Comparison of Transperitoneal and Retroperitoneal Laparoendoscopic Single-site Donor Nephrectomy

Background: Laparoscopic living-donor nephrectomy is the standard technique at high-volume renal transplant centers. Laparoendoscopic single-site donor nephrectomy (LESS-DN) is a relatively novel minimally invasive surgery, which was differed to transperitoneal and retroperitoneal approaches. We present a retrospective analysis of our single-institution donor nephrectomy series comparing the transperitoneal to retroperitoneal LESS-DN with regards to operative outcomes. Materials and Methods: Ten patients who underwent LESS-DN from 2017–2019 were enrolled at our center. The same surgeon performed all cases. The two approaches were compared retrospectively and evaluated for differences in perioperative outcomes, including operation time, console time, blood loss, graft warm ischemia time, postoperative pain, length of stay (LOS), wound size, postoperative pain, and renal function post LESS-DN at less than one year. Results: Total operating time (315 ± 82.69 vs. 191 ± 24.9 min, p = 0.016), console time (224 ± 74.15 vs. 110 ± 19.84 min, p = 0.016), and LOS (8.4 ± 1.82 vs. 4.8 ± 1.10 days, p = 0.013) were signicantly longer in the transperitoneal group. The wound size (44 ± 3.81 vs. 68.2 ± 13.5 mm, p = 0.038) was signicantly smaller in the transperitoneal group. There was no signicant difference in other parameters, including blood loss, warm ischemia time, and postoperative pain from day one to day three. Conclusions: Retroperitoneal LESS-DN results in similar perioperative outcomes as transperitoneal LESS-DN without compromising donor safety, and while providing a faster operation time, console time, shorter LOS, and a trend toward a shorter warm ischemia time.


Introduction
End-stage renal disease (ESRD) has a high prevalence in Taiwan and is a robust economic burden on the national health insurance [1]. Kidney transplantation is one of the main therapies for ESRD, as it provides a better quality of life. It is now a routine medical practice worldwide, especially in high economic countries [2][3][4]. For ESRD patients, the cost of hemodialysis is higher than that for performing transplantation, post-operation care, and further maintenance [5].
Nowadays, the number of patients receiving kidneys from their spouses or family is increasing [6]. Livingdonor kidney transplantation is associated with more advantages, such as a short waiting-list period, elective time of the surgery, and better graft function compared to cadaveric kidney donation [7][8][9][10].
According to the literature, the rst donor nephrectomy surgery was done in 1954 via an open method. It was regarded as the gold standard surgery for almost 45 years [11]. Now, laparoscopic living-donor nephrectomy is the gold standard technique at high-volume renal transplant centers, and laparoendoscopic single-site donor nephrectomy (LESS-DN) is a relatively novel minimally invasive surgery. The procedure can be approached both transperitoneally and retroperitoneally.
Retroperitoneoscopic living-donor nephrectomy provides direct access to the renal hilum without the need to mobilize the colon, but there is a lack of anatomic landmarks to guide orientation, a smaller working space, and a steep learning curve [12].
There are few studies which compare the transperitoneal approach with the retroperitoneal approach regarding laparoscopic donor nephrectomy. In this study, we present a retrospective analysis of our single-institution donor nephrectomy series comparing the transperitoneal to retroperitoneal LESS-DN regarding operative outcomes.

Study Population
This retrospective study included patients who underwent LESS-DN performed by the same team (Dr. C.C. Li and Dr. S.C. Wen) that has signi cant experience in single-site laparoendoscopic surgeries. A total of 10 patients underwent LESS-DN: ve underwent transperitoneal LESS-DN and ve underwent retroperitoneal LESS-DN. Technetium 99 m diethylenetriaminepentaacetic acid (DTPA) scans were used to assess donors' split renal function for preoperative evaluation. The side of the kidney with the more inferior function was chosen, while the donor patient had asymmetry renal function (> 10% difference in glomerular ltration rate). If female patients were desirous of becoming pregnant in the future, the patient underwent right-sided donor nephrectomy to prevent pregnancy-related hydronephrosis [13]. Every living donor renal transplantation was approved by our hospital ethics committee. The present study was approved by the review board of our institution (KMUHIRB-E(I)-20200063). For this type of study informed consent was not required and approved by institutional research committee.

Surgical Technique -Retroperitoneal and Transperitoneal Approaches
Patients received a transperitoneal or retroperitoneal approach according to 'their preferences. LESS-DN was performed through a 5 cm single transumbilical incision for a transperitoneal approach, or a 5 cm incision at the midaxillary line with a muscle splitting technique for a retroperitoneal approach. Regarding a single-port device, we used two kinds of multi-glove ports, GlovePort (Nelis Medical, South Korea) and Lagis port (Lagis Endosurgical, Taiwan). For the transperitoneal approach, a pneumoperitoneum was created following placement of the transumbilical multichannel single-port device. Division of the Toldt line was the rst step, followed by colonic mobilization. The ureter and gonadal vein could be found soon after dissection of the psoas muscle. Lifting the ureter from the psoas muscle facilitated dissection of the renal vein and artery from the surrounding alveolar tissue. We dissected the kidney to remove perirenal fat, spared the adrenal gland, and the ureter was divided. Finally, the kidney was extracted directly by hand-grasping from the wound retractor of the single-port device. For the retroperitoneal approach, the patient was in the 90º full ank position, and we created retroperitoneal space using a balloon dilator after skin incision and nger dissection. After mounting the single-port device, we identi ed the ureter anterior to the psoas muscle and further dissected the renal artery and vein by lifting the ureter. Once the renal artery and vein were thoroughly free from the adjacent alveolar and lymphatic tissue, we unmounted the single-port device and used a hand-assisted technique for perirenal dissection and adrenal division. After dividing the renal pedicles by EndoTA (Medtronic, Minneapolis, MN, USA) and cutting with scissors, we extracted the donor kidney by hand directly after detaching the single-port device.

Postoperative Management
Every patient underwent patient-controlled analgesia and took oral NSAIDs every eight hours for postoperative pain control. The pain was evaluated every two hours on the operation day and every eight hours for the remaining days. Patients were discharged home when pain and oral intake were tolerable without acute complications.

Statistical Analysis
Variables collected from patients included age, sex, side of nephrectomy, body mass index (BMI), operation time, console time, estimated blood loss, warm ischemia time, length of hospital stay, and postoperative pain, which was evaluated via visual analog scale score from days 1-3, as well as the outcomes mentioned above. The size (cm) of the operative wound was measured one month after the operation. The renal function post LESS-DN was followed for one year, and serum creatinine level was checked at 1, 3, 6, and 12 months after surgery. The database with the variables were expressed as median (interquartile range [IQR]) values. To compare outcomes between two independent groups, Mann-Whitney U test (Wilcoxon rank-sum test) was used for non-normally distributed continuous variables, and Fisher's exact test was used for categorical variables. Statistical signi cance was de ned as p < 0.05, and all reported p values were two-sided. Statistical analyses were conducted using IBM SPSS statistical software version 19 (IBM SPSS Statistics for Windows, Version 19.0; IBM Corp., Armonk, NY).

Results
Five patients underwent transperitoneal LESS-DN, and ve underwent retroperitoneal LESS-DN. Table 1 summarizes patient characteristics. No signi cant differences were observed in age, gender, BMI, or laterality. Regarding the laterality of donor nephrectomy between the two groups, nine patients were leftsided, and only one patient was right-sided in the transperitoneal group. .94 s, p = 0.593), and postoperative pain from day one to day three. Although there were no signi cant differences, we observed a trend toward shorter warm ischemia time in the retroperitoneal group. Renal function was followed for one year after LESS-DN and no signi cant differences were observed between the two groups.

Discussion
Living-donor nephrectomy is usually an altruistic act. The surgery is different from other destructive surgeries in that it involves a healthy individual being exposed to the risks of the procedure. The symptoms and discomfort that patients encounter should be minimized in clinical practice. Compared to open donor nephrectomy, laparoscopic donor nephrectomy showed superior donor postoperative recovery and convalescence [14,15], and also equivalent safety and post-nephrectomy outcome in the donor [16].
LESS is a revolutionary laparoscopy because of the advantage of less bleeding, less wound pain, less risk of incisional hernia, and better cosmesis [17]. At our institution, our surgeons experience single-port laparoscopic surgery technique, such as LESS adrenalectomy, herniorrhaphy, partial nephrectomy, and robotic single-port radical prostatectomy in daily practice [18][19][20]. LESS-DN has become the standard procedure for living-donor kidney transplantation since December 2017 in our institution.
This article is a comparison of transperitoneal and retroperitoneal LESS-DN. Based on previous studies, although the transperitoneal approach of laparoscopy provides a broader view and clear anatomic landmarks to gain direct access without bowel manipulation, the retroperitoneal approach of laparoscopy can reduce the violation of abdominal organs and bypass the intraperitoneal adhesion [21,22]. This may contribute to the reduced operation time and even the shortened recovery periods post-surgery in our analysis. In our study, the faster operation time in the retroperitoneal approach group did not lead to more blood loss or a longer warm ischemia time during the surgery compared to the transperitoneal group. The LOS was signi cantly shorter in the retroperitoneal group. Minimal interference of the abdominal organs during the retroperitoneal approach supposedly shortens the duration of bowel recovery and hospital stay. In our study, the wound of the transperitoneal approach was created on the umbilicus. During wound healing, the wound retracted to the inner-side of the umbilicus and the healing scar was less visible in the transperitoneal approach group, as mentioned in other literatures [23]. Thus, the wound size was smaller than in the retroperitoneal approach, although the original incision was the same size. Based on Choi et al.'s study, poor renal function recovery and chronic kidney disease were predicted by unstable renal function at one month postoperatively. Such patients should be followed for more than one year to con rm their nal renal outcomes [24]. After donor nephrectomy, all patients were followed for one year to evaluate the postoperative renal function. There was no signi cant difference between the transperitoneal group and the retroperitoneal group, which indicates that the safety of LESS-DN was identical regardless of the approach method.
The present evidence demonstrates that the retroperitoneal LESS-DN may be a faster surgery without compromising safety under the expertise of an experienced surgeon. There are limitations to this study.
First, there is a small number of patients in our study. Further studies should include more patients to provide more robust evidence. Second, all patients underwent surgeries under the same team. The bias about the surgeon's learning curve could therefore not be neglected in this study.

Conclusion
In our study, retroperitoneal LESS-DN resulted in similar perioperative outcomes as transperitoneal LESS-DN without compromising donor safety. It also provided a faster operation time, console time, shorter length of stay, and a trend toward a shorter warm ischemia time. Future investigations should include more studies and reports to strengthen this conclusion.

List Of Abbreviations
LESS-DN Laparoendoscopic single-site donor nephrectomy LOS length of stay ESRD End-stage renal disease Declarations Availability of data and material All data will be available by contacting the corresponding author. All strains and reagents used in the studies are available upon request.
Code availability Not applicable.
Authors' contributions Chung-Yu Lin wrote the original draft. Wen-Jeng Wu, Ching-Chia Li, Hung-Lung Ke, Yii-Her Chou provides raw database and performed data curation. Sheng-Chen Wen reviewed, and revised the article and he also was responsible for project administration.

Compliance with Ethical Standards
Disclosure of potential con icts of interest The authors declare that they have no con ict of interest.

Disclosure of Funding
No external funding was received for this study.
Ethics approval and consent to participate All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee (KMUHIRB-E(I)-20200063, Institutional Review Board of Kaohsiung Medical University Hospital, Kaohsiung Medical University, Republic of China) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Every living donor renal transplantation was approved by our hospital ethics committee. The present study was approved by the review board of our institution (KMUHIRB-E(I)-20200063). For this type of study, informed consent was not required and approved by institutional research committee.

Consent for publication N/A (Not Applicable)
Informed consent The present study was approved by the review board of our institution (KMUHIRB-E(I)-20200063). The informed consent was waived by Institutional Review Board (IRB) of the KMUH of ethics committee