Guidewire type and prior use affects ureteral stent insertion force.

INTRODUCTION: To improve the success rate and safety of ureteral stent insertion, we sought to identify the effect of guidewire type and prior use upon the force needed to advance a 6Fr ureteral stent over various guidewires. MATERIALS AND METHODS: Two-hundred forty stent insertion trials were performed in an ex vivo porcine urinary tract model. Ten trials were randomly performed over 12 new and 12 used guidewires. For each trial, the force required to advance a 6Fr Cook double-pigtail ureteral stent was recorded. Guidewires included the Olympus Glidewire, Cook Fixed Core, and Boston Scientific Amplatz Super Stiff, Sensor, ZIPwire, and Zebra wire. RESULTS: The mean force needed for stent advancement was the lowest for the new Glidewire (0.18N) and ZIPwire (0.22N), with no significant difference to each other (p = 0.90). The following new wires required increasingly higher stent insertion forces compared to the Glidewire, the Zebra (0.60N; p < 0.01), Fixed Core (1.25N; p < 0.01), Sensor (1.43N; p < 0.01), and Amplatz Super Stiff wires (2.03N; p < 0.01). There was no statistical difference between new and used Glidewires (0.18N versus 0.29N; p = 0.14) and Zebra wires (0.59N versus 0.60N; p = 0.88). All other used wires required a significantly greater advancement force than their new counterparts (p < 0.01). CONCLUSIONS: For the same stent, the force required for stent advancement varies greatly between guidewire types. In addition, used guidewires typically required more force compared to new guidewires. In long or difficult cases, switching to a new wire may improve the ease of stent placement and reduce potential complications.

Elevated Renal Pelvic Pressures during Percutaneous Nephrolithotomy Risk Higher Postoperative Pain and Longer Hospital Stay.

PURPOSE: Renal pelvic pressure may vary during percutaneous nephrolithotomy. We sought to determine the relationship of postoperative pain to endoscope caliber, renal pelvic pressure and hospital stay. MATERIALS AND METHODS: We reviewed the records of 20 percutaneous nephrolithotomies done under ureteroscopic guidance with renal pelvic pressure monitoring. The ureteroscope working channel was connected to a pressure transducer and used to determine renal pelvic pressure at baseline, when irrigating with a 26Fr rigid nephroscope and a 16Fr flexible nephroscope, and during suction. Patient demographics, operative characteristics, Likert pain scores and length of hospital stay were compared as stratified by average renal pelvic pressure. The Mann-Whitney U and Fisher exact tests were used with p <0.05 considered significant. RESULTS: A total of 220 measurements were recorded in 20 patients undergoing single access percutaneous nephrolithotomy. Mean patient age was 55.2 years (range 20 to 77) and mean body mass index was 32.4 kg/m2 (range 18 to 53.3). Rigid nephroscopy resulted in significantly higher average renal pelvic pressure than flexible nephroscopy (30.3 vs 12.9 mm Hg, p = 0.007). Average renal pelvic pressure was 30 mm Hg or greater in 7 patients (35%) undergoing rigid nephroscopy and in none (0%) undergoing flexible nephroscopy (p <0.01). Patients exposed to an average renal pelvic pressure of 30 mm Hg or greater during rigid nephroscopy had significantly higher average pain scores (p = 0.004) and longer hospital stays (p = 0.04) than patients with renal pelvic pressure less than 30 mm Hg. Average renal pelvic pressure 30 mm Hg or greater during rigid nephroscopy was also associated with a longer skin to calyx distance (105.5 vs 79.7 mm, p = 0.03). CONCLUSIONS: Knowledge of the factors that influence renal pelvic pressure and methods to control pressure extremes may improve patient outcomes during percutaneous nephrolithotomy.