544 MATERIALS AND METHODS 1. Patient characteristics and methods This study was conducted on 15 consecutive patients with renal tumors ＜4 cm in size who underwent LPN between March 2009 and March 2011 in our hospital. All surgeries were performed by a single surgeon using the trans- peritoneal approach. The subjects were 5 men and 10 wom- en whose average age was 56 years and average body mass index (BMI) was 23.4; three of the patients had a history of abdominal surgeries. The tumors of seven subjects were in the left kidney, and those of eight subjects were in the right kidney. Regarding tumor location, three were in the upper pole of the kidney, five in the mid portion, and seven in the lower pole (Table 1). No patients had a solitary kidney or multiple renal tumors. Diagnoses were made by using abdominal computed tomography (CT). The operating time, warm ischemia time, and intra- operative estimated blood loss were recorded for each patient. All patients had their pre- and postoperative se- rum creatinine and complete blood count. Postoperative tests were done on the 1st, 3rd, and 5th day, respectively, after surgery. A CT scan was done in the third month to de- TABLE 1. Patients’ characteristics Male/female Mean age (yr) Mean body mass index Tumor site (left/right) Tumor position 　Upper pole 　Mid portion 　Lower pole No. of previous transperitoneal surgeries Characteristics (n=15) 5/10 62 (21-72) 23.4 (16.2-31.3) 7/8 3 5 7 3 (appendectomy: 1, cholecystectomy: 2) Lee et al tect any recurrence or subclinical complications, such as postoperative hematoma, urinoma, or hydronephrosis. 2. Surgical technique The surgery was performed through the transperitoneal approach. With the patient under general anesthesia, the patient was secured on the operating table in the lateral flank position with the affected side up. In the process of the surgery, four trocars were commonly used (two 10 mm trocars and two 5 mm trocars). We used a closed technique using a Veress needle to obtain the initial access and create pneumoperitoneum, which was typically maintained at 12 mmHg. After the colon was mobilized medially, the renal vessels were dissected. Next, the vessel loop was in- troduced via a 10 mm trocar and was winded twice around the vessel using a laparoscopic dissector and right-angle. After the vessel had been looped, both free ends of the vessel loop were clipped by a Hem-o-Lok clip so that it would not come untied. Barium gauze was inserted into the outer cir- cle of the vessel loop to avoid vacular injury (Fig. 1). When this step was completed, the preparation for the transient vascular occlusion was finished. Next, the kidney was stra- tegically defatted down to the renal capsule with the lapa- roscopic monopolar hook, preserving the fat overlying the tumor. The planed line of resection was then scored on the surface of the kidney with the laparoscopic hook. When vas- cular occlusion was required, the additional Hem-o-lok clip was applied to the proximal portion of the vessel loop pull- ing the distal portion (Fig. 2). After this simple procedure, the vascular occlusion was done. There was no need for ad- ditional ports. In three early cases, both the renal artery and the renal vein were clamped. After that time, only the renal artery was clamped. In situations in which excessive bleeding was encountered during resection of the tumor, the tension could be increased with the application of an- other Hem-o-lok clip on a more proximal portion of the ves- sel loop. 　After warm ischemia was started, the tumor was excised FIG. 1. Operative findings. (A) The vessel loop was winded twice around the renal vessel. (B) Barium gauze was inserted into the outer circle of the vessel loop. Korean J Urol 2011;52:543-547