Figure. ClearPetra vacuum-assisted nephrostomy access sheath with dilator and suction side port.

Percutaneous nephrolithotomy (PCNL) is the first-line therapy for management of renal stones larger than 20 mm, per the AUA guidelines.¹ With new advances in technology and technique, miniaturized approaches to PCNL are becoming more common and expanding the indications for the procedure. One such advancement is the introduction of the vacuum-assisted access sheath (VAAS), commercially marketed as the single-use ClearPetra system. This device features a vacuum side port mounted at 45° to the sheath, which is attached to suction through a stone capture system (see Figure). There is a pressure vent incorporated in the side port allowing for rapid adjustments to suction pressure while using this sheath. The sheath is available in multiple sizes from 10Fr/12Fr to 22Fr/24Fr. The manufacturer offers a wide range of VAAS systems, some of which are also advertised for ureteroscopic and cystoscopic use, but our experience is with the mini PCNL system.²

Reusable systems, such as the Storz Minimally Invasive PCNL (MIP) system, for mini PCNL utilize the Venturi effect to clear fragments, where the surgeon slowly pulls the scope back out of the sheath and the pieces follow. While quite effective, our experience has been that this tends to work better in the supine position than the prone position due to gravity assistance. Further, there remains some risk of scattering fragments during the lithotripsy portion of the mini PCNL, especially as the surgeon is working through their learning curve. The use of a VAAS may help to reduce the risk of fragments scattering as well as facilitate more rapid clearance of the pieces. In addition, intrarenal pressure is reduced with the active suction and this may translate into reduced morbidity.^3,4 With the VAAS technology, smaller fragments and stone dust will wash out during laser lithotripsy around the scope without having to pull it back. For larger fragments, the scope is then pulled back into the sheath in a similar fashion to when using the Storz MIP system, but the active suction helps pull the pieces along more forcefully as compared to the Venturi effect alone. Blood clots can also be more readily suctioned out with the VAAS, something that can be quite difficult with the MIP system. The ClearPetra system includes a stone catching trap, so all the fragments removed can be sent for biochemical analysis or culture.

While we primarily utilize a fragmentation approach during mini PCNL, VAAS may increase the feasibility of dusting since the small pieces can be actively removed while continuing to lase the stone. Utilizing a high-powered holmium:YAG laser with pulse modulation or the highly efficient thulium fiber laser may further facilitate the dusting approach. Whether it is faster than a fragmentation approach remains to be determined.⁵

The development of VAAS for mini PCNL represents an important step in the evolution of percutaneous stone surgery. By increasing the efficiency of the procedure, the indications for mini PCNL may broaden, facilitating smaller tract surgery for more patients. Further research evaluating optimal implementation is needed. Nonetheless, the use of VAAS appears to present tangible benefits over standard mini PCNL and an evolution of the surgical technique.