Single-Port Sutureless Partial Nephrectomy for Small Renal Cancer

Background : Laparoscopic single-port (LESS) sutureless partial nephrectomy (PN) is a technically demanding procedure. Here we shared our experience to reduce the warm ischemia time and shorten the learning curve in performing LESS sutureless PN. Materials and methods : Between 2015 and 2018, custom made LESS sutureless PN was performed in 33 patients with small renal cancer. Preoperative, intra-operative and postoperative variables were recorded. Renal function was evaluated by estimated glomerular filtration rate (eGFR) pre- and postoperatively. Results : The average warm ischemia time and the operation time were 11.8 ± 3.9 min and 167.9 ± 37.5 min, respectively. Only 2 patients suffered from massive urinary leakage (>200 mL/day) from the Jackson Pratt drainage tube, but the leakage spontaneously decreased within 7 days after the surgery. eGFR and serum hemoglobin were not found to be significantly different pre- and postoperatively. All tumors were removed without positive surgical margin. All patients were alive without recurrent tumors at mean postoperative follow-up of 16.5 ± 6.4 months. Conclusions : LESS sutureless PN is a feasible surgical method for most patients with small renal cancer with excellent cosmetic results, shorter learning curve without affecting oncological results.


Introduction
In 2009, the American Urological Association (AUA) [1] recommended partial nephrectomy (PN) as the reference standard treatment for most clinical T1 renal masses, even in individuals with a normal contralateral kidney, due to its similar efficacy to radical nephrectomy while also preserving kidney tissue. Since that time, a review of nephrectomy records submitted as part of the American Board of Urology surgeon 3 certification/recertification process revealed that the use of PN has increased from 25% to 39% of all nephrectomies [2]. PN preserves kidney function better and limits long-term development of metabolic as well as cardiovascular disorders.
The European Association of Urology considers PN the treatment of choice for T1b renal cell carcinoma (RCC) [3].
Open PN remains the gold standard procedure in most patients with localized renal cancer. Though no randomized controlled studies have compared the safety and oncological outcomes in terms of renal function and surgical margins, the steep learning curve with laparoscopic partial nephrectomy (LPN) remains a concern [4]. LPN is a technically demanding procedure, even under robotic assistance. Several important challenges, such as preventing perioperative bleeding, reaching hyperthermia after renal artery clamping, reducing warm ischemia time, and performing laparoscopic intracorporeal suturing, must be met during the operation. Despite the ability to achieve renal hyperthermia by delivering cold saline into the renal pelvis, the cooling effect is not qualified during laparoscopic surgery. Gill et al. [5] reported a novel method using ice slush around the kidney; however, it is difficult to replicate during the laparoscopic procedure. Because it is difficult to achieve renal hypothermia during LPN, it is important to reduce the warm ischemia time, which is understood to correlate with subsequent return of renal function [6]. Traditional clamping procedures require a significant warm ischemia time during the suturing process. Hemostatic suturing plays a vitally important role, even in the current era of early unclamping [7], selective clamping [8], and unclamping techniques [9][10][11].
We previously shared our "pressure-cooker" method of performing LPN without intracorporeal suturing [12]. In the current study, we present our technique of laparoendoscopic single-site (LESS) sutureless PN. Our method is shown to reduce the warm ischemia time, and we believe this technique will shorten the learning curve in performing LPN for surgeons who lack experience in intracorporeal suturing. was obtained from all patients prior to their enrollment in the study. Patients with localized renal parenchymal tumor (stage T1N0M0) without endophytic properties or tumor located <4 mm from the collecting system were included. We excluded patients with suspected lymph node or distant metastasis. We quantified the anatomical characteristics of the renal masses using the R.E.N.A.L. nephrometry score [13]. In total, 33 patients undergoing LPN were enrolled in the study.

Approach
We previously published an article reporting our basic sutureless laparoscopic PN method [10]. Patients were placed in flank position with the lesion site elevated to 90 degrees.
The surgeon and assistant stood facing the patient's back. The length of the skin incision was approximately 2.5-3.5 cm according to the tumor diameter. The port incision was made just below the 12 th rib in the posterior axillary line. All procedures were performed using the retroperitoneal approach. A balloon dilator was used to create the retroperitoneal space, which was entered via the exposed thoracolumbar fascia, irrespective of their location. We used the LagiPort (Lagis, Inc., Taichung, Taiwan), a 5 multi-instrument access port designed especially for LESS PN (Figure 1). Gerota's fascia was dissected anteriorly and posteriorly. Next, an incision was made to mobilize the kidney from the perirenal fat, revealing the renal artery and primary tumor. If the tumor margin is not clear, intraoperative ultrasonography is used to better visualize the tumor margin. A fat pad from the perirenal space is prepared and should be located as far away from the tumor as possible.

Tumor excision: The "pressure cooker" method
In the selective renal artery non-clamping patients, a harmonic scalpel was used to remove the tumor, leaving a 0.5 to 1 cm safety margin. In the renal clamping group, the tumor was excised using laparoscopic scissors with bulldog clamps. Vascular disruption with excision was extensively fulgurated. For this procedure, we use monopolar coagulation via laparoscopic scissors to seal off the cross-section of renal calyx or pelvis if any collecting system disruptions are noted. After tumor removal, a hemostatic matrix (FloSeal; Baxter Healthcare, Zurich, Switzerland) is placed into the renal cavity, and a fibrin sealant (Tisseel; Baxter) is injected to cover the entire hemostatic matrix and the surrounding normal renal tissue. At the end of the surgery, the fat pad is placed to cover all of the areas coated with fibrin sealant, and the bulldog clamp is detached. The fat pad covering should be accomplished within 20 seconds to prevent solidifying of the fibrin sealant. The fat pad will adhere to the periphery of the incision field, and the hemostatic matrix will be "cooked" and closed off underneath. After the gelatin matrix and thrombin component are combined, the hemostatic matrix will expand around 20% of the volume upon contact with blood or urine. This reaction will occur soon after removing the bulldog clamp. The hemostatic matrix is engorged within the airtight space covered by the fat pad just like a "pressure cooker," causing extra external pressure to compress the postoperative bleeding ( Figure 2). The tumor specimen can be removed directly through 6 the port using a laparoscopic grasper. We placed a drainage tube in 20 patients, and we do not leave a drainage tube in small and exophytic tumors.

Study population
The preoperative data are shown in Table 1. The average patient age was 59.7 ± 11.1 years (range: 36.0-77.0). Seventeen patients (51.1%) were male. The patient population was generally non-obese with a mean body mass index of 26.8 ± 3.2 (range: 21.9-38.1).

Surgical outcomes
The average operation time was 167.9 ± 37.5 minutes (range: 100-250 minutes). To achieve renal hilar control, the clampless method was used in 6 patients due to tumors in exophytic locations or the majority of tumors had a distinct fibrotic capsule. Bulldog clamps were used for temporary renal artery occlusion in the remaining 27 patients. The average warm ischemia time was 11.8 ± 3.9 minutes (range: 8-26 minutes). The renal clamping strategy was made according to the surgeon, preoperative imaging, intraoperative findings, and intraoperative ultrasound. Mean estimated blood loss was 104.0 ± 105.8 mL (range: 10.0-430.0 mL). Only 1 patient required a perioperative blood transfusion due to large tumor burden. Conversion to conventional laparoscopy or open surgery was not necessary (Table 2). We do not perform the renal cooling technique. After the operation, the renal tumor was removed from the LESS wound. In total, 5 patients had obvious collecting system disruption during the procedures. We did not perform 7 reconstruction of the collecting system. Only 2 patients suffered from massive urinary leakage (>200 mL/day) from the Jackson Pratt drainage tube (Table 3), but the leakage spontaneously decreased within 7 days after the surgery without requiring additional surgery. The mean length of hospital stay was 5.6 ± 1.5 days.

Renal function and haemoglobin level
The preoperative and postoperative estimated glomerular filtration rate (eGFR) was 76.6 ± 22.4 and 69.6 ± 24.3, respectively. There was no significant decrease in eGFR level (p = 0.228). A marginal decrease in haemoglobin level was observed (preoperative vs postoperative; 13.9 ± 1.3 vs 13.3 ± 1.3; p = 0.064) but did not reach statistical significance ( Table 2, 3). No significant difference was found between preoperative and postoperative eGFR and haemoglobin level. Notably, the average skin incision was 2.8 ± 1.1 cm with excellent cosmetic outcomes.

Discussion
PN was initially reported in 1993, and McDougall et al. [14] first reported a wedge resection technique for removal of small, low-stage renal masses via LPN. Since then, LPN has been increasingly used due to refined laparoscopic suturing techniques and the 8 availability of hemosealant substances. Although no randomized study has compared safety and oncological outcomes between LPN and the open technique, the main concern with LPN has always been the steep learning curve [4]. Stifelman el al. [15] reported the first robotic-assisted (RA) PN in 2005, demonstrating that this approach allowed for accurate lesion resection and easier reconstruction of the renal defect. A recent U.S. study [16] using the Nationwide Inpatient Sample database determined practice patterns and perioperative outcomes of open and minimally invasive PN, revealing that RAPN is currently performed more commonly than is LPN. Conversely, LPN is more widely used RAPN also was associated with reduced complications, fewer positive margins, and shorter warm ischemia time [18]. Potential disadvantages of RAPN included cost, training, setup time, and lack of tactile sensation or haptics. The robotic procedure had a lower odds of advantages compared to laparoscopic PN except for in the category of hospital charges.
We think that LPN still has competitive value in patients with small renal tumors. The major concern with LPN is the learning curve. Our technique provides a feasible method Our study identified 5 patients with obvious disruption of the collecting system. We did not perform traditional suture repair of the collecting system. Ploussard et al. [19] showed that even after deep one-third PN, the combinations of FloSeal and Tisseel appeared to sufficiently control the major medullary vascular injuries and replace the conventional deep medullary sutures without compromising operative outcomes in a pig model. We The most important factor in preserving renal function during PN is the percent of nephron mass preserved [6,. In our series, one of our main findings relates to nephron mass preservation, which is of primary importance for functional recovery, consistent with reports from other studies that eGFR of small renal cancer was not significantly different pre-and postoperatively [10][11]. Traditionally, PN relies on clamping of the main artery, with ischemia time considered to correlate with postoperative renal function. Gill et al. [5] shared a novel technique of laparoscopic renal hypothermia with intracorporeal ice slush during PN. A recent report also demonstrated superior renal functional outcomes using a cold ischemia technique with statistical significance from the third postoperative month [24]. Dong et al. [25] also demonstrated that functional recovery from clamped PN is most reliable using hypothermia. However, this cooling procedure was not easy to replicate during laparoscopic surgery; therefore, it is important to reduce the warm ischemia time.
A threshold may exist after the damage from ischemia begins. Thompson et al. [6] demonstrated that every minute is important, and 25 minutes was considered a safe threshold in patients with a solitary kidney. Lane et al. [23] evaluated early and late renal functional outcomes in 1,132 patients with 2 functioning kidneys, showing that a warm ischemia time of <20 minutes is not associated with clinically relevant functional loss compared to that of alternative techniques. Gill et al. [9] was the first to describe a technique of "zero ischemia," which focused special attention on selective branch microdissection of renal vessels in the renal sinus; transient, pharmacologically induced blood pressure reduction timed to coincide precisely with excision of the deep part of the tumor; laparoscopic ultrasound to score the proposed resection margin; and clip ligation of any specific tertiary or quaternary renal artery branches supplying the tumor. The effort to minimize ischemia is accompanied by increased blood loss during the procedure.
The potential impact on the surgical margin may be influenced by the lack of a clear operative field, which may bring surgical challenges for inexperienced operators, especially in larger renal tumors [26]. A current review paper [26] argues that newer strategies focusing on selective clamping and non-clamping can make a complex surgery even more challenging, which may serve to limit the widespread use of PN for management of renal cancers. We believe that our technique should be used in single-site

Consent for publication
The study was conducted according to the principles of the Declaration of Helsinki and supervised by the local Ethics Committee of the Kaohsiung Medical University Hospital.
Written informed consent was obtained from all patients prior to their enrollment in the study.

Availability of data and materials
The datasets used are available from the corresponding author on reasonable request.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.