Radial dilation of ureteral balloons:: Comparative in vitro analysis

Background and Purpose: The dynamics of ureteral balloon expansion may differ with increasing extrinsic compressive forces and inflation pressures. This study compared the ability of ureteral balloons to expand under different conditions. Materials and Methods: The balloons tested were the Cook Accent, Ascend, Ascend AQ, and Pursuit;, the Bard 195503 and UroForce; and the Boston Scientific Microvasive UroMax Ultra. When available, multiple balloon diameters and lengths were tested. With a guidewire in place, the balloon tip was secured by elevated vise grips on either side of the balloon. A string was wrapped around the balloon center once, and incremental increases in load were added (2 g, 42 g, 82 g, 122 g) to represent increasing extrinsic compression. The balloon was inflated with contrast medium, and circumference changes were measured at increments of 2 atm up to burst pressure. Balloons were tested in triplicate for each weight. Results: The majority of the balloons were unable to reach 90% of their expected diameter with larger constrictive loads (122 g) at low inflation pressure (4 atm). The only balloons that achieved a diameter at 4 atm that was at least 90% of the expected diameter with a coefficient of variance (CV) of < 10% at all radial loads were the Pursuit 6 mm X 4 cm (98.2.+/- 2.2%; CV 7.88%), UroMax Ultra 7mm X 4 cm (97.5 +/- 1.4%; CV 5.94%), and the UroMax Ultra 7 mm X 6 cm (101 +/- 1.2%; CV 7.67%). At inflation burst pressure, the balloons able to maintain a diameter at or above 100% of expected with a CV of < 5% at burst pressure were the Ascend AQ 4 mm X 4 cm (116 +/- 1.0%; CV 3.34%) and the Pursuit 6 mm X 4 cm (108 +/- 2.0%; CV 4.53%). Conclusion: Reaching maximum inflation diameter at low pressures in the face of increasing extrinsic compression may help minimize the risk of ureteral injury. Reliable expansion to maximum diameter even with higher extrinsic compressive forces is another important characteristic of ureteral balloons. Balloon material, configuration, and dimensions may contribute to differences in dilation properties.