To determine if partial nephrectomy (PN) confers a renal functional benefit compared to radical nephrectomy (RN) for clinical T2 renal masses (T2RM) when adjusting for tumor complexity characterized by the RENAL nephrometry score.

A 2-center study of 202 patients with T2RM undergoing RN (122) or PN (80) (median follow-up, 41.5 months). RN and PN cohorts were subanalyzed according to RENAL sum as a categorical variable of <10 or ≥10. Primary outcome was median change in estimated glomerular filtration rate (ΔeGFR) between preoperative to 6 months postoperative. Logistic regression–identified prognostic factors and survival models analyzed association between the RENAL sum and the freedom from de novo chronic kidney disease (CKD; eGFR<60 mL/min/1.73m²).

No significant differences existed between PN and RN for RENAL score. ΔeGFR was greater in RN (−19.7) vs PN (−11.9; P = .006). De novo CKD was 40.2% after RN vs 16.3% after PN (P <.001). RENAL score ≥10 (odds ratio, 6.67; P = .025) and RN among patients with RENAL score <10 (odds ratio, 24.8; P <.001) were independently associated with de novo CKD at 6 months by logistic regression. Among patients with RENAL score <10, median CKD-free survival was PN 38 vs RN 16 months (P = .001). Cox proportional hazard demonstrated decreasing risk of CKD for PN vs RN from RENAL 10 (hazard ratio, 0.836) to RENAL 6 (hazard ratio, 0.003; P = .001).

RN is independently associated with decreased renal function compared to PN for T2RM with RENAL sum ≤10, but not >10, with larger relative decrease in eGFR for each decrease in RENAL sum. Further investigation is required to determine optimal candidates for PN in T2RM.