which resulted in smaller wounds and rapid recovery. This operation can be performed using either transperitoneal or retroperitoneal techniques. The advantages of retroperitoneal approach were avoidance of bowel manipulation and it could be direct access to the kidney. Thus the aim of our study was to evaluate the experience of laparoscopic retroperitoneoscopic partial nephrectomy for angiomyolipoma in our center. Materials and Methods: We retrospectively analyzed the medical records of 20

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... nts (17 females and 3 males) who underwent retroperitoneal laparoscopic partial nephrectomies for benign renal tumor (pathology: angiomyolipoma) in Chi-Mei Medical Center from June 2012 to July 2015. All of the surgeries were performed by a single surgeon. The demographic data, characteristic of tumors, peri-operative status and post-operative outcome were analyzed. Results: Twenty-two partial nephrectomies were performed in twenty-one kidneys. The mean age was 48-year-old (27-70). Most of the patients were diagnosed incidentally, only 4 patients (20%) presented with the symptom of flank or abdominal pain. The mean size of tumors which disclosed by CT was 4.9 cm (1-18). Meanwhile the R.E.N.A.L nephrometry score was 6.1 in average. Only one patient who underwent pre-operative TAE due to huge tumor size (18cm). There was a wide range of operative time with mean 176 mins (90-345) related to the complexity of tumors. The average warm ischemic time was 9.4 mins (0-20.7) with 7 partial nephrectomies done in zero-ischemia status. Intra-operative estimated blood loss 173 ml (10-600). No major surgical complications noted. Only 3 patients required blood transfusion perioperatively. Another one patient experienced asymptomatic perirenal hematoma during CT follow-up. The average post-operative length of hospital stay was 3.3 days (2-8). Regarding the renal function, the average decreased of GFR of lesion side after operation was 11% (from 46.5 ml/min to 41.4 ml/min). Two patients revealed residual tumors and one patients showed tumor recurrence by CT during out-patient department follow-up. Conclusion: Laparoscopic retroperitoneoscopic renal surgery can be performed safely and effectively. However, the limited space of retroperitoneum given this procedure more challenging.