During conventional LPN, renal artery clamping could provide good intraoperative visualization and bleeding control, but inevitably causes warm ischemia injury [12]. Warm ischemia injury remains one of the most important factors influencing postoperative renal function during nephron sparing surgery. Several techniques have been developed to preserve better postoperative renal function, such as segmental artery clamping and thermal ablation techniques [13, 14].
The concept of zero-ischemia LPN was firstly introduced by Gill et al. [15]. They tried to eliminate global renal ischemia by meticulous microdissection of tertiary or quaternary renal arterial branches feeding the tumor, which is based on the concept of anatomical renovascular microdissection [3]. However, dissecting tumor feeding arteries from the renal hilum is technically difficult and time-consuming. Off-clamp LPN has been developing and popularizing among the urologic communities [16, 17], and it’s very important to clarify and understand the tumor and renal vascular anatomy before surgery, especially intrarenal relationships of the tumor and feeding arteries.
As many other institutions, we preferred to utilize CTA to evaluate the patients with renal tumors. With the development of technology, CTA could provide high quality images of the renal tumor, vasculature and collecting system as well at any plane [18]. It can also facilitate establishing conventional 3D models to visualize the arterial vasculature within the hilum, guiding in choosing the appropriate hilar approach and intraoperative target orientation during segmental artery clamping [19]. Nevertheless, it cannot clearly clarify the number and location of intrarenal tumor feeding arteries. Moreover, conventional 3D models based on CTA images, typically demonstrate kidney, tumor and renal vasculature as opaque, making it difficult to observe and confirm the tumor feeding arteries [6]. Therefore, it’s essential to develop new radiologic technique for more precisely evaluation of the relevant intrarenal anatomy and for better intraoperative orientation of tumor feeding arteries.
In this series, we reconstructed 3D images to fuse the key anatomic constructions including transparent kidney, semitransparent renal tumors, collecting system, and extra- and intrarenal arterial vasculature (Figure.1C-D). Therefore, we easily identified the number and location of tumor feeding arteries, as well as the relationship between tumors and collecting system before the operation. In addition, we dissected the target tumor feeding arteries more accurately under the guidance of 3D reconstruction, thus decreasing intraoperative OT and EBL in comparison to CTA group.
When compared to conventional CTA, 3D reconstruction techniques have several advantages [20, 21]. Porpiglia et al. compared robotic partial nephrectomies performed with or without the use of hyper-accurated 3D reconstructions, concluding that it allowed for a faithful representation of the kidney arterial vasculature, which could lead to avoiding ischemia of the healthy renal remnant [20].
Similarly, Bertolo et al. compared 3D reconstructions with the standard imaging in the capability of expanding the indications to a nephron sparing surgery for very complex renal masses. More than 20% responders changed their indication from radical to partial nephrectomy after reviewing the 3D reconstruction and it might represent a significant step toward the validation of the use of 3D reconstruction for surgical planning in patients undergoing robotic kidney surgery [21].
In summary, based on our findings, 3D reconstruction could not only provide adequate information about anatomical interrelationship between tumors, renal vasculature and collecting system, but also identify the number and location of tumor feeding arteries clearly. It’s of great use for the surgeons to make preoperative evaluation and determination of appropriate surgery strategy, and to dissect the tumor feeding arteries more precisely during zero-ischemia LPN so as to avoid invisible injury to other interlobar arteries surrounding the tumors.
The present study has some limitations. The patients who received magnetic resonance imaging were not suitable for 3D reconstruction technique, which was based on enhanced CT or CTA images. The median tumor size was 4.0 and 3.75 cm in each subgroup, the technique’s efficacy and safety in the treatment of larger renal tumors remains unknown. In order to preserve better renal function and facilitate tumor resection and renorrhaphy during zero-ischemia partial nephrectomy, robotic assisted nephron sparing surgeries were recommended in the treatment of T1b and other complex renal tumors [4,22], but we are lacking of this experience. Under the guidance of 3D reconstruction, tumor feeding arteries were identified more accurately, but only 91.7% of the tumor feeding arteries were dissected and clamped precisely, without statistical significance in comparison to the conventional CTA technique. In addition, this was a single-center retrospective study with small sample size and short-term follow-up results, thus larger sample size study and long-term follow-up outcomes would be required in near future to confirm our findings.