CHICAGO, IL, USA (UroToday.com) - Wouldn’t it be wonderful if all ureters were 4 mm or larger in diameter; this would certainly make ureteroscopy far simpler and safer? One way to do this would be to place a substance in the irrigant capable of maximally relaxing the ureteral wall. The authors sought to do this by addressing the fact that within the upper ureter/pelvis, there exist ß 1,3 adrenoreceptors which when stimulated cause smooth muscle relaxation.
Accordingly, in this porcine study, pigs were randomized to receive either saline or saline plus 0.1 µg/ml of isoproterenol infusion into the ureter via a 7.8Fr semirigid ureteroscope which was passed alongside a 6Fr catheter; the latter was used for recording pressures within the renal pelvis. The authors noted that the changes in pressure with increasing flow were linear for both the control and test solutions, but the test solution resulted in intrapelvic pressures approximately 10-15 mm Hg lower than the control solution. Of note, on average, the isoproterenol was associated with an increase in heart rate (97 to 109 p<.001) but no changes in blood pressure. In this study though, at 8 ml/min flow, renal pelvis pressures in the control group exceeded 50 mm Hg (implying likely pyelovenous/pyelosinus back flow) while in the test group they did not exceed 40 mm Hg. To date, the authors have not applied this technique clinically.
The concept of using a pharmacological agent in the irrigating solution during ureteroscopy is novel and of intriguing potential. According to the situation a variety of irrigant infusions, with single or multiple pharmaceutical agents, could be used depending upon the goal: relaxing the ureter, decreasing ureteral spasm, precluding inflammation, preventing infection, or eliminating potential tumor cell implantation. A whole near area for investigation in ureteroscopy awaits.
Presented by Joern S. Jakobsen, MD, et al. at the Annual Meeting of the American Urological Association (AUA) - April 25 - 30, 2009 - McCormick Place Convention Center - Chicago, Illinois, USA.