Presented by: Kai Wen Cheng MD
Loma Linda

Introduction

Recently, the influence of renal pelvic pressure (RPP) on surgical outcomes following percutaneous nephrolithotomy (PCNL) has been studied. However, the effect of patient position on RPP has not been published. The aim of this study was to compare RPP between prone and supine PCNL in a benchtop model. 

Materials

Six identical silicone 3D-printed kidney models were placed into anatomically correct prone or supine torsos constructed from an actual prone or supine patient CT scan. A 30 Fr renal access sheath was placed in either the upper, middle, or lower pole calyx of each kidney model for both prone and supine positions. Two 9 mm BegoStones were placed in the respective calyx prior to each trial and RPP was measured in 3 conditions: baseline, during ultrasonic lithotripsy using a 26 Fr rigid nephroscope (RN), and laser lithotripsy using a 16 Fr flexible nephroscope (FN). Five trials were conducted for each of the upper, middle, and lower pole accesses in both prone and supine positions. Statistical comparisons were performed using the Wilcoxon test and a Kruskal-Wallis test followed by a Dunn’s test, with p<0.05 considered significant. 

Results

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The average baseline RPP in the prone position was significantly higher (9.1 mmHg) compared to the supine position (2.7 mmHg; p<0.001). Similarly, the average RPP in the prone position was significantly higher (19.1 mmHg) than in the supine position (5.3 mmHg; p<0.001) when using the RN. Again, the average RPP in the prone position was significantly higher (13.6 mmHg) compared to the supine position (1.6 mmHg; p<0.001) when using the FN. When comparing RPPs for upper, middle, and lower pole access site, the lower pole had lower pressure in the supine position, but all access sites were similar in the supine position. Overall, when combining all RPPs at baseline and with irrigation, with all access sites and types of scopes, the mean RPP was significantly higher in the prone position (14.0 mmHg) compared to the supine position (3.2 mmHg; p<0.001). 

Conclusion

RPPs were significantly higher in the prone position compared to the supine position in all three conditions tested. These higher RPPs seen in prone PCNL, could in part explain the increased incidence of fever and sepsis that has been reported in prone compared to supine PCNL. 

Funding

None

Lead Authors

Kyu Park,
Loma Linda University School of Medicine

Co-Authors

Nicole Mack,
Loma Linda University Health

Cliff DeGuzman,
Loma Linda University Health

Toby Clark,
Loma Linda University Health

Matthew Buell, MD
Loma Linda University Health

Kanha Shete, DO
Loma Linda University Health

Rose Leu, MD
Loma Linda University Health

Akin S. Amasyali, MD
Loma Linda University Health

Ala'a Farkouh, MD
Loma Linda University Health

Elizabeth Baldwin,
Loma Linda University Health

Kai Wen Cheng, MD
Loma Linda University Health

Zhamshid Okhunov, MD
Loma Linda University Health

D. Duane Baldwin, MD
Loma Linda University Health