Background: The reported success rates for treatments of kidney stones with either extracorporeal shock wave lithotripsy (ESWL) or ﬂexible ureterorenoscopy (URS) are conﬂicting. We aimed to compare the efﬁcacy and safety of ESWL and URS for previously untreated renal calculi. Methods: All patients treated with ESWL or URS at our tertiary care centre between 2003 and 2015 were retrospectively identiﬁed. Patients with previously untreated kidney stones and a stone diameter of 5–20 mm were included. Stone-free, freedom from reintervention and complication rates were recorded. Independent predictors of stone-free and freedom from reintervention rates were identiﬁed by multivariable logistic regression and a propensity score-matched analysis was performed. Results: A total of 1282 patients met the inclusion criteria, of whom 999 (78%) underwent ESWL and 283 (22%) had URS. During post-operative follow-up, only treatment modality and stone size could independently predict stone-free and freedom from reintervention rates. After propensity score matching, ESWL showed signiﬁcantly lower stone-free rates [ESWL (71%) versus URS (84%)] and fewer patients with freedom from reintervention [ESWL (55%) versus URS (79%)] than URS. Complications were scarce for both treatments and included Clavien Grade 3a in 0.8% versus 0% and Grade 3b in 0.5% versus 0.4% of ESWL and URS treated patients, respectively. Conclusions: Treatment success was mainly dependent on stone size and treatment modality. URS might be the better treatment option for previously untreated kidney stones 5–20 mm, with similar morbidity but higher stone-free rates and fewer reinterventions than ESWL. Key words: adverse effects, kidney calculi, lithotripsy, minimally invasive surgery, treatment outcome Received: September 22, 2017. Editorial decision: December 6, 2017 V C The Author(s) 2018. Published by Oxford University Press on behalf of ERA-EDTA. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact email@example.com Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/364/4825048 by Ed 'DeepDyve' Gillespie user on 20 June 2018 ESWL versus URS for kidney stones | 365 from reintervention was defined as no need of secondary inter- Introduction vention for residual stone(s) after primary treatment. Urolithiasis is a common disease, representing a relevant public ESWL was performed under general or regional anaesthesia health problem worldwide with a prevalence of 8.8% in the USA depending on patient’s preference. The exact stone location and annual health care costs of USD 3.8 billion [1–3]. Although was identified by X-ray and/or US at baseline and verified regu- kidney stones initially often remain asymptomatic, treatment is larly during ESWL treatment. In general, a maximum of 3000 frequently performed to prevent future problems associated with shock waves were applied to the kidney stone(s) or fewer if the disease (e.g. renal colic, urinary tract infections and impair- complete stone disintegration was observed before. In case of ment of kidney function) . Treatment for kidney stones should double J ureter stenting during ESWL, the stent normally achieve both high stone-free rates and low complication rates. remained for 4–6 weeks or longer depending on the clinical Extracorporeal shock wave lithotripsy (ESWL) and flexible ureter- course. Two different lithotripters were used during the study orenoscopy (URS) are nowadays the most commonly used treat- period: from the start of the study until September 2007, the ment options for kidney stones<20 mm. ESWL was introduced in ESWL treatments were performed on a Dornier DL50 lithotripter the 1980s  and quickly became the gold standard for the treat- (Dornier MedTech, Wessling, Germany). Subsequently, a ment of kidney stones [6, 7]. In the 1990s, URS emerged with the Dornier DLS II (Dornier MedTech) was in operation from advantages of direct visualization and extraction of kidney calculi September 2007 until the end of this study. [8–10]. Currently, the American Urological Association guideline URS was conducted under general or regional anaesthesia recommends ESWL or URS as equivalent first-line interventions depending on patient’s preference. The choice between primary for the treatment of kidney stones< 20 mm . The guidelines of and secondary URS (double J ureter stent 7–14 days before sur- the European Association of Urology (EAU) additionally distin- gery) was based on the surgeon’s preference. A flexible URS was guish between lower pole and non-lower pole kidney stones. introduced for direct vision of the collecting kidney system after They recommend both treatments as equivalent options for kid- insertion of a ureteral access sheet. Irrigation was performed ney stones of 10–20 mm, but favour URS for lower pole stones if using a roller-pump mechanical irrigation device (Uromat; Karl adverse factors (such as anatomy and stone composition) argue Storz, Culver City, CA, USA) and intrarenal pressure levels rang- against ESWL . ing from 100 to 200 mmHg, depending on the individual intrare- A recent meta-analysis including several randomized con- nal anatomy and visibility. trolled trials (RCTs) demonstrated a superior treatment success Stone fragmentation, if required, was performed using a hol- of URS over ESWL when treating lower pole kidney stones . mium: YAG laser. Calculi and fragmented stones were extracted However, evidence regarding optimal treatment of non-lower using a stone basket. At the end of the procedure, the ureteral pole kidney stones is scarce. In this study, we aimed to compare mucosa was reinspected to identify any potential damage or success and complication rates of ESWL and URS in a large perforation and all patients received a double J ureter stent for cohort of patients with previously untreated lower or non-lower 3–10 days. pole kidney stones of 5–20 mm in size. Independent predictors of stone-free and freedom from rein- tervention rates were identified by multivariable analysis using Materials and methods logistic regression including the following covariates: age, gen- der, BMI, largest stone size and number of stones. Odds ratios We retrospectively identified patients with kidney stones treated (ORs) with 95% confidence intervals (CIs) were calculated. To with ESWL or URS at our tertiary care centre between 2003 and assess whether one of the two lithotripters showed relevant dif- 2014. Treatment method was chosen according to the surgeon’s ferences in stone-free and freedom from reintervention rates, and patient’s preferences. Patients with previously untreated kid- we compared both endpoints for each lithotripter in a sensitiv- ney stones and a stone diameter of 5–20 mm were included. ity analysis. Patients with further untreated kidney stones on the contrala- We analysed a propensity score-matched sample from all teral side were included a second time if a treatment was per- included patients to limit the observational character of the formed. Patients with new onset of nephrolithiasis but with a study. For the computation of the propensity score, the following previous history of kidney stones were only included if they were variables were included into a non-parsimonious logistic regres- stone-free for at least 12 months. The study was approved by the sion with ESWL/URS as dependent variable: age, gender, BMI, local ethics committee (STV KEK-ZH 2014-0198). stone size and number of stones. Missing values were replaced Pretreatment stone size and location were generally by multiple regression imputation for the respective analysis. assessed by ultrasonography (US) and radiological examination The validity of the logistic regression was assessed using the [X-ray and or non-contrast computed tomography (CT) of the Hosmer–Lemeshow test. abdomen]. The following preoperative parameters for each Statistical analysis was performed with IBM SPSS Statistics patient were noted: age, gender, body mass index (BMI), stone (Version 21.0; IBM Corp., Armonk, New York, USA). Propensity size, number of stones and stone location (upper calyx, middle score matching was performed using R programming language calyx, lower calyx, pelvis or multiple locations). All periopera- and software environment version 3.1.3 (R Foundation for tive complications until discharge were assessed using the Statistical Computing, Vienna, Austria) using the package Clavien–Dindo grading system . Matching in R . The results for continuous normally distrib- Success rate after intervention was assessed by stone-free uted variables are expressed as means6 standard deviation and freedom from reintervention rates. As primary endpoint, we assessed stone-free rates for each treatment method during (SD) and differences in patient characteristics between two follow-up using X-ray, US or CT. Stone-free was defined as stone groups were compared using Student’s unpaired t-test. Continuous non-normally distributed variables are presented clearance during postinterventional follow-up without any residual fragments>2 mm in the kidney. Retreatment for resid- as median and interquartile ranges (IQR) and analysed using ual stones was recorded during follow-up and freedom from the Mann–Whitney U test. The results for categorical variables reintervention was chosen as secondary endpoint. Freedom are presented as percentage analysed using Fisher’s exact test Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/364/4825048 by Ed 'DeepDyve' Gillespie user on 20 June 2018 366 | C.D. Fankhauser et al. Table 1. Patient characteristics of all patients and the propensity score matched cohort All (n¼ 1282) Propensity score 2:1 matched (n¼ 735) ESWL URS P-value ESWL URS P-value Number of patients (%) 999 (78) 283 (22) 490 (67) 245 (33) Age (6SD) 49.4 (15.0) 50.9 (14.4) 0.124 50.1 (15.0) 50.7 (14.2) 0.685 Female (%) 274 (27.4) 74 (26.1) 0.669 126 (25.7) 71 (29.0) 0.346 Male (%) 725 (72.6) 209 (73.9) 364 (74.3) 174 (71.0) BMI (6SD) 26.74 (4.75) 26.56 (4.64) 0.596 26.6 (4.4) 26.7 (4.9) 0.790 Size of biggest stone, in mm (IQR) 9 (7–11) 8 (6–11) <0.001 8 (6–10) 8 (6–12) 0.988 Number of stones <0.001 0.722 1 stone 74.8% 50.7% 57.0% 57.6% 2 stones 15.1% 25.3% 26.3% 22.2% 3 stones 6.6% 13.3% 11.3% 11.1% >3stones 3.5% 10.7% 5.4% 9.1% Complications (%) <0.001 Clavien II 24 (2.4) 20 (7.1) <0.001 17 (3.5) 17 (6.9) Clavien IIIa 8 (0.8) 0 (0) 0.21 3 (0.6) 0 (0) Clavien IIIb 5 (0.5) 1 (0.4) 0.30 3 (0.6) 1 (0.4) Clavien IV 0 0 0 (0) 0 (0) Bold P-values indicate statistical signiﬁcance. Table 2. Multivariable logistic regression analysis evaluating predictors for (A) stone-free and (B) freedom from reintervention rates after pri- mary treatment for nephrolithiasis Bold P-values indicate statistical signiﬁcance. or chi-square test whenever appropriate. A P-value of<0.05 was The only independent predictors for stone-free rate as defined by multivariable regression analysis were the treatment considered significant. All statistical tests were two-sided. modality [ESWL versus URS; OR 0.421 (95% CI 0.267–0.662), P< 0.001] and the stone size [OR 0.850 (95% CI 0.840–0.920), P< 0.001] (Table 2). The same parameters were also independ- Results ent predictors for lower freedom from reintervention [choice of Of the 1282 patients included in our study, 999 (78%) underwent treatment: ESWL versus URS; OR 0.340 (95% CI 0.203–0.571), ESWL and 283 (22%) had URS for primary treatment of kidney P< 0.001; and stone size; OR 0.797 (95% CI 0.751–0.845), stones. A primary URS was conducted in 154/283 patients P< 0.001]. Our sensitivity analysis for the two different ESWL (54.4%), whereas in 129/283 cases (45.6%), a secondary URS was lithotripters revealed no significant difference in stone-free performed. Patient baseline characteristics partitioned into (4.2%, 95% CI 1.0 to 1.6, P¼ 0.16) and freedom from reinter- ESWL and URS patients as well as the propensity score- vention rates (4.3%, 95% CI 11.5 to 2.9, P¼ 0.26). A visual anal- matched populations are shown in Table 1. ysis of stone-free rate over the whole study period confirmed Patients treated with ESWL and URS showed comparable char- similar results for both lithotripters (Supplementary data, acteristics for age, BMI and gender, but significantly differed Figure S1). regarding median stone size [ESWL versus URS, 9 (IQR 7–11) versus A 2:1 propensity score matching showed an adequate level of 8(IQR 6–11),P< 0.001] and number of stones (P< 0.001) (Table 1). calibration (Hosmer–Lemeshow test: P¼ 0.322). After propensity Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/364/4825048 by Ed 'DeepDyve' Gillespie user on 20 June 2018 ESWL versus URS for kidney stones | 367 score matching, the ESWL group consisted of 490 and the URS group of 245 patients. The matching successfully eliminated the significant differences in median stone size (P¼ 0.988) and in number of stones (P¼ 0.722) (Table 1). However, the two treat- ment modalities still showed significant differences regarding stone-free [ESWL 350/490 (71%) versus URS 206/245 (84%), P< 0.001] and freedom from reintervention rates [ESWL 199/361 (55%) versus URS 133/168 (79%), versus P< 0.001] (Figure 1). In a subgroup analysis, the patients with non-lower pole stones treated with ESWL showed a significantly lower stone- free rate [ESWL 251/368 (68.2%) versus URS 131/159 (82.4%), P< 0.001] as well as a lower freedom from reintervention rate [ESWL 145/276 (52.5%) versus URS 98/127 (77.2%), P< 0.001] compared with the patients treated with URS. The subgroup analysis of lower pole stones revealed nonsignificantly lower stone-free rates after ESWL treatments [ESWL 89/111 (80.2%) versus URS 40/45 (88.9%), P¼ 0.246] but a significantly lower freedom from reintervention rate [ESWL 53/84 (61.1%) versus URS 33/36 (91.7%), P¼ 0.002] than after URS treatments. Only very few relevant perioperative complications for both treatment modalities were recorded. After ESWL, 24 (2.4%) Grade II complications including 22 urinary tract infections (UTIs), one patient with urinary retention and one patient with strong urge to void was recorded. Additionally, 13 out of 999 (1.3%) patients had a Grade IIIa or IIIb complication. Among these, 12 patients were diagnosed with painful ureteral obstruc- tions due to passing fragments and subsequently underwent transurethral stent insertion. Angiography was performed in one patient with a renal haematoma after ESWL. No active bleeding was observed and the angiography was terminated without coiling placement. In the URS group, 20 (7.1%) Grade II Fig. 1. (A) Stone-free and (B) intervention-free rates for ESWL and URS in the pro- complications including 18 UTIs and 2 atrial fibrillations were pensity score-matched cohort. observed. One patient (0.4%) needed a transurethral stent repo- sition because of stent migration (Grade IIIb complication). We did not observe any Grade 4 (life-threatening) complication for Additionally, several cohort studies proposed the superiority either intervention (Table 1). of URS; however, they showed some evident limitations due to the nature of their study design [20–27]. Most of these retrospec- tive cohort studies were small (with a mean of 162 patients) and Discussion no statistical methods to control for confounders were applied. The present study aimed to investigate and compare the treat- To the best of our knowledge, our study including over 1200 ment success of ESWL and URS in a large cohort of patients patients is the largest retrospective study comparing the suc- with untreated renal stones of 5–20 mm in size. Our study cess rates of ESWL and URS for untreated renal calculi. revealed that ESWL was less effective than URS for the treat- Moreover, it is the first non-randomized cohort study that fac- ment of kidney calculi. Treatment modality (in favour of URS) tors in known confounders such as age, sex, BMI, stone size and and stone size were the only independent predictors for stone- number of stones. free and freedom from reintervention rates. After propensity In our study, URS showed significantly better treatment suc- score matching, ESWL showed significantly lower stone-free cess, which is reflected by higher stone-free and freedom from rates and fewer patients with freedom from reintervention reintervention rate in comparison with ESWL. However, the compared with URS. higher stone-free rate after URS would be less game-changing if Our findings are consistent with, and extend those of, prior associated with distinctly higher rates of morbidity. As URS is reports. To date, the efficacy and safety of URS compared with considered as more invasive than ESWL, the assessment of ESWL has been evaluated in a few RCTs and several cohort treatment morbidity is crucial for further comparison of both studies. Recently, five RCTs and two out of three meta-analyses interventions. In our large cohort study, we found a similarly confirmed the superiority of URS in patients with lower pole low perioperative morbidity with very few relevant complica- kidney stones [8–10, 14–17]. For non-lower pole kidney stones, tions (Clavien Grade IIIa or IIIb complications) in both interven- however, only limited evidence exists. Only two RCTs included tion groups. Our data confirmed that both interventions (ESWL non-lower pole stones. The first study failed to accrue a suffi- and URS) are safe procedures, which is in line with previously cient number of patients . The second RCT included only 46 published work [8–10, 14–17, 20–27]. obese patients and showed a significantly higher stone-free rate The most common complications in our cohort were UTIs. In in the URS group (90.4% versus 68%) . The low number of our cohort, 2.2% of all patients undergoing ESWL were diagnosed patients and/or patient selection limits the validity for both with a UTI, which is comparable to other series ranging from 0.5 studies. Thus, the available RCTs are inconclusive regarding to 2.5% [28–30]. Similarly, UTIs were found in 6.4% of all URS treatment of non-lower pole stones. patients, which is comparable to previously published cohorts Downloaded from https://academic.oup.com/ckj/article-abstract/11/3/364/4825048 by Ed 'DeepDyve' Gillespie user on 20 June 2018 368 | C.D. Fankhauser et al. reporting UTI rates ranging from around 7.4 to 7.7% [31, 32]. This Acknowledgements highlights the importance of preoperative urine cultures, which We thank Prof. Dr Seifert of the Department of Biostatistics, should be performed several days ahead of the procedure. Epidemiology, Biostatistics and Prevention Institute, University Whereas for ESWL, the EAU guidelines recommend to prescribe of Zurich, Zurich, Switzerland for his statistical expertise. perioperative antibiotics only in patients with infected stones or bacteriuria, it is recommended to give perioperative antibiotics to every patient before undergoing URS . However, it remains chal- Conflict of interest statement lenging to choose the right antibiotic and to identify patients at None declared. risk for postoperative UTIs because of the poor correlation betweenvoidedurine andstone cultures . The second most common complication in the ESWL group References represented ureter obstruction caused by passing stones and the 1. Antonelli JA, Maalouf NM, Pearle MS et al. 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Clinical Kidney Journal – Oxford University Press
Published: Jan 25, 2018
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