Retrograde Intrarenal Surgery Versus Miniaturized Percutaneous Nephrolithotomy for Kidney Stones >1cm: A Systematic Review and Meta-Analysis of Randomized Trials - Beyond the Abstract

Two main endourological modalities standout today for kidney stones treatment, the retrograde intrarenal surgery (RIRS) and the percutaneous nephrolithotomy (PCNL), by and large, the former for small stones (< 2 cm) and the latter for larger stones (> 2 cm), but technological refinements have broadened both approaches’ indications. Moreover, the miniaturized PCNL (mPCNL) has proved to decrease bleeding, one of PCNL possible complications, while keeping excellent stone-free rates (SFR). Thus, there is an overlapping in the indications for medium-sized stones treatment, generating a constant debate on whether one outperforms the other in terms of effectiveness and safety.


In this PRISMA-compliant systematic review and meta-analysis of randomized trials, we aimed to gather the highest-quality evidence available comparing the effectiveness and safety of mPCNL and RIRS for treating > 1 cm kidney stones, to understand the strengths and limits of both approaches, and set how far we have come.

Seven randomized trials comparing mPCNL and RIRS were included, which reported some of the following outcomes: SFR, hemoglobin drop, transfusion rate, Clavien-Dindo complications, and hospital length of stay (LOS). Quality of evidence aroused some concerns according to the Cochrane Risk of Bias assessment tool, and the GRADE quality scale ranged from moderate to high. Noteworthy, all trials presented issues with risk of bias particularly in the SFR outcome; this was because none of the studies blinded the outcome assessors for the intervention.

From the included studies, 891 patients were treated either by mPCNL (n=441) or RIRS (n=450), of which 85% had lower-pole stones. The mPCNL turned out to be more effective, with a slightly higher SFR (RR: 1.06 [95% CI, 1.01–1.10], p = 0.008). Regarding bleeding, due to mPCNL’s more invasive nature, more bleeding is expected. In fact, hemoglobin drop was higher for mPCNL (MD: 0.35 [95% CI, 0.05–0.65] g/dl, p = 0.02), however, transfusion rates were similar [RD]: 0.01 [95% CI, –0.01 to 0.02], p = 0.45), as well as the Clavien-Dindo complication rates (RR: 1.20 [95% CI, 0.79–1.83], p = 0.39). Lastly, LOS was longer in mPCNL (MD: 1.11 [95% CI, 0.06–2.16] days, p = 0.04). A subgroups analysis going over lower-pole stones solely, found also that mPCNL is more effective (RR: 1.09 [95% CI, 1.00– 1.19] p = 0.05).

Highest quality evidence available to date highlights that both approaches are equally safe, although mPCNL is slightly more effective in terms of SFR. Despite a higher hemoglobin drop is reported for mPCNL, there is no difference in transfusion rate between RIRS and mPCNL.

These results have to be interpreted acknowledging the following limitations: good cost-effectiveness analysis trials between both techniques are lacking, as well as surgical time comparisons, that was not included in this meta-analysis.

What to expect in future trials?

The primary endpoint of effectiveness, the SFR, must be consistently defined between trials, and ideally, only patients with zero fragments on computed tomography are considered stone-free, as well as the stone-volume, to make data uniform. Moreover, it is essential to blind the SFR outcome assessor for the intervention, to reduce bias. Moreover, further trials are expected to also include a quality-of-life endpoint, costs, and lower-pole stones relocation in RIRS.

Despite this still a controversial ever-growing debate, all things considered, surgeons are naturally encouraged to perform their most proficient approach, bearing in mind their strengths and limitations. Nevertheless, although narrow, we cannot look away from the non-negligible mPCNL better effectiveness.

Written by: Mario Basulto Martínez MD, MSc,1 Guido Giusti MD,2 Silvia Proietti, MD,3 Luis Alberto Dorantes-Carrillo, MD,4 Antonio Esqueda-Mendoza, MD,5 Juan Pablo Flores-Tapia, MD,5

  1. Assistant Professor, Department of Urology, Hospital Regional de Alta Especialidad de la Península de Yucatán, Merida, Mexico. 
  2. Head of the European Training Center in Endourology, Department of Urology, IRCCS San Raffaele Hospital, Milan, Italy. 
  3. European Training Center in Endourology, Department of Urology, IRCCS San Raffaele Hospital, Milan, Italy. 
  4. School of Medicine, Universidad Autónoma de Yucatán, Merida, Mexico. 
  5. Department of Urology, Hospital Regional de Alta Especialidad de la Península de Yucatán, Merida, Mexico. 

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