Anatomical Influences In The Treatment Of Lower Calyceal Calculi With FURL:a Prospective Observational Study Based On 3D Reconstruction

BackgroundUrolithiasis is one of the diseases with high incidence of urinary system.Research shows that the overall incidence of urolithiasis in China is 7.54%,and the trend is increasing year by year.At present,treatments for kidney stones include medical expulsive therapy,extracorporeal shock wave lithotripsy(ESWL),percutaneous nephrolithotomy(PNL),retrograde intrarenal surgery(RIRS),laparoscopic surgery,etc.Due to the improvement of endovascular surgical techniques and surgical instruments,RIRS has gradually become an effective treatment for renal calculi.Compared with ESWL and PNL,RIRS had a higher stone free rate(SFR)than ESWL and a lower complication rate than PNL.In fact,the European Urological Guidelines have recommended RIRS as a first-line treatment for kidney stones since 2012.However,the current research on RIRS in the treatment of kidney stones is inadequate in many aspects.First of all,the SFR of a single operation of RIRS reported at home and abroad is 33%-100%,which is quite different,and the conclusions on the influencing factors of SFR after RIRS,including stone location,are inconsistent.Secondly,some scholars believe that the anatomical structure of the lower renal calyces is an independent risk factor for SFR,but the research are retrospective and conclusions are not completely consistent so far.More importantly,all of the research were based on retrograde pyelography(RGP),intravenous urography(IVU)and other two-dimensional images,it is not clear whether there is any difference between them with the real threedimensional calyx structure,and the accuracy of the research results is questioned.Finally,the study continues to use the anatomical parameters established when exploring the influence of anatomical structure on stone removal after ESWL,while the active stone removal of RIRS is essentially different from the passive stone removal of ESWL,and the existing research parameters cannot fully reflect the anatomical characteristics that affect RIRS.ObjectivesTo investigate whether the location of the stone affects the SFR of renal calculi treated by flexible ureteroscopic lithotripsy(FURL)through a retrospective clinical study.Further to investigate whether the anatomical structure of the inferior calyx affects the treatment of lower pole renal calculi by FURL through a prospective observational clinical study based on three-dimensional imaging.MethodsPart 1The clinical data of FURL in the treatment of nephrolithiasis in our center were retrospectively analyzed to explore the influencing factors that affect the SFR of the process.Mainly include: 1.Preoperative data: gender,age,Body Mass Index(BMI),underlying diseases,stone affected side and previous stone surgery history,preoperative indwelling double J tube,and stone characteristics(size,number,location and density);2.Intraoperative data: operation time,whether there is a stone basket for stone extraction;3.Postoperative data: postoperative hospital stay,Clavien-Dindo complication grade,and calculus removal(calculus removal was defined as no residual calculus of any size on KUB 3 months after surgery).Part 21.The caliceal structural differences of the same kidney between 2D and 3D images were compared and analyzed.The measured parameters included: infundibulum-pelvic angle(IPA)(IPA1,Elbahnasy’s method;IPA2,Sampaio’s method),stone pelvis angle(SPA),caliceal pelvis angle(CPA),infundibular width(IW),Infundibular length(IL),caliceal pelvic height(CPH)(2D)/ caliceal pelvis radius(CR)(3D),and maximum cumulative stone diameter;And based on the 3D reconstruction model of renal calyx,the effect of anatomical factors on the outcomes of FURL in the treatment of inferior calyx calculi was prospectively analyzed.2.The first endpoint of the study was whether the lithotripsy was successful during the operation,that is,whether the flexible ureteroscope could successfully enter the renal calyx where the stones were located or the stone basket can assist in the displacement and clearing of the stones;the second endpoint of the study was whether the stones were cleared 3 months after the operation,that is,whether any size stones remained on the KUB.ResultsPart 1A retrospective analysis was performed on 380 cases of renal calculi treated by FURL from January 2017 to June 2019 in our center,including 297 cases(78.2%)of lower calyx calculi or multiple parts containing lower calyx calculi,177 cases(46.6%)of double J tube indwelling before surgery,218 cases(57.4%)of multiple calculi,177 cases(46.6%)of stones larger than 20 mm,and 263 cases(69.2%)of stones were removed with a stone basket during the operation.The overall postoperative SFR was 71.8%.Univariate analysis showed statistical differences in the following variables: stone affected side(P=0.013),cumulative maximum diameter of stones(P=0.000),stone density(P=0.001),stone location(P=0.004),number of stones(P=0.000),stone size(P=0.000),intraoperative stone basketing(P=0.001),and the operation time(P=0.001),multivariate logistic regression analysis of the above P <0.01 variables showed that the following variables were statistically significant: stone location(P=0.004),stone size(P=0.001),and intraoperative stone basketing(P=0.001).Part 2A prospective analysis of 206 cases of renal inferior calyceal calculi treated by FURL from July 2019 to December 2021 was conducted in our center.Paired analysis of parameters measured by enhanced CTU and 3D reconstruction model of the same inferior calyx showed that there were statistically significant differences in IPA,SPA,CPA,IW,CPH/ CR and cumulative maximum diameter of calculi(P < 0.01),while there were no statistically significant differences in IL(P > 0.05).14 cases of intraoperative lithotripsy failed,and the success rate of intraoperative lithotripsy was 93.2%(192/206).Univariate analysis showed that IPA2,SPA,CPA obtained by CTU measurement and CPA obtained by 3D measurement were statistically significant(P < 0.05),the cut-off values are 15.3°,66.0°,40.4° and 57.8°,respectively.6 cases lost follow-up after operation,and the postoperative SFR was 78.5%(146/186).Univariate analysis showed that the cumulative maximum diameter of CTU calculi(P=0.000),cumulative maximum diameter of 3D calculi(P=0.001),calculi volume(P=0.000),volume ratio of stone to calyx(P=0.025),and calculi density(P=0.045)were statistically significance.The above variables were classified into multivariate logistic regression analysis,and the results showed that the following variables were statistically significant: CTU cumulative maximum stone diameter(P=0.001),and three-dimensional cumulative maximum stone diameter(P=0.014).ConclusionsThis study showed that the location and size of the stone and whether the stone basket was used during the operation were independent risk factors affecting the SFR of FURL in the treatment of renal stones.Three-dimensional reconstruction technology is beneficial to correctly understand the anatomy of the renal calyx.FURL has a high success rate of lithotripsy in the treatment of inferior calyceal calculi.Small pelvic calyceal angle(CPA<57.8°)and the location of the stone in the secondary calyx may adversely affect intraoperative lithotripsy.Although the cumulative maximum diameter of calculi is inaccurate in evaluating the size of renal calculi,it is an independent risk factor affecting the SFR of inferior calyx calculi treated by FURL,and can be used as a clinical reference.IPA<30° and other anatomical parameters of the study have not been found to affect the excretion of inferior calyx calculi treated with FURL.