46 suture, articulating needle drivers were used alone for the repair of the resection margin of E1's first procedure and B2's procedure, and an articulating needle driver and rigid needle driver were used concurrently in all other cases. 　The resected parenchymal tissues and each kidney were extracted through a 4 cm extended umbilical incision (Fig. 2, 3). After all procedures were performed, the pig was eu- thanized by use of an extra dose of KCl intravenously. RESULTS All six partial nephrectomies were successfully performed without the need to introduce any additional ports, and all hemostatic procedures were successful in the repair of the vascular and collecting systems on the resection bed and renorrhaphy. Stable vital signs were maintained through- out the procedures, and there were no noticeable compli- cations. 　During the partial resection of the renal parenchyme, an articulating grasper and articulating cold scissors were used in all cases. The mean time for partial resection was 3.1 minutes (range, 2.5-3.3 minutes), and the mean re- section times for the upper and lower pole areas were 3.4 (range, 3-4) and 2.8 (range, 2.5-3.3) minutes, respectively. The experienced (E1, E2) and less-experienced (B1, B2) surgeons’ mean times for partial parenchymal resection were 2.9 minutes (range, 2.5-3.3 minutes) and 3.25 mi- nutes (range, 2.5-4 minutes), respectively. The mean sizes of the resected parenchyma were 2.1 cm (range, 1.9-2.4 cm) and 1.5 cm (range, 1.4-1.6 cm) for the long diameter and depth, respectively. 　Regarding warm ischemic time, E1 recorded 60 minutes on the anterior side of the right kidney upper pole and 35 minutes on the anterior side of the left kidney upper pole. E2 scored 30 minutes on the anterior side of the right kid- ney lower pole and 35 minutes on the anterior side of the left kidney lower pole around the hilar area. For B1 and B2, the warm ischemic times were 47 and 50 minutes for the posterior side of the right kidney lower pole and the posteri- or side of the left kidney lower pole, respectively. The short- est ischemic time, 30 minutes, was achieved by E2 by use of the early unclamping technique during renorrhaphy. The mean warm ischemic time was 42 minutes (range, 30-60 minutes); according to imaginary tumor location, it was 47.3 minutes (range, 35-60 minutes) for upper pole tu- mors and 36.7 minutes (range, 30-50 minutes) for lower pole tumors, respectively. The experienced (E1, E2) and less-experienced (B1, B2) surgeons’ mean ischemic times were 38.8 minutes (range, 30-60 minutes) and 48.5 mi- nutes (range, 47-50 minutes), respectively. The average number of sutures for renorrhaphy was 3.2 (range, 2-5). DISCUSSION The rising demand for minimally invasive surgical proce- dures and the development of surgical techniques to meet such a need has enabled urologists to apply the single-port Korean J Urol 2011;52:44-48 Koo et al surgery techniques to most laparoscopic surgeries in urology. The Cleveland Clinic has reported 100 surgical cases of LESS ranging from nephrectomy to even radical cystectomy [4]. However, there are relatively fewer suc- cessful reports on LESS in partial nephrectomy. Boylu et al reported 10 cases of partial nephrectomies using a por- cine model [5]. At this point in clinical practice, there are only initial case reports of LESS in highly selected cases. Aron et al reported 4 human cases in highly selected pa- tients, but they used an additional 2 mm grasper via a 2 mm Veres needle for the purpose of tissue traction [6]. Our study focused on evaluating in a porcine model the techni- cal feasibility of using a pure LESS technique for perform- ing partial nephrectomy. 　In this study, all six partial nephrectomies were success- fully done without any significant complications. However, there are some obstacles to performing LESS partial neph- rectomy in humans. The most important one is the learning curve. One obvious difference between the LESS surgical technique and pure laparoscopy is the limitation in the movement of the instruments. That limitation makes the LESS surgery difficult and the learning curve for LESS surgery steep. 　Three major procedures make it difficult to manipulate the surgical instruments properly in LESS partial neph- rectomy. These are tumor resection, calyceal suture, and parenchymal suture. For tumor resection, it took only 2.9 minutes for the experienced laparoscopic surgeons, and even for the inexperienced surgeons, it took only 3.3 mi- nutes with the use of the flexible instruments. However, sewing the open calyx and resected renal parenchyma was the most difficult procedure during LESS partial nephrec- tomy. To identify whether the suture technique used in pure laparoscopic surgery could also be adapted for LESS partial nephrectomy, the surgeons in this study did not use any laparoscopic clips, which can make suturing easier and faster. The most difficult procedure in LESS partial neph- rectomy is parenchymal suture. Therefore, reducing the time for this procedure can shorten the warm ischemic time. Many researchers have tried various ways to reduce the warm ischemic time. We tried only interrupted paren- chymal sutures with the sliding knot technique, which is simple and accurate but the most difficult and time-con- suming technique, with the object of identifying the feasi- bility of this suturing technique for LESS partial nephrec- tomy. Therefore, it took from 27 minutes to 57 minutes for the calyceal and parenchymal sutures. 　The articulating instrument is very useful during all of the procedures in LESS surgery, especially for triangu- lation and procuring enough space for the instruments to move freely in the restricted space. In our experience, it was convenient for the right-handers to use the articulating in- strument for the right-side instrument, because the right-hand instrument usually performs the counter-trac- tion to make the dissection easier in contrast with pure lap- aroscopic surgery. However, which hand should use the ar- ticulating instrument depends on the situation. Regarding