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Page 8 of 10 Ditonno et al. Mini-invasive Surg 2023;7:36 https://dx.doi.org/10.20517/2574-1225.2023.62

There is no consensus regarding the optimal cut-off for WIT. While some authors suggest that a maximum
[20]
time of 25-30 min is safe to prevent ischemic damage , other studies dispute these findings and report that
[21]
longer ischemia time does not influence post-operative renal function . A WIT of less than 25 min was
consistently observed across different studies, thereby demonstrating the effectiveness of SP RAPN in
controlling the renal hilum. Another crucial factor in preserving post-operative renal function is EBL. An
EBL exceeding 100 mL was significantly associated with a higher risk of post-operative chronic kidney
disease in patients undergoing NSS . Encouraging results regarding this aspect emerge from our findings
[22]
since most of the studies reported an EBL < 100 mL. However, it is important to acknowledge that most of
these observations were based on a cohort of patients who underwent surgery for smaller and less complex
renal masses.

Convincing evidence arises from the comparison between SP and MP surgery. Although SP surgery had a
longer WIT, there were no significant differences in EBL, OT, LoS, or complication rates. Oncological
outcomes, as indicated by the rate of PSM, were also comparable between the two groups. These direct
comparisons suggest that SP RAPN is a valid alternative to MP RAPN for NSS.

Great differences between SP and MP systems exist, therefore imposing a learning curve, even for
experienced robotic surgeons. Even though not specifically evaluated for RAPN, a considerable learning
curve has been suggested for robot-assisted radical prostatectomy, attributed to variances in the articulation
of instruments, their rigidity, and the level of bedside assistance in the SP approach . The optimal distance
[23]
[24]
between the target and the robotic cannula to ensure proper articulation of the instruments is 5-10 cm .
Therefore, robotic cannula and instruments, as well as any accessory trocar, are placed above the skin,
according to the floating docking technique. This allows for intracorporeal maximum triangulation .
[24]
Furthermore, the endoscope needs more frequent adjustments with respect to MP systems, given the
smaller operating field with this approach . This challenge was compensated by the addition of two sets of
[5]
articulations on the camera to ensure wider movements. These articulations include “camera adjust”, a fixed
articulation that allows arm adjustments while the endoscope remains still, and “camera control”, which
makes the camera move independently from the other instruments. A third method, called the “Cobra
method”, is a configuration that enables the camera to extend outward and move sideways in relation to the
working instruments. If these extra tools are not enough, the entire arm attached to the trocar can be
repositioned with the relocation feature. An additional foot clutch was included to enable this novel set of
movements of the camera and the instruments.

The unique features of the SP system, such as camera flexibility and greater instrument maneuverability,
make it well-suited for operating within a confined surgical field. This technical advantage can be optimally
harnessed in the retroperitoneal space. Hence, an extraperitoneal approach, particularly suitable for the SP
system , has the potential to enhance the benefits typically associated with retroperitoneal surgery. The
[25]
integration of these advantages, such as improved control over hilar structures, reduced OT, shorter LoS,
and decreased post-operative discomfort and pain, with the SP system has the potential to further improve
surgical outcomes.

Overall, early outcomes of SP RAPN are promising. The SP system offers potential advantages, such as
reduced post-operative pain, earlier hospital discharge, and improved cosmetic results. Nevertheless, it must
be considered that existing evidence primarily originates from retrospective studies with limited sample
sizes conducted at high-volume centers by experienced surgeons, which hamper their generalizability.
Hence, while the growing body of evidence supports the feasibility, reproducibility, and safety of SP surgery
for PN, further studies are necessary to validate these findings and assess long-term outcomes.