Comparative Efficacy and Safety of Ultra-Mini-Percutaneous Nephrolithotomy Versus Standard Percutaneous Nephrolithotomy for Renal Calculi: A Systematic Review and Meta-Analysis

UM-PCNL cleared stones as effectively as standard PCNL in 628 patients but with fewer complications and shorter hospital stays.

Journal: International Urology and Nephrology | Published: 2025-08-29 | Type: Systematic Review, Meta-Analysis, RCTs | PMID: 40879969 Authors: Yang Zhichun et al. (Institute of Urology, Lanzhou University Second Clinical Medical College, China) Funding/COI: National Natural Science Foundation of China; authors declare no competing interests

Summary

For kidney stones between 1.0 and 2.5 cm, ultra-mini-percutaneous nephrolithotomy (UM-PCNL) — which uses a 11–14 Fr access tract versus the standard 24–30 Fr — achieves the same stone-free rate as standard PCNL while producing fewer complications. This meta-analysis pooled seven RCTs and found no statistical difference in stone clearance, but UM-PCNL patients went home sooner and lost less hemoglobin postoperatively. The evidence base is thin: 628 patients across seven trials is modest for a meta-analysis making comparative efficacy claims.

Claims

• Stone-free rate: No significant difference between UM-PCNL and S-PCNL (P = 0.65)
• Hospitalization: UM-PCNL significantly shorter (P < 0.00001; specific day difference not reported in abstract)
• Hemoglobin drop: Significantly lower with UM-PCNL (P = 0.0004)
• Overall complication rate: Lower with UM-PCNL (P = 0.0003)
• Calyceal injury: Lower with UM-PCNL (P = 0.008)
• Postoperative fever: Lower with UM-PCNL (P = 0.04)
• No significant difference in operative time, severe hemorrhage, urine extravasation, UTI, or gross hematuria

Study Quality

Seven RCTs with 628 patients (S-PCNL n=317, UM-PCNL n=311) — a respectable design class but a small total sample for a meta-analysis. The PROSPERO registration (CRD42025632409) and PRISMA-P adherence are positives; prospective registration reduces outcome-switching risk. Random and fixed-effects models were applied via Review Manager 5.4, which is standard. The 1.0–2.5 cm stone-size range is the right population to study — S-PCNL is already the established standard above 2 cm, so this is the genuinely contested zone.

The abstract does not report heterogeneity statistics (I²) for any outcome, which is a notable omission. With only seven trials, between-study variance could meaningfully distort the pooled estimates, and readers cannot assess this from what's published here. Effect sizes for hospitalization and hemoglobin drop are also absent from the abstract — the direction of results is clear, but the magnitude is not.

Red Flags

• Only 628 patients across seven RCTs is a small pool; individual trials likely underpowered
• No heterogeneity statistics (I²) reported in abstract — a major transparency gap
• Effect sizes (e.g., mean days saved, mean HB difference) not reported in abstract
• All authors from a single Chinese institution — geographic clustering can introduce selection bias if trials were also predominantly Chinese centers
• Stone-free rate definition likely varies across trials; "stone-free" has no universal threshold in the literature
• Complication grading (Clavien-Dindo) consistency across included trials not mentioned

Strengths

• Restricted to RCTs only — no observational studies diluting the pool
• PROSPERO pre-registration with PRISMA-P compliance
• Clinically relevant comparison targeting the genuinely uncertain stone-size range
• No declared conflicts of interest; public-agency funding with no commercial sponsor

Verdict

This is a methodologically sound meta-analysis in form — PROSPERO-registered, RCTs only, appropriate population — but it is too small and too opaque about heterogeneity to be definitive. Seven trials, 628 patients, and no I² figures mean the safety advantages (fewer complications, shorter stay, less blood loss) are plausible but not settled. The stone-free rate equivalence is the headline finding, and it holds up. Anyone deciding between access sizes for 1–2.5 cm stones should read the full paper for the actual effect sizes, not just the P values summarized here.