A novel spherical-headed fascial dilator is feasible for second-stage ultrasound guided percutaneous nephrolithotomy: A pilot study

OBJECTIVE: In second-stage percutaneous nephrolithotomy (PCNL), because the hydronephrosis has been decompressed, the dilated renal pelvis has resolved and the space is small. Consequently, introduction of the tip of the Amplatz dilator can cause injury to the opposite side of the renal-pelvic mucosa. In this study, we report the experimental and initial clinical performance of a spherical-headed fascial dilator developed specifically for second-stage PCNL. METHODS: The novel spherical-headed dilator was compared with existing tapered-headed dilators in configuration and in puncture resistance utilizing a static puncture test. Subsequently, a pilot clinical study was conducted during which patients scheduled to undergo second-stage PCNL from June 2019 to October 2019 in our center were enrolled. A typical ultrasound guided PCNL procedure was performed with the exception that the new spherical-headed fascial dilator was substituted for a tapered-headed one. RESULTS: Experimentally, stab resistance against polyethylene film was significantly increased using the novel spherical-headed dilator compared to the traditional tapered-headed dilators (p<0.005). In the clinical study, the novel dilators were successfully introduced into the renal pelvis and passed down the collecting system in all eight second-stage PCNL cases. There were no cases of renal pelvic perforation or brisk hemorrhage nor need for transfusion. CONCLUSION: The design of the novel spherical-headed fascial dilator avoided the concentration of pressure at the tapered tip of the current Amplatz dilator by increasing the contact area and uniformly distributing and diffusing the pressure. Therefore, it is feasible to use the spherical-headed fascial dilator for second-stage PCNL.