The Impact of Extended Warm Ischemia Time on Late Renal Function After Robotic Partial Nephrectomy

Purpose: To evaluate the effect of warm ischemia time (WIT) on late renal function in patients undergoing robotic partial nephrectomy (RPN). Patients and Methods: From January 2009 to June 2013, patients with tumors <= 7 cm (cT1) undergoing RPN at our center with at least 1-year renal function data were included. Patients with deterioration of renal function due to coexisting medical conditions and patients with a solitary kidney were excluded from the analysis. We compared our cohort based on three WIT groups, namely, zero ischemia (WIT=0 minutes), limited ischemia (WIT <= 30 minutes), and extended ischemia (WIT >30 minutes). Results: From the 665 patients undergoing RPN, 266 met our inclusion criteria. Median follow up for evaluation of estimated glomerular filtration rate (eGFR) was 24 months. Zero ischemia group had the highest percentage of renal function preservation (92.9%) followed by WIT <= 30 group (89.2%) and WIT >30 group (83.2%). On univariable analysis, pre-existing eGFR, tumor size, RENAL score, and WIT were significant predictors of degree of late eGFR preservation. On multivariable analysis, tumor size, pre-existing eGFR, and WIT grouping remained the only significant predictors of late renal function. There was no statistical significance in degree of late eGFR preservation between zero ischemia and WIT <= 30 groups. However, WIT >30 minutes was a negative predictor of late eGFR preservation when compared to WIT <= 30 minutes. Conclusions: WIT >30 minutes, preoperative eGFR, and tumor size were independent predictors of late eGFR deterioration after RPN in our series. With increase in the use of RPN in more complex tumors, the prolonged WIT associated with resection and reconstruction of such tumors needs to be mitigated.