Per the AUA guidelines, percutaneous nephrolithotomy (PCNL) should be offered as first-line treatment for total stone burden greater than 20 mm and considered for lower pole stones greater than 10 mm. However, disadvantages to this technique include increased blood loss, longer hospital stay, and greater pain compared to ureteroscopy and extracorporeal shock wave lithotripsy.¹ To minimize risks, adjustments have been implemented, including miniaturized PCNL using smaller sheaths and ureteroscopy with direct visualization of antegrade access (endoscopic combined intrarenal surgery [ECIRS]).

Obtaining access to the kidney is the first step. One issue with anterograde access is the amount of fluoroscopy required. A 2020 retrospective study of approximately 650 patients demonstrated a mean time to create retrograde access of 14 minutes with mean fluoroscopy exposure time of 4.5 minutes.² Retrograde nephrostomy creation for PCNL was first described in 1983³ and is currently reemerging into clinical practice. This technique has been improved over the years to provide a more user-friendly means to perform PCNL.

In the U.S., most renal access for PCNL is performed by radiologists. Efforts from the AUA and the Endourological Society successfully increased the number of renal nephrostomy creations performed by urologists from 12.8% in 2007 to 32.3% in 2017. Implementation of updated techniques such as RetroPerc® has the potential to increase the number of urologists performing their own access as well the number of PCNLs performed overall since access to interventional radiologists can be limited.⁴

RetroPerc is an exciting new advancement in endourology. This novel device provides a more intuitive and precise means to obtain percutaneous access to the kidney using a retrograde approach. To obtain access, the surgeon evaluates the preoperative CT scan and selects the best calyx for puncture. Flexible ureteroscopy and retrograde pyelogram identify the calyx of choice. The flexible ureteroscope is positioned in the chosen infundibulum, and the RetroPerc wire is advanced through the flexible ureteroscope (similar to a guidewire) under direct vision and with spot fluoroscopy until it punctures the skin, where it is secured providing through-and-through access. Confirmation of tract is performed by correlating the 12th rib tip on the CT scan to location of wire emerging from the skin in relation to palpated 12th rib, as well as wire emerging in the PCNL safe zone posterior to the posterior axillary line, cranial to the iliac bone, and below the 12th rib. The RetroPerc wire is then replaced by a standard guidewire using an included coaxial sheath, followed by renal dilation with the method of choice. This can be done under direct visualization as well, minimizing fluoroscopy.

Figure 1. CT scan with partial staghorn stone, Guy score III.

Figure 2. Barts flank-free modified lithotomy position.

Figure 3. Fluoroscopy image showing RetroPerc wire deployed in the lower pole and nephrostomy tube in the interpolar calyx.

Figure 4. RetroPerc wire tenting the skin below the posterior axillary line (A), cranial to the pelvic bone (B) and inferior to the 12th rib, in a safe zone for PCNL access.

RetroPerc provides several advantages. Direct visualization of the optimal calyx deploys the device through the infundibulum at the preferred angle and out the flank via retrograde ureteroscopy. This allows for minimal renal trauma, decreased radiation, and optimal positioning of the nephrostomy sheath compared to conventional fluoroscopic access. Additionally, this is typically performed in the modified supine position, optimizing the anesthesia during the case. We have successfully implemented RetroPerc in our institutions and we will discuss some aspects of the technique.

A 31-year-old female presented with a left partial staghorn calculus >3 cm (Guy score III, Fig. 1). We routinely perform the Barts flank-free position for ECIRS (Fig. 2). Flexible ureteroscopy was performed, and the target calyx was identified. The RetroPerc kit was used to obtain access through a more optimal calyx, then nephrostomy tube was provided. (Fig. 3). Fluoroscopy and endoscopic control are performed during the device activation until the surgeon can see the puncture wire tenting the skin (Fig. 4). The wire was then externalized, the nephrostomy tract was dilated to 24Fr, and ECIRS was performed with the standard technique. Total operative time was 105 minutes. Fluoroscopic time from start to establishing access was only 23 seconds. Immediate postoperative CT scan showed 12 mm residual stone that did not require intervention. The patient was discharged home in less than 24 hours without complications.

For these initial cases, we had a clinical proctor in the room providing “hands off” general guidance. The fluoroscopic and operative time to obtain access was much shorter compared to typical anterograde fluoroscopic-guided access. Further cases have continued to be successful without complication. We are now prospectively collecting data from this technology to compare to standard access for ECIRS.

Careful preoperative planning is key for the success of this retrograde approach, specifically regarding CT scan review to plan the precise puncture. Based on our early experience, we feel that RetroPerc can bring significant contributions for urologists interested in performing PCNL who are reluctant to obtain their own access or without access to intervention radiology.