MP20-05 VARIATIONS IN INTRAPELVIC RENAL PRESSURES DURING PERCUTANEOUS NEPHROLITHOTOMY – A PORCINE STUDY

INTRODUCTION AND OBJECTIVES: It has been established that high intrapelvic pressures (IPP) may cause possible spread of infection through pyelo-venous backflow while lower pressures can hinder surgeon’s visualization, decrease venous tamponade and result in increased bleeding. The purpose of this study is to characterize IPP during percutaneous nephrolithotomy. METHODS: A porcine model was utilized to test IPP during rigid and flexible nephroscopy. Pressures were compared in a variety of conditions including single versus two tract access, rigid versus flexible nephroscopy and presence versus absence of suction. Twenty trials were performed for each condition. An independent samples MannWhitney U test was used to compare parameters, with p<0.05 considered statistically significant. RESULTS: In the single tract model, rigid nephroscopy resulted in significantly higher mean pressure (31.35 mmHg) compared to flexible nephroscopy (10.7 mmHg; p < 0.001). The pressure was higher when using a rigid nephroscope in a single tract (31.35 mmHg) compared to when two tracts were present (9.35 mmHg; p < 0.001). In contrast, there was no difference between the flexible nephroscope in a single tract (10.7 mmHg) versus with two tracts (10.9 mmHg; p 1⁄4 0.63) Use of suction with the rigid nephroscope resulted in significantly lower pressure when only one tract was present (-1.3 mmHg) compared to when two tracts were present (1.8 mmHg; p 1⁄4 0.004). CONCLUSIONS: This study demonstrates that addition of a second tract may result in significant alterations in renal IPP, with much lower pressures when using irrigation but higher pressures when using suction when compared to a single tract. This may explain in part why transfusion rates are significantly higher with multiple accesses during PCNL.