With the promotion and popularization of minimally invasive surgery, laparoscopic partial nephrectomy has become the preferred surgical method for T1 renal tumors. The rapid application and development of Da Vinci surgical robots in clinical practice in the past decade has revolutionized surgery. The robotic high-definition 3D stereoscopic field and multi-degree of freedom robotic arm make the operation more precise, especially suitable for the surgery requiring suture reconstruction for partial nephrectomy. A number of domestic and foreign studies have confirmed that in partial nephrectomy (especially for complex and difficult tumors), robotics exerts its significant advantages over laparoscopy [7–10].
The triumph of partial nephrectomy is a goal that urologists continue to pursue, that is, complete resection of the tumor, maximum protection of renal function and no surgical complications. How to protect renal function to the greatest extent has become the focus of attention in partial nephrectomy. On the premise of ensuring negative resection margins, it is important to preserve as much renal parenchyma as possible to protect postoperative renal function. In addition, renal ischemic injury caused by intraoperative renal artery clamping is also one of the important factors causing renal function loss. At present, academia believes that controlling intraoperative warm ischemia time within 30 min or even 25 min is essential for the protection of postoperative renal function.
Based on this, a variety of innovative surgical modes have been proposed to reduce warm ischemia time, including: Renal artery branch clamping technique , off-clamp zero-ischemic techniqueand early unclamping technique. However, it is worth noting that the renal artery branch clamping technique requires thorough and sufficient dissociation of the main renal artery and its branches, with high technical difficulty in separation, and branch clamping is also easy to lead to excessive volume of intraoperative blood loss due to incomplete clamping, and even affect the visual field; however, the unclamping technique is more suitable for superficial small volume tumors, and the surgical field is difficult to operate on due to the large amount of bleeding, and predisposes to the formation of positive resection margins. Baumert et al. proposed the concept of early unclamping technique in 2007, that is, after suturing and closing the inner layer of renal wound under renal artery clamping, relieving the renal artery clamping, opening the blood flow and then continuing to suture and close the outer renal wound edge, so as to achieve the purpose of reducing the warm ischemia time; however, there is a risk of increasing intraoperative bleeding.
Several centers in China and abroad have successively reported the clinical application of early unclamping technique. Zhang et al.  reported 29 cases of laparoscopic partial nephrectomy with early unclamping. The results showed that the mean warm ischemia time was 13.4 min, significantly lower than 21.1 min in the control group. San Francisco et al. reported the application of early unclamping technique in robotic surgery, including a total of 12 patients, with an average warm ischemia time of 16 min and a volume of blood loss of 150 ml, showing good safety and generalizability. Subsequently, Peyronnet et al.reported 222 large cases of early unclamping-based robot-assisted partial nephrectomy. Compared with the standard clamping group, the early unclamping group had larger and more complex tumor volume. The results showed that the warm ischemia time was shortened by nearly 6 min, but accompanied by more blood loss. The modified early unclamping technique implemented by our center, on the basis of the traditional technique, reduced the warm ischemia time by nearly 7 minutes without increasing the volume of intraoperative blood loss by quickly applying 2-3 stitches at a large distance between the outer layers of the wound before the renal artery unclamping, which fully reflects the technical advantages as well as safety and effectiveness of the modified early unclamping.
Renal artery pseudoaneurysm (RAP) and urine leakage are possible complications after partial nephrectomy. In recent years, many foreign literatures have reported that early unclamping technique has certain advantages for preventing postoperative RAP and urine leakage. Motoyama et al.  performed contrast-enhanced CT in 96 patients who underwent robot-assisted partial nephrectomy 3 – 5 days after surgery and found that RAP occurred in 7 patients with traditional clamping but not in the early unclamping group. The study performed by Kondo et al. also confirmed that early unclamping technique could reduce the risk of postoperative RAP. Delto et al. showed that early unclamping techniques may reduce the incidence of RAP and urinary leakage by comparing single-center data with data from other centers. One of the important reasons for these advantages is that in the state of open blood flow, the subsequent targeted suture and hemostasis for the wound, especially for inexperienced beginners, are more helpful to reduce the incidence of complications such as postoperative RAP formation, secondary bleeding and urine leakage.
The reduction of warm ischemia time brought about by early unclamping technique has a positive effect on postoperative renal function protection. The data of our center also showed that, the decrease of renal function in the modified early unclamping group was slightly lower than that in the standard clamping group as revealed by the reexamination at 3 months after surgery. The reason for the absence of statistically significant difference in postoperative renal function between the two groups may be attributed to the fact that the preoperative renal function of all enrolled patients was normal, and the overall warm ischemia time of most patients was within 25 minutes. For patients with complex tumors, solitary kidney tumors, or tumors with chronic renal insufficiency, modified early unclamping technique significantly reduces warm ischemia time and may have a more significant effect on postoperative renal function protection, which needs to be verified by further studies.
In the traditional early unclamping technique, the inner layer is unclamped after suturing. We found in the clinical practice that, at this time, the renal blood flow was restored, and more bleeding often occurred, making the visual field poor, especially for the deeper and larger wound surface, on which the outer suture tension makes it more difficult after renal congestion. The modified early unclamping technique proposed by us takes only 1 minute to quickly apply 2-3 stitches at large intervals in the outer layer of the wound before the renal artery unclamping, which significantly reduces the wound bleeding after restoring the renal blood flow, and reduces the tension of the subsequent suture. This not only reduces the warm ischemia time, but also compensates for the defects of increased volume of intraoperative blood loss caused by the traditional technique. In recent years, we have completed a certain number of modified early unclamping laparoscopic partial nephrectomies, with some preliminary experience gained: First, secure inner suturing is an important step in surgery. There are many open arterioles or venules in the deep part of the wound after tumor resection. When the first layer of suture is performed, the barbed suture must be "bottomed out" to firmly suture and prevent subsequent excessive bleeding. At the same time, for the occurrence of collecting system damage, the exact closure gap can effectively prevent postoperative leakage; secondly, during the inner layer suture, the needle insertion and needle withdrawal should be appropriately close to the wound edge. After tightening the suture, the wound edge on both sides can be closely aligned; otherwise the congestion and tension of the renal parenchyma are too large after opening the blood flow, which is not conducive to subsequent suture. In addition, this modified technique is especially suitable for deeper and larger complex types of tumors, which can significantly reduce warm ischemia time and oozing after open blood flow, making the operation more easy to complete and more beneficial to patients.