Comparison of the Prone Split-Leg Position with the Traditional Prone Position in Percutaneous Nephrolithotomy: A Propensity Score-Matching Study

Abstract

Background and Objective:

Several positions have been described for percutaneous nephrolithotomy (PCNL). The aim of this study was to compare the safety and effectiveness of the traditional prone position PCNL (TP-PCNL) and the prone split-leg position PCNL (PSL-PCNL).

Patients and Methods:

A retrospective review was made of the data of 212 patients who underwent prone PCNL in PSL or TP between January 2017 and November 2019. The demographic and preoperative clinical data were used for propensity score-matching (PSM). Following the PSM based on a multivariable logistic regression model, the PSL-PCNL and TP-PCNL groups were compared in preoperative, perioperative, and postoperative parameters. All surgical procedures were performed by an experienced endourologist.

Results:

After PSM, 51 patients from the PSL-PCNL group were matched to 51 TP-PCNL patients. The stone burden was not statistically significant between the two groups (p = 0.388). The mean operation time of the two groups was significantly different (81.5 ± 32.4 minutes vs 93.1 ± 25.9 minutes, respectively, p = 0.026). The hemoglobin decrease in the PSL-PCNL group was greater than that in the TP-PCNL group (−17.7 ± 16.9 g/L vs 13.1 ± 10.9 g/L, p < 0.001). Both groups had similar stone-free rates after 2 weeks (p = 0.49). No significant difference was observed between the groups in the total complication rate (p = 1).

Conclusions:

The application of PSL in PCNL simplifies the surgical procedure and shortens the operating time. Another important advantage is that it allows retrograde intrarenal surgery and ureteroscopy to be performed simultaneously. We recommend the PSL to be applied in PCNL for renal stone patients.

Introduction

Urolithiasis is a common urinary system disease. The reported frequency in China is 5%–10%, and >10% in southern China, one of the highest rates in the world, and the number of patients is rising with an annual incidence of 150–200 per 100,000.¹ With technological developments in recent years, minimally invasive surgeries, including percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS), have become more mature and have gradually replaced the traditional open surgery in the treatment of urinary stones.² PCNL has become the main technique in urinary calculus surgery as there is less bleeding, fewer complications compared with open surgery and its rate of stone removal is high.³ It is often recommended to patients with calculus >2 cm and those with staghorn renal stone.⁴

In recent decades, there have been developments in PCNL position, including the traditional prone position (TP), prone split-leg position (PSL), and supine position.⁵ In the past, PCNL was generally applied with the traditional approach, which is to first generate artificial hydronephrosis with retrograde renal pelvis catheterization in the lithotomy position and then to shift into the prone position.^6,7 However, the change of position in this method influences the effectiveness and the safety of surgery. In case of a cardiac or respiratory emergency, management with the patient in the prone position is difficult for anesthesiologists. Moreover, repositioning the patient prolongs the operating time and increases the workload of the surgical team.^8,9

PCNL in the PSL was first introduced by Thomas Lehman in 1988. In this position, the patient is in the prone position with the legs 60°–80° apart from each other so that retrograde renal pelvis catheterization or ureteral stone fragmentation can be applied.¹⁰ Although the PSL is a modified position in TP-PCNL, it has been shown to be effective from several perspectives.^10

–13 The aim of this study was to analyze patients who underwent PCNL surgery in our hospital and to evaluate the differences in effectiveness and safety between the PSL and the traditional PCNL position.

Patients and Methods

This is a retrospective cohort study to compare the efficacy and safety of patient in the PSL-PCNL and the TP-PCNL and was conducted at a single institution between January 2017 and November 2019. Approval for this study was granted by the Local Ethics Committee of the First Affiliated Hospital of Guangzhou Medical University, Guangzhou, China. The approval number is medical research ethics 2020 No. K-41. As this study was designed retrospectively, written informed consent was not required. It also should be noted that all medical and personal data used in this study remained confidential.

The inclusion criteria were pelvic, caliceal single or multiple renal stones ≥2 cm, or extracorporeal shockwave lithotripsy failure stones. A nephrostomy tube was not applied to any case before PCNL. Preoperative urinary CT scan, urinary ultrasound, and intravenous pyelography were performed routinely. Exclusion criteria were set as patients with insufficient preoperative correction of coagulopathy, any serious heart or respiratory condition, underlying renal tumor, or the inability to tolerate prone position surgery.

All PCNL surgeries were completed by a urologist, Dr. YD Liu, who has extensive experience of both TP-PCNL and PSL-PCNL. A total of 212 patients were candidates for PCNL surgery in our Minimally Invasive Surgery Center of the Department of Urology. Patients were assigned to two different groups. The study group of the PSL comprised 94 cases and the control group of the TP comprised 118 cases. All patients with urinary tract infection received sensitive antibiotics for ∼1 week before surgery. Prophylactic antibiotics were administered to patients without urinary tract infection both before and after surgery.

The preoperative, intraoperative, and postoperative data of both groups were recorded. Preoperative data included age, gender, body mass index (BMI), stone location, stone burden, serum creatinine (SCr) and hemoglobin levels, and the presence or absence of urinary tract infection. Before propensity matching, stone burden was calculated according to the maximum cross-sectional area of the stone. In case of multiple stones, the total of the maximum cross-sectional area of all individual stones was used. Guy's stone score (GSS), which consists of four grades, was used to grade the complexity of PCNL. The GSS has been reported to be significantly associated with operative time and length of hospital stay.^14,15 Intraoperative data included the operating time, the number of access, the size of access, intraoperative bleeding, blood transfusion, migration of fragments, and any injury to adjacent organs, such as the liver, duodenum, spleen, and major vessels.

In this study, the total operative time was calculated as the time starting from the induction of general anesthesia and intubation of the patient to the patient was awake postoperatively. Postoperative data included the postoperative SCr and hemoglobin levels, postoperative length of hospital stay, residual stone size, and removal time of nephrostomy tubes. The success of PCNL was defined as stone free or residual fragment <4 mm. Postoperative complications were classified using the Clavien grading system adapted for PCNL.¹⁶ In this study, the primary outcome is operation time. The secondary outcomes are acquisition from stone-free rate, frequency of intraoperative stones migrate into distal ureter, and complication rate.

Propensity score-matched (PSM) analysis can control confounding factors and eliminate bias arising from patient selection. Therefore, a PSM analysis was applied using a multivariable logistic regression model based on the demographic and other preoperative data.¹⁷ In the comparisons of these data between the groups, t-tests were used for continuous variables and χ² tests for categorical variables. Statistical analyses were performed with SPSS version 25 software. A value of p < 0.05 was considered statistically significant.

Operative technique

In the study group, after induction of general anesthesia, the patient was placed in the prone position with the lower extremities split on the operating table. After routine surgical disinfection and draping, an externalized open-ended 5F ureteral catheter was inserted to the level of the renal pelvis with a ureteroscope. A 16F Foley catheter was then placed and fixed in position with the open-ended ureteral catheter.

In the control group, the patient was placed in the lithotomy position. Then, the externalized open-ended 5F ureteral catheter was advanced to the level of the renal pelvis with a ureteroscope. The patient was then moved into the prone position and routine surgical disinfection and draping were applied. The rest of the PCNL procedure was generally similar to the traditional PCNL procedure for both groups. Under fluoroscopic and ultrasonographic guidance, the puncture location was determined. When the 18G coaxial needle pierced the properly targeted renal calix, urine flowed out, and a 0.089 cm flexible tip guidewire was introduced into the targeted calix. Sequential Amplatz dilators were used to dilate the tract between the skin and renal papilla. Then, Amplatz sheath was introduced to the pelvicaliceal system to maintain the tract.

The maximum diameter of the tracts was 22F, and the most frequently used tract diameter was 18F. If the kidney on the operation side is without hydronephrosis, normal saline can be injected into the collecting system through the open-ended ureteral catheter to provide artificial hydronephrosis.

Utilizing ultrasonic combined with pneumatic lithotripsy or holmium laser, the stones were fragmented and extracted with grasping forceps. Fluoroscopy was applied to check for any residual stone intraoperatively. Ureteroscopic lithotripsy was applied if stone fragments were detected in the distal ureter and then a 6F Double-J stent was placed in all cases. Subsequently, one or more 14F nephrostomy tubes were placed or the skin was sutured (tubeless procedure). At ∼2 weeks after the PCNL, the patient was recalled for kidney, ureter, and bladder radiograph (noncontrast CT scan was applied for nonopaque stones) to evaluate the stone-free rate and whether the Double-J stent could be removed.

Results

A total of 212 patients were analyzed using PSM. With the help of a multivariable logistic regression model, pairs of patients in the PSL group or the TP group were derived using 1:1 greedy nearest neighbor matching within a propensity score of 0.02. With this strategy, 102 patients were enrolled in our study; 51 patients from the PSL-PCNL group were matched to 51 TP-PCNL patients. The patient characteristics between the new groups were seen to be well matched. There were no significant differences between the control group and the study group in respect of age, gender, BMI, hypertension, diabetes, stone location, SCr, leukocyturia, nitrite positivity in urine, urine culture, stone burden, CT value (Hounsfield unit), hydronephrosis, and GSS (p > 0.05 for all) (Table 1).

Table 1.

Characteristics of Patients Receiving Prone Split-Leg Position or Traditional Prone Position Percutaneous Nephrolithotomy Before and After Propensity Score-Matching

Variable	Before matching (n = 212)			After matching (n = 102)
Variable	PSL-PCNL (n = 94)	TP-PCNL (n = 118)	p	PSL-PCNL (n = 51)	TP-PCNL (n = 51)	p
Demographics
Age (mean ± SD), years	52.9 ± 12.5	52.3 ± 11.8	0.713	52.0 ± 13.1	52.8 ± 12.0	0.766
Gender, n (%)			0.337			0.840
Male	52 (56.3)	73 (61.9)		30 (58.8)	31 (60.8)
Female	42 (44.7)	45 (38.1)		21 (41.2)	20 (39.2)
BMI (mean ± SD), kg/m²	23.4 ± 3.4	23.9 ± 4.5	0.374	23.6 ± 3.17	23.8 ± 4.08	0.845
Hypertension, n (%)	13 (13.8)	30 (25.4)	0.037	9 (17.6)	7 (13.7)	0.586
Diabetes, n (%)	5 (5.3)	11 (9.3)	0.273	2 (3.9)	3 (5.9)	0.647
Stone site, n (%)			0.023			0.552
Left	57 (60.6)	53 (44.9)		28 (54.9)	25 (49.0)
Right	37 (39.4)	65 (55.1)		23 (45.1)	26 (51.0)
SCr (median [interquartile range] or mean ± SD), μmol/L	97.1 (83.6–128.0)	98.3 (76.7–147.0)	0.902	106.8 ± 37.4	122.2 ± 89.0	0.914
Leukocyturia, n (%)	40 (42.6)	55 (46.6)	0.555	18 (35.3)	23 (45.1)	0.313
Nitrite, n (%)	22 (23.4)	27 (22.9)	0.929	6 (11.8)	12 (23.5)	0.119
Urine culture, n (%)	22 (23.4)	27 (22.9)	0.929	11 (21.6)	13 (25.5)	0.641
Stone burden (median [interquartile range] or mean ± SD), mm²	571.0 (256.5–1161.0)	288.0 (190.0–566.0)	0.001	468.4 ± 481.9	489.9 ± 339.7	0.388
CT value (mean ± SD), HU	927.5 ± 248.9	884.4 ± 311.4	0.279	909.2 ± 252.8	931.8 ± 309.9	0.707
Hydronephrosis, n (%)			0.002			0.490
None	20 (21.2)	8 (6.8)		6 (11.8)	5 (9.8)
Mild	35 (37.2)	46 (39.0)		21 (41.2)	20 (39.2)
Moderate	28 (29.8)	32 (27.1)		16 (31.4)	16 (31.4)
Severe	11 (11.7)	32 (27.1)		8 (15.7)	10 (19.6)
Guy's value, n (%)			0.003			0.852
I	10 (10.6)	23 (19.5)		8 (15.7)	5 (9.8)
II	51 (54.3)	73 (61.9)		32 (62.7)	35 (68.6)
III	24 (25.6)	19 (16.1)		8 (15.7)	10 (19.6)
IV	9 (9.6)	3 (2.5)		3 (5.9)	1 (2.0)

BMI = body mass index; CT = computed tomography; HU = Hounsfield unit; PCNL = percutaneous nephrolithotomy; PSL = prone split-leg position; SCr = serum creatinine; SD = standard deviation; TP = traditional prone position.

After matching, the frequency of access of kidneys in both groups was 100%. Multiple percutaneous nephrostomy tracts were established in both groups (21.6% vs 2.0%, p < 0.05). The mean operative time (81.5 ± 32.4 minutes vs 93.1 ± 25.9 minutes) was a significant index (p = 0.026). The difference in hemoglobin change was statistically significant between the two groups (−17.7 ± 16.9 g/L vs 13.1 ± 10.9 g/L, p < 0.001).

Migration of stone fragments to the ureter (3.9% vs 9.8%) was found to be similar in the two groups (p = 0.240). The success rate (stone-free rate) after 2 weeks (72.5% vs 78.4%) was similar in two groups (p = 0.49). The changes in SCr (6.9 ± 21.2 μmol/L vs 5.7 ± 25.2 μmol/L, p = 0.219), leukocyte count (1.68 ± 4.10 × 10⁹/L vs 1.04 ± 3.11 × 10⁹/L, p = 0.38), and neutrophilic granulocytes (8.17% ± 19.5% vs 9.82% ± 14.0%, p = 0.625), and the frequency of tubeless procedure (31.4% vs 29.4%, p = 0.803), were comparable between the PSL-PCNL group and the TP-PCNL group. The mean postoperative hospital stay in the PSL-PCNL group was similar to that of the TP-PCNL group (2.5 ± 2.4 days vs 3.2 ± 4.5 days, p = 0.514) (Table 2).

Table 2.

Intraoperative and Postoperative Data Variables

	Group 1 (PSL-PCNL)	Group 0 (TP-PCNL)	p
Methods of lithotripsy			0.006
Pneumatic lithotripsy	23 (45.1%)	39 (76.5)
Ultrasonic lithotripsy	1 (2.0%)	2 (3.9%)
Ultrasonic combined with pneumatic lithotripsy	8 (15.7%)	4 (7.8%)
Holmium laser	19 (37.3)	6 (11.8%)
Guiding methods of paracentesis			<0.001
Ultrasonography	30 (58.8%)	48 (94.1%)
Fluoroscopy	1 (2.0%)	3 (5.9%)
Ultrasonography+fluoroscopy	20 (39.2%)	0 (0.0%)
Rate of access	51 (100%)	51 (100%)	1
Number of tracts	1.4 ± 0.7	1.0 ± 0.14	0.003
Number of tracts			0.02
Rate of single	40 (78.4%)	50 (98.0%)
Rate of multiple	11 (21.6%)	1 (2.0%)
Size of tracts			0.110
18F	60 (87.0%)	39 (75.0%)
20F	2 (2.9%)	5 (9.6%)
22F	7 (10.1%)	8 (15.4%)
Hemoglobin level (g/dL)
Before operation	132.8 ± 22.5	132.4 ± 24.8	0.843
After operation	115.1 ± 24.1	119.0 ± 22.6	0.408
Change	−17.7 ± 16.9	13.1 ± 10.9	<0.001
SCr level (μmol/L)
Before operation	106.8 ± 37.4	122.2 ± 89.0	0.914
After operation	113.7 ± 31.7	116.5 ± 79.7	0.263
Change	6.9 ± 21.2	5.7 ± 25.2	0.219
Leukocyte level ( × 10⁹/L)
Before operation	7.2 ± 2.4	7.8 ± 2.3	0.285
After operation	8.9 ± 3.8	8.8 ± 3.5	0.899
Change	1.68 ± 4.10	1.04 ± 3.11	0.38
Neutrophilic granulocyte level (%)
Before operation	61.0 ± 13.6	64.1 ± 10.7	0.357
After operation	69.2 ± 17.2	73.9 ± 13.2	0.243
Change	8.17 ± 19.5	9.82 ± 14.0	0.625
Nephrostomy tubes			0.803
Tubeless (%)	16 (31.4%)	15 (29.4%)
Time of removing nephrostomy tube ≤24 hours	22 (43.1%)	20 (39.2%)
Time of removing nephrostomy tube >24 hours	13 (25.5%)	16 (31.4%)
Mean operative time (minutes)	81.5 ± 32.4	93.1 ± 25.9	0.026
Mean hospital stay (days)	2.5 ± 2.4	3.2 ± 4.5	0.514
Success rate (%)	37 (72.5%)	40 (78.4%)	0.490
Complication	7 (13.7%)	7 (13.7%)	1
Rate of death	0 (0.0%)	0 (0.0%)	1
Intraoperative stones migrate into distal ureter	2 (3.9%)	5 (9.8%)	0.240
Difficult to place the ureteral catheter	2 (3.9%)	0 (0.0%)	0.311

A total of 14 complications (13.73%) developed, as 7 (13.73%) in the PSL-PCNL group and 7 (13.73%) in the TP-PCNL group (Table 3). In the PSL-PCNL group, one patient (1.96%) required opioid analgesics (Clavien grade I), one patient (1.96%) had postoperative fever (Clavien grade I), one patient (1.96%) had minimal hydrothorax managed by watchful waiting (Clavien grade I), two patients (3.92%) required angioembolization (Clavien grade IIIB), one patient (1.96%) had systemic inflammatory response syndrome (Clavien grade IIIA), and one patient required thoracic closed drainage (Clavien grade IIIA).

Table 3.

Complication Rates of Traditional Prone Position Percutaneous Nephrolithotomy and Prone Split-Leg Position Percutaneous Nephrolithotomy According to the Clavien Grading System

	Clavien grade	PSL-PCNL	TP-PCNL
Fever	Clavien grade I	1 (1.96%)	2 (3.92%)
Pain	Clavien grade I	1 (1.96%)	1 (1.96%)
Hematuria	Clavien grade I	0 (0.00%)	1 (1.96%)
Minimal hydrothorax	Clavien grade I	1 (1.96%)	0 (0.00%)
SIRS	Clavien grade IIIA	1 (1.96%)	0 (0.00%)
Bleeding requiring embolization	Clavien grade IIIB	2 (3.92%)	1 (1.96%)
Thoracic closed drainage	Clavien grade IIIA	1 (1.96%)	0 (0.00%)
Requiring ICU management	Clavien grade IVA	0 (0.00%)	2 (3.92%)
Account		7 (13.73%)	7 (13.73%)

ICU = intensive care unit; SIRS = systemic inflammatory response syndrome.

In the TP-PCNL group, one patient (1.96%) required opioid analgesics (Clavien grade I), two patients (3.92%) had postoperative fever (Clavien grade I), one patient (1.96%) had bleeding without the need for blood transfusion (Clavien grade I), one patient (1.96%) required angioembolization (Clavien grade IIIB), and two patients (3.92%) were admitted to the intensive care unit (Clavien grade IVA), one diagnosed with congestive heart failure, bacteremia, and pneumonia and the other with septic shock and acute pancreatitis (Table 3).

Discussion

Since the first definition of PCNL surgery in 1976, PCNL has undergone some changes and modifications to increase its effectiveness and safety and to be a more practical surgery.^3,18 One of these main changes is that PCNL has become applicable in different positions.^19,20 Currently, several patient positions can be used in PCNL. The main two choices are the supine position and prone position. According to the European Association of Urology guidelines, PCNL in the prone or supine position is equally safe.²¹ The prone position has several disadvantages related to the cardiovascular and respiratory systems, especially in patients with comorbidities. In addition, there is a theoretical and anecdotal risk of eye complications.²²

Despite the potential development of these complications may occur, there are advantages of the prone position as it is less associated with adjacent organ injury and most urologists prefer the prone position and its modifications.^9,23 The prone position also provides the obvious advantage of a large surface area for renal puncture. Therefore, the TP-PCNL is the most commonly used position for patients undergoing PCNL. However, there are some shortcomings in TP-PCNL, such as the need to turn the patient from the lithotomy position to the prone position, longer operation durations, or not having the possibility of treating stone fragments, which may migrate to the ureter during the procedure.

The PSL-PCNL can overcome the above drawback of TP-PCNL. It has been reported that PSL-PCNL can overcome some weakness of TP-PCNL and has similar advantages to the supine position.¹⁰ In a study by Grasso and colleagues., antegrade and retrograde interventions were well applied simultaneously in the PSL to 41 of 111 patients, with acceptable complication rates.¹¹ Due to the anatomical structure of the renal calices in the body, the posterior calices are preferred to accomplish renal access in safety.^6,24,25 In other words, the PSL not only provides a renal puncture area as large as the TP but also provides the possibility to perform endoscopic combined intrarenal surgery (PCNL and ureteroscopic procedures in the same session).¹³ Therefore, stones that have migrated to the ureter during the operation can be easily fragmented using ureteroscopic lithotripsy in the same session.

In this study, the stone-free rates of the two groups were similar (p > 0.05). However, a statistically significant difference between the groups with a shorter mean operating time in the PSL-PCNL group was observed (p < 0.05). In the TP-PCNL method, the process of the placement of an open-ended 5F ureteral catheter to the level of the renal pelvis followed by turning the patient from the lithotomy position to the prone position can take some time.

In the current study, placement of an open-ended 5F ureteral catheter in two patients in the PSL-PCNL group was achieved with the help of flexible cystoscopy. The reason for the first patient was the erection of the penis after anesthesia, and in the second patient, difficulty in locating the ureteric orifice with the ureteroscope. In both patients, the problem was easily managed with the use of a flexible cystoscope. Although it is not easy to locate the target ureteral orifice in the PSL, in our experience, the learning curve of placing an open-ended 5F ureteral catheter with the help of a ureteroscope in PSL-PCNL is not long. The time taken to place an open-ended 5F ureteral catheter may be associated with the experience of the urologist and a junior attending physician can grasp the skill easily after two or three PSL-PCNL procedures. Moreover, in PSL-PCNL surgery, the process of changing the patient position can be avoided. The reasons mentioned above may be an explanation for the shorter operation time in PSL-PCNL.

Furthermore, some studies have reported that the rate of postoperative infection is closely related to the operating time.²⁶ Therefore, to a certain degree, PSL-PCNL can decrease the rate of postoperative infection, but further more detailed studies are required on this subject.

In this study, the rate of multiple percutaneous nephrostomy tracts was observed to be statistically significantly higher in the PSL-PCNL group than in the TP-PCNL group. The results in this study were obtained mainly from TP-PCNL from 2017 to the first half of 2018, whereas the results from the second half of 2018 to November 2019 were predominantly from PSL-PCNL. Recent studies have shown that establishing multiple mini-tract in PCNL is safe,^27,28 which may encourage the surgeon to create more access. It can be speculated that this may be the reason that the rate of multiple tracts in PSL-PCNL was higher than that in TP-PCNL. The fall in hemoglobin in the PSL-PCNL group can be explained by more multiple percutaneous nephrostomy tracts having been established in the PSL-PCNL group. The number of percutaneous nephrostomy tracts can be considered to influence the hemoglobin level.²⁹

Some studies have shown that multiple tract and ultrasonographic combined with fluoroscopic guidance can increase operation time, and the pneumatic lithotripsy and holmium laser lithotripsy had similar operation time.^30
–32 In this study, we analyzed the correlation between puncture mode, tract number, lithotripsy method, and operation time and found that there was no correlation (Supplementary Table S1). Therefore, we have reason to believe that in this study, the higher multiple-tract rate, the higher combined guidance rate, and the higher holmium laser lithotripsy rate in the PSL-PCNL group do not affect the conclusion that the operation time in the PSL-PCNL group is shorter than that in the TP-PCNL group.

It has been reported that migration of the stone fragments, especially to the distal ureter, remains a problem during PCNL. The present study results revealed that the incidence of intraoperative stone migration to the distal ureter in the TP-PCNL group was higher than that in the PSL-PCNL group. As the upper segment of the ureter expands during the procedure, intraoperative single or multiple pulse settings of pneumatic lithotripsy and the process of changing the patient position from the lithotomy position to the prone position may explain the difference between the two groups.³³ In the PSL-PCNL group, stone migration to the distal ureter was observed in two patients and the stones were easily fragmented with ureteroscopy without changing the patient position. In the TP-PCNL group, there were five cases of stone migration to the distal ureter. The stones were cleared after changing the position of the patient from the prone position to the lithotomy position. Therefore, nursing personnel seem to subjectively prefer the PSL as the workload is reduced, with a lesser frequency of patient position change.

No statistically significant difference was determined between the groups in this study in respect of mean length of hospital stay, success rate, SCr level, tubeless rate, and the time of nephrostomy tube removal (p > 0.05). Overall, the complication rates of the PSL-PCNL and TP-PCNL groups showed no statistically significant difference.

As no statistically significant difference was observed in most of the results, there was not seen to be any gross disadvantage of PSL-PCNL and it can save time in surgery. Therefore, the benefits of PSL-PCNL can be said to be that the time of surgery can be reduced, and it allows endoscopic combined intrarenal surgery. Thus, the surgeon can change freely between PCNL, ureteroscopic lithotripsy, or RIRS, as necessary.^34,35

A limitation of this study was the nonrandomized controlled design, and therefore, internal validity bias may be unavoidable. However, the use of a PSM method should have overcome bias caused by any difference in patient characteristics. Additionally, in this study, we have only used the preoperative parameter for PSM without intraoperative parameter. This is a limitation of this study. Future studies in a prospective manner or with at least PSM including preoperative and intraoperative parameters may better elucidate the advantages and disadvantages of these methods.

Conclusions

In conclusion, in the treatment of urinary calculi, the PSL simplifies the surgical procedure and shortens operating time. It is also more convenient for combined therapy, such as PCNL combined with ureteroscopic lithotripsy to treat stone fragments, which have migrated to the distal ureter intraoperatively. The PSL-PCNL should be considered a preferable technique, which is easily applicable and has significant advantages. Nevertheless, further studies with greater patient numbers are required to better elucidate this topic. As PSL-PCNL enables endoscopic combined intrarenal surgery (PCNL and ureteroscopic procedures in the same session), this could significantly increase the stone-free rate, but the exact effect of endoscopic combined intrarenal surgery requires further verification.

Ethical Approval

All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.

Footnotes

Authors' Contributions

Y.Li. had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Y.Li. Acquisition of data: G.Y., Y.Le., Z.L., H.Z., Y.Z., D.C., and X.W. Analysis and interpretation of data: G.Y., C.C., and Y.Le. Drafting of the article: G.Y., Y.Le., and H.Z. Critical revision of the article for important intellectual content: Y.Li. and M.A.K. Statistical analysis: G.Y. Supervision: Y.Li.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

Supplementary Material

Supplementary Table S1

Abbreviations Used

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