Associate Professor of Urology University of British Columbia
Introduction: Ureteral access sheaths (UAS) facilitate ureteroscopy and one reported benefit is reduced intrarenal pressure. We sought to determine if the position of the UAS made a difference in renal pressure utilizing a concept pressure-sensing ureteroscope. We also sought to determine if different UAS sizes could impact renal pressure.
Methods: A concept single use digital flexible ureteroscope with pressure monitoring technology (Boston Scientific, USA, concept device/technology, not available for sale) was utilized in this study. Utilizing a live-anesthetized porcine model, pressure was verified by measuring pressure through a 5Fr ureteral catheter (via monitor HP78354A as a reference) compared to readings from the concept ureteroscope. Next, an anesthetized porcine model was tested with different sized ureteral access sheaths (UASs) (11/13, 12/14, and 13/15 Fr) in 3 different locations within the urinary system: 1. in the renal pelvis, 2. below the ureteropelvic junction and 3. in the distal ureter. A pressurized bag at 150mmHg was used to deliver irrigation. Pressure measurements were taken with each parameter using the concept ureteroscope after the renal collecting system had reached a steady state.
Results: Intra-renal pressure readings from the concept ureteroscope strongly corelated with the reference device (p=0.972). The lowest pressures occurred with the UAS in the renal pelvis for the 2 largest UAS sizes. If the UAS is below the UPJ, pressure significantly increased in the 11/13 and 12/14 UASs. Only the 13/15 reduced pressure when below the UPJ. None of the UASs in the distal ureter reduced pressure significantly from control. The 12/14 UAS in the renal pelvis had statistically lower pressure than control (p=0.001) and the 11/13 (p < 0.0001), but was not as low as the 13/15 (p=0.033).
Conclusions: Overall, the largest UAS (13/15Fr) offered the lowest pressure in most positions. . Placing the UAS in the distal ureter did not significantly reduce intrarenal pressure with any UAS. This data suggests to ideally use a >12/14Fr sized UAS in the renal pelvis to obtain the least pressure reduction during ureteroscopy. Further studies are needed to evaluate the clinical significance and sequelae of intra-renal pressure and to determine safe levels.
Source of Funding: This work was supported by Boston Scientific Inc.