Objective: To describe the surgical efficacy, efficiency, and safety of retroperitoneal robot-assisted partial nephrectomy (R-RAPN) versus transperitoneal robot-assisted partial nephrectomy (T-RAPN).

Methods: We retrospectively reviewed a prospectively maintained database of a single surgeon’s robot-assisted partial nephrectomies between September 2022 and February 2024. Baseline characteristics, tumor characteristics, operative and perioperative parameters were collected. Thirty-day complications and 3-6 month follow-up creatinine and hemoglobin were gathered. Descriptive statistics, including means, standard deviations, and frequencies, were calculated for all relevant variables. Normality and homogeneity of variances assumptions were assessed for continuous variables.

Results: A total of 71 patients were included, 32 in the T-RAPN group and 39 in the R-RAPN group. Mean age, BMI, baseline eGFR, Charlson Comorbidity index, RENAL nephrometry score, and tumor size were comparable between both cohorts. Both groups had similar rates of endophytic and cystic lesions. The T-RAPN group was comprised of predominantly anterior tumors while the R-RAPN group had predominantly posterior tumors (p<0.001). Mean OR time was 21 minutes shorter in the R-RAPN group although failing to achieve statistical significance (186min vs 165min, p=0.121). Estimated blood loss was significantly lower in the R-RAPN group (328ml vs. 173ml, p=0.047). Clamp time was 6 minutes shorter in the R-RAPN group, approaching statistical significance (p=0.076). More patients in the R-RAPN group were performed using off-clamp enucleation compared to the T-RAPN cohort (19% vs 44%, p=0.026). Subgroup analysis for BMI >35 and anterior tumors demonstrated similar outcomes for OR time, estimated blood loss, clamp time, and postoperative day 1 hemoglobin drop between R-RAPN and T-RAPN. In posterior tumors, R-RAPN had shorter operative and clamp time, less estimated blood loss compared to T-RAPN, although failing to achieve statistical significance.

Conclusion: R-RAPN is an efficient and effective approach to performing partial nephrectomy, with potential superior surgical outcomes in those with posteriorly located tumors.