{"Affiliation":[{"label":"Affiliation","value":"Medicine, Faculty of","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","classmap":"vivo:EducationalProcess","property":"vivo:departmentOrSchool"},"iri":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","explain":"VIVO-ISF Ontology V1.6 Property; The department or school name within institution; Not intended to be an institution name."},{"label":"Affiliation","value":"Alumni","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","classmap":"vivo:EducationalProcess","property":"vivo:departmentOrSchool"},"iri":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","explain":"VIVO-ISF Ontology V1.6 Property; The department or school name within institution; Not intended to be an institution name."},{"label":"Affiliation","value":"Non UBC","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","classmap":"vivo:EducationalProcess","property":"vivo:departmentOrSchool"},"iri":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","explain":"VIVO-ISF Ontology V1.6 Property; The department or school name within institution; Not intended to be an institution name."},{"label":"Affiliation","value":"Urologic Sciences, Department of","attrs":{"lang":"en","ns":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","classmap":"vivo:EducationalProcess","property":"vivo:departmentOrSchool"},"iri":"http:\/\/vivoweb.org\/ontology\/core#departmentOrSchool","explain":"VIVO-ISF Ontology V1.6 Property; The department or school name within institution; Not intended to be an institution name."}],"AggregatedSourceRepository":[{"label":"Aggregated Source Repository","value":"DSpace","attrs":{"lang":"en","ns":"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider","classmap":"ore:Aggregation","property":"edm:dataProvider"},"iri":"http:\/\/www.europeana.eu\/schemas\/edm\/dataProvider","explain":"A Europeana Data Model Property; The name or identifier of the organization who contributes data indirectly to an aggregation service (e.g. Europeana)"}],"Citation":[{"label":"Citation","value":"Uro 2 (1): 49-54 (2022)","attrs":{"lang":"en","ns":"https:\/\/open.library.ubc.ca\/terms#identifierCitation","classmap":"oc:PublicationDescription","property":"oc:identifierCitation"},"iri":"https:\/\/open.library.ubc.ca\/terms#identifierCitation","explain":"UBC Open Collections Metadata Components; Local Field; Indicates a bibliographic reference for the resource if it has been previously published."}],"Creator":[{"label":"Creator","value":"Wong, Victor K. F.","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/creator","classmap":"dpla:SourceResource","property":"dcterms:creator"},"iri":"http:\/\/purl.org\/dc\/terms\/creator","explain":"A Dublin Core Terms Property; An entity primarily responsible for making the resource.; Examples of a Contributor include a person, an organization, or a service."},{"label":"Creator","value":"Lundeen, Colin J.","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/creator","classmap":"dpla:SourceResource","property":"dcterms:creator"},"iri":"http:\/\/purl.org\/dc\/terms\/creator","explain":"A Dublin Core Terms Property; An entity primarily responsible for making the resource.; Examples of a Contributor include a person, an organization, or a service."},{"label":"Creator","value":"Paterson, Ryan","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/creator","classmap":"dpla:SourceResource","property":"dcterms:creator"},"iri":"http:\/\/purl.org\/dc\/terms\/creator","explain":"A Dublin Core Terms Property; An entity primarily responsible for making the resource.; Examples of a Contributor include a person, an organization, or a service."},{"label":"Creator","value":"Scotland, Kymora B.","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/creator","classmap":"dpla:SourceResource","property":"dcterms:creator"},"iri":"http:\/\/purl.org\/dc\/terms\/creator","explain":"A Dublin Core Terms Property; An entity primarily responsible for making the resource.; Examples of a Contributor include a person, an organization, or a service."},{"label":"Creator","value":"Chew, Ben","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/creator","classmap":"dpla:SourceResource","property":"dcterms:creator"},"iri":"http:\/\/purl.org\/dc\/terms\/creator","explain":"A Dublin Core Terms Property; An entity primarily responsible for making the resource.; Examples of a Contributor include a person, an organization, or a service."}],"DateAvailable":[{"label":"Date Available","value":"2022-04-14T15:22:21Z","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/issued","classmap":"edm:WebResource","property":"dcterms:issued"},"iri":"http:\/\/purl.org\/dc\/terms\/issued","explain":"A Dublin Core Terms Property; Date of formal issuance (e.g., publication) of the resource."}],"DateIssued":[{"label":"Date Issued","value":"2022-02-16","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/issued","classmap":"oc:SourceResource","property":"dcterms:issued"},"iri":"http:\/\/purl.org\/dc\/terms\/issued","explain":"A Dublin Core Terms Property; Date of formal issuance (e.g., publication) of the resource."}],"Description":[{"label":"Description","value":"A retrospective review was conducted to evaluate intraoperative and patient outcomes following simultaneous bilateral percutaneous nephrolithotomy (SB-PCNL). Target stone characteristics, operative time, hospitalization length, post-operative complications, blood loss, opioid use, pain, and stone-free rates were evaluated. In total, 42 patients with large renal stones (>20 mm\u00b2) were identified for this study, and 38% of them achieved stone-free status with no residual fragments apparent on post-operative day one CT imaging. The maximum mean residual fragment size was 3.67 mm\u00b2 and average number of residual fragments following the procedures was 1.63. The rates of blood loss, post-operative complications, opioid use, and pain from the study cohort were similar to the reported outcomes of studies conducted by others. The potential benefits of a single procedure and anesthesia to treat bilateral stone burdens, lower total pain medication prescribed, and lower hospital costs render SB-PCNL as an attractive option in the treatment of bilateral kidney stones.","attrs":{"lang":"en","ns":"http:\/\/purl.org\/dc\/terms\/description","classmap":"dpla:SourceResource","property":"dcterms:description"},"iri":"http:\/\/purl.org\/dc\/terms\/description","explain":"A Dublin Core Terms Property; An account of the resource.; Description may include but is not limited to: an abstract, a table of contents, a graphical representation, or a free-text account of the resource."}],"DigitalResourceOriginalRecord":[{"label":"Digital Resource Original Record","value":"https:\/\/circle.library.ubc.ca\/rest\/handle\/2429\/81189?expand=metadata","attrs":{"lang":"en","ns":"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO","classmap":"ore:Aggregation","property":"edm:aggregatedCHO"},"iri":"http:\/\/www.europeana.eu\/schemas\/edm\/aggregatedCHO","explain":"A Europeana Data Model Property; The identifier of the source object, e.g. the Mona Lisa itself. This could be a full linked open date URI or an internal identifier"}],"FullText":[{"label":"Full Text","value":"\u0001\u0002\u0003\u0001\u0004\u0005\u0006\u0007\b\u0001\u0001\u0002\u0003\u0004\u0005\u0006\u0007Citation: Wong, V.K.F.; Lundeen, C.J.;Paterson, R.F.; Scotland, K.B.; Chew,B.H. Safety and Efficacy ofSimultaneous Bilateral PercutaneousNephrolithotomy. Uro 2022, 2, 49\u201354.https:\/\/doi.org\/10.3390\/uro2010007Academic Editor: Tommaso CaiReceived: 17 November 2021Accepted: 7 February 2022Published: 16 February 2022Publisher\u2019s Note: MDPI stays neutralwith regard to jurisdictional claims inpublished maps and institutional affil-iations.Copyright: \u00a9 2022 by the authors.Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms andconditions of the Creative CommonsAttribution (CC BY) license (https:\/\/creativecommons.org\/licenses\/by\/4.0\/).ArticleSafety and Efficacy of Simultaneous BilateralPercutaneous NephrolithotomyVictor K. F. Wong 1, Colin J. Lundeen 1, Ryan F. Paterson 1, Kymora B. Scotland 2,* and Ben H. Chew 11 Department of Urologic Sciences, University of British Columbia, 2775 Laurel Street,Vancouver, BC V5Z 1M9, Canada; kfvwong@alumni.ubc.ca (V.K.F.W.); colin.lundeen@ubc.ca (C.J.L.);paterson@mail.ubc.ca (R.F.P.); ben.chew@ubc.ca (B.H.C.)2 Department of Urology, University of California, 200 Medical Plaza Driveway #140,Los Angeles, CA 90095, USA* Correspondence: kscotland@mednet.ucla.edu; Tel.: +1-310-825-5603Abstract: A retrospective review was conducted to evaluate intraoperative and patient outcomesfollowing simultaneous bilateral percutaneous nephrolithotomy (SB-PCNL). Target stone character-istics, operative time, hospitalization length, post-operative complications, blood loss, opioid use,pain, and stone-free rates were evaluated. In total, 42 patients with large renal stones (>20 mm2)were identified for this study, and 38% of them achieved stone-free status with no residual fragmentsapparent on post-operative day one CT imaging. The maximum mean residual fragment size was3.67 mm2 and average number of residual fragments following the procedures was 1.63. The rates ofblood loss, post-operative complications, opioid use, and pain from the study cohort were similar tothe reported outcomes of studies conducted by others. The potential benefits of a single procedureand anesthesia to treat bilateral stone burdens, lower total pain medication prescribed, and lowerhospital costs render SB-PCNL as an attractive option in the treatment of bilateral kidney stones.Keywords: bilateral calculi; PCNL; percutaneous nephrolithotomy; renal stones; urolithiasis1. IntroductionUrolithiasis poses a significant healthcare burden amongst the working-age popula-tion, with prevalence and incidence rates increasing globally. In the United States alone,the prevalence has increased from approximately 3% in the 1980s to 10% in the 2010s [1].Approximately 7% of women and 13% of men will develop a kidney stone during theirlifetime [2]. Although not all kidney stone episodes require treatment, surgical interventionis warranted if stones are symptomatic, associated with obstruction or infection, or pose athreat to renal function [3]. When the total stone burden for a urolithiasis patient exceeds20 mm2 on cross sectional imaging, percutaneous nephrolithotomy (PCNL) is the gold-standard surgical intervention recommended by the American Urological Association [4].This procedure has demonstrated the highest stone-free rate for larger stones when com-pared to other endourological modalities [3]. Despite this, PCNL accounts for only 5% of allstone-related procedures. This is in large part due its invasive nature, higher complicationrates, and more technical demands compared to ureteroscopy or extracorporeal shockwavelithotripsy [5,6]. For patients requiring bilateral PCNL procedures, complications are aneven greater concern [7].Traditionally, large bilateral renal stones were treated with unilateral PCNL (U-PCNL)procedures performed in a staged fashion (one kidney per surgery visit). This was thoughtto reduce morbidity, renal injury, infection, and a prolonged anesthetic time associatedwith simultaneous bilateral PCNL (SB-PCNL), where both kidneys are operated on in thesame surgery under the same general anesthetic [8]. However, with advances in anesthesia,antibiotic therapies, and surgical techniques, SB-PCNL may now be a safe and feasibleoption in treating patients with a large, bilateral stone burden. Furthermore, SB-PCNL hasUro 2022, 2, 49\u201354. https:\/\/doi.org\/10.3390\/uro2010007 https:\/\/www.mdpi.com\/journal\/uroUro 2022, 2 50the potential to reduce overall hospitalization, limit exposure to repeat anesthetic, obviatethe need for re-operation, and shorten a patient\u2019s return-to-work interval. [9\u201311]. Despitethese potential benefits of SB-PCNL, there have been concerns amongst urologists aboutthe potential for acute renal failure, increased blood loss, prolonged operative times, andpostoperative respiratory distress. As a result, SB-PCNL has not been widely adopted [11].At our high-volume tertiary hospital, most patients requiring bilateral PCNL undergoSB-PCNL in one surgical session rather than coming back for two surgeries (one for eachkidney). In this retrospective cohort study, we aimed to investigate the safety and efficacyof SB-PCNL.2. Materials and MethodsThis study was approved by the University of British Columbia Clinical ResearchEthics Board (UBC CREB) (Approval Number: H14-00475). Electronic Medical Recordsat Vancouver General Hospital were queried for patients who underwent PCNL proce-dures between 2010 and2015. Demographic, stone characteristics, intraoperative andpost-operative data were recorded. CT scans were analyzed using Philips IntelliSpacePACS 4.4.541 (Koninklijke Philips, Amsterdam, The Netherlands) to confirm stone locationand to determine stone characteristics.All procedures were performed by two fellowship-trained endourologists with asurgical load of >100 PCNL procedures per year. All patients underwent general anesthesiaand were placed in the prone position and fluoroscopy-guided renal access was achievedbilaterally using 30F access sheaths prior to stone manipulation. Standard PCNL wasperformed synchronically. Stone fragmentation was then undertaken for one kidney, andupon completion, the other kidney was then addressed. Renal stone fragmentation andevacuation were achieved using the Shockpulse-SE dual action lithotripter (OlympusMedical Systems, Center Valley, PA, USA) and holmium:YAG laser lithotripsy (Odysseylaser, Cook, Spencer, IN, USA). Five French Nephrostomy tubes were placed at the end ofeach procedure. Stone clearance was confirmed using flexible nephroscopy and fluoroscopy.A low-dose, non-contrast CT-KUB was performed on post-operative day one to assess forthe presence of residual fragments or adjacent organ injury. This is routinely performed atour institution after PCNL. The stone-free rate was defined as the absence of stone. Thestone-free rate and residual fragment size were assessed for both kidneys. Statistical dataanalysis was conducted using RStudio Software Version 1.2.5001.3. Results3.1. Patient and Stone CharacteristicsA total of 42 SB-PCNL patients who presented with large renal stones (>20 mm2)treated with PCNL were identified for this study. Patient demographics and pre-operativestone characteristics are summarized in Table 1. The mean age and BMI of patients includedin this study were 57.7 years of age and 30.2, respectively. The stone surface areas of eachindividual kidney (right and left) of SB-PCNL subjects were 767 mm2 for the right kidneyand 501 mm2 left kidney (Table 1). The total stone surface area treated with SB-PCNL was1280 \u00b1 1120 mm2. Within our cohort, the largest stone of the patient was most commonlyfound in the renal pelvis.3.2. Operative Time and HospitalizationThe operative time in this study was defined by the time from the initiation to thecessation of anesthesia. The mean operative time was found to be 250\u00b1 47.0 min. Establish-ing the day of the PCNL operation as day one of hospitalization, patients who underwentSB-PCNL were hospitalized for a mean duration of 3.60 \u00b1 2.11 days (Table 2).Uro 2022, 2 51Table 1. Patient demographic and target stone size.Simultaneous Bilateral PCNLPatients, n 42Sex, M\/F 25\/17Age, Mean (SD) 57.7 (12.7)Mean BMI (SD), n 30.2 (7.55)Number of Stones, Mean (SD) 3.10 (3.81)Stone Surface Area per Kidney (mm2), Mean(SD)Right Kidney = 767 (991)Left Kidney = 501 (516)Total Stone Surface Area Treated with PCNL(mm2), Mean (SD) 1280 (1120)Table 2. Intraoperative data.Simultaneous Bilateral PCNLMean operative time, minutes (SD) 250 (47.0)Mean length of hospitalization, days (SD) 3.60 (2.11)Patients Re-admitted, n (%) 4 (9.52)Patients admitted into ICU, n (%) 3 (7.14)Patients requiring a blood transfusion, n (%) 5 (11.9)Mean hemoglobin changes following PCNL, g\/L 22.69 (16.9)Patients with post-operative complications, n (%) 10 (23.8)Patients with Clavien\u2013Dindo Grade 1, n 5 (11.9)Patients with Clavien\u2013Dindo Grade 2, n 5 (11.9)3.3. Complications Post-PCNLPost-operative complications were classified according to the Modified Clavien Classi-fication System [12]. Overall, no Modified Clavien Classification grade 4\u20135 complicationswere observed within the study cohort. A total of three patients were admitted into theICU, and four were re-admitted into the hospital post-procedure. Intraoperative blood lossas calculated by the post-operative change in hemoglobin levels was 22.69 g\/L (Table 2). Atotal of five patients required a blood transfusion related to their SB-PCNL procedure.3.4. Residual Fragments and Stone-Free RatesStone-free status was defined as the absence of any residual fragments visualized oncomputerized tomography (CT) imaging post-operative day one. The stone-free rate was38% (Table 3). The maximum residual fragment size was 3.67 \u00b1 1.95 mm2. The averagenumber of residual fragments following the procedures was 1.63 \u00b1 0.49 stones.Table 3. Residual fragments post-PCNL.Simultaneous Bilateral PCNLPatients with residual fragments following PCNL, n (% SFR 1) 26 (38% SFR 1)Mean number of residual fragments following PCNL, n (SD) 1.63 (0.49)Mean maximal Size of residual fragments, n (SD) 3.67 (1.95)1 Stone-free Rate (SFR).3.5. Opioid UseInpatient narcotic use was recorded from the post-anesthesia care unit records andin-hospital medication administration records (Table 4). Intraoperative, in-ward, and totalnarcotic use was measured in total morphine equivalent dose (MED). The total mean MEDUro 2022, 2 52dose for the duration of hospitalization for patients included in this study was 80.9, with23.8 per day. Post-operative pain was assessed with a standard numerical analogue scaleranging from 0 to 10. The maximum reported mean pain score was 5.33 \u00b1 2.73.Table 4. Opioid-use and pain data.Simultaneous Bilateral PCNLMean anesthesia morphine equivalent dose, MED 1 (SD) 18.5 (22.0)Mean in-ward morphine equivalent dose, MED 1 (SD) 63.0 (79.0)Total morphine equivalent dose for duration ofhospitalization, MED 1 (SD) 80.9 (89.3)MED 1 per day of stay, MED 1 (SD) 23.8 (24.3)Mean highest pain score at rest, pain score (SD) 5.33 (2.73)1 Morphine Equivalent Dose (MED).4. DiscussionBilateral PCNL is typically performed in a staged manner, dictated by the preference ofthe performing urologist along with patient and stone characteristics. Previous studies haveindicated that SB-PCNL is a safe and effective method for the treatment of bilateral kidneystones in a variety of patients without increased morbidity [8,10,11,13]. With improvementsin anesthetic methods and techniques, longer procedures are safer and more feasible thanin the past. This potentially circumvents the need to undergo staged procedures, allowingfor a decreased overall hospital length of stay, rapid resumption of daily activities for apatient\u2019s post-procedure, and an increased total number of patients receiving treatmentsince two procedures would not be required [14].In this study, patients who underwent SB-PCNL had shorter operative times (in total)and length of hospitalization when compared to patients who underwent staged bilateralPCNL procedures from studies conducted by others [11]. Other centers have comparedstaged U-PCNLs (two separate U-PCNLs to treat bilateral stone burden) to SB-PCNL andresults suggest that SB-PCNL results in shorter total operative times and hospital stay [11].While not seen directly in this study, we would expect these results to be similar in ourinstitution. Consequently, total hospital costs (e.g., surgeon, anesthesia, nursing time) mayalso be a significant factor in the justification for SB-PCNL.Stone-free rate in our study was defined as the absence of any residual fragmentsvisualized on post-operative CT imaging. With the stone-free rate of 38% for SB-PCNL, ourrates are comparable to those achieved by other studies comparing SB-PCNL to U-PCNLor staged bilateral PCNL. Other urologists who performed SB-PCNL were able to achievesimilar stone-free rates compared to staged bilateral PCNL [8\u201311]. Additionally, 78.6%of SB-PCNL residual fragments were 4 mm or smaller in size in our study. In regard toadmissions post-procedure, there were no significant difference in readmission rates orcomplications compared to rates from other studies [8\u201311]. Taken together, our data suggestthat SB-PCNL patients are not adversely affected by the lower stone free-rates; however,we did not look at long term re-operation rates. The Canadian Urological Associationguidelines for the management of ureteral calculi suggest that 95% of ureteral stones 2 to4 mm in size will pass spontaneously [15]. Moreover, in a study on residual fragments post-PCNL by Emmott et al., only 16.5% of patients with residual fragments >4 mm requiredre-intervention [16]. Thus, we contend that SB-PCNL for bilateral stone patients can bewarranted due to its potential benefits compared to staged U-PCNL despite the lowerstone-free rates in our study.One of the main concerns regarding the indication for SB-PCNL is the potential risk ofincreased complications. Kadlec and colleagues found that SB-PCNL resulted in a higheroverall complication rate than unilateral PCNL using the Modified Clavien System forclassification [17]. However, in our study, the total number of complications as well asUro 2022, 2 53the stratification of complications into the Modified Clavien Classification System didnot show a high rate of complications with only a total of 10 patients (23.8%) havingcomplications (five in Grade 1 and five in Grade 2 of the Clavien\u2013Dindo Classification).Furthermore, blood loss during SB-PCNL and the percentage of patients requiring bloodtransfusions during the procedure were quite low, at 11.9% (Table 2). It should be notedthat hemoglobin changes may result from blood loss and may also be dilutional [18].Nephrostomy tubes were placed at the end of SB-PCNL procedures without obviousadverse effects on patient outcomes.Beyond complications, opioid use in the post-operative setting is a major concern. Theprescription of opioids during hospitalization has been routine within the hospital settingfor post-operative pain management. Clinical opioid-use data from the United Stateshave suggested that there has been an increase in opioid prescriptions for minor invasivesurgeries in recent years [19]. The prescription of opioids in these circumstances increasesthe risk of patients using opioids chronically as well as the development of opioid-usedisorders [20,21]. As such, due to the necessity for only one procedure, opioid use maypotentially decrease overall in patients who undergo SB-PCNL. It can be deduced thatwhen U-PCNL is conducted in a staged manner for the treatment of bilateral stones, thetotal MED prescribed to patients for pain management would increase.Our study has several limitations. First, due to a lack of staged U-PCNL procedures atour hospital, we could not compare SB-PCNL to staged unilateral PCNL. Ideally, SB-PCNLwould be compared directly to staged U-PCNL. Second, we did not assess the long-termre-operation rates of the SB-PCNL patients to see the impact of an increase in residualfragments. Lastly, this study is retrospective in nature and, as such, the results may beinfluenced by unintentional biases.5. ConclusionsDespite these limitations, our study suggests that simultaneous bilateral PCNL (SB-PCNL) is safe and efficacious for patients requiring surgical management of large bilateralstones. Opioid use, pain, blood loss, overall complications, and re-admission rates werecomparable to unilateral PCNL (U-PCNL) or staged bilateral PCNL reported by otherstudies. However, SB-PCNL may lead to more residual fragments. Further prospectivestudies comparing staged U-PCNL versus SB-PCNL are required to determine the optimaltreatment timing for patients with substantial bilateral stone burden. From the resultsobtained in this study, future work from our center will compare these two modes oftreatment in a prospective fashion to determine the optimal treatment timing for patientswith substantial bilateral stone burden to improve patient outcomes.Author Contributions: Conceptualization, V.K.F.W. and B.H.C.; methodology, V.K.F.W., C.J.L., K.B.S.and B.H.C.; validation, K.B.S., R.F.P. and B.H.C.; formal analysis, V.K.F.W.; data curation, V.K.F.W.and C.J.L.; writing\u2014original draft preparation, V.K.F.W. and C.J.L.; writing\u2014review and editing,K.B.S., B.H.C. and R.F.P.; supervision, K.B.S., R.F.P. and B.H.C. All authors have read and agreed tothe published version of the manuscript.Funding: This research received no external funding.Institutional Review Board Statement: The study was conducted according to the guidelines of theDeclaration of Helsinki and approved by the Institutional Review Board (or Ethics Committee) of theUniversity of British Columbia (protocol code H14-00475, 4 January 2015).Informed Consent Statement: Patient consent was waived due to the de-identified retrospectivenature of this study.Data Availability Statement: No application.Conflicts of Interest: The authors declare no conflict of interest.Uro 2022, 2 54References1. Scales, C.D., Jr.; Smith, A.C.; Hanley, J.M.; Saigal, C.S.; Urologic Diseases in America Project. Prevalence of Kidney Stones in theUnited States. Eur. Urol. 2012, 62, 160\u2013165. [CrossRef] [PubMed]2. L\u00f3pez, M.; Hoppe, B. History, epidemiology and regional diversities of urolithiasis. Pediatr. Nephrol. 2010, 25, 49\u201359. 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