As the surgeon gained RALPN experience, the procedure was able to be used in more complex cases, such as patients with larger tumors and worse kidney function. However, the complication rate did not change throughout the study period. In the introductory period, male sex and a high RENAL N-component score were associated with longer WIT. In the intermediate period, a large tumor and high N-component and total RENAL scores were associated with longer WIT, but in the late period, only a high RENAL L-component score was associated.
Over the past decade, robotics rapidly spread across all surgical fields, with tremendous innovation in urological surgeries . Presently, robot techniques are routinely applied safely and effectively to urological operations. The success of RALPN may be primarily influenced by a surgeon’s experience and confidence. In this study, the indication for RALPN for RCC was influenced by tumor size during the early period . However, as the surgeon’s experience with RALPN increased, the indication for RALPN expanded, eventually becoming the standard procedure for T1a and T1b RCC at our institution. Other studies have also reported similar data [19, 20]. In our early period, tumors < 4 cm in diameter were suitable for the robotic platform, but tumors > 4 cm in size were also treated with RALPN in the later periods. In period 3, 47% of tumors were stage cT1b (18/38; Table 1), and RALPN was performed by our institute’s most experienced surgeon. Furthermore, during the late period, patients with less kidney function, such as RCC in the solitary kidney, were also candidates for RALPN.
Objectively evaluating the difficulty of a partial nephrectomy has been attempted ever since the introduction of the laparoscopic partial nephrectomy. The RENAL score is a well-validated method for this purpose and is used to evaluate RALPN patients. However, these scores are primarily validated from laparoscopic partial nephrectomies and may be inadequate for assessing robotic procedure difficulties [10, 21]. Nevertheless, each RENAL score component focused on representative points regarding the kidney tumor dissection. The N-component indicates the nearness of the tumor to the collecting system or sinus. For a less experienced surgeon, an open collecting system and a large vessel injury would be troublesome , potentially resulting in longer WIT during the early experience period. The L-component indicates the tumor location relative to the polar lines. A high L-component score included hilar tumors in patients with a large tumor. In our late period, most cases were considered highly complex tumors because of their large diameter (median, 39.5 mm) and high total RENAL score (median, 8). In these complicated cases, a central tumor lesion affected WIT because a major parenchymal defect across a central kidney lesion is difficult to cope with. To suture between surgical margins, a deep suture is needed to avoid parenchymal fracture and postoperative hemorrhage. However, this suture potentially causes injury to major vessels and the collecting system . Thus, careful suturing is required, resulting in longer WIT .
Dissection and suturing skills evolve with increasing experience, and obtaining skills other than laparoscopic partial nephrectomy is a relatively rapid process. Zeuschner et al. reviewed RALPN outcomes and suggested that 35 cases were the minimum required number to acquire adequate RALPN skills . The complication rate did not change throughout our study, which could be explained by the fact that the cases were carefully selected to match the surgeon’s skill during each period.
A pseudoaneurysm was the main complication in this study. As RALPN use increased, fewer pseudoaneurysm cases after laparoscopic partial nephrectomy were expected . However, pseudoaneurysms remain at a low but constant rate in the robotic era . In this study, all pseudoaneurysms cases were successfully managed by arterial embolization. Based on these findings derived and our study’s complication rate, we conclude that RALPN is a safe procedure.
Our study had several limitations. First, this was a retrospective review of data from patients treated at a single institution, and multi-center, prospective studies are still needed. Second, Second, WIT risk evaluation was only investigated by RENAL score-related factors and clinical factors and did not include C-index or PADUA score. Third, long-term follow-up of kidney function was lacking. Almost all of our WIT was less than 25 min, and it is uncertain if such a short WIT affects kidney function. Although this is not the first study on this topic, to our knowledge, ours is the first to assess WIT risk factors in complex patients. Furthermore, a single surgeon performed surgery on a sufficient number of patients, emphasizing the relevance of our study results.