Prone vs supine percutaneous nephrolithotomy: does position affect renal pelvic pressures?

Area of Science:

• Urology
• Nephrology
• Surgical Technology

Background:

• Percutaneous nephrolithotomy (PCNL) is a key procedure for kidney stone removal.
• The choice of patient positioning (prone vs. supine) for PCNL can influence surgical outcomes.
• Understanding intrarenal pressure dynamics is crucial for optimizing PCNL techniques.

Purpose of the Study:

• To measure and compare renal pelvic pressure (RPP) between prone and supine PCNL using a benchtop model.
• To investigate the impact of different nephroscope types and access sites on RPP in both positions.

Main Methods:

• Utilized six identical silicone kidney models within anatomically correct prone and supine torsos derived from CT scans.
• Placed a 30-Fr renal access sheath in upper, middle, or lower calyx for both positions.
• Measured RPPs at baseline and during irrigation with rigid and flexible nephroscopes, performing five trials per condition.

Main Results:

• Average baseline RPP was significantly higher in the prone position (9.1 mmHg) compared to the supine position (2.7 mmHg).
• RPP remained significantly higher in the prone position when using both rigid and flexible nephroscopes.
• No significant difference in RPP was observed based on upper, middle, or lower pole access sites in either position.
• Overall mean RPP was significantly higher in the prone position (14.0 mmHg) versus the supine position (3.2 mmHg) across all tested conditions.

Conclusions:

• Renal pelvic pressure is consistently and significantly higher in the prone position compared to the supine position during simulated PCNL.
• These elevated pressures in prone PCNL may contribute to observed differences in clinical outcomes, such as postoperative fever and stone-free rates.
• The findings suggest that pressure dynamics should be considered when choosing patient positioning for PCNL.