 out of 10,000 patients undergoing CT exams could potentially receive cumulative effective doses > 100 mSv in a single day. Recurrent imaging with CT, fluoroscopically guided interventions, and hybrid imaging modalities such as positron emission tomography/computed tomography (PET/CT) is more prevalent today than ever before. Presently, we do not know the cumulative doses that patients may be receiving across all imaging modalities combined. Furthermore, patients with diseases with longer life expectancies are being exposed to high doses of radiation enabling radiation effects to manifest over a longer time period. The emphasis in the past on improving justification of imaging and optimization of technique and practice has proved useful. While that must continue, the current situation requires imaging device manufacturers to urgently develop imaging technologies that are safer for patients as high doses have been observed in patients where imaging has been justified through clinical decision-support and optimized by keeping doses below the national benchmark doses. There is a need to have a critical look at the fundamental principles of radiation protection as cumulative doses are likely to increase in the coming years.

Dual-Energy Multidetector Computed Tomography: A Highly Accurate Non-Invasive Tool for in Vivo Determination of Chemical Composition of Renal Calculi

Introduction. Computed tomography is more accurate than excretory urography in evaluation of renal stones due to its high sensitivity and temporal resolution; it permits sub-millimetric evaluation of the size and site of calculi but cannot evaluate their chemical composition. Dual-energy computed tomography allows evaluating the chemical composition of urinary calculi using simultaneous image acquisition at two different energy levels. The objective of the research was to determine renal stone composition using dual-energy multidetector computed tomography, and its correlation with post-extraction chemical analysis of stones. Materials and Methods. This prospective study was conducted in the Department of Radiodiagnosis and Imaging from September 2017 to March 2019. A total of 50 patients with urolithiasis at the age of 18-70 years were included in the study. Dual-energy computed tomography ratios of various stones were noted, and preoperative composition of calculi was given based on their colour and dual-energy computed tomography ratio. These results were compared with the post-extraction chemical analysis of stones (using Fourier infrared transform spectroscopy as the standard comparative method.) Results. The most common type of calculi in our study population was calcium oxalate stones (78%) followed by uric acid stones (12%), cystine stones (6%) and hydroxyapatite stones (4%). The dual-energy ratio of calcium oxalate, uric acid, cystine and hydroxyapatite stones ranged from 1.38-1.59, 0.94-1.08, and 1.20-1.28 and 1.52-1.57, respectively, with the mean dual-energy ratio of 1.43, 1.01, 1.25 and 1.55, respectively. Dual-energy computed tomography was found to be 100% sensitive and specific for differentiating uric acid stones from non‑uric acid stones. The sensitivity and specificity in differentiating calcium oxalate calculus from non‑calcium oxalate calculus was 97.5% and 90.9%, respectively, with 96% accuracy and kappa value of 0.883 suggesting strong agreement. Conclusions. Dual-energy computed tomography is highly sensitive and accurate in distinguishing between various types of renal calculi. It has vital role in management as uric acid calculi are amenable to drug treatment, while most of non-uric acid calculi require surgical intervention.

Impact of the adherence to medical treatment on the main urinary metabolic disorders in patients with kidney stones

Objective

To assess the effect of the adherence to medical treatment on urinary parameters in the 24-h metabolic study of patients with kidney stones.

Methods

A retrospective, longitudinal, descriptive, and observational study was carried out by reviewing the hospital electronic medical record from 2014 to 2018. The adherence to drug treatment was measured 6 months after its initiation, and the numerical values of the metabolic studies were compared. Wilcoxon tests were performed to compare the difference before and after treatment.

Results

Ninety patients were evaluated, with 73.3% of adherence. The 180-day overall adherence rate was 61.2% in patients treated with a single drug and 85.4% in patients treated with multiple drugs. There is a statistically significant increase in citrate levels in patients with good adherence in comparison with non-adherent patients (p=0.031 vs. p=0.528).

Conclusions

Medical treatment and dietary measures in patients with kidney stones have an initial impact at 6 months on the values of the main urinary metabolic alterations that predispose to calculi formation; the most significant is seen in those patients with adherence to medical treatment for hypocitraturia.

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.

Systematic Evaluation of Smartphone Applications for the Medical Management of Nephrolithiasis

Objective: The aim of this study was to comprehensively evaluate the quality of patient-oriented, mobile health applications (apps) available for medical management of kidney stone disease (KSD). Materials and Methods: A systematic search was performed to identify apps from the Apple and Google Play app stores. Eligible apps were divided into two categories: (1) fluid apps and (2) dietary apps. Descriptive characteristics were summarized and app quality was independently evaluated on the basis of technical quality, usability, clinical value, and privacy/security. The validated Mobile App Rating Scale (MARS) was the backbone for the evaluation framework. Results: In total, 31 apps (18 fluid apps and 13 dietary apps) were included. Fluid apps outscore dietary apps in all dimensions of MARS quality. All but one fluid app exceeded the minimum acceptable MARS score of 3.0 vs 46% of dietary management apps. Dietary apps feature less functionality and most are limited to noninteractive informational content. While most data-capturing apps provide a privacy policy and ensure that security measures are taken to protect user identity, only 36% offer users choice or consent for secondary use of their data after data have already been collected. Overall, only one app has undergone any form of real-world clinical investigation. Conclusions: Fluid management apps outperform dietary apps in technical quality, usability, and clinical value at the cost of greater privacy/security risks. Despite not being targeted to patients with KSD, they are higher in most quality measures and offer greater functionality to support long-term disease management compared with dietary apps.

Atlas of scoring systems, grading tools and nomograms in Endourology: A comprehensive overview from The TOWER Endourological Society research group

INTRODUCTION

With an increase in the prevalence of kidney stone disease (KSD), there has been a universal drive to develop reliable and user-friendly tools such as grading systems and predictive nomograms. An atlas of scoring systems, grading tools and nomograms in Endourology is provided in this paper.

METHODS

A comprehensive search of world literature was performed to identify nomograms, grading systems and classification tools in endourology related to KSD. Each of these were reviewed by the authors and have been evaluated in a narrative format with details on those which are externally validated and their respective citation count on google scholar.

RESULTS

A total of 54 endourological tools have been described in our atlas of endourological scoring systems, grading tools and nomograms. Of the tools, 23 (43%) are published in the last 3 years showing an increasing interest in this area. This includes 5 for percutaneous nephrolithotomy (PCNL), 6 for flexible ureteroscopy (fURS), 3 for semi-rigid URS (sURS), 9 for shockwave lithotripsy (SWL), 2 for stent encrustations, 3 for intra-operative appearance at the time of URS and 3 to classify intra-operative ureteric injury. There were 3 tools for renal colic assessment, one each for prediction of future stone event, stone classification and stone impaction and 2 for need of emergency intervention in ureteric stone. While 2 tools are related to stone recurrence, 6 are related to post-procedural complications. There are now 2 tools for simulation in endourology and 5 for patient reported outcome measures (PROMS).

CONCLUSIONS

A number of reliable and established tools exist currently in endourology. Each of these offers their own respective advantages and disadvantages. While nomograms and scoring systems can help in the decision making, these must be tailored to individual patients based on their specific clinical scenarios, expectations and informed consent.

Microbial genetic and transcriptional contributions to oxalate degradation by the gut microbiota in health and disease

Over-accumulation of oxalate in humans may lead to nephrolithiasis and nephrocalcinosis. Humans lack endogenous oxalate degradation pathways (ODP), but intestinal microbes can degrade oxalate using multiple ODPs and protect against its absorption. The exact oxalate-degrading taxa in the human microbiota and their ODP have not been described. We leverage multi-omics data (>3000 samples from >1000 subjects) to show that the human microbiota primarily uses the type II ODP, rather than type I. Furthermore, among the diverse ODP-encoding microbes, an oxalate autotroph, Oxalobacter formigenes, dominates this function transcriptionally. Patients with inflammatory bowel disease (IBD) frequently suffer from disrupted oxalate homeostasis and calcium oxalate nephrolithiasis. We show that the enteric oxalate level is elevated in IBD patients, with highest levels in Crohn's disease (CD) patients with both ileal and colonic involvement consistent with known nephrolithiasis risk. We show that the microbiota ODP expression is reduced in IBD patients, which may contribute to the disrupted oxalate homeostasis. The specific changes in ODP expression by several important taxa suggest that they play distinct roles in IBD-induced nephrolithiasis risk. Lastly, we colonize mice that are maintained in the gnotobiotic facility with O. formigenes, using either a laboratory isolate or an isolate we cultured from human stools, and observed a significant reduction in host fecal and urine oxalate levels, supporting our in silico prediction of the importance of the microbiome, particularly O. formigenes in host oxalate homeostasis.

Predictors of Repeat Surgery and Stone-related Events After Flexible Ureteroscopy for Renal Stones

OBJECTIVES

To evaluate the risk of repeat surgery and stone-related events after flexible ureteroscopy (fURS) for renal stones, and to identify their predictive factors.

PATIENTS AND METHODS

This was a single-center, retrospective cohort study of patients (n = 664) who underwent fURS for renal stones with or without concomitant ureteral stones between January 2012 and December 2019. The primary outcomes were time to ipsilateral stone-related surgical intervention and any stone-related event (including ipsilateral renal colic, symptomatic ureteral calculi, obstructive urinary tract infection, and surgical intervention).

RESULTS

During median follow-up of 31.1 months, 103 (15.5%) and 135 (20.3%) patients experienced surgical intervention and any stone-related event, respectively. The estimated 2-year intervention-free survival and stone-event-free survival was 86.9% and 81.6%, respectively. On Cox multivariate analysis, younger age (hazard ratio [HR] 0.96), history of stone surgery (HR 2.17), larger preoperative stone burden (HR 1.03), and larger residual fragment (HR 1.09) showed an association with future intervention. Use of the four identified risk factors (age ≤60, history of stone surgery, stone burden ≥20 mm, and residual fragment ≥4 mm) allowed stratification of patients based on the risk of future intervention (low [score: 0-1], intermediate [2], and high [3-4] risk). The estimated 2-year intervention-free survival rates in low-, intermediate-, and high-risk groups were 96.2%, 86.4%, and 71.3%, respectively.

CONCLUSION

Patients undergoing fURS are at risk of future ipsilateral surgical intervention and stone-related events. Our simple predictive tool can facilitate treatment decision-making by identifying patients who are at high risk of recurrence.

Factors influencing extracorporeal shock wave lithotripsy efficiency for optimal patient selection

Introduction

Current literature suggests various predictors related to the stone and patient, which could influence stone fragmentation and clearance rates.

Aim

To establish clinical characteristics of stone disease for patients undergoing extracorporeal shockwave lithotripsy (ESWL) which may predict the success of the procedure.

Material and methods

One hundred and nine patients with renal stone disease diagnosed by non-contrast computed tomography (NCCT) who underwent ESWL between January 2015 and December 2019 were included in the study. Endpoints: patient being stone free (SF) or when < 4 mm fragments were detected. Age, gender, location, skin-to-stone distance, maximum stone length, stone volume, stone surface area, mean stone Hounsfield units (HU) and highest HU score were explored in uni- and multivariate regression analysis.

Results

Stone size revealed the highest prognostic power for ESWL failure, where OR for stone volume and stone surface area were 1.06 (1.03–1.10) and 1.04 (1.02–1.06), respectively (all p < 0.01) while a tendency was observed for skin-to-stone distance 1.02 (1.00–1.03). The amount of energy applied during the procedure to one cubic millimeter of stone volume (SMLI/stone volume) was predictive for treatment success (OR = 0.60, 95% CI: 0.41–0.87, p < 0.01). Stone volume (OR = 1.06, 95% CI: 1.00–1.14, p = 0.01) and stone surface area (OR = 1.03, 95% CI: 1.01–1.06, p = 0.02) remained as statistically significant prognostic factors for treatment failure.

Conclusions

Both greater stone volume and stone surface area, as well as lower power delivered per stone volume unit during the ESWL procedure, were found to be significant factors and could be useful to predict treatment failure.

Analysis of 114 Pedigrees of Renal Stone Patients: A Retrospective Review

BACKGROUND

 Renal and ureteric stones (RS) can form due to genetic, metabolic, environmental, and diet-hydration related factors. Studies have shown that patients with family history (FH) of RS have higher likelihood of recurrence.

MATERIALS AND METHODS

 We conducted a retrospective cross-sectional study on 114 pedigrees to investigate the impact of FH on recurrence of RS and examine patterns of inheritance.  Results: Family history of renal stone disease was found in 42% of all patients. There was a significant increase of stone recurrence in RS patients with a positive FH (p=0.001). Seventy-one percent of patients with recurrent stones had at least one family member with RS. Interestingly, male penetrance was higher in RS recurrence, where a greater proportion of males had no FH of RS, indicating that there may be other factors involved as well.  Conclusion: Family history in RS patients should be continuously explored for the possible underlying genetic influence, whilst keeping in mind the dietary habits of the family.

Analysis of Primary Hyperparathyroidism Screening Among US Veterans With Kidney Stones

Importance

Approximately 3% to 5% of patients with kidney stones have primary hyperparathyroidism (PHPT), a treatable cause of recurrent stones. However, the rate of screening for PHPT in patients with kidney stones remains unknown.

Objectives

To estimate the prevalence of parathyroid hormone (PTH) testing in veterans with kidney stones and hypercalcemia and to identify the demographic, geographic, and clinical characteristics of veterans who were more or less likely to receive PTH testing.

Design, Setting, and Participants

This cohort study obtained Veterans Health Administration (VHA) health records from the Corporate Data Warehouse for veterans who received care in 1 of the 130 VHA facilities across the United States from January 1, 2008, through December 31, 2013. Historical encounters, medical codes, and laboratory data were assessed. Included patients had diagnostic or procedural codes for kidney or ureteral stones, and excluded patients were those with a previous serum PTH level measurement. Data were collected from January 1, 2006, to December 31, 2014. Data analysis was conducted from June 1, 2019, to January 31, 2020.

Exposures

Elevated serum calcium concentration measurement between 6 months before and 6 months after kidney stone diagnosis.

Main Outcomes and Measures

Proportion of patients with a serum PTH level measurement and proportion of patients with biochemical evidence of PHPT who underwent parathyroidectomy.

Results

The final cohort comprised 7561 patients with kidney stones and hypercalcemia and a mean (SD) age of 64.3 (12.3) years. Of these patients, 7139 were men (94.4%) and 5673 were white individuals (75.0%). The proportion of patients who completed a serum PTH level measurement was 24.8% (1873 of 7561). Across the 130 VHA facilities included in the study, testing rates ranged from 4% to 57%. The factors associated with PTH testing included the magnitude of calcium concentration elevation (odds ratio [OR], 1.07 per 0.1 mg/dL >10.5 mg/dL; 95% CI, 1.05-1.08) and the number of elevated serum calcium concentration measurements (OR, 1.08 per measurement >10.5 mg/dL; 95% CI, 1.06-1.10) as well as visits to both a nephrologist and a urologist (OR, 6.57; 95% CI, 5.33-8.10) or an endocrinologist (OR, 4.93; 95% CI, 4.11-5.93). Of the 717 patients with biochemical evidence of PHPT, 189 (26.4%) underwent parathyroidectomy within 2 years of a stone diagnosis.

Conclusions and Relevance

This cohort study found that only 1 in 4 patients with kidney stones and hypercalcemia were tested for PHPT in VHA facilities and that testing rates varied widely across these facilities. These findings suggest that raising clinician awareness to PHPT screening indications may improve evaluation for parathyroidectomy, increase the rates of detection and treatment of PHPT, and decrease recurrent kidney stone disease.

The Risks of Stone Diagnosis and Stone Removal Procedure After Different Bariatric Surgeries

Introduction: Nephrolithiasis is common after malabsorptive bariatric surgery; however, the comparative risk of stone formation after different bariatric surgeries remains unclear. We seek to compare the risk of stone diagnosis and stone procedure after gastric banding (GB), sleeve gastrectomy (SG), short-limb Roux-en-Y (SLRY), long-limb Roux-en-Y (LLRY), and biliopancreatic diversion with duodenal switch (BPDDS). Patients and Methods: Using an administrative database, we retrospectively identified 116,304 patients in the United States, who received bariatric surgery between 2007 and 2014, did not have a known kidney stone diagnosis before surgery, and were enrolled in the database for at least 1 year before and after their bariatric surgery. We used diagnosis and procedural codes to identify comorbidities and events of interest. Our primary analysis was performed with extended Cox proportional hazards models using time to stone diagnosis and time to stone procedure as outcomes. Results: The adjusted hazard ratio of new stone diagnosis from 1 to 36 months, compared to GB, was 4.54 for BPDDS (95% confidence interval [CI] 3.66-5.62), 2.12 for LLRY (95% CI 1.74-2.58), 2.15 for SLRY (95% CI 2.02-2.29), and 1.35 for SG (95% CI 1.25-1.46). Similar results were observed for risk of stone diagnosis from 36 to 60 months, and for risk of stone removal procedure. Male sex was associated with an overall 1.63-fold increased risk of new stone diagnosis (95% CI 1.55-1.72). Conclusions: BPDDS was associated with a greater risk of stone diagnosis and stone procedures than SLRY and LLRY, which were associated with a greater risk than restrictive procedures. Nephrolithiasis is more common after more malabsorptive bariatric surgeries, with a much greater risk observed after BPDDS and for male patients.

Medical evaluation and pharmacotherapeutical strategies in management of urolithiasis

Treatment of urolithiasis depends on several important factors which include stone location, size, composition, and patient symptoms. Although significant advancements have been made in the surgical management of urolithiasis in the last decade, pharmacotherapy which can prevent the formation of new stones and decrease the recurrence of urolithiasis has not experienced the same level of success. Currently, urolithiasis is regarded as a complicated syndrome that is determined by numerous factors, and any treatment plan for urolithiasis should be individualized while considering any potential damage arising from stone-forming factors. This review introduces the most popular methods currently used to evaluate urolithiasis and the pharmacotherapy of urolithiasis based on patient-specific factors.