Randomized Controlled Trial Comparing Retroperitoneal Laparoscopic Pyelolithotomy Versus Percutaneous Nephrolithotomy for the Treatment of Large Renal Pelvic Calculi: A Pilot Study

Abstract

Purpose:

To evaluate the efficacy and safety of retroperitoneal laparoscopic pyelolithotomy (RLP) versus percutaneous nephrolithotomy (PCNL) for large renal pelvic calculi using a randomized controlled trial.

Materials and Methods:

Patients with large renal pelvic calculi were prospectively randomized using matched-pair analysis (1:1 scenario) into either the RLP group or the PCNL group. The patients in each group underwent the procedure accordingly. Treatment efficacy, safety, and complications were evaluated after surgery.

Results:

Finally, 178 eligible patients were included and the demographics and mean stone size of two groups were similar. We found no significant differences in the mean postoperative hospital stay (4.5±2.3 vs. 4.3±1.3 days), rate of blood transfusion (0% vs. 1.1%), conversion rate (0% vs. 3.4%), and rate of total postoperative complication (p>0.05). The procedural duration and mean drop in hemoglobin levels were significantly lower in the RLP group as compared with the PCNL group (90.87±33.4 vs. 116.8±44.4 minutes, p<0.001; 0.9±0.5 vs. 1.7±1.3 g/dL, p<0.001, respectively). Significant differences were also observed in the stone-free rate (98% vs. 90%, p=0.03) and postoperative fever rate (3.4% vs. 13.5%, p=0.02).

Conclusions:

Current evidence suggests that PCNL and RLP are both effective and safe for the treatment of large renal pelvic calculi. Our study shows that, compared with the PCNL approach, RLP for large renal pelvic stone resulted in shorter operative time, less bleeding, less postoperative fever, and a higher stone-free rate. Data from larger, multicenter randomized controlled trials of high quality are needed to further confirm our findings.

Introduction

Kidney stone is one of most common urologic benign disease.¹ Currently, there are many kinds of optimal therapeutic approaches for large renal calculi (>2 cm in diameter), such as shock wave lithotripsy (SWL),² percutaneous nephrolithotomy (PCNL),³ open surgery, and laparoscopy.⁴ In the 2013 EAU guideline, PCNL was recommended as the first choice for large stones (>2 cm in diameter). However, PCNL may not suit for all large stones, such as complex stone burden, large staghorn stone, and anatomical abnormalities. With the development of technique in laparoscopic surgery, laparoscopic pyelolithotomy (LP), especially retroperitoneal laparoscopic pyelolithotomy (RLP), was increasingly used to treat renal pelvic calculi.^5

–8 For a patient with large renal calculi, which approach should a surgeon choose? And what is the evidence? In 2012, we performed a meta-analysis exploring the comparative effectiveness of LP and PCNL.⁹ The results showed that both PCNL and LP were safe and effective for large renal pelvic calculi. However, all the included studies in this meta-analysis were Non-Randomized Concurrent Controlled Trial (NRCCT). It is thus clear that there is a lack of randomized controlled data comparing RLP with PCNL for large renal pelvic calculi. Consequently, we performed this randomized controlled trial to obtain higher grade evidence.

Patients and Methods

Study design

We did a two-arm randomized, single-center, open-label, controlled trial of patients with large renal pelvic calculi in the Zhongnan Hospital of Wuhan University. This randomized controlled trail was designed by the professional staff and was reported following the proposed Consolidated Standards of Reporting Trials (CONSORT) Statement.¹⁰

We followed the current edition of the Declaration of Helsinki and our study was approved by the local Ethics and Research Committee. Informed consent was obtained from all participants, who declared that they had read the participation information booklet and understood the purposes and requirements of the study. All participants signed an informed consent form before enrollment.

Participants were randomly assigned to two groups by a ratio of 1:1; the random sequence was generated by STATA software (Version12.0; Microsoft Windows). The serial numbers were allocated by sequentially numbered, opaque, sealed envelopes (SNOSE) until to receive one of two interventions. Each group was completed by a registered and experienced surgeon, who did not take part in the follow on test and evaluation, and all the outcome assessors were blinded to the treatment.

Participants

Participants were all from Wuhan City at the Zhongnan Hospital of Wuhan University (Hubei Province, China). The inclusion criteria were as follows: (1) must have attained the age of 18 and have completed civil capacity, (2) must understand the purpose and requirements of the study and be willing to sign a written consent form, (3) diagnosed with large renal pelvic calculi (>2 cm in diameter, including Staghorn stone), located in the complete or partially extrarenal or intrarenal pelvis as shown by the kidney-ureter-bladder (KUB) film and spiral computed tomography (CT). We excluded participants with a history of associated congenital anomalies, recurrent pyelonephritis, kidney tumors, or upper ureteral calculi. All participants with positive urine cultures were treated according to standard procedures before their allocated study interventions.

Interventions

Technique of RLP

A bladder catheter of a suitable size, initially, was inserted in the lithotomic position under general anesthesia. We moved the participants to the lateral decubitus position and adjusted the operation table for a retroperitoneal approach. A 10-mm trocar was placed in the midaxillary line midway between the 12th rib and iliac crest (for light source and camera). CO₂ was filled from this hole to maintain the pneumoperitoneum at 15 mm Hg. Two additional operating ports were placed with guidance provided by the index finger placed in the retroperitoneum, at a distance of 7–8 cm from either side of the light source port, along a line parallel and inferior to the costal margin.⁴ Dissection access sites for right and left hand were created by a 10-mm and a 5-mm port, respectively. An optional 5-mm port was placed at 3–4 cm above the camera port along the anterior axillary line (Fig. 1A). The retroperitoneal compartment was revealed and subsequent searching along the ureter toward the medial margin of the psoas muscle, whether extrarenal pelvis or intrarenal pelvis, we separated the renal sinus and fully exposed the renal pelvis in the renal sinus. A curvilinear or longitudinal pyelolithotomy incision was made to the shape and size of the located calculi. After pyelolithotomy, the calculi were removed, and then placed in a specimen retrieval bag. We then inserted a Double-J ureteric stent. After flushing the renal pelvis and calyces repeatedly with normal saline, we sutured the incision of the renal pelvis. A suction drainage tube was placed in the peripelvic tissues and passed through the lateral port. Finally, the laparoscope and all the trocars were pulled out and the incision was sutured. Figure 1B–C shows a large renal pelvic calculus removed by RLP. Video 1 showed the patient's operation process (the video can be accessed by contacting the corresponding author).

FIG. 1.

A case of retroperitoneal laparoscopic pyelolithotomy. (A) Port sites according to the access. 1, camera port; 2, operating port; 3, optional port; PAL, posterior axillary line. (B) Preoperative CT demonstrates a large renal pelvic calculus. (C) A laparoscopic view toward the posterior aspect of the left kidney. 1, left kidney; 2, ureter; 3, stone.

Technique of PCNL

Patients were subjected to general anesthesia and placed in the lithotomy position. A 5F ureteral catheter was inserted. The patients were switched to the prone position and percutaneous access was obtained under type B supersonic diagnostic observation. Nephroscopy was performed using a rigid standard nephroscope. Stone fragmentation and removal were accomplished using a variety of lithotriptors (ultrasonic, ultrasonic/pneumatic, and/or holmium laser). A Double-J ureteric stent and/or an 18–20F nephrostomy tube were placed in patients as required at the end of PCNL.

Outcomes

We obtained the following data for each group: operative time (minute), days of hospital stay (day), drop in hemoglobin levels (g/L), stone-free rate (%), blood transfusion rate (%), failure procedure/conversion rate (%), and postoperative complications. All outcome assessors were blinded to treatment allocation.

Sample size

Using the previously reported outcomes for stone-free rate from our meta-analysis,⁹ the rate was 98.7% and 89% in LP and PCNL, respectively. Following published guidelines,¹¹ we calculated the sample size based on 80% statistical power at a 5% significance level aimed to detect a difference between the two groups. A sample size of 74 was deemed necessary for each arm. By allowing for an attrition rate of 20%,¹² we estimated that a total sample size of 178 participants (89 per group) would be sufficient, with an expected drop-out rate of 15 participants.

Statistical analysis

The statistical analysis was performed by Stata software. Student's t-test and chi-square test were appropriately used. Differences in continuous outcomes were analyzed as mean differences with their 95% confidence intervals (CIs); for dichotomous binary data, we used the risk ratios and their 95% CIs. A two-sided p-value of less than 0.05 was considered to represent statistical significance.

Results

Participants

We performed this study between 2nd January 2009 and 2nd July 2013. During the study period, a total of 240 consecutive participants were assessed for eligibility and 178 were eventually included in the study and randomized in a 1:1 fashion to RLP (n=89) and PCNL (n=89). Figure 2 shows the flow process of participants through trial. Table 1 presents the characteristics of eligible participants. We found no significant differences between them. All kidney stones were located in the renal pelvis; the mean stone size in the RLP and PCNL groups was similar (2.93±1.02 vs. 3.0±0.96 cm, respectively [p>0.05]). Other demographics such as age, preoperative urinary tract infection, and maximum follow-up duration were also similar between them.

FIG. 2.

The flow process of participants through trial.

Table 1.

Characteristics of Eligible Participants

	Group 1 (RLP)	Group 2 (PCNL)	p-Value
Number of cases	89	89	NS
Mean age (year)	55.63±10.98	53.15±11.54	NS
BMI (kg/m²)	23.29±3.37	22.67±3.19	NS
UTI (%)	18 (20%)	14 (16%)	NS
Pyonephrosis	4 (4.5%)	2 (2.2%)	NS
Mean stone size (cm)	2.93±1.02	3.0±0.96	NS
Staghorn stone (%)	15 (16.9)	17 (19.1)	NS
Max. follow-up time (month)	3	3	NS

BMI=body mass index; NS=not significant; PCNL=percutaneous nephrolithotomy; RLP=retroperitoneal laparoscopic pyelolithotomy; UTI=urinary tract infection.

Outcomes

Table 2 shows the main results. Compared with the PCNL group, the mean operation time was significantly shorter in the RLP group (90.87±33.4 vs. 116.8±44.4 minutes, p<0.001). The mean drop in hemoglobin levels was significantly lower in the RLP group (0.9±0.5 g/dL) as compared with that in the PCNL group (1.7±1.3 g/dL) (p<0.001). At 3 months, the stone-free rate was higher among participants who underwent RLP (98% vs. 90%, p=0.03). No statistically significant difference was found between the RLP and PCNL groups regarding the mean postoperative hospital stay (4.5±2.3 vs. 4.3±1.3 days, p=0.48). In the RLP group, 89 patients' operations were all successful, no transfusion, no failure procedure/conversion. However, in the PCNL group, the procedure was terminated in three patients (3.4%) due to uncontrolled bleeding. Two of them received RLP a week later, and the stones were removed completely. The remaining adverse bleeding case suffered relatively more blood loss and the participant was subjected to open surgery immediately after blood transfusion. For postoperative complications, there were no statistically significant differences between the PCNL and RLP groups in bleeding (3.4% vs. 0%, p=0.08) and prolonged urinary leakage (0% vs. 3.4%, p=0.08). In addition, postoperative fever was significantly lower in the RLP group as compared with the PCNL group (3.4% vs. 13.5%, p=0.02).

Table 2.

Operative and Postoperative Data

	Group 1(RLP)	Group 2(PCNL)	RR/MD [95% CI] ^a	p-Value
Effectiveness
Mean operative time (minute)	90.87±33.4	116.8±44.4	−25.93 [−37.47, −14.39]	<0.001
Mean drop in hemoglobin level (g/dL)	0.9±0.5	1.7±1.3	−0.80 [−1.09, −0.51]	<0.001
Mean postoperative hospital day (day)	4.5±2.3	4.3±1.3	0.20 [−0.35, 0.75]	NS
Stone-free rate (%)	87 (98%)	80 (90%)	1.09 [1.01, 1.17]	0.03
Blood transfusion (%)	0 (0%)	1 (1.1%)	0.33 [0.01, 8.07]	NS
Failure procedure/conversion rate (%)	0 (0%)	3 (3.4%)	0.14 [0.01, 2.73]	NS
Complication^b
Postoperative fever (Grade II)	3 (3.4%)	12 (13.5%)	0.25 [0.07, 0.86]	0.02
Uncontrolled bleeding (Grade III)	0 (0%)	3 (3.4%)	0.14 [0.01, 2.73]	NS
Prolonged urine leakage (Grade I)	3 (3.4%)	0 (0%)	7.00 [0.37, 133.57]	NS

Differences in continuous outcomes were measured by the MDs and its 95% CIs, while RRs and its 95% CIs for binary outcomes.

All complications were reported using the Clavien Classification of Surgical Complications.

CIs=confidence intervals; MDs=mean differences; RRs=risk ratios.

Discussion

Since PCNL was first introduced by Fernstrom and Johansson in 1976,¹³ it has been accepted worldwide as the main approach in the management of large renal stones (>2 cm).^3,14 Laparoscopic surgery is a newer method, which is similar to open surgery in principles, with additional advantages, including minimal blood loss and short hospital duration.⁶ However, it is not the most popular option for the treatment of renal pelvic stone among urologists.¹⁵ Currently, successful laparoscopic treatment of renal pelvic calculi have been reported. Gaur et al.¹⁶ described the success of using RLP for the treatment of complex staghorn calculi, and Ramakumar et al.¹⁷ demonstrated the effectiveness of RLP as a therapeutic modality of renal calculi concomitant correction of a ureteropelvic junction (UPJ) obstruction in 2002. However, the indications have not been yet defined. Therefore, we analyzed the outcomes of RLP and compared it with PCNL, which was an established technique, using a matched-pair analysis.

Our study shows homogenous preoperative data of the two groups, with no significant differences in sex, age, body mass index, or stone size. We found that the mean operation time of RLP was significantly shorter compared with PCNL. This observation is different to that reported by Meria et al.,³ who reported a longer operation duration with the transperitoneal laparoscopic approach (TLP) when compared with PCNL. As known to all, the operative time could be influenced by many variables such as the type of approach, surgeon's experience, and the different equipment used. We feel that the shorter mean operative time associated with RLP could be due to the following: (1) compared with TLP, the anatomical structure of the RLP procedure (retroperitoneal approach) is easier and it needs less vascular anatomy; (2) compared with PCNL, stones in RLP can be removed intactly, which reduces the likeliness of residual stones as well as operation time.

Compared with PCNL, another advantage of RLP is that the procedure does not cause trauma to renal parenchyma. Therefore, depending on access localization and dilation technique, the risk of bleeding associated with PCNL is higher. Indeed, bleeding is the most frequent and important complication in patients undergoing PCNL. In our study, despite our conservative approach, the drop in hemoglobin levels was significantly higher in the PCNL group as compared with the RLP group (p<0.001).

There were no significant differences between the two groups in conversion rate, blood transfusion, postoperative hospital stay, or postoperative complication (except postoperative fever). This is in agreement with various published data,^3,6,15 which also showed a lack of significant difference between groups in these endpoints.

In the RLP group, three patients with struvite kidney stones suffered from postoperative infectious fever. Other three patients who had complications with postoperative urinary leakage were cured after retroperitoneal continuous drainage. At the 3-month follow-up, two cases of residual kidney stones were reported; the calculi were found to be located in the minor renal calices and thus could not be accessed during the operation. The high stone-free rate achieved in the RLP group was due to the successful intact removal of the stone, which is in contrast to PCNL. In the PCNL group, disintegration of the stone by ultrasonic lithotripsy may have left some residual stones, and the scattering of stone fragments may reduce success rates.

In the PCNL group, there were three cases of procedure termination because of uncontrolled bleeding, which might be caused by morbid obesity and nonhydronephrosis. We also found that in the PCNL group, the patients with pelvic stones combined with pyonephrosis should be treated by percutaneousnephrostomy to manage infection first, and then to remove the stone. However, in the RLP group, we were able to remove the calculi and treat pyonephrosis simultaneously, shorten the hospital stays, and reduce the medical costs.

Overall, in patients who experienced unsuccessful endourological management and/or SWL, complex renal anatomy, or concomitant repair of the UPJ obstruction, RLP serves as a viable alternative; PCNL might be more available for patients with struvite stones and multiple calyceal stones.

Our study has the following limitations. First, we made no records of any subjective intraoperative findings like dissection difficulties or tissue quality. Second, we did not analyze the anatomy of the renal pelvis. Stones located in a kidney with an extrarenal pelvis are easier to remove than those located within an intrarenal pelvis. Third, our findings would be influenced by many variables such as the surgeon's experience, approach route, and different equipment. Fourth, our study is small (n=178), and thus, only large differences between groups could be detected.

Conclusions

In summary, current evidence indicates that PCNL and RLP are both safe and effective for treatment of large renal pelvic calculus, however, the results of this study show RLP seems to be more advantageous. These findings need to be further confirmed by data obtained from large, multicenter randomized controlled trials of adequate quality.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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