New Longitudinal Component of the RENAL Nephrometry Score for Predicting the Operative Complexity in Transperitoneal Robot-Assisted Partial Nephrectomy

Background: In transperitoneal robot-assisted partial nephrectomy (RAPN), an L score of 3 points according to the RENAL nephrometry scoring system does not necessarily denote operative complexity. This study aimed to assess the efficacy of the newly defined longitudinal component to analyze the operative complexity of RAPN. Materials and Methods: We retrospectively analyzed transperitoneal RAPNs performed by a single experienced surgeon for renal tumors between 2017 and 2020. L component was defined as L'1 for midlocated tumors, L'2 for >50% below the polar line, and L'3 for >50% above the polar line. Multivariate regression analysis was performed to test associations between prolonged console time and preoperative factors. The perioperative outcomes were compared among the three cohorts of L' components using propensity score matching: L'1 vs L'3 and L'1 vs L'2. Results: A total of 220 cases (L'1: 107, L'2: 65, L'3: 48) were analyzed. The median console time was prolonged (>130 minutes) in 55 patients (median 108, interquartile range: 90-130 minutes). Longitudinal location (L'3 odds ratio [OR]: 2.93, p = 0.01; L'2 OR: 2.32, p = 0.04), high Mayo adhesive probability score (p = 0.001), multiple renal arteries (p = 0.03), and large size (p = 0.04) were significantly associated with prolonged console time. After matching, 26 cases of L'1 and L'3 and 43 cases of L'1 and L'2 were selected. Console time (108 minutes vs 132 minutes, p = 0.017) and warm ischemia time (17 minutes vs 22 minutes, p = 0.03) were significantly longer in L'3 than in L'1. The difference in console time between L'1 and L'2 was not statistically significant (100 minutes vs 111 minutes, p = 0.08). Conclusion: In the new longitudinal assessment, upper location predicted prolonged console time compared with a middle or lower location. The L' component may help preoperatively assess operative complexity.