Intrarenal Pressure with Vacuum-Assisted Ureteral Access Sheaths Using an In Situ Cadaveric Porcine Model

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. 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. 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. 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.