This study evaluated the efficiency and safety of RSAP-LPN. Considering the advantages of renal function perseveration, PN has become the new standard surgical treatment for T1a(13) and selected T1b tumors(14, 15). Along as the popularity of da Vinci system using in urological surgery worldwide, RA-LPN has be applied in the treatment of small renal tumor(1). A meta-analysis involving 3418 patients showed that though RA-LPN had a longer operation time than OPN, it had the superiority of shorter hospital stay, less perioperative complications, and less blood loss, and it appeared an efficient alternative to open surgery(16).
In order to minimize the length of the scar and the reduce the morbidity associated with conventional laparoscopic surgery, LESS techniques have raised significant interest in the whole world(17). Raman et al.(8) and Kaouk et al.(18) successively performed single-incision nephrectomies, preliminary confirmed that LESS technology used in nephrectomy was feasible. A comparative study showed that LESS nephrectomy had cosmetic advantages and offered the similar perioperative outcomes and short-term measures compared to conventional laparoscopic nephrectomy(19). A multi-center clinical trial involving 190 patients with RCC showed that, because of the less risk of postoperative complications, it was feasible for experienced surgeons to safely and effectively perform LESS-PN, especially for those who with low PADUA scores(20).
In 2008, Kaouk et al. firstly reported compared single-port laparoscopic PN(N = 5) and RASP-LPN(N = 2). For RASP-LPN, neither of them changed to open or traditional laparoscopic surgery, proving the feasibility of robot-assisted LESS surgery(9). In 2014, Kaouk et al. carried out a prospective trial, which included 8 patients with kidney cancer, using the Da Vinci SP system to carry out RN and PN respectively(21). No additional incisions were added and none of the patients who received PN had postoperative complications. After 3 years follow-up, all patients had good renal function, and no one had tumor recurrence. This clinical trial also proved once again that the Da Vinci system will not bring additional surgical risks to patients.
For PN, transperitoneal and retroperitoneal are the common approaches to perform the surgery. For patients with a history of abdominal surgery, retroperitoneal surgery was a better choice. Abdominal surgery could affect the relative position of the various organs of the abdomen, making it difficult to find the location of the kidney by transperitoneal approach. By contract, the retroperitoneal approach could help finding the renal hilum more directly and quickly. Especially for posterior tumor, the shorter surgery path made the renal artery blocking more efficiently, reducing the probability of blood transfusion. Besides, there were less interferences for abdominal organs intraoperatively and less complications of nearby organs for the retroperitoneal approach(22). A meta-analysis including 6 clinical trials presented that, for those patients with dorsal RCC, retroperitoneal PN could avoid peristalsis effectively by finding the renal hilum to enter the kidney to achieve the purpose of reducing the operation time and ensuring the safety of the operation(23). In 2019, Malki et al. compared the outcomes of retroperitoneal RALPN (N = 110) and transperitoneal RALPN (N = 17) in obese patients (BMI ≥ 30), the results showed that retroperitoneal RALPN was associated with less blood loss, shorter surgical time and shorter WIT compared with transperitoneal RALPN(24), being considered reducing the restrictions of patients and benefiting more patients with obesity. None of the patients in our study was obesity (BMI ≤ 25.0) or had a history of diabetes or cardiovascular diseases. A research showed that obese patients had a trend toward higher EBL, longer operative time and WIT(25). Considering the accumulation of body fat, it was harder to prepare operative space in retroperitoneum for obese patients than normally sized patients. And we must admit that the BMI and fundamental diseases could influence the outcomes of the surgery, so there might be a discrepancy with the research results between western institutions’ and ours.
In 2009, Petal et al. firstly compared results of RALPN for patients with tumors > 4 cm (N = 15) and ≤ 4 cm (N = 56)(26). No significant differences were found between groups for EBL, total operative time, hospital stay, complication rates, and change in estimated glomerular filtration rate(eGFR). But it could be seen that patients with larger tumors had longer median WIT (25 vs 20 min; p = 0.011). In 2012, Tiu et al. obtained the similar results on RASP-LPN with patient whose tumors > 4cm (N = 47) and ≤ 4cm (N = 20(27). Above-mentioned results both confirmed the feasibility and safety of RALPN, especially RASP-LPN for huge renal tumors. In our study, the tumor size of case 3 was 66.6mm, the successfully completed operation haven’t produced additional complications but gained similar prognosis with other 3 cases. Thus, some guidance for our institution to carry out RASP-LPN for renal tumor > 4cm could be offered in the future.
In this study, we used the existing Si platform and adopted a multi-channel laparoscopic surgical approach system. Different from the more common GelPOINT advanced access platform (Applied Medical, Rancho Santa Margarita, CA), the platform FreePort we used was interchangeable for all laparoscopic surgery. The characteristic that not limited to the robotic surgery use made it more economical to patients.
The main disadvantage of RASP-LPN was the collision of robotic arms. Different from the traditional multi-site surgery, single-port surgery meant the robotic arms were concentrated in a narrower space. Especially when dissecting the kidney, the collisions would happen frequently. Besides, the traditional laparoscopic instruments we used were not as flexible as the double-jointed instruments, increasing the difficulty of the surgery. To reduce external collisions and provide extra space for the movement of the robotic arm, we tried keeping the endoscope away from the surgical field and abducting the proximal robotic arms. In our study, a 30° upwards endoscope was used to provide a clearer vision, with the cooperation of manual adjustment to change the distance between the lens and the robotic arms. According to our results, the tumors located in the upper or lower pole of the kidney, especially those exogenous tumors, were more suitable to accepted the RASP-LPN. For those selected tumors, it was easier to determine the position when entering the posterior peritoneum, and would reduce the difficulty of the surgery objectively. Our study was lack of cases with endogenous or anterior tumors, needed further exploration was needed to evaluate the indications of retroperitoneal RASP-LPN.
Our study was limited by its retrospective analysis of a single institution and single surgeon experience. Nevertheless, the inclusion of multiple institutions or surgeons would inevitably expand the sample size and improve the credibility of the results, it simultaneously increased the heterogeneity because of the differences in personal skills. And the 3-months follow-up period restricted the prediction of the long-term complications and prognosis, which was necessary access the oncological and functional outcomes. Besides, selection biases were inevitable due to the retrospective design and small sample size. Despite the learning curve, we still planned to continue using the technique in more patients to help other surgeons overcome the barriers of RASP-LPN.