This meta-analysis is the first study to compare the perioperative outcomes and postoperative recovery renal function. We found no significant difference in the estimated blood loss, hospital stay, postoperative complication rate, positive surgical margin and transfusion between the RPN and LPN groups. The postoperative renal function, operating time, conversion rate to radical nephrectomy and warm ischemia time were lower in the RPN group than in the LPN group. In our meta-analysis, the pooled data of warm ischemia time indicated a shorter warm ischemia time in the RPN group than in the LPN group. Choi et al reported a similar outcome to ours (p = 0.005).
Regarding the conversion rate to radical nephrectomy, our meta-analysis found that the RPN group had a lower conversion rate than the LPN group. However, Aboumarzouk et al conducted a meta-analysis including 717 patients and found that the conversion rate was not significantly different between the RPN and LPN groups (p = 0.84). The cause may be due to different baseline characteristics in different studies.
In our meta-analysis, the patients in the RPN group showed better recovery in the postoperative renal function than those in the LPN group. The RPN group showed a low warm ischemia time and a satisfactory postoperative eGFR rate. The postoperative renal function was thought to be associated with the duration of warm ischemia time. When the warm ischemia time was > 30 min, the postoperative eGFR rate decreased.
In our study, the warm ischemia time was lower in the RPN group than in the LPN group, causing quick renal function recovery. The cause may be attributed to using precise handling instruments, three-dimensional magnified vision and precise dissection of the renal pedicle, and better conducted tumor resection with robotic assistance. Kopp et al performed a study to analyze the related factors associated with postoperative renal function after partial nephrectomy. They found that the RENAL score could predict the estimated glomerular filtration rate and warm ischemia time. In our meta-analysis, the pooled data of the warm ischemia time showed high heterogeneity. This finding may be related to the tumor location and surgeons with different surgical skills. Recently, Bertolo et al reported a study indicating that different reconstruction methods could shorten the ischemia and operating times. The different suture skills may be the causes of high heterogeneity. Daniel et al found that prolonged warm ischemia time is related with worse perioperative outcomes. However, a comparative study performed by Homayoun et al found that the prolonged warm ischemia time associated needs to be mitigated in RPN.
In our meta-analysis, we found that the operative time was shorter in the RPN group than in the LPN group. Choi et al performed a meta-analysis comparing RPN and LPN to treat renal tumors. They found no significant difference between the two groups. This finding was not consistent with our study findings.
We found that intraoperative complications were lower in the RPN group than in the LPN group. However, Zhang et al found no significant difference between the groups (p = 0.78). Zhang et al performed a meta-analysis and found that the intraoperative complications showed no statistically significant difference between the groups. In our study, we included patients with a RENAL nephrometry score ≥ 7, which may explain the difference with Zhang’s study. Additionally, different surgeons have different surgical skill levels for RPN or LPN.
Our meta-analysis also found that the positive surgical margin showed no statistically significant difference between the RPN and LPN groups (p = 0.45). Similarly, Zhang et al performed a meta-analysis and found no statistically significant difference between the RPN and LPN groups (p = 0.61). Aboumarzouk et al also reported a similar outcome (p = 0.93).
In our meta-analysis, the estimated blood loss showed no statistically significant difference between the RPN and LPN group. Zhang et al also found that the estimated blood loss exhibited no statistically significant difference between the groups (p = 0.75). This finding is consistent with our study findings. However, the high heterogeneity in the estimated blood loss was likely due to the difference in familiarity of surgeons to the surgical process. However, Chang et al also performed a propensity-score-matching study and found that RPN resulted in a significantly lower mean estimated blood loss than LPN (p = 0.025). Several systematic reviews and meta-analyses reported similar outcomes[9, 11, 25].
In our study, we reported that a statistically significant difference was found in the intraoperative complications between the RPN and LPN groups (p = 0.04). Similarly, Cacciamani et al performed a meta-analysis found that RPN was superior for intraoperative complications. However, Gu et al. conducted a propensity score-based analysis indicated that no statistically significant difference was found between RPN and LPN groups.
Our study had several limitations. First, we did not include RCTs. This can lower the evidence of our study. Second, the included studies had different RENAL scores, which could increase the heterogeneity and lower the confidence of our meta-analysis. Additionally, the different studies reported variable tumor sizes and we did not balance these data, which could affect the warm ischemia time and postoperative renal function. We did not adjust the common baseline characteristics of patients. The different definitions of nomenclature and functional outcomes could lead to heterogeneity. Third, we did not evaluate the oncological outcomes regarding overall survival, recurrence-free survival and cancer-specific survival. In our meta-analysis, some studies did not perform propensity score-based analysis, a finding that could increase the heterogeneity. Alimi et al conducted a multicenter study involving different surgeons that also increased the heterogeneity. Regarding high heterogeneity, we did not conduct sensitivity analysis or subgroup analysis. We also did not identify the causes of high heterogeneity. We compared the perioperative outcomes and postoperative renal function outcomes.