MP30-01 PATIENTS ARE AT RISK FOR PYELOVENOUS BACKFLOW DURING PERCUTANEOUS NEPHROSTOLITHOTOMY

Abstract

INTRODUCTION AND OBJECTIVES: The pressure in the renal pelvis may have a significant effect upon patient outcomes during percutaneousnephrostolithotomy (PCNL). Pressures greater than 30mm Hg can cause pyelovenous backflow with its increased risk for urosepsis. Meanwhile, low renal pelvic pressure (RPP) can lead to collapse of the collecting system, impaired visualization and greater blood loss. The purpose of this study was to determine the influence of nephroscope type and the use of suction upon renal pelvic pressures obtained duringPCNL. METHODS: During PCNL performed in the prone split leg position, ureteroscopic directed US guidance was utilized to establish a 30 Fr access sheath. Once the access was established the working channel of the ureteroscope was connected to a pressure transducer and utilized to determine RPP at baseline, when irrigating using a 26 Fr rigid nephroscope with and without suction, and during irrigation with a 16 Fr flexible nephroscope. Pressure readings were randomly obtained during the case. Patient demographics and access location were also recorded. A Mann-Whitney U test was used to compare the RPP during rigid and flexible nephroscopy, with p<0.05 considered statistically significant. RESULTS: A total of 148 measurements were recorded in 16 patients undergoing PCNL. Mean patient age was 53.6 years (20-71) and BMI was 33.0 (18-53.3). All patients had single tract access including 14 patients with upper pole and 2 patients with lower pole access. Rigid nephroscopy resulted in significantly higher average RPP compared to flexible nephroscopy (30.4 vs. 11.6 mmHg; p<0.001). The mean RPP was greater than 30 mmHg (the threshold for pyelovenous backflow) in 5 patients (31.3%) using the rigid nephroscope and in no patient using the flexible nephroscope. The use of suction resulted in significantly lower renal pelvic pressure (1.0 mmHg) when compared to both rigid (p<0.001) and flexible nephroscopy (p<0.001). CONCLUSIONS: Use of the rigid nephroscope resulted in renal pelvic pressure greater than the threshold for pyelovenous backflow in 31.3% of patients. The RPP is significantly lowered by the use of the flexible nephroscope or suction. Knowledge of the factors that influence RPP and methods to control the pressure extremes may improve patient safety during PCNL.