Aim: To analyze the results of nephron sparing surgery (NSS) in patients with complex and large kidney tumors (R.E.N.A.L. 10-12).
Materials and methods: A total of 361 interventions for kidney neoplasm were performed from 2013 to 2018, including 207 (57,34%) NSS. The complex renal tumors were defined using R.E.N.A.L. nephrometry score. In 44 patients, tumors had a R.E.N.A.L. score of 10-12 (21,26%). Postoperative complications were classified using Clavien-Dindo system. Estimated glomerular filtration rate (eGFR) was assessed before operation and on the 1st-3rd postoperative day.
Results. Among tumors with R.E.N.A.L. score of 10-12, T1a, T1b and T2 stages were found in 13,64%, 70,45% and 15,91% cases, respectively. Robot-assisted partial nephrectomy was performed in 95%, while laparoscopic procedure was done in 5% of patients. Median operation time was 190 [170; 215] min, while median blood loss was 150 [100; 300] ml. There were 2 intraoperative complications (4,55%). Intraoperative complications were recorded in 2 (4.55%) patients. Postoperative complications developed in 22.73% of cases, including 3 patients with Grade I-II (6.82%) and 7 patients with Grade III complications (15.91%). Total, segmental ischemia and zero-ischemia was used in 31 (70.45%), 12 (27.27%) and 1 (2.27%) patients, respectively. The median duration of total ischemia was 20.0 [17; 25] min. A positive surgical margin was found in 1 (2.27%) patient. In 46.51% of cases, there was no decrease in eGFR in the early postoperative period. In 28% of patients, eGFR decreased by more than 20%. On average, GFR declined by 6.01%.
Conclusion. NSS in patients with complex renal tumors is an effective alternative to radical nephrectomy, which provides an acceptable level of postoperative complications, with moderate decrease in eGFR and low rate of positive surgical margin.

Keywords: kidney cancer, partial nephrectomy, complications, robot-assisted partial nephrectomy