This study was specifically designed to investigate the effectiveness of vamPCNL for the treatment of kidney stones by means of trifecta status, namely SFR, no complications after a single session and no auxiliary procedures. We found the trifecta was achieved in six out of ten patients in our cohort and that higher stone volume, along with multiple calices involved by stones, were negative predictors of trifecta status.
MiniPCNL is nowadays recognized as one of the standard treatment options in the field of stone surgery [19]. In recent years, technological developments have been introduced to increase performance and reduce the burden of the procedure. However, limited scoring metrics are used in clinical practice to objectively evaluate miniPCNL outcomes in terms of SF status and complications. Recently, EL-Nahas et al. proposed the trifecta scoring as a way of standardizing miniPCNL outcomes [10]. To the best of our knowledge, the trifecta metric has never been validated in vamPCNL series, which is one of the latest technological evolutions in percutaneous stone surgery.
Previous studies have demonstrated the efficacy and safety of vamPCNL for the treatment of kidney stones. Lai et al. analysed and compared a series of 75 patients treated with vamPCNL and 75 individuals who underwent PCNL with a peel-away access sheath. Authors showed that vamPCNL was associated with higher SF rate but shorter OT and lower infectious complications than standard procedures [7]. Lievore et al. found lower rates of infectious complications, shorter OT and reduced patient’s effective dose in 104 patients treated with vamPCNL as compared to 52 patients who underwent miniPCNL [8]. Recently, a meta-analysis conducted by Zhu et al. demonstrated an improvement in safety and efficiency in procedures with vacuum-assisted sheath compared to those with conventional sheath [20]. These results highlighted higher SFR while reducing operative time and postoperative infection by using vacuum-assisted technology.
In light of the emerging evidence supporting a clinical benefit of vamPCNL compared to classic miniPCNL, this procedure has never been validated in terms of objective metrics such as the trifecta status.
EL-Nahas et al., were the first to introduce trifecta scoring in PCNL [10]. Authors analysed 944 patients submitted to miniPCNL and found that trifecta was achieved in 84% of cases. Independent unfavorable risk factors were number of caliceal groups affected by the stones and number of percutaneous tracts [10]. In the current series, trifecta status was achieved in approximately 60% of cases. Our results show that patients who achieved trifecta status had smaller stone volume, a higher rate of single stones and less calyces involved than -trifecta participants, suggesting that the more complex the stone, the more difficult is to obtain trifecta in vamPCNL. This finding is also supported by previous literature in which caliceal stone distribution was found to be a significant predictor of SFR after PCNL [21]. Similarly, the number of caliceal involvement emerged as a risk for complications in standard PCNL [22]. As a matter of fact, this can be explained by missing some fragments in calices away from the percutaneous access or increasing the risks of complications with multiple punctures. As a matter of fact, endoscopic combined intrarenal surgery (ECIRS) has been found to be a safe and effective procedure for treating large and complex renal stones [23]. A systematic review and meta-analysis showed that ECIRS had higher one-step SFR and lower complications compared to PCNL for complex stones [23]. The combination of both retrograde and antegrade approaches is used to identify remaining auxiliary fragments inaccessible to the nephroscope, such as stones located adjacent to the PCNL entrance and minor calices, thus improving SFR. Moreover, the combined approach reduces the need for multiple kidney access with consequent lower rates of complications. As a whole, ECIRS could be the technique of choice in case of large stones or stones in multiple calices.
We also found that operative time and length of stay were shorter in + trifecta patients than those who did not achieved trifecta status. Therefore, trifecta achievement gains even more importance in terms of clinical outcomes and reduction of hospitalization costs. It should be mentioned that the hospitalization time for PCNL in our study was longer compared to other reports in which length of stay for uncomplicated PCNL is progressively shortening [24]. Several procedural and management-related factors were associated with longer hospitalization time: failed ureteral canalization during antegrade pyelography on day 2 was usually managed with repeated pyelography the next day; bleeding from the nephrostomy tube or urethra was managed with observation and laboratory testing; fever was managed with parental antibiotics in accordance with the Infections Disease department (in few cases with treatment > 10 days). As a whole, patients with longer hospitalization were those with higher severity of complications: two patients had postoperative sepsis and were treated with 3 weeks of parenteral antibiotics, two patients had urine leakage and were treated with retrograde stenting, three patients had postoperative bleeding and underwent embolization.
This study provides a standardized definition for the global outcome of kidney stone treatment (among which the most important are SFR and complication), that can be applicable for any procedure (standard, mini, micro PCNL). From a clinical and scientific point of view standardization of outcome evaluation for any surgical intervention is important for comparing different procedures and tailoring the best treatment for each patient. For instance, the identification of clinical characteristics not associated with trifecta achievement in miniPCNL could change the treatment plan to different procedures (e.g. standard PCNL with ballistic energy) or the postoperative care in order to reduce potential PCNL-related complications (e.g. extended antibiotic prophylaxis, stone culture, DJ positioning). Alternatively, -trifecta patients could be identified as those who might benefit from more intense follow up imaging (CT-based) ore immediate second look surgery to achieve stone free status.
It should be mentioned that SFR in our series (76.4%) was lower compared to that reported by different Authors for the treatment of > 2 cm kidney stones with PCNL (range 86%-94%) and similar to that of retrograde intrarenal surgery (RIRS) (61%-80%) [25–27]. Of note, it was consistently reported that RIRS was associated with shorter hospitalization time, lower rates of complications and acceptable efficacy than PCNL, therefore it should be considerate as an alternative treatment option in this group of patients [26]. However, in the previous series, Authors considered SF also cases with residual fragments of < 4 mm, thus partially explaining the difference in SFR with our series.
This study is innovative because it is the first in the published literature to investigate and validate the trifecta scoring in vamPCNL, which is the most innovative armamentarium of miniaturized PCNL. The second strength of the study is that we have analysed a homogenous cohort of patients with a thorough clinical and perioperative evaluation. In particular, SFR, in our study, was based on CT scan performed within 3 months after the procedure; conversely, EL-Nahas et al., used plain X-ray in 85% of cases [10]. This could be the reason for the higher SF (90% vs. 76%) and trifecta rate (86% vs. 60%) observed in their cohorts compared to our study.
Limitations of this study are the single centre-based and retrospective design study, which raises the possibility of selection biases. Thereof, larger prospective studies across different centres and cohorts are needed to externally validate our findings.