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Page 2 of 8 Magaribuchi et al. Mini-invasive Surg 2024;8:6 https://dx.doi.org/10.20517/2574-1225.2023.81

INTRODUCTION
In the field of small renal cell carcinoma, partial nephrectomy (PN) has been established as a standard
[3]
[1,2]
treatment strategy and is recommended by the EAU Guidelines . To achieve the goal of preserving renal
function in PN, techniques such as the zero-ischemia approach are being researched . As minimally
[4]
invasive surgical techniques advance, both laparoscopic (LPN) and robot-assisted PN (RAPN) have become
[5-8]
increasingly common for treating cT1 and some cT2 renal tumors, with good outcomes reported .
In cases where a tumor is primarily located within the kidney (endophytic tumor), it can be difficult to
visually locate the tumor and determine the extent of resection required. This increases the complexity of
the surgical technique and the risk of complications . Surgeons typically use preoperative computed
[9]
tomography (CT) scans to understand the anatomical characteristics of the tumor and vascular system, but
in cases where it is challenging to visually identify the tumor, intraoperative ultrasound is an effective and
common method for confirming its location .
[10]
With the advancements in technology, it has become easier to reconstruct three-dimensional (3D) images
[11]
from the two-dimensional (2D) images taken from preoperative CT scans . Using these reconstructed 3D
kidney models can improve the accuracy of locating difficult-to-see tumors and blood vessels, leading to
research into navigation systems for LPN and RAPN that utilize these models. This 3D navigation
technology has the potential to improve treatment outcomes of PN and expand its indications even in
challenging cases such as endophytic renal masses . This review will discuss the use of 3D kidney models
[12]
in navigation for LPN and RAPN.

CURRENT STATE OF 3D NAVIGATION IN MINIMALLY INVASIVE PN
Three main navigation methods using 3D models include 3D printed models, augmented reality (AR), and
virtual reality (VR) . A systematic review conducted in 2022 has reported significant improvement in
[13]
surgical outcomes when using these techniques for navigation during RAPN surgeries . However, while
[14]
their utility is acknowledged, some opinions suggest that there is insufficient evidence to demonstrate
[15]
improvement in surgical outcomes , and there may still be room for debate regarding sufficient scientific
evidence for their effectiveness. When conducting navigation using 3D models, information about the renal
tumor and blood vessels is first extracted from contrast-enhanced CT scans, and a 3D model is then created.
Information captured in contrast-enhanced CT scans is processed through segmentation and then
reconstructed into 3D. It is further optimized for medical purposes, and then navigation is performed using
[11]
3D printers, AR, or VR [Figure 1].

3D printed model
[13]
For patient education, 3D printed models tend to be preferred , and there have been reports of improved
patient understanding of their anatomical structure and surgical approach . In navigation for PN, these
[16]
models have been used for preoperative training and surgical simulations, with reports indicating
significantly less blood loss compared to when navigation was not performed . There have also been
[17]
reports of a significant decrease in warm ischemia time when 3D printed models were employed for
[18]
preoperative planning and intraoperative navigation . In addition, it has been reported that they are not
only useful for patient education but also for resident education, and they are beneficial in achieving the
trifecta during the initial implementation of RAPN [19,20] .

VR
VR, a technology that provides an independent virtual world, is used for preoperative simulation and
training in surgical navigation . When used during surgery, 3D models are displayed side-by-side on
[21]