Superior calyceal access versus other calyceal access in percutaneous nephrolithotomy: a systematic review and meta-analysis

doi:10.21203/rs.3.rs-1408102/v1

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Superior calyceal access versus other calyceal access in percutaneous nephrolithotomy: a systematic review and meta-analysis

https://doi.org/10.21203/rs.3.rs-1408102/v1

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Purpose: To determine the effectiveness and safety of superior calyceal access compared with other calyceal access in percutaneous nephrolithotomy (PCNL).

Methods: This meta-analysis was carried out according to preferred reporting items for systematic reviews and meta-analysis (PRISMA). We searched Pubmed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI) to identify relevant studies for this meta-analysis. Failed stone clearance event and complication event are two main outcomes, operation time and hospital stay time are two secondary outcomes. Relative data were extracted and assessed by using RevMan 5.3, Stata 15.0 and R 4.0.2.

Results: 16 studies (8541 participants) were identified and included in this meta-analysis. Pooled results indicated that superior calyceal access could offer less failed stone clearance than other calyceal access (OR: 0.64, 95%CI: 0.47-0.88, P=0.006). No complication difference was found (OR: 1.10, 95%CI: 0.78-1.56, P=0.57). Superior calyceal access could offer shorter operation time (SMD: -0.57, 95%CI: -0.98, -0.15, P=0.007). No hospital stay difference was found (SMD: 0.07, 95%CI: -0.09, 0.22, P=0.38). Large heterogeneity was detected in stone clearance comparison (I²=71%, P<0.001) and operation time (I²=97%, P<0.001). Significant publication bias was also identified in stone clearance comparison (P=0.026). These defects weaken the credibility of results.

Conclusion: Despite the considerable heterogeneity and publication bias, superior calyceal access in PCNL may bring better stone clearance rate, shorter operation time, with no increase in postoperative complication and hospital stay for patients with kidney stones. This finding still needs to be verified by larger randomized controlled trials.

Percutaneous nephrolithotomy

superior calyceal access

meta-analysis

stone clearance

complication

Kidney stones are a common disease in urology department, with prevalence rates of 1%-20%(1). As the advancement of surgical technology, minimally invasive surgery represented by percutaneous nephrolithotomy (PCNL) has become the preferred treatment for urinary calculi(2). Choosing the appropriate kidney calyces to establish a PCNL channel has always been the focus of PCNL related research. A large-scale multi-center prospective study published in 2012 provided important evidence for this topic. It was found that superior calyceal access could cause more complications, more extended hospital stays, and lower stone clearance rate than inferior calyceal access (3). However, it is worth noting that there are significant differences in the stone positions between the experimental and control groups in this study. However, a randomized controlled clinical trial provided different conclusions from previous studies(4). In this RCT, when treating lower calyx and renal pelvis stones, superior calyceal access showed a better stone clearance rate and similar postoperative complication rate compared with inferior calyceal access. Except for the representative large-sample multicenter prospective cohort study and RCT, the conclusions of many other published articles are not consistent(5,6). Given the inconsistency of previous studies on this topic, we have carried out this meta-analysis with the intention of merging and analyzing published data to provide a higher level of evidence.

1.1 Literature search and inclusion criteria

This meta-analysis was carried out according to preferred reporting items for systematic reviews and meta-analysis (PRISMA). We searched Pubmed, Embase, Web of Science, China National Knowledge Infrastructure (CNKI) to identify relevant studies. The latest search date was Dec 1, 2021. The searching keywords included percutaneous nephrolithotomy, PCNL, superior calyx, upper calyx, superior calyceal access, and upper calyceal access. Furthermore, the reference part of every candidate literature was manually screened to find possible data sources.

Detailed inclusion criteria were as follows: Patients with kidney stones were treated with percutaneous nephrolithotomy. Intervention in this analysis was superior calyceal access. The comparison was conducted between superior calyceal access and other calyceal access. The primary outcomes were stone clearance and complication events. Other outcomes, such as operation time and hospital stay time, were not compulsory. Exclusion criteria were as follow: Reviews, meta-analysis, letters, comments, case serials, and conference abstract were excluded. Studies focused on comparison middle and inferior calyceal access or published earlier than 2000 were excluded neither. Studies that did not offer enough information or data which could be used for meta-analysis were excluded. Two independent authors carried all the title screening, abstract screening, and full-text review (YM, LL).

Non-randomized primary articles were evaluated by the Newcastle-Ottawa Scale (NOS) system, and two independent reviewers performed the evaluation procedure. According to the NOS scales, 7–9 score studies were thought of as high-level quality, 5–6 score studies were considered moderate-level, and < 5 score studies were low-level quality. Low-level quality studies should not be involved in the meta-analysis.

1.2 Meta-analysis

This study compared the efficacy and safety of superior calyceal access applied in the percutaneous nephrolithotomy. In efficacy comparison, the primary outcome was the postoperative stone clearance for two types of access. However, in the safety comparison, since some included studies did not offer detailed data about complications, only the overall complication rate was compared in this analysis. Data on the number of the failed stone clearance event, the number of patients with postoperative complications, and the total number of patients were extracted from the included studies. The operation time and hospital stay time were also extracted from included studies to compare superior calyceal access and other calyceal access.

Two authors carried out the data extracting procedures and double-checked them independently (YCM and LL). The data pooling procedures were performed with RevMan 5.3, Stata 15.0 and R 4.0.2. Statistical significance was defined as P < 0.05. The primary outcomes' 95% confidential intervals (95%CI) were also provided. For a continuous variable, standard mead difference was calculated and synthesized as an estimate. Odds ratio (OR) was calculated and synthesized as the main effect size for discontinuous variable. Heterogeneity was evaluated by I² and Q tests. When I² > 50%, heterogeneity was considerable, and a random-effects model should be used. To identify potential factors contributing to heterogeneity, subgroup analyses were conducted to offer more information. Forest plots were produced to display the main results. In addition to funnel plots, Egger's test was used to detect publication bias. Any detected publication bias was reanalyzed using the trim-and-fill method to evaluate the effect of the publication bias on the meta-analysis results.

After database searching, 778 studies were identified. After the screening procedures and quality evaluations were applied, the original data extracted from 8 studies were included in the quantitative analysis(3–18). Figure 1 shows the screening flow chart. In all, 16 studies (total 8451 patients) compared the efficiency (failed stone clearance) and safety (complication occurrence) between the superior calyceal access and other calyceal access; 13 studies were included in the comparison of the operation time, and 8 studies were included in the comparison of hospital stay as secondary outcomes. Of the 16 studies, 1 was RCT, 7 were prospectively designed, and 8 were retrospectively designed. Table 1 provides detailed information about the included studies.

Table 1

characteristics of included studies. PCNL = Percutaneous nephrolithotomy, NR = not reported, PCS = prospective cohort study, RCS = retrospective cohort study.
Author	Year	study design	Study location	Total participants	Superior calyceal access participant	Other calyceal location	Other calyceal access participant	kidney stone location or type	PCNL type	Guided method	Stone clearance definition (residual size)	NOS
M. Amaresh	2021	PCS	India	126	63	inferior calyceal	63	multiple	Standard and mini PCNL	X-ray fluoroscopy	Residual calculi at 1 month (4mm)	7
Vishwajeet Singh	2015	RCT	India	100	50	inferior calyceal	50	multiple	Standard PCNL	X-ray fluoroscopy	Auxiliary procedures needed	/
Faruk Özgör	2015	RCS	Turkey	360	42	inferior and middle calyceal	318	multiple	Standard PCNL	X-ray fluoroscopy	Residual calculi at 3 month (4mm)	7
Ahmet Tefekli	2012	PCS	Multi centre	3515	403	inferior calyceal	3112	multiple	Standard PCNL	X-ray fluoroscopy or ultrasonography	Residual calculi at 1 month(NR)	8
Rohit Singh	2014	PCS	India	94	43	inferior calyceal	51	staghorn calculi	Standard PCNL	X-ray fluoroscopy	Auxiliary procedures needed	7
Kyle A. Blum	2018	PCS	USA	76	17	inferior calyceal	59	staghorn calculi	Standard PCNL	X-ray fluoroscopy	Residual calculi at 1 month (NR)	6
MONISH ARON	2004	PCS	India	102	69	inferior calyceal	33	inferior calyceal calculi	Standard PCNL	NR	Residual calculi at 1 day (2mm)	7
Suxi Huang	2021	RCS	China	258	206	inferior calyceal	52	inferior calyceal calculi	Standard PCNL	ultrasonography	Residual calculi at 3 day (4mm)	8
Liquan Zhou	2018	RCS	China	1438	415	inferior and middle calyceal	1023	multiple	Standard PCNL	X-ray fluoroscopy or ultrasonography	Residual calculi at 3 day (4mm)	6
Yu Zhang	2021	RCS	China	379	146	inferior and middle calyceal	233	staghorn calculi	Standard PCNL	X-ray fluoroscopy	Residual calculi at 1 day (4mm)	6
Sedat Oner	2018	PCS	Turkey	77	10	inferior and middle calyceal	67	multiple	Standard PCNL	X-ray fluoroscopy	Residual calculi at 1 day (4mm)	7
NELSON RODRIGUES NETTO	2004	RCS	Brazil	86	16	inferior and middle calyceal	70	staghorn calculi	Standard PCNL	ultrasonography	Residual calculi at 1 day (5mm)	6
Ricardo MO Soares	2019	RCS	USA	329	227	inferior and middle calyceal	102	multiple	Standard PCNL	X-ray fluoroscopy	Residual calculi at 1 day (3mm)	7
Charles U. Nottingham	2020	PCS	USA	767	112	inferior and middle calyceal	655	multiple	Standard PCNL	X-ray fluoroscopy	Residual calculi at 1 day (NR)	8
Patrick L. Vande Lune	2019	RCS	USA	591	424	inferior and middle calyceal	167	multiple	Standard PCNL	X-ray fluoroscopy	Residual calculi at 1 day (NR)	7
Yan Song	2016	RCS	China	153	45	inferior and middle calyceal	108	Pelvic calculi	Standard PCNL	ultrasonography	Residual calculi at 1 day (5mm)

There were 16 studies (comprising 8451 participants, 2288 superior calyceal access, and 6163 other calyceal access) included in the comparison of failed stone clearance(3–18). In the overall synthesis, superior calyceal access could be offered less failed stone clearance than other calyceal access (Mantel-Haenszel statistic [M-H] random model, OR: 0.64, 95%CI: 0.47–0.88, P = 0.006, Fig. 2A). The heterogeneity of overall synthesis was significant (I² = 71%, P < 0.001). According to the egger test (P = 0.026) and funnel plot (Fig. 3A), significant publication bias was detected. The Trim-and-fill method was applied to adjust the effect of publication bias on the stability of the results. After adding 6 additional studies, the pooled result was insignificant (OR:0.87, 95%CI:0.60–1.24, P = 0.437, Fig. 4). Many interesting things were found in the subgroup analysis (Table 2). Compared with studies in other parts of the world, more positive results have been published in Asia (OR: 0.47, 95%CI:0.34–0.66, P < 0.001). Different from prospective studies, retrospectively designed studies support the conclusion that superior calyceal access can provide better stone clearance than other calyceal access (OR: 0.62, 95%CI: 0.44–0.88, P = 0.007). There were also 16 studies (comprising 8451 participants, 2288 superior calyceal access, and 6163 other calyceal access) included in the complication comparison meta-analysis(3–18) In the overall synthesis, no significant complication difference was detected between superior calyceal access and other calyceal access (M-H random model, OR: 1.10, 95%CI: 0.78–1.56, P = 0.57, Fig. 2B). The heterogeneity of synthesis was significant (I² = 76%, P < 0.001). No publication bias was found by egger’s test (P = 0.568) and funnel plot (Fig. 3B). Detailed subgroup analysis about safety information were offered in Table 3, and there was no significant difference in any subgroup.

Table 2

Subgroup analyses of failed stone clearance. OR = Odds ratio; RCT = Randomized controlled trials; PCS = prospective cohort study;RCS = retrospective cohort study; PCNL = Percutaneous nephrolithotomy; NR = Not reported.
	Pooled OR for failed stone clearance		Heterogeneity
Subgroup	OR (95%CI)	P value	I²	P value
Recent 5-year study (Yes)
Yes	0.63 (0.45, 0.87)	0.006	61.7%	0.005
No	0.63 (0.31, 1.27)	0.197	67.0%	0.010
Study design
RCT	0.10 (0.01, 1.95)	0.129	/	/
PCS	0.70 (0.41, .18)	0.179	67.5%	0.005
RCS	0.62 (0.44, 0.88)	0.007	60.6%	0.013
Study location
Asia	0.47 (0.34, 0.66)	< 0.001	34.8%	0.129
America	0.90 (0.70, 1.16)	0.411	0.0%	0.504
Sample size > 200
Yes	0.73 (0.50, 1.06)	0.094	82.4%	< 0.001
No	0.46 (0.28, 0.75)	0.002	0.0%	0.497
Other access type
inferior calyceal access	0.45 (0.19, 1.04)	0.063	83.8%	< 0.001
inferior and middle calyceal access	0.74 (0.58, 0.93)	0.010	28.4%	0.192
Types of kidney stones
Pelvic calculi	0.79 (0.20, 3.05)	0.727	/	/
staghorn calculi	0.72 (0.50, 1.05)	0.086	0.0%	0.645
inferior calyceal calculi	0.26 (0.15, 0.45)	< 0.001	0.0%	0.728
Not specified	0.75 (0.50, 1.10)	0.143	74.7%	< 0.001
Types of PCNL
Standard PCNL	0.67 (0.49, 0.92)	0.012	71.3%	< 0.001
Standard PCNL + mini PCNL	0.19 (0.04, 0.95)	0.043	/	/
Guide method
X-ray fuoroscopy	0.78 (0.61, 1.01)	0.056	19.4%	0.264
ultrasonography	0.38 (0.18, 0.83)	0.015	30.4%	0.238
X-ray fuoroscopy or ultrasonography	0.82 (0.30, 2.25)	0.706	95.4%	< 0.001
NR	0.30 (0.11, 0.82)	0.019	/	/
Clearance definition
Additional treatment needed	0.36 (0.12, 1.03)	0.056	0.0%	0.367
Residuals identified by imaging	0.67 (0.48, 0.93)	0.015	73.3%	< 0.001

Table 3

Subgroup analyses of complication OR = Odds ratio; RCT = Randomized controlled trials; PCS = prospective cohort study;RCS = retrospective cohort study; PCNL = Percutaneous nephrolithotomy; NR = Not reported.
	Pooled OR for complication		Heterogeneity
Subgroup	OR (95%CI)	P value	I2	P value
Recent 5-year study (Yes)
Yes	1.00 (0.62, 1.60)	0.983	78.8%	< 0.001
No	1.38 (0.86, 2.20)	0.184	53.6%	0.056
Study design
RCT	0.72 (0.23, 2.24)	0.566	/	/
PCS	1.09 (0.62, 1.89)	0.771	55.7%	0.035
RCS	1.16 (0.69, 1.94)	0.581	84.7%	< 0.001
Study location
Asia	0.84 (0.51, 1.39)	0.488	76.7%	< 0.001
America	1.65 (0.87, 3.13)	0.125	64.2%	0.025
Sample size > 200
Yes	1.16 (0.74, 1.83)	0.513	87.0%	< 0.001
No	0.97 (0.61, 1.56)	0.914	16.3%	0.302
Other access type
inferior calyceal access	1.38 (0.98, 1.93)	0.601	86.2%	< 0.001
inferior and middle calyceal access	0.79 (0.33, 1.91)	0.066	60.2%	0.010
Types of kidney stones
Pelvic calculi	1.24 (0.49, 3.15)	0.647	/	/
staghorn calculi	1.35 (0.71, 2.58)	0.361	45.9%	0.136
inferior calyceal calculi	0.30 (0.06, 1.54)	0.150	80.5%	0.023
Not specified	1.32 (0.92, 1.91)	0.133	71.9%	< 0.001
Types of PCNL
Standard PCNL	1.15 (0.81, 1.63)	0.432	77.1%	< 0.001
Standard PCNL + mini PCNL	0.40 (0.10, 1.62)	0.200	/	/
Guide method
X-ray fuoroscopy	1.37 (0.90, 2.10)	0.148	61.9%	0.005
ultrasonography	0.57 (0.12, 2.75)	0.486	86.9%	< 0.001
X-ray fuoroscopy or ultrasonography	1.23 (0.68, 2.23)	0.487	90.1%	0.001
NR	0.73 (0.22, 2.45)	0.615	/	/

In this analysis, operation time and hospital stay were also synthesized and compared as secondary outcomes. There were total of 13 studies (1525 superior calyceal access and 5239 other calyceal access) included in the operation time comparison(3–13,17,18). Because the reported operation time in different studies was quite different, the primary effect size we used was standard mean differences (SMD). After the data synthesis, we found that superior calyceal access could offer shorted operation time compared with other calyceal access (Inverse variance weighted method, IVM, SMD: -0.57, 95%CI: -0.98, -0.15, P = 0.007). The heterogeneity was extremely large (I² = 97%, P < 0.001). The funnel plot was asymmetric, but no publication bias was detected by egger’s test (P = 0.074) (Fig. 3C). Hospital stay comparison was conducted among 8 studies (672 superior calyceal access, 3839 other calyceal access)(3–7,12,13,17) and we found that there was no significant difference (IVM, SMD: 0.07, 95%CI: -0.09, 0.22, P = 0.38) without significant heterogeneity (I² = 42%, P = 0.10). No publication bias was detected by funnel plot (Fig. 3D) and egger’s test (P = 0.408).

The choice of access for PCNL is essential and has resulted in a strong debate. According to the meta-analysis results, superior calyceal access may offer a better stone clearance rate than other calyceal access (M-H random model, OR: 0.64, 95%CI: 0.47–0.88, P = 0.006). However, significant heterogeneity and considerable publication bias weaken this finding. After the publication bias adjustment conducted with the trim-and-fill method, the stone clearance difference between superior calyceal access and other calyceal access became insignificant (six studies added, OR:0.87, 95%CI:0.60–1.24, P = 0.437). In the safety comparison, no significant difference was detected between superior calyceal access and inferior calyceal access (OR: 1.08, 95%CI: 0.76–1.53, P = 0.68). However, this result was still affected by considerable heterogeneity and potential publication bias. The combination of operation time and hospital stay was secondary outcome in this analysis. There was no significant difference in the hospital stay between using superior calyceal access and other calyceal access (IVM, SMD: 0.07, 95%CI: -0.09, 0.22, P = 0.38, Fig. 2D). Similar to stone clearance, although there were significant differences in the operation time (IVM, SMD: -0.57, 95%CI: -0.98, -0.15, P = 0.007, Fig. 2C), the considerable heterogeneity leads to an important impact on the stability of the conclusion (I² = 97%, P < 0.001).

The surgeon's choice of access site is often affected by many factors, including but not limited to the location and size of the stone, other conditions of the patient, the surgeon's technical preferences, and so on(3). According to a previous study, superior calyceal access PCNL may be a better choice for patients with superior calyceal stones, staghorn stones. Its main advantage lied in anatomical proximity and ease of instrumentation(3). Many other reports also believed that superior calyceal access is more widely used in complex kidney stones(8,9). The characteristic of the superior calyceal access is that the superior calyx is usually discharged by a single funnel-shaped calyx, the internal space is relatively large(19). At the same time, the probability of large calculus inside the superior calyx is much less than that of the middle and inferior renal calyx, which is also very conducive to maximizing the operating space and flexibility of the device inside the kidney(20). Compared with other pathways, the access through the superior calyx also allows the device to be aligned with the long axis of the kidney, thereby facilitating access to the renal pelvis and other calices and obtaining a satisfactory stone-free rate, fewer punctures, and fewer complications (8). Although some studies believed that the middle calyceal access could treat both superior and inferior calyx(21), when the passage through the middle calyx forms a very small acute angle with the superior calyx and inferior calyx, it was often challenging to perform completely stone cleaning(20). The main problem with PCNL using the inferior calyx access is just the opposite of the advantages of the superior calyx. The inferior calyx has a more complicated structure and a smaller inner space of the calyx, it also has a larger angle with the long axis of the kidney, and all these factors may affect the stone clearance rate(20). Actually, the choice of inferior calyceal access and superior calyceal access is more dependent on the habits of the doctor and even the tradition of the hospital(3).

In terms of complications, the most important difference between superior calyceal access and inferior calyceal access is that the establishment of the upper calyx channel often requires supracostal puncture, which may increase the probability of chest-related complications such as pneumothorax even lung injury(5). In a study focused on the supracostal puncture, it was pointed out that the risk of hydrothorax after supracostal puncture was low (3.31%), which was within an acceptable range(22). Although some studies have pointed out that superior calyceal access can bring more complications, this study combined with more published data and found that it does not bring more complications.

There were still some limitations of this analysis. First, although the main component studies were prospective designed studies, there was only 1 RCT included in this meta-analysis. Second, although the pooling result indicated that superior calyceal access could offer a better stone clearance rate, the heterogeneity and publication bias weaken the evidence level. More and large-scale randomized studies should be performed in the future focused on this topic (23).

Despite the considerable heterogeneity and publication bias, superior calyceal access in PCNL may bring better stone clearance rate, shorter operation time, with no increase in postoperative complication and hospital stay for patients with kidney stones. This finding still needs to be verified by larger randomized controlled trials.

Ethics approval and consent to participate

Not applicable

Consent for publication

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Availability of data and materials

All the data used in this analysis is published in previous studies and available from the corresponding author on reasonable request.

Competing interests

All authors have no conflicts of interest or financial ties to disclose. The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved

Funding

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Authors' contributions

(I) Conception and design: TJ

(II) Administrative support: TJ

(III) Provision of study materials or patients: YM, LL

(IV) Collection and assembly of data: YM, LL, ZL

(V) Data analysis and interpretation: YM, LL, ZL

(VI) Manuscript writing: All authors

(VII) Final approval of manuscript: All authors

Acknowledgement

Not applicable

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No competing interests reported.

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Superior calyceal access versus other calyceal access in percutaneous nephrolithotomy: a systematic review and meta-analysis

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