Intraoperative conversion from partial to radical nephrectomy: Predictive factors and outcomes.

483 Background: Predictive risk factors for intraoperative conversion from partial to radical nephrectomy (RN) are poorly quantified. We evaluated preoperative predictors of conversion in a cohort of patients undergoing planned partial nephrectomy (PN). Methods: A prospectively maintained database was reviewed to identify patients who were scheduled to undergo (open, laparoscopic, or robot-assisted) PN that were converted to RN between 1990 and 2015. Reasons for conversion were collected from the operative report. Patient demographics and perioperative variables were evaluated including body mass index (BMI), tumor size, nephrometry score, hilar tumors, procedure type, intraoperative complications, and oncologic outcome. Results: A total of 2298 patients underwent successful PN. The rate of conversion to RN was 4% (n=99) patients. The median patient age was 60 years and median BMI was 30 kg/m 2 . The median American Society of Anesthesiologists (ASA) score was 3 and median Charlson Comorbidity Index (CCI) was 2. The median tumor size for the converted cases was 4.5 cm (1.0-10.1) and median nephrometry score was 9. Histology was clear cell-RCC in 79% of the tumors. A total of 30 patients had completely endophytic tumors. The most common reasons for conversion were hilar/renal sinus extension of the renal mass in 38 (38%) patients, positive surgical margin on frozen section or gross assessment in 27 (27%) patients, insufficient renal remnant in 27 (27%) patients, and excessive intraoperative bleeding in 7 (7%) patients. RN was performed open in 79, laparoscopically in 9, and robot-assisted in 11 cases. Intraoperative complications occurred in 1 (1%) patient underwent an attempted robot-assisted PN resulted in an injury to a major renal artery branch requiring conversion to RN. Patients were followed up for a median of 33 months. In the converted cohort, evidence of disease at last follow-up was found in 13 (13%) patients. Conclusions: The rate of conversion to RN was low in patients undergoing PN in this series. The most common reason for conversion was hilar/renal sinus extension of these complex renal masses while positive surgical margin and insufficient renal remnant were contributing equally at lower rates.