Anatomic complexity quantitated by nephrometry score is associated with prolonged warm ischemia time during robotic partial nephrectomy

Objective To assess the association between nephrometry score (NS) and prolonged warm ischemia time (WIT) in patients undergoing robotic partial nephrectomy (RPN) for clinically localized renal masses. Methods We queried our prospectively maintained kidney cancer database to identify all patients undergoing RPN for localized tumors from 2007-2012. Patient and tumor characteristics were compared between complexity groups using analysis of variance and chi square tests. Multivariate logistic regression models were used to examine the relationship between NS complexity and warm ischemia >30 minutes. Results Three hundred seventy-five patients (mean age, 59 ± 11 years; mean Charlson comorbidity index, 1.0 ± 1.3) undergoing RPN under warm ischemia for clinically localized renal tumors (mean tumor size, 3.1 ± 1.5 cm; mean NS, 6.8 ± 1.8) met inclusion criteria and had NS available. Stratified by complexity, groups differed with respect to age at surgery, tumor size, proximity to the hilum, collecting system entry, estimated blood loss, and operative time (all P values ≤.05). Significant differences in mean WIT were observed when comparing low (19.4 12.1 minutes), intermediate (28.6 12.8 minutes), and high (36.1 13.7 minutes) NS complexity groups (P.0001). Adjusting for confounders, patients with intermediate (odds ratio, 2.1; confidence interval, 1.2-3.9) and high (odds ratio, 3.7; confidence interval, 1.1-11.8) NS complexity were more likely to require prolonged WIT when compared with patients with low complexity tumors. Conclusion In our large institutional cohort, quantification of anatomic complexity using the NS is associated with WIT >30 minutes in patients undergoing RPN for localized renal tumors. This provides further evidence that standardized reporting of tumor anatomic complexity affords meaningful outcome comparisons.