Renal Pelvic Pressure in Percutaneous Nephrolithotomy: The Effect of Multiple Tracts

Introduction: During percutaneous nephrolithotomy (PCNL), elevated renal pelvic pressures (RPPs) may spread infection through pyelovenous backflow whereas decreased pressures can hinder observation and increase bleeding. The purpose of this study was to evaluate the effects of multiple access tracts and different sized endoscopic equipment on RPP in a porcine model. Materials and Methods: RPP was measured in one- vs two-tract access, rigid vs flexible nephroscopy, and suction vs no suction. Twenty trials were performed for each condition. An independent samples Mann-Whitney U-test was used to compare parameters, with p < 0.05 considered significant. Results: With one tract, rigid nephroscopy resulted in higher mean pressures (31.35 mm Hg) than flexible nephroscopy (11.1 mm Hg; p < 0.001). The RPP was higher with rigid nephroscopy in one tract (31.35 mm Hg) than when two tracts were present (9.35 mm Hg; p < 0.001). In contrast, there was no difference in pressure during the use of a flexible nephroscope in one (11.1 mm Hg) vs two tracts (10.7 mm Hg; p = 0.63). Use of suction with the rigid nephroscope resulted in significantly lower pressures with one (-1.3 mm Hg) than with two tracts (1.8 mm Hg; p = 0.004). Conclusion: In PCNL, RPP is significantly affected by an additional tract during rigid nephroscopy and suctioning but not when using a flexible nephroscope. Understanding the effects of multiple tracts and equipment type on RPP may improve the safety of PCNL.