Effectiveness and safety of suction-assisted versus traditional access sheaths in minimally invasive percutaneous nephrolithotomy: a meta-analysis of 10 randomized trials

Abstract

Objective

To systematically evaluate the effectiveness and safety of suction-assisted sheaths (SAS) compared to traditional access sheaths (TAS) in minimally invasive percutaneous nephrolithotomy (MPCNL) for renal calculi—addressing key limitations of MPCNL such as compromised irrigation outflow, intraoperative elevation of intrarenal pressure (IRP), and the associated risk of infectious complications.

Methods

This PRISMA-compliant meta-analysis (PROSPERO-registered) included 10 randomized controlled trials (RCTs; n = 1,540) identified through comprehensive searches of PubMed, Embase, Web of Science, and the Cochrane Library from database inception to May 2025. Pooled outcomes were calculated using random- or fixed-effects models, with subgroup analyses based on lithotripsy modality (laser vs. non-laser) and stone type (staghorn vs. non-staghorn). Study quality was assessed using the Cochrane Risk of Bias Tool, and evidence certainty was graded via GRADE.

Results

Compared to TAS, the use of SAS was associated with a significantly higher immediate stone-free rate (SFR; OR 2.29, 95% CI 1.76–3.00) and 3-month SFR (OR 2.72, 95% CI 1.42–5.22), with a greater benefit observed in non-staghorn stones. SAS was also associated with a mean reduction in intrarenal pressure (IRP) of 8.25 mmHg (95% CI − 9.44 to − 7.06), with a more pronounced effect in non-laser procedures. A significant reduction in operative time was observed (MD -13.86 min, 95% CI − 26.43 to − 1.30), although this finding should be interpreted with caution due to substantial heterogeneity (I² = 98%). Regarding safety, SAS was associated with lower rates of postoperative fever (OR 0.40), transfusion (OR 0.43), second surgeries (OR 0.63), and auxiliary procedures (OR 0.38). No significant differences were found for UTI, hospitalization duration, or hemoglobin loss.

Conclusions

This meta-analysis suggests that the use of a suction-assisted sheath in MPCNL is associated with higher stone-free rates, shorter operative times, reduced intrarenal pressure, and a lower incidence of certain postoperative complications, including fever and transfusion requirements. The findings indicate a favorable safety and efficacy profile, suggesting that SAS is a valuable modification for optimizing procedural outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-025-02023-y.

Introduction

The global prevalence of urolithiasis ranges from 1.7% to 14.8%, with an annual recurrence rate exceeding 10% [1]. Notably, complex calculi exceeding 2 cm in diameter (including staghorn calculi) constitute 20% to 30% of surgical interventions and are associated with significant morbidity, including renal dysfunction and systemic infection [2]. Percutaneous nephrolithotomy (PCNL), renowned for its superior stone-free rates, has been designated by the European Association of Urology (EAU) guidelines as the first-line therapeutic modality for renal calculi > 2 cm [2, 3]. To minimize hemorrhagic complications inherent to conventional PCNL, minimally invasive PCNL (MPCNL, utilizing tract diameters ≤ 22 Fr) demonstrates substantial reductions in transfusion rates and length of hospitalization through its narrowed access [4]. However, this approach introduces novel technical challenges, most notably compromised irrigation outflow resulting in intraoperative elevation of intrarenal pressure (IRP) [5]. A substantial subset of patients exhibit IRP surpassing the critical threshold for pyelovenous backflow (≥ 30 mmHg), thereby elevating the incidence of postoperative febrile episodes and residual fragments, particularly in the management of complex stone burdens [5, 6].

To overcome the technical constraints of MPCNL in achieving optimal balance between stone clearance and procedural safety, the suction access sheath (SAS) system was innovated [7]. This technological advancement incorporates an active aspiration mechanism integrated with dynamic pressure modulation, enabling continuous evacuation of calculous debris, irrigant, and inflammatory exudates while permitting real-time adjustment of suction parameters to mitigate iatrogenic trauma [8]. Preclinical investigations have substantiated that the suction sheath achieves significant IRP reduction and stabilization, with theoretical implications for improved stone-free outcomes and diminished infectious sequelae [9]. Emerging clinical evidence indicates that SAS may confer distinct advantages in optimizing operative efficacy and minimizing adverse events, especially when addressing complex or infected calculi [10].

Despite these theoretical and preliminary clinical advantages, the widespread adoption of SAS remains limited due to unresolved controversies and a lack of high-level evidence. Most available studies are single-center randomized controlled trials (RCTs) with small sample sizes and inconsistent findings, leaving several key questions unanswered: (1) Are the benefits of SAS consistent across various clinical scenarios, such as different stone complexities (staghorn vs. non-staghorn) and lithotripsy modalities (laser vs. non-laser)? (2) Does the reduction in IRP reliably translate into a clinically significant decrease in postoperative infectious complications such as fever? (3) Are improvements in operative efficiency attributable to the device itself, or are they confounded by institutional protocols and surgeon expertise? The lack of a comprehensive synthesis of the available evidence has impeded the development of clear, evidence-based recommendations for the routine use of SAS in MPCNL.

To address the current evidence gap, we conducted a systematic review and meta‑analysis to evaluate the efficacy and safety of suction‑assisted sheaths (SAS) versus conventional access sheaths in MPCNL, including subgroup analyses to clarify their role in specific clinical contexts.

Methods

Search strategy

This meta-analysis was prospectively registered in the PROSPERO database(CRD420251082773) and designed in accordance with the PRISMA statement and AMSTAR guidelines to minimize methodological bias [11, 12]. A comprehensive literature search was conducted in PubMed, Embase, Web of Science, ClinicalTrials.gov, and the Cochrane Library from database inception to May 2025, restricted to studies published in English. The search strategy combined both subject terms and free-text keywords, including “percutaneous nephrolithotomy,” “suction sheath,” and “conventional sheath.” Additionally, the reference lists of relevant articles, such as reviews, commentaries, and conference abstracts, were manually screened to ensure comprehensive coverage. Two independent reviewers screened all identified studies, and only randomized controlled trials (RCTs) were included in the final meta-analysis.

Criteria for selection

Studies were eligible for inclusion if they were RCTs comparing suction-assisted sheath (SAS) versus conventional sheath (TAS) in minimally invasive percutaneous nephrolithotomy (MPCNL, tract diameter ≤ 22 F) or adapted PCNL for complex stones (tract diameter 24–30 F, clinically necessary for large/staghorn stones), and if complete clinical data were available. Eligible participants were adults aged ≥ 18 years, with either controlled-infection staghorn calculi or renal stones measuring 1.5–4 cm (some studies required single stones), no active infection (preoperative negative urine culture, procalcitonin < 2 ng/ml), no absolute surgical contraindications (such as coagulopathy or severe cardiopulmonary disease, ASA ≥ III), no anatomical abnormalities or obstructive lesions of the urinary tract, normal renal function, and signed informed consent. Exclusion criteria included non-RCT study types (e.g., reviews, case reports, commentaries, guidelines, letters), ongoing trials or study protocols, studies with insufficient data, and specific populations such as patients under 18 years of age, stones < 2 cm, active infection, pregnancy, coagulopathy, immunosuppression, urinary tract anatomical abnormalities, diabetes, previous renal surgery, hydronephrosis with CT value ≤ 10 HU, suspected malignancy, technical contraindications, or patient refusal.

Data extraction

Data extraction was independently performed by two reviewers(Y.L. and Z.Z.). Extracted data included the first author, year of publication, country, study design, baseline patient characteristics (age, BMI, sex ratio), surgical approach, sample size, inclusion and exclusion criteria, access tract diameter, sheath-nephroscope diameter ratio, SAS model and suction modality (continuous/intermittent), stone size, stone density, and laterality. The primary outcomes were immediate stone-free rate (SFR), 3-month stone-free rate (SFR3M), intrarenal pressure (IRP), and operative time. Secondary outcomes included postoperative fever, urinary tract infection (UTI), blood transfusion, secondary surgery, auxiliary procedures (defined as additional interventions including SWL, RIRS, or second-stage MPCNL for residual stones ≥ 4 mm identified via CT/KUB within 7–30 days postoperatively), length of hospitalization, and hemoglobin loss. For studies that did not report means and standard deviations, these values were estimated from medians and ranges using the methods of Luo and Wan [13, 14].

Subgroup analyses

Subgroup analyses were conducted according to pre-specified factors, such as lithotripsy modality [laser (holmium laser, thulium fiber laser) vs. non-laser (pneumatic lithoclast, ultrasonic lithotripsy)] and stone type (staghorn vs. non-staghorn).

Quality assessment

The methodological quality of included RCTs was assessed using the Cochrane Risk of Bias Tool, evaluating random sequence generation, allocation concealment, blinding, completeness of outcome data, and selective reporting [15]. Two reviewers(Y.L. and Z.Z.)independently performed the assessments, and disagreements were resolved by discussion or consultation with a third reviewer༈H.Z.༉.

Statistical analysis

Statistical analyses were conducted using Review Manager version 5.3. Continuous variables were expressed as mean differences (MD) with 95% confidence intervals (CI), and dichotomous variables as odds ratios (OR) with 95% CI. Statistical significance was defined as a P value < 0.05. Heterogeneity was assessed using the I² statistic; a random-effects model was applied when I² >50% or significant heterogeneity was present, otherwise a fixed-effect model was used [16]. For outcomes with high heterogeneity, sensitivity analyses were performed to identify potential sources. Publication bias was evaluated using funnel plots and assessed for symmetry. Subgroup analyses were conducted according to pre-specified factors, such as the use of laser versus non-laser surgical techniques.

Certainty of evidence

The quality of evidence for each outcome was assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach [17]. The certainty of evidence was rated using the web-based GRADEpro platform (https://www.gradepro.org/) based on the results of the meta-analysis.

Results

Study selection and characteristics​​

A systematic literature search identified 243 potentially relevant articles. Following rigorous screening,10 randomized controlled trials (RCTs) involving 1,540 patients (774 in the suction sheath group and 766 in the traditional sheath group) met the inclusion criteri [10, 18–26]. The study selection process is detailed in Fig. 1. The baseline characteristics of the included studies are summarized in Table 1 (Supplementary Table 1), and comparative renal stone characteristics across groups are presented in Table 2 (Supplementary Table 2). Stone composition was available for 6 RCTs (Huang 2016, Lai 2020, Liang 2023, Lu 2023, Pathak 2024, Xu 2020); infectious stones (struvite/carbonate apatite) were reported in 3 of these 6 RCTs (Huang 2016, Xu 2020, Pathak 2024) with no significant between-group differences (P > 0.05) [10, 21–24, 26]. In trials without infectious stones (Lai 2020, Liang 2023, Lu 2023), strict inclusion criteria ensured preoperative sterile urine, ruling out baseline bias in infection-related stone burden [10, 22, 23].

Fig. 1.

Flowchart of study inclusion

Quality of the RCTs​​

All included studies were RCTs. Methodological quality, assessed using the Cochrane Risk of Bias Tool, revealed no high-risk biases across domains (random sequence generation, allocation concealment, blinding, incomplete outcome data, and selective reporting), with results visualized in Fig. 2 and Fig. 3. However, funnel plot analysis suggested potential publication bias for primary outcomes, including stone-free rate (SFR), intrarenal pressure (IRP), and operative time (Supplementary Figures).

Fig. 2.

Risk of bias graph

Fig. 3.

Risk of bias summary

Results of meta-analysis​

Primary outcomes​

SFR

In the pooled analysis of nine studies, the experimental group demonstrated a significantly higher stone-free rate (SFR) compared to the control group (OR = 2.29, 95% CI: 1.76–3.00, P < 0.00001; I² = 37%). Subgroup analysis based on lithotripsy modality showed that both the laser group (OR = 3.10, 95% CI: 1.48–6.48, P = 0.003; I² = 64%) and the non-laser group (OR = 2.86, 95% CI: 1.67–4.88, P < 0.0001; I² = 0%) achieved significantly higher SFRs than controls, with no significant difference between subgroups (P for interaction = 0.86). Further subgroup analysis according to stone type revealed that, while the intervention was associated with a significantly improved SFR in both staghorn (OR = 1.64, 95% CI: 1.14–2.35, P = 0.007; I² = 47%) and non-staghorn stones (OR = 3.42, 95% CI: 2.27–5.14, P < 0.00001; I² = 0%), the effect was more pronounced in the non-staghorn subgroup (P for subgroup difference = 0.008). These findings indicate that the intervention consistently improves SFR across different modalities and stone types, with a particularly marked benefit in patients with non-staghorn stones (Fig. 4).

Fig. 4.

Forest plot of SFR. Subgroup analyses are presented based on the use of laser (laser vs. non-laser) and stone morphology (staghorn vs. non-staghorn calculi)

SFR3M

At the 3-month postoperative follow-up, pooled analysis of five studies demonstrated that the experimental group had a significantly higher stone-free rate (SFR3M) compared to the control group (OR = 2.72, 95% CI: 1.42–5.22, P = 0.003; I² = 0%), indicating a consistent benefit of the intervention. Subgroup analysis by lithotripsy modality revealed that both the laser group (OR = 2.36, 95% CI: 0.98–5.67, P = 0.05; I² = 0%) and the non-laser group (OR = 3.20, 95% CI: 1.20–8.54, P = 0.02; I² = 0%) tended to favor the intervention, with no significant difference between subgroups (P for interaction = 0.65).Further analysis according to stone type showed a statistically significant benefit in the non-staghorn stone group (OR = 2.71, 95% CI: 1.31–5.62, P = 0.007; I² = 0%). For staghorn stones, a non-significant trend towards a higher SFR3M was observed (OR = 2.74, 95% CI: 0.63–11.82, P = 0.18); however, the wide confidence interval, which crosses unity, indicates considerable uncertainty regarding the effect in this subgroup. No significant subgroup difference was observed between stone types (P for subgroup difference = 0.93). Collectively, these results suggest that the intervention significantly improves the 3-month postoperative stone-free rate, particularly in patients with non-staghorn stones, and that this benefit is consistent across different lithotripsy modalities (Fig. 5).

Fig. 5.

Forest plot of SFR3M. Subgroup analyses are presented based on the use of laser (laser vs. non-laser) and stone morphology (staghorn vs. non-staghorn calculi)

IRP

Pooled analysis of four studies demonstrated that the intervention group had a significantly lower intrarenal pressure (IRP) compared to the control group (MD = -8.25, 95% CI: -9.44 to -7.06, P < 0.00001; I² = 73%), indicating a robust reduction in IRP associated with the intervention. Subgroup analysis by lithotripsy modality showed that both the laser (MD = -7.58, 95% CI: -8.32 to -6.83, I² = 16%) and non-laser groups (MD = -9.09, 95% CI: -9.89 to -8.29, I² = 0%) experienced significant decreases in IRP compared to controls, with a statistically significant difference between subgroups (P for subgroup difference = 0.007), suggesting a potentially greater effect in the non-laser group. Further analysis by stone type revealed that the intervention significantly reduced IRP in both staghorn (MD = -8.23, 95% CI: -9.89 to -6.56, I² = 91%) and non-staghorn stone subgroups (MD = -8.38, 95% CI: -10.04 to -6.72, I² = 0%), with no significant difference between these subgroups (P for subgroup difference = 0.90). Collectively, these results indicate that the intervention consistently and significantly reduces intrarenal pressure across different lithotripsy modalities and stone types, with the effect being particularly pronounced in the non-laser subgroup (Fig. 6).

Fig. 6.

Forest plot of IRP. Subgroup analyses are presented based on the use of laser (laser vs. non-laser) and stone morphology (staghorn vs. non-staghorn calculi)

Operation time

Pooled analysis of eight studies showed that the intervention group was associated with a significantly shorter operation time compared to the control group (MD = -13.86 min, 95% CI: -26.43 to -1.30, P = 0.03; I² = 98%), despite substantial heterogeneity among studies. Subgroup analysis according to lithotripsy modality revealed that the laser group had a more pronounced reduction in operation time (MD = -17.55 min, 95% CI: -24.23 to -10.87, I² = 86%), while the non-laser group also showed a reduction, though not statistically significant (MD = -9.98 min, 95% CI: -36.13 to 16.17, I² = 99%), with no significant difference between subgroups (P for subgroup difference = 0.58). Further analysis by stone type demonstrated that both staghorn and non-staghorn stone subgroups benefited from a reduction in operation time with the intervention, and no significant difference was observed between these subgroups (P for subgroup difference = 0.99). Overall, these findings indicate that the intervention can effectively reduce operation time, particularly in procedures utilizing laser lithotripsy, with consistent effects observed across different stone types (Fig. 7).

Fig. 7.

Forest plot of operation time. Subgroup analyses are presented based on the use of laser (laser vs. non-laser) and stone morphology (staghorn vs. non-staghorn calculi)

Secondary outcome measures

Fever

Pooled analysis of eight studies demonstrated that the intervention group had a significantly lower incidence of postoperative fever compared to the control group (OR = 0.40, 95% CI: 0.28–0.57, P < 0.00001; I² = 0%), indicating a robust protective effect of the intervention in reducing this complication. The results were highly consistent across studies, with no significant heterogeneity detected. These findings suggest that the intervention is associated with a substantial reduction in the risk of postoperative fever (Fig. 8).

Fig. 8.

Forest plot of fever

UTI

Pooled analysis of two studies showed no significant difference in the incidence of postoperative urinary tract infection (UTI) between the intervention and control groups (OR = 0.69, 95% CI: 0.25–1.85, P = 0.46; I² = 0%), with low event rates observed in both groups. The results were consistent across studies, as indicated by the absence of heterogeneity. These findings suggest that the intervention does not significantly affect the risk of postoperative UTI (Fig. 9).

Fig. 9.

Forest plot of UTI

Transfusion

Pooled analysis of seven studies demonstrated that the intervention group had a significantly lower risk of requiring postoperative blood transfusion compared to the control group (OR = 0.43, 95% CI: 0.25–0.74, P = 0.002; I² = 19%), indicating a substantial reduction in transfusion rates associated with the intervention. The results were consistent across studies, with low heterogeneity observed. These findings suggest that the intervention is effective in decreasing the incidence of postoperative transfusion (Fig. 10).

Fig. 10.

Forest plot of transfusion

2nd surgery

Pooled analysis of five studies demonstrated that the intervention group had a significantly lower risk of requiring a second surgical procedure compared to the control group (OR = 0.63, 95% CI: 0.42–0.96, P = 0.03; I² = 0%), indicating a statistically significant reduction in the need for reoperation associated with the intervention. The results were consistent across studies, with no observed heterogeneity. These findings suggest that the intervention can effectively decrease the incidence of second surgeries following the initial procedure (Fig. 11).

Fig. 11.

Forest plot of 2nd surgery

Auxiliary procedure

Pooled analysis of three studies showed that the intervention group had a significantly lower risk of requiring auxiliary procedures compared to the control group (OR = 0.38, 95% CI: 0.20–0.71, P = 0.003; I² = 0%), indicating a substantial reduction in the need for additional surgical interventions associated with the intervention. The results were highly consistent across studies, as evidenced by the lack of heterogeneity. These findings suggest that the intervention is effective in decreasing the incidence of auxiliary procedures following the primary treatment (Fig. 12).

Fig. 12.

Forest plot of auxiliary procedure

Hospitalization

Pooled analysis of four studies showed no significant difference in the length of hospital stay between the intervention and control groups (MD = -0.82 days, 95% CI: -3.57 to 1.92, P = 0.56; I² = 97%), with substantial heterogeneity observed among the included studies. These findings indicate that the intervention does not have a significant impact on hospitalization duration following the procedure (Fig. 13).

Fig. 13.

Forest plot of hospitalization

Hemoglobin loss

Pooled analysis of seven studies revealed no significant difference in hemoglobin loss between the intervention and control groups (MD = -1.15, 95% CI: -2.90 to 0.61, P = 0.20; I² = 98%), with considerable heterogeneity observed across studies. These findings indicate that the intervention does not significantly affect perioperative hemoglobin loss compared to the control (Fig. 14).

Fig. 14.

Forest plot of hemoglobin loss

Sensitivity analysis for operative time

To address high heterogeneity (I²=98%) in operative time, a leave-one-out sensitivity analysis was performed by sequentially excluding each of the 8 RCTs reporting operative time. The pooled mean difference (MD) remained negative in all iterations (range: − 18.49 to − 11.92 min), confirming consistent shortening of operative time with SAS. Excluding 4 studies (Du 2018, Fathi 2025, Huang 2016, Lu 2023) slightly weakened statistical significance (P = 0.07–0.08), while exclusions of Kankaria 2024, Lai 2020, Liang 2023, and Xu 2020 retained significance (P = 0.05 to < 0.00001). No single study dominated the pooled result; the largest change occurred when excluding Kankaria 2024 (MD=–18.49 min, P < 0.00001, I²=87%), but heterogeneity persisted (I²=87%–98%), indicating variability from consistent sources rather than outliers.

Evidence grading

In accordance with the GRADE methodology, the evidence derived from our systematic review was systematically collated and synthesized to present a comprehensive summary of the findings (Supplementary Table 3).

Discussion

Minimally invasive percutaneous nephrolithotomy (MPCNL) has become a mainstay in the management of renal calculi measuring 1–3 cm, offering advantages such as reduced bleeding and expedited recovery compared to standard PCNL [4]. However, the narrow working channels characteristic of MPCNL inherently compromise irrigation outflow, frequently resulting in elevated intrarenal pressure (IRP) beyond the critical threshold of 30 mmHg [6]. This hydrodynamic imbalance predisposes patients to pyelovenous backflow and endotoxin translocation, thereby increasing the risk of infectious complications—a fundamental limitation that continues to restrict the broader adoption of MPCNL [27, 28]. Efforts to mitigate IRP-related risks while preserving procedural efficiency have driven the evolution of access sheath technology, culminating in the development of suction-assisted systems (SAS) that integrate continuous negative pressure during lithotripsy [7].

Our comprehensive meta-analysis, encompassing 10 randomized controlled trials and 1,540 patients, provides evidence suggesting that SAS is associated with improved therapeutic outcomes compared to traditional access sheaths (TAS). Pooled analysis demonstrated a 23.7% improvement in immediate stone-free rates (SFR) and 18.4% higher 3-month SFR with SAS, with non-staghorn stones exhibiting maximal benefit. This observed superiority may be attributed to SAS’s dynamic suction mechanism, which actively evacuates debris during lithotripsy—an action consistent with the “vacuum cleaner effect” postulated in mechanistic studies—by potentially preventing fragment migration to inaccessible calyces [29]. Crucially, SAS reduced mean IRP by 8.25 mmHg, consistently maintaining subcritical pressure levels that mitigate bacterial translocation [30]. This dual action translated into a 41% reduction in postoperative fever and 32% lower transfusion rates, underscoring SAS’s role in curtailing infectious and hemorrhagic sequelae.

Notably, two included trials (Lai 2020, Khargi 2025) utilized ultrasound lithotripters with inherent suction capabilities—Cyberwand in Lai 2020 and Swiss LithoClast^® Trilogy in Khargi 2025—which rely on hollow probes to evacuate stone fragments locally [10, 18]. Our data confirm that SAS delivers incremental clinical value beyond this built-in suction. Ultrasound-induced suction is limited to the probe tip and cannot regulate IRP below the pyelovenous backflow threshold (≥ 30 mmHg), whereas SAS reduced IRP by a pooled 9.09 mmHg (95% CI: − 9.89 to − 8.29; I² = 0%) in non-laser procedures (including ultrasound lithotripsy). This translated directly into clinical outcomes: Lai 2020 reported a 62% lower postoperative fever rate in the SAS group (8% vs. 21.1%) and a 33% higher immediate SFR (84.2% vs. 63.1%, P = 0.037), despite both groups using ultrasound suction [10]. Khargi 2025 further demonstrated synergistic benefits: combining ultrasound with SAS yielded a 54% lower peak IRP (19.09 mmHg vs. 41.8 mmHg with ultrasound alone, P = 0.019), confirming that SAS addresses unmet needs of lithotripter-specific suction [18].

A notable observation from our safety analysis is the discrepancy between the significantly lower transfusion rate (OR = 0.43, 95% CI: 0.25–0.74; P = 0.002) and the non-significant pooled difference in hemoglobin loss (MD = − 1.15 g/dL, 95% CI: − 2.90 to 0.61; P = 0.20). This can be explained by two factors: (1) uniform transfusion thresholds across studies (Hb < 70 g/L or ≥ 30 g/L drop from baseline), with SAS primarily reducing the proportion of patients crossing this clinical trigger even when mean loss is similar; and (2) extreme heterogeneity in hemoglobin loss (I² = 98%) due to variability in case complexity, measurement timing, and reporting units, which dilutes the pooled mean difference. In contrast, transfusion rate—a binary endpoint—is less susceptible to such variability and showed consistent reduction across trials (I² = 19%), making it a more reliable indicator of SAS’s hemorrhagic benefit.

SAS integration enhanced operational efficiency, reducing mean operative time by 13.86 min (P = 0.03), though high heterogeneity (I²=98%) necessitates careful interpretation of this magnitude. Three key factors drive this variability: (1) Divergent definitions of “operative time”: Studies like Du 2018 and Xu 2020 included tract dilation (adding 10–15 min) in their timing, while Kankaria 2024 and Pathak 2024 only measured “scope-in to scope-out” duration [20, 21, 24, 25]. (2) Surgeon learning curves for SAS: Early adopters (e.g., Du 2018, with < 50 SAS cases) reported longer, more variable operative times, whereas experienced surgeons (e.g., Liang 2023, with > 100 SAS cases) achieved smaller but more consistent time savings—Liang 2023 explicitly noted that operative time decreased by 10–12 min after approximately 20 SAS cases, reflecting improved proficiency in suction pressure modulation and fragment size management [23, 25]. (3) Equipment differences: SAS models with integrated pressure regulation (e.g., ClearPetra) and laser lithotripsy (which produces finer debris) yielded more pronounced time reductions (MD=-17.55 min) compared to basic SAS designs and non-laser modalities (MD=-9.98 min, P = 0.45). This learning curve also contributes to operative time heterogeneity, as early studies introduce greater variability in technique execution [31]. Subgroup analyses provided additional insights into SAS’s utility. For stone type, SAS was associated with a significantly improved 3-month SFR in non-staghorn stones (OR = 2.71, 95% CI: 1.31–5.62; P = 0.007). In contrast, the effect in staghorn stones was not statistically significant (OR = 2.74, 95% CI: 0.63–11.82; P = 0.18), and the wide confidence interval suggests a high degree of uncertainty for this subgroup. This lack of a clear significant effect may reflect the higher complexity of staghorn stones, which have larger surface areas and greater risk of residual fragments in inaccessible calyces—even with SAS’s suction capability. For lithotripsy modality, both laser (OR = 3.10, P = 0.003) and non-laser subgroups (OR = 2.86, P < 0.0001) benefited from SAS, with non-laser procedures (pneumatic lithoclast, ultrasonic lithotripsy) experiencing more pronounced IRP reduction (MD=–9.09 mmHg vs. − 7.58 mmHg in laser, P = 0.007), as SAS compensates for the less efficient debris clearance of non-laser energy sources [32].

A primary limitation of this meta-analysis is the clinical and technical heterogeneity across included studies, such as varied access tract diameters (14–30 F) and different SAS models. A second key limitation is the substantial statistical heterogeneity observed for several outcomes, notably operative time (I²=98%) and hemoglobin loss (I²=98%). While our sensitivity analysis for operative time confirmed the direction of the effect, this high degree of variability suggests the magnitude of these findings should be interpreted with caution, as it is likely influenced by factors like surgeon experience and procedural definitions, as previously discussed. Furthermore, another limitation is the absence of a formal cost-effectiveness analysis, and the long-term economic impacts remain unquantified, meriting future evaluation [22].

The findings from our analysis may help inform clinical decision-making for MPCNL. The pooled results suggest several potential applications: First, the data indicate that SAS may be particularly beneficial in cases with a high-risk of residual fragments, such as those involving complex or large-volume calculi. Second, a notable benefit was observed when SAS was used with laser lithotripsy… Third, regarding procedural technique, the parameters used in the included studies could provide a reference for clinical practice. For instance, some protocols initiated suction pressures between − 80 and − 100 mmHg, followed by intraoperative adjustments based on visual feedback, which appeared effective in balancing fragment evacuation and potential trauma.

SAS technology aims to address two significant challenges in MPCNL: elevated IRP and inefficient fragment clearance [33]. While our study clarifies several aspects of SAS utility, it also identifies key areas for future research: (1) head‑to‑head trials of different SAS systems with formal cost‑effectiveness analyses; (2) long‑term outcomes beyond 12–24 months; and (3) “smart” suction systems with real‑time IRP monitoring and automated pressure modulation.

In summary, our meta-analysis provides high-level evidence supporting the routine use of SAS in MPCNL for improved stone clearance, lower complication rates, and enhanced procedural efficiency. The incremental benefits of SAS—even when ultrasound lithotripters with inherent suction are used—and its ability to address key limitations of MPCNL position it as a valuable tool in endourology. Greater standardization of operative protocols and further investigation into long-term cost-effectiveness will be essential to maximize patient outcomes and advance the standard of care.

Conclusion

This meta-analysis suggests that the use of a suction-assisted sheath (SAS) in MPCNL is associated with improved stone-free rates, shorter operative times, reduced intrarenal pressure, and a lower incidence of certain postoperative complications, such as fever and transfusion requirements. The findings indicate a favorable safety and efficacy profile for SAS in MPCNL, suggesting it is a valuable modification for optimizing procedural outcomes.

Authors’ contributions

H.Z. and Y.Z. were responsible for the study conception and design. Y.L. and Z.Z. performed the literature search, data acquisition, quality assessment, and statistical analysis. Y.L. and Z.Z. drafted the main manuscript text. H.Z. and Y.Z. provided critical revision of the manuscript for important intellectual content and supervised the project. All authors reviewed and approved the final manuscript.

Funding

Declaration:

No funding was received for this work.

Data availability

The datasets analyzed during the current study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study is a systematic review and meta-analysis of previously published randomized controlled trials. No new data were collected from human participants by the authors. Therefore, approval from an Institutional Review Board (IRB) or Ethics Committee and participant consent were not required.

Competing interests

The authors declare no competing interests.