In 2011, a California group reported technical success in treating kidney stones by adapting a robotic-assisted cardiac catheter ablation device. That ureteroscope had three bendable sections, each with two degrees of freedom at the tip, controlled by wires.
After modifying the device, researchers at Brigham and Women’s Hospital compared it with a standard flexible ureteroscope. In the Journal of Robotic Surgery, they say the robotic device was more maneuverable and facilitated precision aim at targets in each renal calyx while reducing the force on the renal pelvic wall.
The authors are Satoshi Kobayashi, MD, PhD, and Nobuhiko Hata, PhD, of the National Center for Image-guided Therapy in the Department of Radiology, Daniel A. Wollin, MD, MS, urologic surgeon in the Division of Urology, Adam S. Kibel, MD, chief of the Division, and colleagues.
The researchers constructed phantom kidney models using CT urograms from five randomly selected patients.
The robotic ureteroscope could access the lower pole calyx even in a model where the infundibulopelvic angle was <30°. Access there with the flexible ureteroscope was difficult. The high maneuverability of the robotic device included accuracy in placing the tip in the intended location.
When accessing right-renal phantom models with a posterior calyx angle ≥20°, insertion of the flexible ureteroscope into the posterior calyx was complicated by the limited range of motion in the dorsiflexion of the left-hand joint and limited external rotation of the left forearm.
As the flexible ureteroscope explored the three calyces, the number of contact points increased. In comparison, the three bendable sections of the robotic ureteroscope reached each calyx while avoiding most possible contact points with the renal pelvis.
The flexible and robotic ureteroscopes were also compared with regard to:
- Time—There were no significant differences between ureteroscopes in the length of time needed to access each calyx (upper pole, middle and lower pole) or the length of time needed to aim at the targets in each calyx
- Force—With the robotic ureteroscope, the maximum force needed to access the lower pole calyx and the maximum force used to aim at targets in the lower pole calyx were significantly lower than with the flexible scope; there were no between-group differences for other calyces
- Distance—In all calyces, the standard deviation of the tip position from the target was smaller for the robotic ureteroscope than the flexible ureteroscope, as was the distance from the center of the target to the center of the scope’s image
The improved maneuverability of this novel robotic ureteroscope may lead to avoidance of forceful contact between the scope and the renal pelvis. Thus, it’s likely to reduce the risk of complications such as bleeding, infection and perforation. These study results also suggest greater accuracy of ureteroscope movement.