Introduction: Vacuum-assisted ureteral access sheaths (V-UASs) are a new tool designed to evacuate dust or small fragments during retrograde intrarenal surgery (RIRS). There are reports of increased stone-free rates, decreased infections, and decreased operative time with V-UAS usage. The optimal technique and setting for V-UAS has yet to be described. Herein, we investigate real-time intrarenal pressure (IRP) throughout a range of settings using V-UAS in a porcine RIRS model. Materials and Methods: Ureteroscopy was performed in three female porcine cadaver kidneys through a ClearPetra V-UAS. IRP was recorded through a percutaneous catheter at different inflow pressures, sheath sizes, sheath distance from the ureteropelvic junction, and suction settings. Magnitude of change in delta IRP (dIRP) was compared at various settings. Results: There was no statistical difference in IRP when comparing no suction with vent inactivated. As expected, IRP decreased with larger sheath size and lower irrigation pressures. Average IRP dropped ∼18 mm Hg with suction activation (42.30 mm Hg, vent inactivated; 24.45 mm Hg IRP, suction activated; p < 0.0001). Irrigation pressure and sheath size did not make a difference in the dIRP. dIRP was significantly greater at lower suction settings compared with max suction (25.44 dIRP at 200 mm Hg suction, 10.26 mm Hg dIRP at max suction, p = 0.04). In a subset of observations, IRP paradoxically increased to higher than IRP with no suction at all after >5 seconds of activated suction. Conclusion: Use of V-UAS during RIRS can lower mean IRP; however, this effect could reverse with extended suctioning especially under conditions of high vacuum (>200 mm Hg) owing to outflow tract collapse. Our results suggest urologists should use lower suction settings and short, <5-second bursts to maximize therapeutic benefit, and minimize potential shortcomings of V-UAS during RIRS.
Keywords: intrarenal pressure; retrograde intrarenal surgery; ureteroscopy; urolithiasis; vacuum-assisted ureteral access sheath.