To obtain better surgical outcomes, preoperative evaluation of partial nephrectomy is critical, and a scoring system is an effective tool for evaluation.13 Since the publication of the RENAL scoring system in 2009,8 it has played an essential role in standardized preoperative evaluations, strengthening the comparability among different partial nephrectomies and facilitating communication.20
The SPARE score may reflect the trend of score development. The SPARE scoring system streamlines the elements of the score, removing the less consistent elements of the polar location and removing the involvement of the UCS, which is difficult to determine15. In most previous nephrometry scoring systems, the assignment is usually 1, 2, or 3. SPARE abandoned this approach and uses regression analysis to calculate different assignments. In previous studies on retroperitoneal laparoscopic scoring, early modifications were based on changes in the RENAL score based on surgical experience21, which may not be widely used. The DDD score is a novel score based on retroperitoneal PN22. D1 increases the weight of the tumor diameter in the score, and D3 obviously includes the advantages of the ABC score. Although there are no studies on the consistency of the consistency of the DDD score, it has excellent consistency in our small-scale preliminary experiments. RNP may be the latest scoring system developed for retroperitoneal nephrectomy23, adding elements of MAP24, which is inconsistent with the original intention of the authors who developed the MAP scoring system. The use of RNP requires further clinical validation.
Current research on comparisons of various scoring systems focuses on open surgery and robot-assisted laparoscopic surgery. However, system comparisons in the retroperitoneal laparoscopic environment are lacking, and currently, there are no comparisons of scores for RLPN. The novel DDD and RNP scoring systems have been designed for retroperitoneal laparoscopic partial nephrectomy, which are more straightforward and easier to use than the previous nephrometry scoring system. In single-center retrospective studies22,23, the predictive effects according to the DDD and RNP scoring systems were similar to the RENAL scoring system. Whether the DDD and RNP scoring systems have any obvious advantages may require further verification.
RLPN has distinct characteristics from TLPN. The space in the posterior peritoneum is relatively narrow, and although it is more difficult to resect a tumor in the lower pole than in the upper pole, RLPN facilitates exposure of the renal artery without occlusion of the renal vein. Because of the characteristics and advantages of RLPN, RLPN is a good surgical approach. If the surgeon has sufficient experience and the proper technique is applied, compared to TLPN, the operation time and blood loss of RLPN may be shorter, and the postoperative results and oncologic effects of these techniques are similar25,26. Despite advances in robot-assisted surgery, retroperitoneal laparoscopic partial nephrectomy is still the standard and most popular procedure in many areas.27
Currently, RENAL and PADUA are still the most widely used scores, DAP and NeRhRo are the most popular scores among the second-generation scoring systems, and SPARE is the most recent innovation. After ten years of optimization, it remains unclear which score is most advantageous and most suitable for the retroperitoneal laparoscopic environment. Thus, the goal of our study was to perform a comparison of these scores.
In the preoperative evaluation of partial nephrectomy, we typically use scores to predict the difficulty of the operation, the warm ischemia time and the possibility of high-level complications. Since most studies include patients with Clavien–Dindo complications ≥ grade 2, a warm ischemia time (WIT) ≤ 20 min was used as the criterion for Trifecta outcomes.28 Therefore, we compared the predictive ability of the different scores for these factors.
Although there were some differences in the AUCs for predicting high-grade complications and a WIT > 20 min, the differences were not significant, which was basically consistent with the results of the existing research. In a previous study that compared the RENAL, PADUA, and NePhRO scores in open PN,29 these scores were found to be significantly associated with ischemia time. Except for the C-index, the other scores were identified as being correlated with serious complications. In another study, RENAL and DAP were compared for laparoscopic partial nephrectomy, and DAP was found to be better correlated than RENAL with warm ischemic time and estimated blood loss.30 Because the SPARE score is a novel score that is well accepted, we hypothesized that it may perform better than PADUA and RENAL. However, one study showed that SPARE had no significant advantage for predicting EBL and ischemia time outcomes in PN over the other two classic scores20. The SPARE score is less involved and may be easier to calculate than the PADUA score. Nevertheless, the ability of the SPARE score to predict complications in PN is similar to that of the PADUA score15.
Another important aspect of scoring is standardization, which increases comparability and communication. Thus, the consistency of the score is also an important issue that we need to consider20. In our study of interobserver variability, DAP with its relatively simple design and fewer scoring elements than the other systems had relatively good consistency. The consistency of NePhRo was also excellent, possibly because its zoning concepts are more direct and aligned with the way clinicians think. PADUA, on the other hand, has more elements than the other systems, with poor consistency at the polar location. Meanwhile, SPARE gains consistency after streamlining.
The currently used scoring systems, after streamlining the parameters, may improve consistency if appropriate parameters are selected that are easy for clinicians to grasp. However, if the selected parameters are not clearly defined and are not easy to learn, the consistency of the scoring system may decline. Therefore, to improve scoring, on the one hand, the scoring system should be simple and easy to learn and remember, and on the other hand, the scoring system should improve the ability to predict the difficulty and complications of surgery and should also improve consistency as much as possible. With the improvement of techniques in all aspects of surgery, scoring has become more challenging.
As far as we know, this is one of the first investigations to evaluate various scores solely to evaluate RLPN. We completed a comprehensive evaluation of the most commonly used scoring systems, providing theoretical support for the use of these scores in retroperitoneal circumstances. Our study had some limitations, which should be noted. First, the number of patients recruited from our single institution was relatively small. As these operations took place over a prolonged period, the surgeon continuously developed his operative skills, and there were very few operations with a WIT > 20 min. This result is close to the average observed in clinical institutions across China. In addition, some other widely used scores and scores specifically designed for RLPN, such as the ABC, DDD and RNP scores, should have been included. Finally, this was a single surgeon, single center retrospective study, which has inherent limitations in its research design.