Determinants and Implications of Excised Parenchymal Mass on Robotic-Assisted Partial Nephrectomy Outcomes.

Objectives: To evaluate the association between excised parenchymal mass (EPM) and postoperative renal function (eGFR) following robotic-assisted partial nephrectomy (RAPN). EPM is the amount of healthy renal parenchyma excised during partial nephrectomy in order to achieve safe surgical margins.

Methods: We evaluated 406 consecutive RAPN performed by a single surgeon to eliminate variations in technique as a factor in EPM. EPM (mL) = (specimen volume * π/6) - (tumor volume * π/6). RENAL score was categorized as easy (4-6), moderate (7-9), or hard (10-12). EPM was grouped into four categories: ≤ 3.9 mL, 4.0-9.9 mL, 10.0-17.7 mL, and >17.7 mL. eGFR was evaluated preoperatively, postoperative day 1 (POD1), 1 month, and 6 months postoperatively.

Results: Median age was 63 years (22-84 years), 252 (62.1%) were male, and median EPM was 9.9 mL (interquartile range 3.9 to 17.7 mL). The median EPM and interquartile range for each RENAL category was 3.7 mL (2.0, 7.9), 12 mL (5.7, 19.4), and 16.2 mL (7.9, 24.3), respectively. Higher EPM was associated with worse changes in eGFR at POD1 (P = 0.005) and 1 month after RAPN (P = 0.002) but was not statistically significant at the 6-month time period (P = 0.35) CONCLUSION: Increased tumor complexity is associated with an increase in EPM during RAPN. Increased EPM is associated with eGFR decline at POD1 and 1 month post RAPN but not at 6 months postoperatively.