Perioperative outcomes of PN have been investigated in several studies. However, studies comparing RAPN with LAPN are scarce [8]. To date there is only one randomized controlled trial comparing RAPN versus LAPN [9]. In the present investigation, 30 patients with renal tumors proven on radiological investigation underwent partial nephrectomy by the laparoscopic or the robotic procedure. In order to ensure that the operations were of comparable complexity, only patients with low-complexity and moderate-complexity tumors were included in the study. Patients were randomized in single-blind fashion and were unaware of the surgical method being used.
Neither of the two surgical methods was associated with a higher level of risk in regard to positive resection margins. This is in accord with previous prospective and retrospective studies and meta-analyses [2, 3, 10, 11]. Furthermore, we registered no major difference in operating time or ischemia time. Previous studies have reported diverse data in regard to ischemia times; meta-analyses mention the superiority of robot-assisted partial nephrectomy [3, 4, 10–12]. However, large-scale prospective randomized studies will be needed to corroborate these data. In the meta-analyses published so far, heterogeneous factors such as surgical technique (transperitoneal or retroperitoneal access) have not been taken into account.
In the present investigation, however, we observed no significant difference in ischemia time. Therefore, the potential benefit of robot-assisted surgery in this regard is yet to be established. This is especially because the duration of ischemia is correlated with the restoration of renal function and an ischemia time in excess of 25 minutes is associated with a significant deterioration of GFR [13]. In the present investigation, the two groups had comparable levels of renal function preoperatively and during the entire hospital stay. However, six months postoperatively we noted a significant deterioration of creatinine levels in the LAPN group. The duration of ischemia cannot be regarded as the reason for the deterioration of renal function because the two groups did not differ significantly in this regard. One hypothesis for the deterioration in the LAPN group is that a smaller quantity of renal parenchyma was removed in the RAPN group. Previous investigations have shown that a significantly smaller volume of renal tissue is resected during robot-assisted PN [10, 14], and this probably affects the preservation of renal function as strongly as the duration of ischemia [15, 16].
Furthermore, we registered greater blood loss in the LAPN group, which is also reflected in the Hb levels measured 4 hours postoperatively. Sims et al. discovered that greater blood loss reduces the secretion of AVP from the pituitary, which in turn has detrimental effects on mitochondrial function and renal function [17]. The occurrence of acute renal failure after pancreatic surgery was investigated in a retrospective study, and a significant association was noted between greater blood loss (> 500 ml) and the development of postoperative renal failure [18]. In the long term, acute postoperative renal failure has a harmful effect on the recovery of renal function [19]. Thus, a further hypothesis to explain the difference in renal function between the two groups could be greater intraoperative blood loss in the LAPN group. Several studies have shown greater intraoperative blood loss in LAPN [20, 21].
We were able to show, for the first time in a prospective setting, that neither of the surgical procedures was associated with a benefit in regard to postoperative pain. This is correlated with the results of a propensity-score matching analysis [22]. In the present study, the two groups required nearly equal quantities of analgesics, including opiates.
We registered more frequent complications in the LAPN group. However, our search of the published literature revealed diverse data in this regard. While the majority of retrospective studies and meta-analyses showed no difference in perioperative and postoperative complications [3, 10, 11, 23, 24], two large-scale trials and a level 2b meta-analysis did reveal significant differences [4, 20, 21]. Complications, especially severe complications, were less frequent after robot-assisted partial nephrectomy. A subgroup analysis of our data showed significant differences: more frequent severe complications were observed for moderate-complexity tumors operated on by the laparoscopic approach (Table 3). In addition, postoperative Hb levels differed significantly between patients who received laparoscopy for moderate-complexity tumors and those who received robot-assisted surgery for low-complexity tumors (Table 2). Three retrospective studies have compared LAPN and RAPN partial nephrectomy for moderate- and high-complexity tumors [25–27]. The results demonstrated the superiority of robotic surgery in regard to blood loss, operating time, risk of conversion to nephrectomy, and the preserved volume of renal parenchyma.
The main limitation of the present study is its small sample size, which may have resulted in a potential bias in the subgroup analyses. Designed as a pilot study, its purpose was to obtain relevant data in a prospective randomized comparison. Currently, surgeons lack any clear published recommendation in favor of a specific procedure for partial nephrectomy because the studies published so far, largely retrospective in nature, have yielded similar results in regard to oncological safety and peri- as well as postoperative outcomes.
However, the results of prospective studies do correlate with our data: advantages were noted for RAPN in regard to postoperative outcomes such as complications, blood loss, and renal function. Further prospective randomized studies will be needed to confirm these conclusions and issue recommendations regarding a specific surgical procedure, considering tumor complexity if necessary.
A further limitation of the present study is the relatively short follow-up period of six months, which permits no statement about recurrence rates after the respective surgical procedures.