Single-Session Bilateral Supine Percutaneous Nephrolithotomy: Safety and Efficacy

Egyptian retrospective study of 52 patients found a 75% primary stone-free rate for simultaneous bilateral kidney stone removal in one supine session

Journal: Urologia | Published: 2025-12-04 | Type: Retrospective case series | PMID: 41342193 Authors: Mahmoud F Rohiem et al. (Departments of Urology, Port-Said, Minia, and Zagzig University Hospitals, Egypt) Funding/COI: Funding not reported; authors declare no conflicts of interest

Summary

This retrospective series examined whether bilateral kidney stones (2–5 cm per side) can be cleared in a single operative session using the supine percutaneous nephrolithotomy (PCNL) position rather than the traditional staged or prone approach. Of 52 patients treated between 2019 and 2023, three-quarters achieved primary stone-free status. Kidney function dipped measurably on postoperative day 1 but returned to baseline within a week, which the authors frame as evidence of safety — though the absence of a comparison arm makes that framing a stretch.

Claims

• Primary stone-free rate (≤2 mm residual on CT): 75% (39/52 patients)
• Residual insignificant fragments >2 mm but <6 mm: 11.6% of patients
• Ancillary procedures required: 13.4% of patients
• Mean operative time for both sides combined: 126.5 ± 22.9 minutes
• Mean hemoglobin drop post-procedure: 1.9 ± 0.99 g/dL
• Serum creatinine rose significantly at day 1 (p < 0.0001), normalized by day 7 (p = 0.403) and 1 month (p = 0.471)
• GFR dropped significantly at day 1 (p < 0.0001), normalized by day 7 (p = 0.95) and 1 month (p = 0.07)

Study Quality

This is a retrospective single-arm case series — the weakest design for establishing safety and efficacy claims. There is no control group: no comparison to staged bilateral PCNL, no comparison to prone positioning, no comparison to ureteroscopy or shock wave lithotripsy. The 75% stone-free rate cannot be attributed to the single-session supine approach specifically because we have no baseline for what stone-free rates look like in comparable patients treated differently. The study was retrospectively registered, meaning the protocol was not pre-specified before data collection, opening the door to outcome selection.

The patient population is narrow — stones specifically 2–5 cm in the renal pelvis — limiting generalizability. At 52 patients across a 4.5-year window at multiple institutions, the accrual rate is low, and no power calculation is reported. The follow-up for stone-free status extends only to 1 month, which is inadequate to assess recurrence, long-term renal function, or delayed complications.

Red Flags

• No comparison group. Every efficacy claim floats in a vacuum.
• Retrospective design with retrospective trial registration (SPS/URS_008) — the sequence raises concerns about outcome fishing.
• Funding not disclosed. For a surgical technique study from multiple academic centers, the absence of any funding statement is a gap.
• 52 patients over 4.5 years across at least three hospitals suggests this is uncommon practice, not a mature high-volume technique — which undercuts the safety argument.
• 1-month maximum follow-up captures neither delayed complications nor recurrence.
• Hemoglobin drop of 1.9 g/dL is reported without transfusion rates, obscuring the clinical significance of blood loss.
• Stone-free definition of ≤2 mm is standard, but reporting "insignificant" residual fragments of 2–6 mm in 11.6% of patients softens what is effectively a failure to clear the stone.

Strengths

• Pre- and post-operative CT used for stone-free assessment — appropriate imaging standard
• Renal function tracked at multiple timepoints (day 1, week 1, 1 month) with actual p-values reported
• Operative time and hemoglobin data are concrete and reported with standard deviations
• Authors are appropriately cautious in recommending the procedure only at tertiary centers with expert surgeons

Verdict

A 52-patient retrospective series with no control arm and 1-month follow-up cannot establish that single-session bilateral supine PCNL is "safe and effective" — it can only report what happened in 52 patients at these specific hospitals. The 75% stone-free rate may look acceptable, but without knowing what staged procedures or alternative positioning would have achieved in the same patient population, the number means little. The creatinine and GFR data normalizing by day 7 is reassuring, but again, uncontrolled. This paper is a feasibility signal at best — hypothesis-generating, not hypothesis-confirming. It does not move clinical practice.