The Application of R.E.N.A.L. Nephrometry Score In Laparoscopic Partial Nephrectomy With Zero Ischemia And Sutureless

Background: To evaluate the application of R.E.N.A.L. nephrometry score (RNS) in laparoscopic partial nephrectomy (LPN) with zero ischemia and sutureless surgery, and to explore the ecacy and safety of zero ischemia and seamless LPN in the treatment of renal cell carcinoma. Methods: The clinical data of 67 patients with renal cell carcinoma treated by LPN in the aliated Hospital of Guizhou Medical University from January 2016 to July 2020 were analyzed retrospectively. The patients were divided into renal artery occlusion group (n=31) and non-occlusion group (n=36). All cases were divided according to their RNS (low, moderate, and high), and the perioperative condition, postoperative complications, postoperative recovery and changes of renal function in the two groups were analyzed. Results: According to the RNS, all cases were classied in low-complex. Both groups successfully completed the operation without operative complications. Compared with the renal artery occlusion group, the non-occlusion group had a shorter operation time (35.51±20.48 min), shorter hospital stay (6.72±4.39 d), and no signicant difference in intraoperative blood loss(50.39±30.19 ml). During the 6-month follow-up, the creatinine value of the renal function in the non-occlusion group (78.47±10.98μmol/L) was lower than that in the occlusion group(98.21±8.06μmol/L). Conclusion: Zero-ischemia sutureless LPN technique can effectively reduce the time of ischemia and avoid renal ischemia-reperfusion injury. This surgical technique may be a feasible surgical method for the treatment of low RNS renal cell carcinoma. than in rural areas(3), the incidence rate in 50 ~ 70 years old(4). A preoperative anatomical scoring system is conducive to the comparison between treatment options and evaluation of postoperative outcomes in patients with small renal tumo(5). The R.E.N.A.L. nephrometry score (RNS) proposed by Kutikov and Uzzo(6) is based on the ve most reproducible and pertinent features that characterize renal tumor critical anatomical attributes. Previous studies(7) have demonstrated its superiority in predicting perioperative outcomes. It also plays an important role in guiding the formulation of surgical plans(8).


Background
Renal cell carcinoma (RCC) is a malignant tumor that originated from the urotubule epithelial system of the renal parenchyma (1). Male patients with renal cell carcinoma were 1.8 times higher than females (2). The incidence in urban areas is 4.3 times higher than that in rural areas (3), and the incidence rate is higher in 50 ~ 70 years old (4).
A preoperative anatomical scoring system is conducive to the comparison between treatment options and evaluation of postoperative outcomes in patients with small renal tumo (5). The R.E.N.A.L. nephrometry score (RNS) proposed by Kutikov and Uzzo(6) is based on the ve most reproducible and pertinent features that characterize renal tumor critical anatomical attributes. Previous studies (7) have demonstrated its superiority in predicting perioperative outcomes. It also plays an important role in guiding the formulation of surgical plans (8).
Operation is the standard treatment for RCC. At present, partial nephrectomy (PN) has gradually become the standard surgical method for treating RCC (9,10). PN aims to achieve a higher disease-free survival rate and maximize kidney function (11) and laparoscopic partial nephrectomy (LPN) has been widely used in RCC (10). After the rst case of LPN showed that this surgical technique has many advantages compared with open surgery, it has developed signi cantly. Clamping the renal pedicle vessels can block the blood supply in the operation area, which is bene cial to the accurate cutting with a cold knife during operation, but renal ischemia-reperfusion injury sometimes increases the risk of damaging renal function (12,13). Therefore, it is always an important direction of modi ed LPN operation to reduce the time of renal ischemia (14). Can the operation be performed smoothly without blocking the renal artery in LPN (15)? What level of RCC is suitable for this operation? In this study, zero ischemia and sutureless LPN was reported, and evaluate the perioperative and prognostic effects of patients by RNS.

Clinical data
The clinical data of patients who received LPN treatment from January 2016 to July 2020 were analyzed retrospectively. According to the surgical method of LPN, 67 patients with renal tumors were divided into renal artery occlusion group (n = 31) and non-occlusion group (n = 36).

Medical records and RNS evaluation
All patients underwent enhanced computed tomography (CT) before the operation to determine the size and location of the tumor, the location of renal vessels and the thickness of renal parenchyma. All patients had normal serum creatinine, blood, urine and stool routine, liver and renal function, electrolyte, blood coagulation test, electrocardiogram, chest positive and lateral lm, heart function and lung function examination if necessary.
By reviewing imaging examinations, including CT(16), RNS was used to assess the complexity of RCC. All CT data were evaluated by a senior urologist. According to Kutikov and Uzzo, the ve components of RNS include the radius (maximum diameter), exogenous/endogenous characteristics, the distance between the lesion and the collecting system or renal sinus, the position of the anterior or posterior part of the lesion, and the position of the lesion relative to the polar line. According to the RNS system, tumor complexity is de ned as low, intermediate and high if the R.E.N.A.L score is 4-6, 7-9 or 10-12, respectively. 3.1.1 Establish a surgical passage: The patient was placed in a lateral recumbent position and raised the lumbar bridge. After the general anaesthesia took effect, the scalpel cut a 1~2cm longitudinal incision under the 12 costal margin of the retroaxillary line, bluntly separated the muscular layer and lumbar dorsal fascia with long arc hemostatic forceps, put the self-made balloon into the retroperitoneal space, and in ated air 500~700ml expanded the retroperitoneal space. Laparoscopic ports (Trocar) were established at the dilated ori ce, under the costal arch of the anterior axillary line and above the iliac ridge of the axillary midline, respectively. The pneumoperitoneum was established after CO 2 was lled into the abdominal space, and a 30-degree laparoscope was used during the operation.
3.1.2 Surgical procedure: Opened the Gerota fascia with the combination of blunt and sharp separation, and dissected along with the renal fat capsule until the tumor was exposed. Dissect the dorsal surface of the kidney along with the psoas major muscle, free the renal pedicle to expose the renal artery, block the main renal artery and branch artery, and then perform partial nephrectomy along the edge of the tumor about 0.5cm normal renal tissue. After that, the renal wound was sutured with self-retaining barbed sutures to reconstruct the residual nephron(17) ( gure 1). After loosening the vascular clamp and con rming that there was no active bleeding, the resected tissue was taken out for pathological examination. The surgical drainage was indwelling, closed the surgical passage and the operation was nished.
3.2 Non-occlusion group: LPN with zero ischemia and sutureless via retroperitoneal approach.
3.2.1 Establish a surgical passage: The way of establishing surgical passage was the same as that of the Renal artery occlusion group.
3.2.2 Surgical procedure: Opened the Gerota fascia with the combination of blunt and sharp separation, and dissected along with the renal fat capsule until the tumor was exposed. In general, it is not necessary to dissociate the renal pedicle to expose the renal artery. Scissors sharp separation and attractor blunt separation were used to remove the tumor along with the normal renal tissue of 0.5cm at the edge of the tumor. In case of blood spurting from small blood vessels, the hemostatic treatment should be done immediately by electrocoagulation. After the tumor was completely removed, the tumor bed was treated with unipolar electrocoagulation and repeated electrocoagulation (spray coagulation 80W 110W) ( gure 1). Con rming that there was no active bleeding, the tumor bed was lled with absorbable hemostatic gauze, and the resected tissue was taken out for pathological examination. The surgical drainage was indwelling, closed the surgical passage and the operation was nished.

Observation index and statistical processing:
The statistical analysis indexes included operation time, blood loss, postoperative drainage time, postoperative hospital stay and follow-up of renal function. All the measurement data in this study are expressed by mean±standard deviation (x±s), and the counting data are expressed by percentage (%). All the data were analyzed by T-test and statistically processed by SPSS22.0, and P < 0.05 was statistically signi cant.

Results
All the 67 operations were successful, and there was no signi cant difference between the two groups in sex, age, tumor stage, tumor number, tumor diameter, tumor location and so on. The RNS scores of all 67 patients were low (4-6 pts). The analysis of pathological specimens showed that the tumor and the outer capsule were removed and surrounded by the healthy parenchyma of 0.5~1.0cm, the surgical margin was negative, which was in line with the expectation.
In the renal artery occlusion group, the average operation time (OT) was 75min (61~88min), and the average intraoperative blood loss(IBL) was 48mL (29~78mL). In the non-occlusion group, the average OT was 36min (15~56min) and the average IBL was 50mL (20~80mL) ( Table 1). In the non-occlusion group, 36 cases did not block the renal artery during the whole operation, and the renal ischemia-reperfusion injury was eliminated. No intraoperative or postoperative organ injury, pneumothorax, urinary stula, postoperative bleeding or secondary infection occurred in all cases. The drainage tube was removed 2~3 days after surgery, and there was no signi cant difference between the postoperative drainage volume and the indwelling time of the drainage tube. In the occlusion group, the postoperative gastrointestinal recovery time was 47.48h (12h-52h), and the hospital stay was 11.16 days (7d-14d). In the non-occlusion group, the postoperative gastrointestinal recovery time was 10.28 hours (6-24 hours), and the hospital stay was 6.72 days (3-10 days). The postoperative recovery was better in the non-occlusion group (Table 1).
We paid a follow-up visit to the patients 6 months after the operation, and CT showed no signs of local recurrence or distant metastasis. The renal function was monitored 6 months after the operation, and the serum creatinine (Scr) in the occlusion group was signi cantly higher than that in the non-occlusion group (Table 1).
Laparoscopic partial nephrectomy (LPN) with renal artery occlusion is the standard surgical method for the treatment of partial RCC, the key step is to block the renal pedicle vessels to obtain a clear eld of vision when removing the tumor. But at the same time, it also increased the intraoperative steps, increased the di culty of the operation, and increased the probability of postoperative complications (18). And the study shows that the time of renal warm ischemia should be controlled within 30min, otherwise it will cause serious damage to renal function (19). For this reason, shortening or avoiding warm ischemia time as much as possible has become the key to the improvement of LPN surgery. Among them, robot-assisted surgical LPN technology can reduce the ischemic time to an acceptable level (20,21), but it requires advanced equipment and an operational basis, so it is still not feasible to be used in the large-scale treatment of RCC (22).
According to related research (23) and practice, traditional laparoscopic surgery has been improved, and it is proved that zero ischemia (18,24) and sutureless (25)(26)(27) LPN technique is feasible for the treatment of small, exogenous and peripheral RCC. Compared with the traditional renal artery occlusion, there is no signi cant difference in the sample statistics of IBL.
Zero ischemia sutureless LPN can minimize the impact on renal function because it does not block the renal artery and has no warm ischemia and reperfusion injury (28). There is no need to dissociate the renal pedicle and renal artery during the operation (29), and the wound of the tumor bed is not sutured after the tumor is resected, which reduces the operation steps, reduces the di culty of the operation, and shortens the operation time. The highpower electrocoagulation can not only effectively stop bleeding, but also inactivate the possible residual tumor tissue at the surgical margin and effectively reduce the risk of tumor residue. At the same time, no suture is retained in the kidney after the operation, which not only saves the surgical consumables and reduces the cost of operation, but also does not need to worry about the risk of re-bleeding caused by kidney cutting with movable sutures after the operation (30). patients can get out of bed as soon as possible and reduce postoperative complications. improve the speed of postoperative recovery.
Among the technical points, the most important thing of zero ischemia sutureless LPN is to control bleeding and ensure the visual eld of operation. Therefore, the use of attractor and the intervention of high-power electrocoagulation hemostasis become the key. To increase the safety of the operation, it is still recommended to fully expose the renal artery before removing the tumor, to block the blood supply at any time when the bleeding is di cult to control. When cutting the renal parenchyma with a cold knife, if you encounter blood oozing from the renal tissue, you can attract and maintain a clear eld of vision through the attractor. If you encounter the case of blood spurting from small blood vessels, you need to use electrocoagulation immediately and continue to remove the tumor after the bleeding is controlled. After resection, the tumor bed should be fully electrocoagulation, and the wound should be lled with absorbable hemostatic gauze to ensure the hemostatic effect.
We retrospectively analyzed 67 patients with renal tumors treated by LPN at our solitary center. According to the RNS, all 67 patients had low-complex tumors. The OT and warm ischemia time in the Renal artery occlusion group were signi cantly higher than those in the non-occlusion group. These data suggest that zero-ischemia sutureless technique has an advantage in LPN surgery for low complexity renal tumors.
The limitation of this study is that the sample size of the single center study is relatively small. Another limitation is that the results may be affected by the surgeon's learning curve for LPN. The average follow-up time is 6 months, and the follow-up period is relatively short, which may not accurately re ect the postoperative renal function of the patients. In the future, we plan to conduct randomized, large sample size and multicenter studies to further verify our results.

Conclusion
RNS is a standard and feasible classi cation system for evaluating renal tumors and can be used to evaluate the complexity of tumors. We use the RNS system to evaluate the feasibility and applicability of the improved LPN scheme.
Zero ischemia sutureless LPN technique can reduce the time of renal ischemia, and even completely avoid ischemia-reperfusion injury, thus reducing the risk of damage to residual nephron function. This technique may be a feasible and effective surgical method for the treatment of low complexity renal tumors.
In the future, we will apply this procedure to more cases to improve this LPN technique and explore more feasibility.   Figure 1 Illustration of renal artery occlusion LPN and zero ischemia and sutureless LPN

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