Urolithiasis (2014) 42:127–131 DOI 10.1007/s00240-013-0618-z


Prospective randomized trial comparing shock wave lithotripsy and flexible ureterorenoscopy for lower pole stones smaller than 1 cm Nevzat Can Sener • M. Abdurrahim Imamoglu • Okan Bas • Ufuk Ozturk • H. N. Goksel Goktug • Can Tuygun • Hasan Bakirtas

Received: 15 May 2013 / Accepted: 23 October 2013 / Published online: 13 November 2013 Ó Springer-Verlag Berlin Heidelberg 2013

Abstract In this study, we aimed to compare the success and complications of flexible ureterorenoscopy (F-URS) with its advanced technology and the accomplished method of shock wave lithotripsy (SWL) in the treatment of lower pole stones smaller than 1 cm. One hundred and forty patients were randomized as 70 undergoing SWL (Group 1) and 70 undergoing F-URS (Group 2). Patients were evaluated by plain X-ray and urinary ultrasound 1 week and after 3 months following SWL. The same procedure was done for F-URS patients 1 week after surgery and after 3 months. Success rates were established the day following the procedure and after 3 months. Fragmentation less than 3 mm was considered success. Mean operative time was 44 ± 7.4 min for Group 2 and mean fluoroscopy duration was 51 ± 12 s. In F-URS group, all the patients were stone free after 3 months (100 %). Group 1 had 2.7 ± 0.4 sessions of SWL. Sixty-four patients were stone free in that group after 3 months (91.5 %). The procedure yielded significant success in FURS group, even though patients underwent SWL for 2.7 ± 0.4 sessions and F-URS for 1 session (p \ 0.05). With higher success and similar complication rates, fewer sessions per treatment, and advances in technology and experience, we believe F-URS has a N. C. Sener (&) Department of Urology, Numune Education and Research Hospital, Ministry of Health, Adana, Turkey e-mail: [email protected] M. Abdurrahim Imamoglu  U. Ozturk  H. N. Goksel Goktug  C. Tuygun  H. Bakirtas Department of Urology, Diskapi Yildirim Beyazid Education and Research Hospital, Ministry of Health, Ankara, Turkey O. Bas Department of Urology, Onkoloji Education and Research Hospital, Ministry of Health, Ankara, Turkey

potential to be the first treatment option over SWL in the future. Keywords

SWL  F-URS  Lower pole stone

Introduction Kidney stones have been treated by open surgery before. However, with technological advances, extracorporeal shock wave lithotripsy (SWL), percutaneous nephrolitotomy (PNL) or flexible ureterorenoscopy (F-URS) became standard treatment options. Many recent publications consider F-URS as the selected treatment method for many stones [1]. In urolithiasis guidelines, F-URS have become the first-line treatment for many occasions [2]. Physicians need to address lower pole stones individually. Even though they have a lesser potential for damaging the kidney, treatment is more complicated, especially for smaller stones. With its less invasive nature, F-URS is the real ‘‘minimal invasive’’ treatment method for lower pole stones. On the other hand, SWL is not an operation and may be performed more safely without the risks of anesthesia. These options create a dilemma in choosing the best option for treatment. PNL is the first option of treatment for larger stones [2], but for smaller stones, a dilemma is present. There are several research papers considering SWL and/or F-URS to treat small-sized kidney stones [3, 4]. However, there is a lack of prospective randomized trials comparing these modalities for lower pole kidney stones smaller than 1 cm. In European Association of Urology (EAU) Guideline of urolithiasis, the first treatment option for lower pole kidney stones smaller than 1 cm is SWL and second option is F-URS [2]. In this study, we aimed to compare the safety



and efficacy of these methods on lower pole kidney stones \1 cm.

Materials and methods After the approval of local ethics committee, 140 patients applied to our clinic with single lower pole stones \1 cm between August and October 2012 were enrolled in the study. They were randomized into two groups to receive either SWL (Group 1) or F-URS (Group 2). The main criteria for patient enrollment were having lower pole stones smaller than 1 cm. The study protocol was explained to the patients and success, possible complications, invasiveness, and the need for anesthetics and hospitalization were discussed. After the informed consent of the patients was obtained for both procedures, the patients were randomized using an online randomization tool [5]. Patients with a history of previous ipsilateral kidney surgery, solitary kidney, acute urinary tract infections, anatomic variations, and steep infindibulopelvic angle (\30°) were excluded from the study. Patients with infections were treated with antibiotics and then treated by F-URS. Patients with solitary kidneys and anatomic variations were also treated by F-URS, but were not included in the study. Patients with steep infindibulopelvic angles were treated by mini-PNL. The patients were evaluated by X-ray, urinary ultrasound (USG), and intravenous urography (IVU) preoperatively. USG was performed by an experienced uroradiologist. When the radiologist was unsure about the stone-free status, spiral computerized tomography (CT) was applied. CT was also used for non-opaque stones. Postoperative analysis included urinary USG and plain X-rays after 1 week following each session of SWL and 3 months after the procedure. The patients, who underwent F-URS were evaluated by urinary USG and plain X-rays 1 week and 3 months after the procedure. SWL was performed on an outpatient basis. The patients treated by F-URS were hospitalized and discharged on the day after the operation. For F-URS, preoperative stenting was not performed. An access sheath of 11–13F was placed in the operation. The stones were placed on to the upper pole or renal pelvis and disintegrated there. With the achievement of stone sizes smaller than 3 mm, the operation was ended. After the procedure, a JJ stent was not placed unless a complication occurred. Electrohydraulic extracorporeal lithotripter (Multimed Classic; Elmed, Ankara, TURKEY) was used for SWL (In each lithotripsy session, 2,500–3,000 shocks were given at 14–17 kV.), and flexible ureterorenoscope (Flex-X, Karl Storz, Tuttlingen, Germany) and Holmium laser (Ho YAG


Urolithiasis (2014) 42:127–131

Laser; Dornier MedTech; Munich, Germany), for flexible ureterorenoscopy. At the most, patients in SWL group underwent three courses of SWL therapy. For each procedure, fragmentation \3 mm was considered successful. Each procedure was performed by a single surgeon. To evaluate and compare the complications of procedures, modified Clavien classification was used. Statistical analyses were performed using the Statistical Package for Social Sciences version 20.0 software (SPSS Inc., Chicago, IL, USA). In addition to the frequency and percentage distributions of the data, Student’s t test was used in group comparisons, and Mann–Whitney U test was used for comparisons of variables between categorical data. A value of p \ 0.05 was considered statistically significant.

Results The mean age for Group 1 was 42.9 ± 5.6 and 45.4 ± 6.4 for Group 2 (p = 0.814), respectively. The mean stone size was 8.2 ± 1.2 and 7.8 ± 1.3 mm, respectively. Demographic parameters of the patients are summarized in Table 1. There were two patients in need of CT. One patient had a non-opaque stone that was treated by F-URS and for the other patient, USG did not provide a definitive outcome, and thus, CT confirmed the stone-free status of the patient. Table 1 Patient demographics and operation outcomes among groups

Mean patient age

Group I (n = 70)

Group II (n = 70)

42.9 ± 5.6

45.4 ± 6.4

Sex Male












Stone size (mm)

8.2 ± 1.2

7.8 ± 1.3

Success rate

91.5 %*

100 %*






Complication gradea




– 0

– 0




4 (5.7 %)

3 (2.8 %)

Total * p \ 0.05 a

According to modified Clavien Grading System

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In F-URS group, mean operative time was 44 ± 7.4 min and fluoroscopy duration was 51 ± 12 s. In SWL group, mean fluoroscopy duration was 24 ± 12 s. Fluoroscopy duration was significantly lower for SWL group (p \ 0.05). After 1 week, 34 patients (48.6 %) managed by SWL were stone free, while 38 patients (52.3 %) in F-URS group were stone free (p = 0.176). With USG assessment, the residual stones (all but 6 \ 3 mm) were found to be located in the lower pole in SWL group, and in the upper pole and pelvis in F-URS group. During the postoperative evaluation, 70 patients in Group 2 (100 %) had no residual stones at 3 months. In SWL group, the patients received a mean of 2.7 ± 0.4 sessions of SWL. In this group, 64 patients (91.5 %) were stone free at 3 months. Six patients with symptomatic residual stones ([3 mm) were treated by F-URS. When stone clearance outcomes were compared, there was a statistical significant advantage in favor of Group 2 (p \ 0.05) (Table 1). In Group 1, three patients had severe pain treated by analgesics and one patient had a subcapsular hematoma treated by a JJ catheter and hospitalization. Three patients (4.2 %) in Group 2 faced complications. Two of these patients had fever in postoperative first 24 h and one patient had a urinary tract infection treated by oral ciprofloxacin. Complications are summarized in Table 1.

Discussion According to EAU guidelines on urolithiasis, SWL is the first line of treatment for lower pole stones \1 cm and F-URS is considered a second-line treatment [2]. In the study, we aimed to present and compare the outcomes of SWL and F-URS cases. In the study by Ilker et al. [6], 219 patients were treated by SWL. Success rates were 59, 77, and 64 % for lower, middle, and upper calyx stones, respectively. If the study is narrowed to solitary lower calyx stones, the authors report 68 % success rate. When all the stones \1 cm were analyzed, the overall success improved to 81 %. El-Asmy et al. [7] reported their 14-year SWL experience and presented 77 % success. They treated 596 patients that were followed for 3 months following SWL therapy. When a cutoff of 400 mm2 was selected, they reported a 2.8-fold treatment advantage. They also stated stone size, location, and congenital abnormalities as markers for stone clearance. In results, they stated a 69.8 % stone-free rate regardless of the stone size. Even though they did not consider stone location, our 87 % success rate is better than what the authors presented.


Danuser et al. [8] studied the effect of collective system anatomy on SWL clearance of lower pole stones at 2007. They performed SWL on 96 lower pole stones of 5–35 mm and evaluated the outcomes and reported significant correlation of stone fragmentation with infindibulopelvic angle and calyx height, but could not find any relation with stone clearance rate with any anatomic variation. When they compared patients with stones \1 cm, they found similar stone-free rates even using more frequent shock waves. Lin et al. [9] presented their cases about the same issue and they reported significantly better stone-free rates for patients with wider infundibulum ([4 mm) and stones \1 cm. EAU guidelines state similar outcomes for F-URS as SWL, but because of invasiveness of the procedure, they recommend F-URS for second-line treatment [2]. SWL, however, is not a non-invasive procedure. D’Adessi et al. [10] recited that SWL is a serious procedure and that its complications should be considered before applying on patients. Complications of SWL may occur with stone passage, infections, and renal or adjacent tissue injury. Complications with stone passage take place when stones [2 cm are treated by SWL, as steinstrasse occur at a 40 % rate if JJ stent is not placed [11, 12]. We did not encounter this complication because our patient group did not have stones [1 cm. Renal complications may be the most important complications following SWL. Hemorrhage caused by direct tissue damage may be perirenal, intrarenal, or subcapsular. If only symptomatic patients are included, the complication is experienced at about 1 %. If hematomas are screened that percentage may increase to fourfold [13]. One of our patients suffered from subcapsular hematoma. A JJ stent was placed and hematoma resolved without any additional interventions. Grasso and Ficazzola [14] presented their F-URS results of 90 patients with lower pole stones. They grouped the patients according to stone size and found 95 % success rate in\1 cm group. Jung et al. [3] presented their series of F-URS outcomes on SWL-resistant kidney stones. Their cases had a mean of 9-mm kidney stones. They reached 76 % success rate after two sessions. Authors pointed out the need of a second procedure in the presence of lower pole stones greater than 1 cm. We have a success rate of 100 % in a single session. This success may be because of the exclusion of patients with steep infindibulopelvic angle. High success rates are presented for F-URS with lower pole stones \1 cm. Wen et al. unveiled their study comparing SWL and F-URS for pilots. They found 100 % stone-free rate in F-URS group as compared to 35 % in SWL group [15]. Tawfiek et al. [16] presented the results of their 23 cases with a mean diameter of 7 mm. They revealed 87 % success rate in 3 months. Hollenbeck et al.



[17] presented 87 % success rate. They encountered 8 % severe postoperative pain in need of hospitalization. Schuster et al. [18] stated 89 % success and minimal complications in a series of 95 patients. Pearle et al. [19] found similar success rates, but encountered 6 % collective system perforation. In our study, similar to literature, the stone-free rate was 100 % in 3 months. Even though overall complication rate for F-URS is between 9 and 25 % [2], most complications of F-URS are not major and no intervention is needed for treatment. Geavlete et al. [20] reported their complication rates of 2,735 procedures. They reported less serious complications, such as mucosal injury (1.5 %), renal colic (2.2 %), and JJ stent malpositioning (0.77 %); as well as more serious ones: fever or sepsis (1.13 %), ureteral avulsion (0.1 %), and ureteral strictures (0.1 %). In addition, they reported possible damage to urethra and ureter with instrumentation. Complications concerning general anesthesia should also be kept in mind. Our complication rates are similar to those presented in the literature. Because we only performed F-URS for smaller stones and relatively more simple cases, and have a shorter follow-up duration, more serious complications might have been avoided. In the current literature, there is very little evidencebased studies comparing F-URS and SWL for \1 cm kidney stones of lower pole. The only comparative study revealed similar outcomes of success and complications with both methods. Pearle et al. [19] had a multi-institutional study, which may cause concern of uniformity, but also can be considered to have a broader applicability. They revealed less success rates than our study; 65 % for SWL and 72 % for F-URS groups. To address that difference, one can consider the technique for F-URS, which they fragmented 57 % of their stones in situ. We also have a significantly larger population for the study, which may have also caused this difference. In our study, even with a smaller number of sessions (1 vs. 2.7 ± 0.4) F-URS presented significantly better stone clearance outcomes than SWL did, with similar complication rates. A similar study with larger stones was conducted by ElNahas et al. [21]. The authors designed a match-pair analysis for the treatment of lower pole stones between 10 and 20 mm and obtained a similar stone-free rate as in our F-URS group (86.5 %). The complication rates were 13.5 % for F-URS and 8 % for SWL group. In their study, 37 patients underwent F-URS, and 68 patients underwent SWL. The main difference between that study and ours is the stone sizes. They have a lower stone-free rate and higher complication rate for F-URS group than our study. The lack of consideration of lower pole infindibulopelvic angle may be a factor for this difference, as well as the stone size. Considerable limitations are present in this study. One of the most important ones is pre and postoperative use of


Urolithiasis (2014) 42:127–131

CT. Because of the relatively high cost of the CT in a developing country like ours, a CT could not be performed in all cases. However, CT was used with an undetermined case and confirmed the diagnosis of the ultrasound. The anatomy of the lower pole is not discussed in the study. We excluded patients with steep infindibulopelvic angles, and other anatomical variations were not considered. Another limitation is that we did not remove fragments after fragmentation with F-URS. Because we performed stone displacement to renal pelvis or upper pole and disintegrated them to fragments smaller than 3 mm, but we did not remove residual stones.

Conclusion SWL and F-URS are treatment options for lower pole stones \1 cm. As this study suggests, with higher success and similar complication rates, with fewer sessions per treatment, advances in technology and increased experience, we believe F-URS has been a serious alternative option against SWL. Conflict of interest All the authors declare that there is no conflict of interest with any financial organization.

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Prospective randomized trial comparing shock wave lithotripsy and flexible ureterorenoscopy for lower pole stones smaller than 1 cm.

In this study, we aimed to compare the success and complications of flexible ureterorenoscopy (F-URS) with its advanced technology and the accomplishe...
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