Int Urol Nephrol DOI 10.1007/s11255-014-0732-z

UROLOGY - ORIGINAL PAPER

Ureteroscopic lithotripsy in Trendelenburg position for proximal ureteral calculi: a prospective, randomized, comparative study Jiahua Pan • Wei Xue • Lei Xia • Hai Zhong Yinchao Zhu • Zhebin Du • Qi Chen • Yiran Huang



Received: 19 January 2014 / Accepted: 29 April 2014 Ó Springer Science+Business Media Dordrecht 2014

Abstract Purpose We conducted a prospective, randomized, comparative study to compare the clinical outcome between the Trendelenburg position ureteroscopic lithotripsy (tURSL) and the conventional position ureteroscopic lithotripsy (cURSL) for the management of single proximal ureteral stone. Methods From January 2012 to September 2013, consecutive patients with single proximal ureteral calculi less than 2 cm and planned for ureteroscopic lithotripsy at our institution were enrolled in this study. The eligible patients were randomized into cURSL group and tURSL group according to sequence of random numbers generated by computer. In tURSL group, patients were turned into a Trendelenburg lithotomy position with head down 30° while the conventional lithotomy position was applied in cURSL group. URSL was performed using a 6/7.5F semirigid ureteroscope with holmium laser. When retropulsion occurred, the stones fragments were followed by semi-rigid ureteroscope up to the renal collecting system. The Olympus P5 flexible ureteroscope was used if there was any suspicion of stone migration into lower calices or incomplete stone fragmentation by semi-rigid ureteroscope. Patients’ demographics between the two groups, perioperative course, clinical outcome and complication rates were compared. Data were analyzed using Chi-square Jiahua Pan and Wei Xue have contributed equally to this study. J. Pan  W. Xue  L. Xia  H. Zhong  Y. Zhu  Z. Du  Q. Chen (&)  Y. Huang Department of Urology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, No.1630 Dong Fang Road, Shanghai 200127, China e-mail: [email protected] J. Pan e-mail: [email protected]

test, Fisher’s exact test or Student’s t test. Binary logistic regression analysis was applied to estimate the effects of surgical position and stone size on stone migration. Results A total of 355 cases were finally analyzed in this study (176 in cURSL group and 179 in tURSL group). The mean operative time was significantly prolonged in cURSL group than in tURSL group, while the stone-free rate (SFR) at 4 weeks was significantly higher in tURSL group. A statistically significant difference was found in stone migration rate between the two groups (26.7 vs. 43.6 %, P = 0.001). In the stone migration subsetting, less stones fragments were found to migrate into lower calices in tURSL stone migration subgroup (P = 0.000). Also, the flexible ureteroscope utilization as well as the operative time was significantly decreased in tURSL stone migration subgroup (25.5 vs. 72.3 %, P = 0.000), (44.96 ± 11.0 min vs. 59.17 ± 9.2 min, P = 0.000) with higher SFR after retrograde intrarenal surgery (RIRS) (96.2 vs. 74.5 %, P = 0.000). Conclusion The tURSL was safe and highly efficacious for the management of proximal ureteral calculus, especially in nonobese patient. Even with important stone migration risk, it rendered higher SFR and less operative time compared with cURSL. Moreover, less utilization of flexible ureteroscope and decreased deflection time in tURSL could potentially reduce the medical cost. Keywords Trendelenburg ureteroscopic lithotripsy  Proximal ureteral stone  Stone migration  Retrograde intrarenal surgery

Introduction Even though shock wave lithotripsy (SWL) remains the first choice of treatment for most of the proximal ureteral

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calculus, the ureteroscopic lithotripsy (URSL) has also become a first-line therapy for its significantly greater stone-free rate (SFR) [1]. However, the proximal migration of stones or stone fragments is always an intractable problem for such a technique. In recent studies, the stone migration rate during semi-rigid ureteroscopic holmium laser lithotripsy for proximal ureteral calculus was about 20–44 % [2, 3], which hampered its use in these cases. With modern, small caliber flexible ureteroscopes, the SFR could be increased to 96 % or higher [4]. Nevertheless, the flexible ureteroscopic intrarenal lithotripsy associates with evidently increased operative time and health-care cost according to our previous study [5]. Moreover, the flexible ureteroscope and its accessories are not yet available in all urological centers, especially in developing countries. Placing the patients in a Trendelenburg position (head down) could theoretically encourage the migration of the proximal ureteral stone or stone fragments into the upper calices [6], or at least away from the lower pole calices, which makes it possible for semi-rigid ureteroscope to treat the migrated calculus directly in the renal collecting system. Such a technique would potentially decrease the operative time and the use of flexible ureteroscopes. However, to our knowledge, there has not been any comparative study between Trendelenburg position and conventional lithotomy position ureteroscopic lithotripsy for proximal ureteral calculi so far. We conducted a prospective, randomized study comparing the safety and clinical value of Trendelenburg position and conventional lithotomy position in ureteroscopic laser lithotripsy for single proximal ureteral calculi less than 2 cm in diameter.

Patients and methods From January 2012 to September 2013, consecutive patients with single proximal ureteral calculi less than 2 cm and planned for ureteroscopic lithotripsy at our institution were enrolled in this study. The proximal ureter was defined as the segment above the sacroiliac joints in noncontract CT scan [7]. Patients less than 18 years old, pregnant, or with solitary kidney, positive urine culture, severe cardiovascular or respiratory comorbidities, serum creatinine level [1.5 mg/ dL or coexisted ipsilateral upper urinary tract pathologies were excluded from the study. Certainly, those who declined to participate in this prospective, randomized, comparative study were also excluded. The eligible patients were randomized into conventional position ureteroscopic lithotripsy (cURSL) group and Trendelenburg position ureteroscopic lithotripsy (tURSL) group. Sequence of random numbers was generated by computer and then assigned to consecutive patients. Demographic data, including gender, age, body mass index

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(BMI), history of extracorporeal shock wave lithotripsy (ESWL), as well as stone side, stone size and hydronephrosis grade were recorded. The preoperative upper urinary tract imaging assessment included kidney, ureter, bladder X-ray (KUB), urinary tract ultrasonography and noncontrast abdominal CT scan. Operative time, hospital stay, stone migration, flexible ureteroscope utilization, peri-operative complication and SFR were addressed and compared between the two groups. The study protocol was approved by the ethical committee of the faculty of medicine. All patients enrolled in this study signed an informed consent before the surgery. Trendelenburg ureteroscopic laser lithotripsy Patients were turned into a Trendelenburg lithotomy position with head down 30° under general anesthesia. After a TerumoTM hydrophilic guide wire was placed into the renal pelvis, a 6/7.5 F wolf semi-rigid ureteroscope was inserted along the guide wire until the stone location. The LumenisTM holmium laser was applied as an energy source set at 0.8–1.0 J and a rate of 6–10 Hz. When retropulsion occurred, the stones or stones fragments were followed by semirigid ureteroscope up to the renal collecting system, and then, a lithotripsy was performed in renal pelvis, middle calices or even in upper calices. The Olympus P5 flexible ureteroscope and a 200-lm laser fiber were used if there was any suspicion of stone migration into lower calices or incomplete stone fragmentation by semi-rigid ureteroscope. A 4.7F double-J ureteral stent, which remained for 2 weeks postoperatively, was placed at the end of the procedure in all the cases. A noncontrast abdominal CT scan was scheduled 4 weeks after the surgery, and residual fragments C2 mm were considered significant. Statistical analysis Proportions of the variables were analyzed using Chi-square test or Fisher’s exact test. Continuous variables with normal distribution were expressed as the mean ± SD and compared with Student’s t test. Binary logistic regression analysis was applied to estimate the effects of surgical position and stone size on stone migration. Statistical significance was set at P \ 0.05, and all the P values were two-sided. The SPSS 18.0 was applied to perform the data analysis.

Results A total of 362 cases met with the inclusion criteria were enrolled in this study. According to the computer-generated randomization list, 180 cases were assigned to cURSL group, whereas 182 cases were assigned to tURSL group.

Int Urol Nephrol Table 1 Patients’ baseline characteristics of cURSL group and tURSL group cURSL group (n = 176)

tURSL group (n = 179)

cURSL group (n = 176)

tURSL group (n = 179)

P

Operative time (min) ± SD

41.74 ± 11.6

37.03 ± 8.8

0.000

Stone migration and stone size

47 (26.7)

78 (43.6)

0.001

Pretreatment size of migrated stone (mm) ± SD

11.04 ± 3.1

11.90 ± 3.3

0.293

Stone diameter 11–20 mm

21/47 (44.7)

51/78 (65.4)

0.023

Stone diameter 6–10 mm

26/47 (55.3)

27/78 (34.6)

P

Gender Male

Table 2 Clinical outcome of cURSL group and tURSL group

110 (62.5)

117 (65.4)

0.574

Female Age ± SD

66 (37.5) 49.23 ± 13.8

62 (34.6) 50.26 ± 13.3

0.474

BMI (kg/m2) ± SD

23.50 ± 3.5

24.03 ± 3.6

0.163

History of ESWL

38 (21.6)

35 (19.6)

0.635

Stone side (left/right)

97/79

86/93

0.183

Stone size (mm) ± SD

10.31 ± 2.9

10.01 ± 3.3

0.359

Stone diameter 11–20 mm

61 (34.7)

70 (39.1)

0.385

Stone diameter 6–10 mm

115 (65.3)

109 (60.9)

None

14 (8.0)

11 (6.1)

Grade I

41 (23.3)

53 (29.6)

Grade II

86 (48.9)

76 (42.5)

Grade III

27 (15.3)

34 (19.0)

Grade IV

8 (4.5)

5 (2.8)

Hydronephrosis 0.409

In 7 patients (4 in cURSL group and 3 in tURSL group), a primary insertion of ureteroscope was failed. Therefore, a total of 355 cases (176 in cURSL group and 179 in tURSL group) were finally analyzed in this study. The demographic data and the clinical features of the patients were listed in Table 1. No statistical difference was found in the patients’ demographics between the two groups, in terms of gender, age, BMI, history of ESWL as well as stone side, stone size and hydronephrosis degree. The clinical outcomes of the two groups were compared in Table 2. The mean operative time was significantly prolonged in cURSL group than in tURSL group (41.74 ± 11.6 vs. 37.03 ± 8.8 min, P = 0.000), while the SFR at 4 weeks was significantly higher in tURSL group than in cURSL group (93.2 vs. 98.3 %, P = 0.000). A statistically significant difference was found in stone migration rate between the two groups (26.7 vs. 43.6 %, P = 0.001). The pretreatment size of migrated stone was larger in Trendelenburg group but there was no statistical difference identified. However, when subdivided stone diameter with a 10-mm cutoff value, we could find that there were more large stones migrated into the renal collecting system in tURSL group than in cURSL group, respectively (P = 0.023). The incidence of complications, such as fever, gross hematuria and collecting system perforation, was comparable in both groups. There was no ureteral avulsion occurred in this study. The relationship between the degree of hydronephrosis and stone migration rate or stone-free rate at 4 weeks after surgery was summarized in Table 3. In cURSL group, no

Stone migration and hydronephrosis None

4/14

7/11

Grade I

10/41

25/53

Grade II

25/86

32/76

Grade III Grade IV

6/27 2/8

12/34 2/5

Hospital stay (days) ± SD

1.14 ± 0.4

1.12 ± 0.4

0.519

Overall stone free at 4 weeks

164 (93.2)

176 (98.3)

0.016

Fever

15 (8.5)

11 (6.1)

0.390

Gross hematuria

2 (1.1)

3 (1.7)

0.666

Ureteral perforation

4 (2.3)

2 (1.1)

0.398

Complications

Ureteral avulsion

0 (0.0)

0 (0.0)



Overall complication

21 (11.9)

16 (8.9)

0.356

statistical difference of stone migration rate was found among the subgroups of different hydronephrosis degrees (P = 0.995). However, in tURSL group, even the difference among the subgroups was statistically insignificant either, there appeared to be a decreasing trend of stone migration with the aggravation of hydronephrosis. As for the stone-free rate at 4 weeks after surgery, there was no statistical difference among the subgroups of different hydronephrosis degrees in cURSL group (P = 0.475). Nevertheless, in tURSL group, the SFR at 4 weeks after surgery was significantly reduced with the hydronephrosis increased. The SFR was 100, 100, 98.7, 97.1 and 80.0 % in zero, grade I, grade II, grade III and grade IV hydronephrosis subgroup, respectively. In our study, there were 73 cases previously treated by ESWL. The relationship between the history of ESWL and stone migration during the procedure or stone-free rate at 4 weeks after surgery was shown in Table 4. In cURSL group, 6 out of 38 cases with history of ESWL (15.8 %) presented the stone migration while the stone migration rate was 29.7 % in patients without previous ESWL. In tURSL group, the stone migration rate was also lower in patients with history of ESWL (34.3 vs. 45.8 %). However, such a difference was not statistically significant in both groups. In addition, the stone-free rate at 4 weeks after

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Int Urol Nephrol Table 3 The relationship between the degree of hydronephrosis and stone migration rate or stone-free rate at 4 weeks after surgery

Degree of hydronephrosis None

P

Grade I

Grade II

Grade III

Grade IV

Stone migration cURSL group

4/14 (28.6)

10/41 (24.4)

25/86 (29.1)

6/27 (22.2)

2/8 (25.0)

0.955

tURSL group

7/11 (63.6)

25/53 (47.2)

32/76 (42.1)

12/34 (35.3)

2/5 (40.0)

0.538

Stone free at 4 weeks cURSL group

14/14 (100)

40/41 (97.6)

78/86 (90.7)

25/27 (92.6)

7/8 (87.5)

0.475

tURSL group

11/11 (100)

53/53 (100)

75/76 (98.7)

33/34 (97.1)

4/5 (80.0)

0.020

Table 4 The relationship between the history of ESWL and stone migration during the procedure or stone-free rate at 4 weeks after surgery History of ESWL ?

Table 6 RIRS in cURSL stone migration subgroup and tURSL stone migration subgroup cURSL stone migration subgroup (n = 47)

tURSL stone migration subgroup (n = 78)

P

Stone migration into lower calyx

28/47 (59.6)

7/78 (9.0)

0.000

Flexible ureteroscope utilization

34/47 (72.3)

20/78 (25.6)

0.000

Operative time (min) ± SD

59.17 ± 9.2

44.96 ± 11.0

0.000

Stone free at 4 weeks

35/47 (74.5)

75/78 (96.2)

0.000

P -

Stone migration cURSL group

6/38 (15.8)

41/138 (29.7)

0.086

tURSL group

12/35 (34.3)

66/144 (45.8)

0.217

Stone free at 4 weeks cURSL group

36/38 (94.7)

128/138 (92.8)

0.499

tURSL group

34/35 (97.1)

142/144 (98.6)

0.482

Table 5 The impact of stone size and Trendelenburg position on upward stone migration Candidate variable

OR

95 % CI

P

Stone size

1.320

1.215–1.435

0.000

Trendelenburg position

2.546

1.563–4.417

0.000

surgery in patients with or without history of ESWL was also fairly close in cURSL group as well as in tURSL group. In addition, the binary logistic regression analysis was used to evaluate the impact of stone size and Trendelenburg position on upward stone migration (Table 5). The analysis yields a statistically significant association between stone size and stone migration (odds ratio (OR) 1.320, 95 % confidence interval (CI) 1.215–1.435) as well as Trendelenburg position and stone migration (OR 2.546, 95 % CI 1.563–4.417). The details of the stone migration subsetting of the 2 groups were summarized in Table 4. During the procedure, upward stone migration occurred in 47 cases in cURSL group while in 78 cases in tURSL group. Less stone or stones fragments were found to migrated into lower calices in tURSL stone migration subgroup (P = 0.000). Since most of the stone fragments moved into renal pelvis, middle calices or upper calices, the flexible ureteroscope utilization, as well as the operative time, was significantly

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decreased in tURSL stone migration subgroup (P = 0.000) with a higher SFR after intrarenal surgery (96.2 vs. 74.5 %, P = 0.000) (Table 6).

Discussion The stone migration usually results from the ureteroscope insertion, high irrigation pressure, laser burst or stone manipulation by the laser probe when treating the proximal ureteral stone endoscopically. Therefore, the semi-rigid ureteroscopic laser lithotripsy for proximal ureteral calculus often associates with a limited SFR, an increased operative time and the need of further flexible ureteroscopic lithotripsy [8, 9]. In a report from Mayo Clinic, the use of flexible ureteroscopes has largely increased from 12 % in 1992 to 37 % in current series [10]. However, as a fragile and expensive medical instrument, the flexible ureteroscope is not always available in all urological centers, especially in developing countries. In this case, a number of anti-retropulsion devices, such as Stone Cone, PercSys Accordion and NTrap, have been released in the market in recent years to address the problem of stone migration. These ureteral occlusion devices could significantly diminish stone migration and the need for the auxiliary procedure [11, 12]. Meanwhile, the anti-retropulsion devices might also increase the medical cost of URSL and could have the potential risk of ureteral injury.

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When stone migration occurs, the usual attempt is tilting the patient to a head-up position and controlling irrigation pressure. Placing the patient in a head-up position was thought to decrease the stone migration risk using gravity to counteract the retropulsive energy of the migrating stone. However, as the force with which calculus was propelled upwards was stronger than partial gravitational pull, positioning was thought to be really ineffective to prevent the stone migration [13]. Actually, it is even more important to prevent the calculus from moving into the lower calices than other part of the renal collecting system. Koo et al. [14] found that even with modern flexible ureteroscope, the initial SFR was only 64.9 %, the retreatment rate was 16.2 % and the auxiliary procedure rate was 21.6 % for the lower pole calculus. Hence, we placed the patients in a Trendelenburg position during URSL in order to help direct the stone fragments cephalad, away from the lower calices, which might decrease the overall operative time as well as the use of flexible ureteroscope and increase the SFR. In our study, we found that in tURSL group, the stone migration rate is significantly higher than in cURSL group, while the mean operative time of the former was shorter. Furthermore, if we only focused on the cases with stone migration into the renal collecting system, the difference in mean operative time between the 2 groups became even larger. This might be related to less stone migration to the lower calices and lower utilization of flexible ureteroscope in tURSL group. Of all the 78 cases having stone migration in tURSL group, only 7 cases (9.0 %) presented lower calices stone fragments. However, 28 out of 47 (59.6 %) cases with stone migration in cURSL group had stone debris in lower pole, which was correlated to the significantly higher utilization of flexible ureteroscope in this group. Shredding the calculus in the upper calices or renal pelvis by a semi-rigid ureteroscope is certainly easier and faster than treating the lower pole calculus by a flexible ureteroscope. Fernandez et al. [15] found that the mean operative time of intrarenal flexible ureteroscopic lithotripsy for renal calculus (mean diameter 12 mm) was 61 min. In another study of flexible ureteroscopic in situ lithotripsy for lower pole calculi, Hollenbeck et al. [16] reported that the mean operative time was 64 min for the renal calculus measuring 7 mm in diameter. These clinical outcomes were similar to the results of our study. The degree of hydronephrosis was another important factor during URSL. Even though there was no statistical difference of stone migration rate found among the subgroups of different hydronephrosis degrees in both groups, there appeared to be a decreasing trend of stone migration with the aggravation of hydronephrosis in tURSL group. On the one hand, the stone retropulsion is more likely to occur in Trendelenburg position. On the other hand, an

important hydronephrosis usually implies a severe ureteral obstruction caused by calculus and surrounding inflammatory polypus, which might hamper the stone migration during URSL. In tURSL group, even though the stone migration rate was relatively high in zero and grade I hydronephrosis subgroup, the stone fragments were more likely to move into the renal pelvis or upper calyx when the hydronephrosis was limited, where the stone debris were easier to treat and then be evacuated. Nevertheless, with the development of the hydronephrosis, the SFR was significantly decreased. With important hydronephrosis, even in Trendelenburg position, the stone fragments were possible to get into lower calyx and it is extremely difficult for the flexible ureteroscope to access the deep-seated stone fragments in lower calyx with severe hydronephrosis. In our study, the three cases with significant stone residual in tURSL group were all found to have lower pole stone migration as well as mild to severe hydronephrosis. Our study showed that the history of previous ESWL neither significantly influenced the stone migration nor the stone-free rate at 4 weeks after the surgery. However, such a result may not very conclusive to describe the relationship between history of ESWL and stone migration rate or stone-free rate after surgery because the time from ESWL to URSL varies from one to another in this cohort. As a tertiary endourology center, lots of our patients were referred from other hospitals or neighborhood clinics. For example, the longest time between ESWL and URSL in this study was 14 months even though most of the cases had their URSL 2 weeks after their last ESWL session. Thus, further prospective randomized study should be designed to elucidate the effect of ESWL on stone migration rate and stone-free rate of their subsequent URSL. Our binary logistic regression analysis showed that, besides the Trendelenburg position, the stone size was another significant risk factor, which was found to influence the stone migration rate. For the migrated stones, even their pretreatment size seemed to be larger in tURSL group, it was not statistically significant. However,when subdivided stone diameter with a 10-mm cutoff value, we could find that there were more large stones migrated into the renal collecting system in tURSL group. Nevertheless, this phenomenon did not actually occurred in cURSL group. In a recent study, Hong et al. [17] found the success rate of URSL for proximal ureteral calculus significantly decreased as the size of the stone increased. Also, it is widely accepted that larger stone size correlates with a decreased SFR [18]. By contraries, Elsheemy et al. [19] reported that the stone size was not a significant predictor for stone migration during conventional lithotomy position URSL. However, when interpreting the data about the stone size and cephalad migration, precaution must be taken as the stone diameter we recorded was the

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pretreatment stone size before the calculus shredding. In other words, a previously large stone could be smashed into small pieces and then migrated to the renal collecting system. In the present study, the tURSL achieved a better SFR than cURSL, even though the stone migration rate of the former was significantly higher. The difference of SFR between the groups became much more important when considering only the cases with stone migration and treated by RIRS, which might result from two major causes. First of all, it was more likely to get a higher SFR when most of the migrated stone fragments were located in upper pole or renal pelvis in tURSL group. In a review of 667 URSL interventions, Rippel et al. [20] reported that the stone location in the kidney was significantly associated with SFR. Similarly, Riley et al. [21] also found that patients with large lower pole stone burden had significant lower SFR after RIRS. Nowadays, even with the new flexible ureteroscopes, the lower pole calices can be accessed only in 93 % of cases [22]. Secondly, the stone debris located in the upper calices, middle calices or renal pelvis after lithotripsy could easily and spontaneously pass out with urine, while it would be rather difficult for the lower pole fragments. Trendelenburg position ureteroscopic lithotripsy was also a safe and reliable procedure. There was no statistical difference in perioperative complication rate between the 2 groups. No major complication occurred in this study, and most minor complications were urinary tract infection and hematuria, which was similar to the results of CROES Ureteroscopy Global Study [23]. The low complication rate was likely due to the advent of new small-diameter semirigid and flexible ureteroscopes [10]. Furthermore, it is noteworthy that placing the patients in Trendelenburg position could also reduce the medical cost of URSL for proximal ureteral calculus due to less utilization of flexible ureteroscope and less deflection time for treating the lower pole calculus. The flexible ureteroscope is an expensive medical instrument with relatively poor durability. Landman et al. [24] demonstrated that the initial purchase and maintenance cost were about 1000 USD per case if flexible ureteroscope lasted for 25 cases. What’s more, after the initial purchase, the cumulative cost of the disposables was even more expensive than the cost of purchase and upkeep of the flexible ureteroscope [25]. In developing countries, the public health resources are limited, and the flexible ureteroscopes are not available in a large number of centers [26], and choosing a cost-effective treatment is particularly important for the urologists. Our study had some limitations. First of all, it was a ‘‘nonblinded’’ study, as the surgeons were aware of patients’ surgical position. Therefore, any subjective preference to one of the positions might lead to bias in part of

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the results. However, such kind of bias appears frequently in a lot of surgical prospective studies, and it is hard to be completely eliminated. Secondly, the stone composition was not evaluated in all the cases. Since the stone composition might influence the stone migration rate and operative time for both groups, it could cause the bias in data analysis. Finally, the average BMI of the patients was 23–24 in our study, which meant there were few obese patients enrolled in the current research. Thus, our result might not completely represent the safety and clinical outcome of cURSL or tURSL for upper ureteral calculus in the whole population. Considering the potential surgical risk of semi-rigid URSL for upper ureteral stones in obese patient, we do not recommend the routine use of semi-rigid ureteroscope in such cases.

Conclusion Our prospective, randomized, comparative study showed that tURSL was safe and highly efficacious for the management of proximal ureteral calculus, especially in nonobese patient. Even with important stone migration risk, it rendered higher SFR and less operative time compared with cURSL. Moreover, less utilization of flexible ureteroscope and decreased deflection time in tURSL could potentially reduce the medical cost. Acknowledgments The study was supported by Shanghai Pudong Scientific Research Grant (PWZxkq2010-03) and Renji Medical Research Seed Project (RJZZ13-016). Conflict of interest

There is no conflict of interest to be declared.

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Ureteroscopic lithotripsy in Trendelenburg position for proximal ureteral calculi: a prospective, randomized, comparative study.

We conducted a prospective, randomized, comparative study to compare the clinical outcome between the Trendelenburg position ureteroscopic lithotripsy...
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