Urolithiasis DOI 10.1007/s00240-014-0641-8

Original Paper

Factors influencing the failure of extracorporeal shock wave lithotripsy with Piezolith 3000 in the management of solitary ureteral stone Insang Hwang · Seung‑Il Jung · Kwang Ho Kim · Eu Chang Hwang · Ho Song Yu · Sun‑Ouck Kim · Taek Won Kang · Dong Deuk Kwon · Kwangsung Park 

Received: 27 June 2013 / Accepted: 22 January 2014 © Springer-Verlag Berlin Heidelberg 2014

Abstract  Studies of predictive factors of extracorporeal shockwave lithotripsy (ESWL) failure in patients with ureteral stones have not yielded results sufficient to prevent ESWL failure. The present study investigated patients with ureteral stone and analyzed the predictive factors of ESWL failure. Ninety patients with ureteral stone treated from January 2006 to June 2012 using ESWL for ureteral stone were enrolled. Patient’s demographic data including age, gender, body mass index (BMI), symptoms and calculous characteristics including location, size, episode and the grade of hydronephrosis were recorded. Statistical results were performed using univariate and multivariate analyses for the predictive factors of ESWL failure. In univariate analysis, calculous location, size, and grade of hydronephrosis between two groups displayed significant differences (p 25 kg/m2 [Odds ratio (OR) = 3.5, 95 % confidence interval (CI) 1.1–11.0], calculous size ≥1 cm (OR  = 10.5, 95 % CI 3.0–36.2), calculous location (midureter; OR = 8.49, 95 % CI 1.5–45.7) and severe grade of hydronephrosis (OR = 12.3, 95 % CI 1.9–79.5). In conclusions, ESWL failure can be predicted in cases of obesity, calculous size exceeding 1 cm, mid-ureteral stone and severe hydronephrosis. When we consider calculous management in patients with these risk factors, initial surgical approach is recommended instead of ESWL. Electronic supplementary material  The online version of this article (doi:10.1007/s00240-014-0641-8) contains supplementary material, which is available to authorized users. I. Hwang · S.-I. Jung (*) · K. H. Kim · E. C. Hwang · H. S. Yu · S.-O. Kim · T. W. Kang · D. D. Kwon · K. Park  Department of Urology, Chonnam National University, 42, Jebongno, Gwangju, Donggu 501‑757, Republic of Korea e-mail: [email protected]

Keywords Lithotripsy · Ureterolithiasis · ESWL · Ureteroscopy

Introduction Extracorporeal shockwave lithotripsy (ESWL) has been successful for ureteral stones over the last decade [1, 2]. The success rate of ESWL treatment is influenced by stone size, location, composition, degree of obstruction, symptom and number of episodes [3–6]. However, it is not certain which factors influence the outcome of ESWL. The prediction of ESWL failure is important to reduce unsuccessful repetitive treatment, hospital costs, and psychological burden on patients with ureteral stone. So, it is necessary to obtain pretreatment predictive factors to ensure optimal patient selection and appropriate clinical decision-making. Some patients had a ureteral obstruction with hydronephrosis. Especially, ureteral obstruction not only decreases renal function but also decreases ureteral peristalsis and pressure, which affects stone migration [7]. Some authors have reported that stone-induced urinary obstruction reduced the success rate of ESWL in treating ureteral stones [4, 8], but others did not [9, 10]. Thus, we focused whether the degree of stone-induced hydronephrosis affects the treatment outcome of ESWL. In the present series, we investigated predictive factors of these ESWL failure compared with cases of ESWL success.

Patients and methods This retrospective observation study was carried out in accordance with the principles of the Declaration of Helsinki.



Patients A total of 90 patients underwent ESWL for single ureteral stone from January 2006 to July 2012. We included patients who had stone size >3 mm, solitary stones and no evidence of urinary tract infection or acute renal failure. We excluded children, pregnancy, urosepsis, ureteral stricture, uncorrected coagulopathy and anticoagulated cases, and multiple stones on the ipsilateral side. Patients were subdivided into two groups. Group A consisted of patients who underwent additional ureterorenoscopic stone removal (URS) treatment after ESWL failure, and Group B consisted of patients who underwent successful ESWL treatment only. Definitions ESWL treatment was considered failure if the patient had stone >3 mm after the first session of ESWL. Treatment outcome was evaluated by plain radiograph of kidney, ureters and bladder (KUB) film and kidney bladder ultrasonography (KBUS) 1–2 weeks after ESWL session. The degree of obstruction was classified as none, mild, moderate, or severe according to the findings on ultrasonography or abdomen CT scan. The cases without calyceal or pelvic dilation were classified as none hydronephrosis, pelvic dilation only were classified mild hydronephrosis, and cases accompanied by mild calyx dilation were classified as moderate hydronephrosis, by severe calyx dilation and those with calyx dilation accompanied by renal parenchyma atrophy as severe hydronephrosis. ESWL treatment The Piezolith 3000, a third-generation electrohydraulic shockwave lithotripter with ultrasonic and fluoroscopic stone localization, was used. The depth of penetration of this lithotripter can be adjusted continuously from 0 to 165 mm. All radiopaque stones in the upper, mid, and lower ureter segments were localized by fluoroscopy with patients in the supine or a 30° oblique position, while distal ureteral stone were localized ultrasonographically with the patient in the supine position and with a full bladder. Radiolucent stones were localized by ultrasonography. A maximum of 3,000 shockwaves were delivered to a maximal power of 89– 102 MPa and energy of 0.91–1.08 mJ/mm2 at 120 shocks/ min during one session. The ESWL treatment was performed or supervised by same urologist (S. I. J) in all patients. Statistical analysis SPSS version 19.0 (SPSS, Chicago, IL) was used for statistical analysis. We compared the clinical characteristics


between the two groups. The categorical variables were analyzed by Fisher-exact test (two-tailed). Univariate and multivariate analyses using a logistic regression (stepwise forward procedure) generated an adjusted odds ratio (OR), representing the effect on ESWL failure. Statistical significance was set at p 61.5 years 22 (48.9) Sex (%)  Male 25 (54.3)  Female 25 (56.8) BMI (%) 25 (47.2)  ≤25 kg/m2 25 (67.6)  >25 kg/m2 Symptom (%)  Pain 30 (52.6)  Hematuria 9 (69.2)  Incidental 6 (66.7)  Others 5 (45.5) Location (%)  Upper ureter 21 (44.7)  Mid-ureter 14 (82.4)  Lower ureter 15 (57.7) Size (%)  61.5 Sex (female) BMI >25 kg/m2 Symptom  Pain  Hematuria  Incidental Locationa  Mid-ureter  Lower ureter Size  ≥1 cm Episode  Recurred Hydronephrosisb  Mild  Moderate

0.5 1.1 2.3

0.2–1.3 0.4–2.5 0.9–5.5

0.581 0.814 0.058

1.3 2.7 2.4

0.3–4.8 0.5–14.0 0.3–14.8

0.663 0.244 0.347

5.7 1.6

1.4–22.8 0.6–4.4

0.012 0.289







2.0 4.0

0.6–6.6 0.8–18.8

0.207 0.08




 Severe a

  Upper ureter as reference


 None as reference

patient’s median age was 61.5 years (range 26–82 years). The Group A had more mid-ureter stones, significantly larger stones (p  = 0.001) and higher degree of hydronephrosis than the Group B (p = 0.024). No statistically significant differences were found between two groups with respect to age, sex, body mass index (BMI), symptom and episode. In univariate analysis, calculous location, size, and grade of hydronephrosis between both groups were significantly

Table 3  Multivariate analysis of influencing factors on the ESWL failure Variables

Adjusted odds ratio

95 % confidence intervals

p value

3.5 Size (≥1 cm) 10.5 Locationa Mid-ureter 8.49 Lower ureter 2.09 Hydronephrosisb Mild 2.5 Moderate 3.3

1.1–11.0 3.0–36.2

0.6–9.8 0.5–22.8

0.027 0.001 0.040 0.013 0.241 0.066 0.189 0.211




BMI >25 kg/m2



  Upper ureter as reference


 None as reference

1.5–45.7 0.6–7.2

different (p 25 kg/ m2 (OR = 3.5, 95 % CI 1.1–11.0), calculous size ≥1 cm (OR = 10.5, 95 % CI 3.0–36.2), mid-ureter calculous location (OR = 8.49, 95 % CI 1.5–45.7), and severe grade of hydronephrosis (OR = 12.3, 95 % CI 1.9–79.5) (Table 3). Age, sex, symptoms, and episode did not influence the treatment outcome.

Discussion ESWL has been considered the first-line therapy for ureteral stones. However, there is a great variation in treatment outcome between lithotripters. Furthermore, the optimal management of pelvic ureteral stones remains controversial despite the results of several studies [10–13]. For optimal treatment, it would be useful to have pre-ESWL prognostic data and it is important to identify the patients who are the most at risk of failure to direct them to alternative treatment modalities. The results of our univariate analysis agree with those of several other studies reporting an association of unsuccessful outcome with stone size, location and presence of obstruction, and absence of association between age, sex, symptoms, and episode history [14–16]. Multivariate analysis revealed that BMI, stone size, location of calculi, and obstruction (severe hydronephrosis) were the significant independent predictors of failure in ESWL. In univariate analysis, we showed the presence of obesity reached borderline significance. However, in multivariate analysis, the obesity increased the risk of ESWL failure 3.5-fold (p = 0.027). Studies have emphasized that skin-tostone distance and shockwave absorption by tissues along their pathway may influence failure [4, 5, 17]. Concerning stone size, it has been reported that patients with stones ≥1 cm in their largest dimension fail more frequently and have more risk of ESWL failure [3, 6, 18]. Recent studies have shown that stone size is an independent predictor of the stone clearance rate after ESWL. In our series, this variable increased the risk of ESWL failure 10.5-fold compared with stones 10 mm than in those with stones ≤10 mm. el-Assmy et al. [19] reported that the presence of hydronephrosis did not significantly affect the success of ESWL in the management of solitary lumbar ureter stones ≤20 mm in length. However, the presence of hydronephrosis significantly increased the re-treatment rate and prolongs the time to stone clearance. Meanwhile, another study reported that only stones exceeding 10 mm and the presence of perinephric fat stranding were independent predictive factors for failure of ESWL. BMI and other secondary signs including hydronephrosis were not a significant predictor of ESWL failure [6]. It is still controversial whether the hydronephrosis influences the success of treatment of ESWL. Presently, the presence of severe hydronephrosis (grade 3 and 4) appeared to be a significant predictor of ESWL failure. Patients with severe hydronephrosis exhibited a 12-fold greater risk of an unsuccessful outcome than patients with normal urinary drainage. The likelihood of treatment failure increased as the degree of hydronephrosis increased. Generally, ureteral stones cause ureteral obstruction that results in the development of hydronephrosis. The continuous obstruction causes a higher degree of obstruction. We believe that impacted stones produce moderate-to-severe hydronephrosis. Impacted stones do not respond to ESWL treatment satisfactorily. In patients with ureteral stones and severe hydronephrosis, endourological management should be the optimal choice of treatment [20, 21]. In our country, we should decide retreatment option within third ESWL session. When we perform ureteroscopic treatments after the failure of ESWL, the all costs of ESWL should be refunded to patients by the regulation of National Health Insurance Corporation. So, predictive factors of ureteroscopic treatment after ESWL failure are


important to Korean urologist to prevent refund of medical cost and to make an insurance claim. One of the limitations of this study could be the lack of findings of computerized tomography (CT). CT scan can suggest many finding of stone; Hounsfield unit, stone volume, inflammation of ureter and skin to stone length. However, in our study, all patients were not checked abdomen CT scan. Another limitation is the low number of patients included. Further studies with large group sample sizes, comparing urologist’s skills and the use of different lithotripters are needed to verify our preliminary results. In addition, there is an issue about the characteristics of piezoelectric lithotripter. One of the advantages of this lithotripter is anesthetic-free treatment due to the relatively low energy density at the skin entry point of the shockwave [22]. However, the low energy density can hamper its ability to effectively break urinary stones [22]. Therefore, the success rate of larger stone can be influenced by the type of lithotripter in this study. The results of this study cannot be generalized to all types of lithotripter. Also, this is a retrospective study. The setting of ESWL is one of limitations in this study. In recent studies which compared the effectivenessbetween different pulse rates, lower pulse rate was more effective [23].

Conclusions The results of the present retrospective study suggest that ESWL failure for ureteral stone can be predicted when patients have one of the following risk factors: BMI >25 kg/m2, stone size ≥1 cm, mid-ureter stone, and severe hydronephrosis. Surgical management should be offered when confronted with patients with these risk factors. Conflict of interest No competing financial interests exist.

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Factors influencing the failure of extracorporeal shock wave lithotripsy with Piezolith 3000 in the management of solitary ureteral stone.

Studies of predictive factors of extracorporeal shockwave lithotripsy (ESWL) failure in patients with ureteral stones have not yielded results suffici...
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