Original Paper

Urologia Internationalis

Received: August 23, 2013 Accepted: September 18, 2013 Published online: January 28, 2014

Urol Int 2014;92:468–472 DOI: 10.1159/000355828

Pneumatic Lithotripsy versus Holmium:YAG Laser Lithotripsy for the Treatment of Single Ureteral Stones: A Prospective, Single-Blinded Study Sebastiano Cimino a Vincenzo Favilla a Giorgio I. Russo a Alberto Saita a Giuseppe Sortino a Tommaso Castelli a Massimiliano Veroux b Massimo Madonia c Giuseppe Morgia a c

Department of Urology, b Vascular Surgery and Organ Transplant Unit, University of Catania, Catania, and Department of Urology, University of Sassari, Sassari, Italy

Key Words Ureteroscopy · Lithiasis · Stone-free rate · Laser lithotripsy · Predictive factors · Hounsfield unit

Abstract Objective: The aim of this prospective single-blinded study was to analyze the stone-free (SF) rates between pneumatic lithotripsy (PL) and laser lithotripsy (LL) for the treatment of single and primary ureteral stones and to evaluate potentially predictive factors of a SF status. Material and Methods: From January 2010 to January 2011, 133 consecutive patients with single and primary ureteral stones were prospectively enrolled. Uni- and multivariate logistic regression were performed to estimate predictive factors of a SF status. Results: The SF rate in the PL group was 80.7 and 86.1% in the LL group (p = 0.002). Success rates with regard of stone position were not significantly different between groups. At univariate logistic regression, middle ureteral stone (OR 3.33, p = 0.04), distal ureteral stone (OR 4.4, p = 0.02), LL (OR 3.05, p = 0.04) and Hounsfield units (HUs) (OR 1.07, p = 0.03) were significantly predictive factors of a SF status. At a multivariate logistic regression, middle ureteral stone (OR 5.58, p = 0.01), distal ureteral stone (OR 7.87, p < 0.01), LL (OR 2.4, p = 0.02) and HUs ≥1,200 (OR 1.15, p = 0.02) were significantly associated with a SF status. Conclusions: LL significantly in-

© 2014 S. Karger AG, Basel 0042–1138/14/0924–0468$39.50/0 E-Mail [email protected] www.karger.com/uin

fluences the SF status after ureteroscopy, allowing a higher SF rate when compared to PL. HUs may significantly influence this success rate. © 2014 S. Karger AG, Basel

Introduction

In the course of the last decade up to the present day, the treatment of urinary lithiasis has changed considerably. Traditionally, extracorporeal wave lithotripsy (SWL) was preferred for the treatment of stones located in the kidneys and for less accessible stones located in the proximal ureters [1]. The introduction of smaller flexible and semi-rigid ureteroscopes has led to safer and more efficacious treatment methods [1]. Indeed, ureteroscopy (URS) has become one of the most important techniques in the management of urinary lithiasis. With an increase in efficacy and a reduction in complications, URS is now considered to be an efficient primary choice for the management of ureteral stones. Different techniques, such as pneumatic lithotripsy (PL) and laser lithotripsy (LL), are available for intracorporeal lithotripsy. PL has many advantages: relatively low cost, easy management and a high stone-free (SF) rate. Dr. Giorgio Ivan Russo, MD Department of Urology University of Catania, Piazza Università IT–95124 Catania (Italy) E-Mail giorgioivan @ virgilio.it

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a

Material and Methods From January 2010 to January 2011, 133 consecutive patients with single and primary ureteral stones were prospectively enrolled in this study. All subjects gave written informed consent before entering the study, which was conducted in accordance with the Declaration of Helsinki and the Human Ethics Committee approved the study protocol. Patients were randomized according to a computergenerated random sequence with a 1:1 ratio in two groups: PL and LL. The study was single-blinded because none of the patients knew which group they belonged to and surgeon and operating staff were informed about the randomization choice and the stone position at the operating room. Exclusion criteria were anomalies of the upper urinary tract and impacted stones, defined as a stone that remained fixed at the same site with hydronephrosis for more than 1 month. Three patients were excluded because they were found to have anomalies of the urinary tract including 1 horseshoe kidney, 1 complete duplicated system, 1 incomplete duplicated system, and 13 for impacted stones. Before surgery, all patients were evaluated by plain abdominal film of the kidney, NCCT, urinalysis, urine culture, serum biochemistry and coagulation tests. The stones were viewed with helical NCCT (Aquilion 64; Toshiba, Tokyo, Japan) (120 kVp, 300 mA, 0.5–1.0 s, collimation 5 mm, pitch 1:1), and a standard renal stone viewing protocol that uses soft-tissue settings (width 350/length 50) was used. Each procedure was performed using general anesthesia with patients placed in a lithotomy position. LL was performed with an 8/9.8-Fr semi-rigid ureteroscope (Wolf GmbH, Knittlingen, Germany) and with a laser set at 0.5–1 J energy pulse and 5–10 Hz frequency over a 200-μm laser fiber.

Comparison between PL and LL

PL (Swiss Lithoclast) was performed using an 8/9.8-Fr semirigid ureteroscope (Wolf GmbH). To prevent stone migration, we used a 1.9-Ff zero-tip nitinol stone basket (Boston Scientific) to retrieve stone fragments. A double-J ureteral stent was routinely inserted at the end of each procedure. No additional therapies were required by the patients. The double-J stent was removed 4 weeks after surgery on an outpatient basis. Failure of URS was defined as ureteral stones migrating into the kidney during URS, the inability to access the stone or ending the procedure because of complications. We performed plain NCCT in postoperative month 3 to determine the SF status. The outcome was defined by stone status as follows: having no detectable stones (SF), residual stone fragments ≤4 mm (‘residual fragments’), and residual stone >4 mm diameter (‘treatment failure’). The first two classifications were defined as efficient outcomes, as reported in a recent study [6]. Preoperative factors analyzed included stone area (mm2), stone volume (mm3), stone side (right or left), age, sex, body mass index, stone location and the average attenuation coefficient as measured by Hounsfield unit (HUs). The maximum diameter was evaluated on plain kidneys, ureters, and bladder (KUB) radiography. The stone volume was obtained from measurements on three-dimensional reconstructions of the stone, using 5-mm axial and 3.5-mm reconstructed coronal NCCT. The stone maximum diameter on KUB and stone length, width, and height on NCCT were determined using digital calipers (Synapse-PACS Software Program System; Fujifilm, Tokyo, Japan). All NCCT scans were interpreted by a single urologist. Stone area was calculated using the following formula: maximum diameter × width × π × 1/4, while stone volume was calculated using the following formula: length × width × height × π × 1/6. Complications connected with the procedure were interpreted according to the Clavien-Dindo Classification System. Statistical Analysis The PL and LL groups were compared using a χ2 test (Pearson 2 χ test) and contingency tables. A comparison was also made between each group considering all stone locations and using cumulative contingency tables. Uni- and multivariate logistic regression were performed to estimate the predictive factors of a SF status. A cut-off of 1,200 HUs for the maximum attenuation coefficient was set and included at the multivariate logistic regression analysis. All tests were completed using SPSS version 19 software (SPSS, Inc., IBM Corp., Somers, N.Y., USA). Significance was considered as p < 0.05 for all statistical comparisons.

Results

A total of 117 patients were enrolled, 57 in the PL group and 60 in the LL group. Table 1 lists the baseline characteristics of our cohort. No statistical differences were observed at baseline between the two groups. The SF rates were 80.7% in the PL group and 86.6% in the LL group in postoperative month 3 (p < 0.05). Success rates with regard of stone position were not significantly different between groups (Fisher’s exact test, p > 0.05). FailUrol Int 2014;92:468–472 DOI: 10.1159/000355828

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On the other hand, it is associated with a possibility of stone push-up, with a higher chance of stone migration when dealing with proximal ureteral stones than for distal ureteral stones [2]. LL is safe and is able to fragment all stones regardless of their composition. The current generation of flexible, actively-deflectable fiber-optic endoscopes makes virtually every part of the kidney accessible, including the lower pole. This technique produces a shockwave that reduces the likelihood of retropulsion of stones or stone fragments when compared to PL [2–4]. Using LL, calculi are fragmented with a success rate of between 80 and 95% [5]. Nevertheless, many reports have examined the utility of different parameters like stone burden, stone area, stone volume or the maximum and average attenuation coefficient to predict the success rate of stone treatment [6]. In this respect, the possibility of having such predictors would be helpful in order to better select the kind of fragmentation in relation to preoperative variables. The aim of this prospective single-blinded study was to analyze the SF rates between PL and LL for the treatment of single and primary ureteral stones and to evaluate potentially predictive factors of a SF status.

Table 1. Baseline characteristics of patients

PL group Patients, n Median age, years, mean ± SD Male/female Body mass index, mean ± SD Stone position, n, % Proximal ureter Middle ureter Distal ureter Stone maximum diameter, mm, mean ± SD Stone area, mm2, mean ± SD Stone volume, mm3, mean ± SD Hounsfield units, mean ± SD Mean operation time, min, mean ± SD

LL group

57 51 (23–67) 31/26 25.82±1.2

60 48 (25–65) 38/22 25.23±0.8

18 (31.58) 16 (28.07) 23 (40.35) 10.2±0.4 71.64±51 446.88±304.9 1,067±41.32 61±21

13 (21.66) 20 (33.33) 27 (45) 11±0.52 72.04±42.49 454.81±252.82 1,081±51.88 60±25

Table 2. Uni- and multivariate logistic regression of predictive factors of SF status

Univariate OR

p value

OR

p value

0.96 (0.93–1.00) 0.64 (0.31–0.88) 0.45 (0.15–0.67)

0.05 0.63 0.78

0.95 (0.91–0.99) 0.87 (0.41–0.94) 0.55 (0.20–0.84)

0.03 0.23 0.34

1.00 (reference term) 3.33 (0.91–12.11) 4.40 (1.22–15.80) 1.00 (0.99–1.01) 1.00 (0.99–1.01) 0.98 (0.96–1.10) 1.07 (0.38–2.95) 3.05 (1.00–9.30) 0.99 (0.97–1.02)

0.04 0.04 0.02 0.99 0.65 0.99 0.03 0.04 0.92

1.00 (reference term) 5.58 (1.32–23.51) 7.87 (1.85–33.51) 0.87 (0.67–1.2) 0.25 (0.1–0.5) 0.99 (0.88–1.03) 1.15 (0.23–5.73) 2.4 (1.7–8.4) 0.76 (0.52–0.93)

0.09 0.01 0.005 0.35 0.62 0.35 0.02 0.02 0.45

ure of URS was reported in 6 (10.53%) patients of the PL group for stone migration and in 1 (1.66%) subject of the LL group for ureteral perforation. Bleeding that led to termination of the procedure was reported in 1 (1.75%) subject of the PL group and in 1 (1.66%) of the LL group. The mean operating time was 60 (±25) min in the LL group and 61 (±21) min in the PL group, without significant differences (p = 0.68). At univariate logistic regression, middle ureteral stone (OR 3.33, p  = 0.04), distal ureteral stone (OR 4.4, p  = 0.02), LL (OR 3.05, p = 0.04) and HUs (OR 1.07, p = 0.03) were significantly predictive factors of a SF status. At a multivariate logistic regression, middle ureteral stone (OR 5.58, p = 0.01), distal ureteral stone (OR 7.87, p < 470

Urol Int 2014;92:468–472 DOI: 10.1159/000355828

0.01), LL (OR 2.4, p = 0.02) and HUs ≥1,200 (OR 1.15, p = 0.02) were significantly associated with a SF status (table  2). 25 patients (21.37%) reported 25 intraoperative and 18 postoperative complications according to the Clavien classification, with a significant difference in term of intrarenal stone migration in favor of LL (table 3).

Discussion

Medical management is the first recommended approach for urinary lithiasis. When it fails and when the stone diameter exceeds 6–7 mm, removal is indicated [1]. URS occupies an essential place as a mini-invasive techCimino/Favilla/Russo/Saita/Sortino/ Castelli/Veroux/Madonia/Morgia

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Age, years Male vs. female Body mass index Stone location Proximal ureter Middle ureter Distal ureter Stone maximum diameter, mm Stone area, mm2 Stone volume, mm3 Hounsfield units, ≥1,200 vs.

Pneumatic lithotripsy versus holmium:YAG laser lithotripsy for the treatment of single ureteral stones: a prospective, single-blinded study.

The aim of this prospective single-blinded study was to analyze the stone-free (SF) rates between pneumatic lithotripsy (PL) and laser lithotripsy (LL...
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