Robotic transperitoneal versus retroperitoneal approach for anterior renal mass nephron-sparing surgery

Robotic nephron-sparing surgery is traditionally performed via a transperitoneal (TP) approach. However, the retroperitoneal (RP) approach has gained popularity, particularly for posterolateral renal masses. The RP approach is associated with shorter operative time, less blood loss, and shorter length of stay, while preserving oncologic outcomes in selected masses. Here, we aim to assess the feasibility of the RP approach in excising anterior renal masses. Patients ≥ 18 years of age who underwent robotic nephron-sparing surgery for anterior renal masses were retrospectively identified (2008-2022). Baseline demographics, tumor characteristics, and perioperative data were collected and characterized based on TP vs RP approaches. Wilcoxon rank sum test and Pearson's Chi-squared test were used to compare continuous and categorical variables, respectively. Two hundred and sixteen patients were included-178 (82.4%) underwent TP approach and 38 (17.6%) underwent RP approach. Baseline demographics, preoperative tumor size, and renal nephrometry scores were similar. The RP approach was associated with shorter operative (150 vs 203 min, p < 0.001) and warm ischemia time (12 vs 21 min, p < 0.001), and less blood loss (20 vs 100 cc, p = 0.002) (Table 1). The RP approach was associated with shorter length of stay (1 vs 2 days, p < 0.001) and less total complications (5.3% vs 19.1%, p = 0.038). Major complication (Clavien-Dindo Grade > 3) rates were similar. There was no difference in positive surgical margin rates or pathologic characteristics. Robotic RP approach for nephron-sparing surgery is feasible for eligible anterior tumors and is associated with favorable perioperative outcomes with preserved negative surgical margin rates. Table 1 Patient baseline demographics Overall Transperitoneal Retroperitoneal p value Median/N IQR/% Median/N IQR/% Median/N IQR/% N 216 178 82.4% 38 17.6% Age (years) 60.5 (52.1-67.7) 60.4 (52.8-67.7) 61.6 (49.1-69.2) 0.393 Sex Male 126 58.3% 100 56.2% 26 68.4% Female 90 41.7% 78 43.8% 12 31.6% 0.165 Race White 162 75.0% 137 77.0% 25 65.8% Asian 4 1.9% 2 1.1% 2 5.3% Black 21 9.7% 18 10.1% 3 7.9% Hispanic 26 12.0% 18 10.1% 8 21.1% Other 2 0.9% 2 1.1% 0 0.0% 0.197 Body mass index (kg/m²)  < 25 32 14.8% 25 14.0% 7 18.4% 25-30 68 31.5% 55 30.9% 13 34.2% 30-35 60 27.8% 50 28.1% 10 26.3% 35 +  56 25.9% 48 27.0% 8 21.1% 0.808 Prior abdominal surgery Yes 118 54.6% 104 58.4% 14 36.8% No 98 45.4% 74 41.6% 24 63.2% 0.015 Prior kidney surgery Yes 10 4.6% 9 5.1% 1 2.6% No 206 95.4% 169 94.9% 37 97.4% 0.518 Chronic kidney disease stage ≥ 3 Yes 45 20.8% 38 21.3% 7 18.4% No 171 79.2% 140 78.7% 31 81.6% 0.687 Charlson comorbidity index 0 138 63.9% 116 65.2% 22 57.9% 1 46 21.3% 38 21.4% 8 21.1% 2 19 8.8% 13 7.3% 6 15.8%  ≥ 3 13 6.0% 11 6.2% 2 5.3% 0.412 Tumor size (cm) 2.7 (2-3.6) 2.8 (2-3.5) 2.55 (2-3.7) 0.796 Tumor laterality Left 100 46.3% 78 43.8% 22 57.9% Right 116 53.7% 100 56.2% 16 42.1% 0.114 Clinical T stage cT1a 186 86.1% 152 85.4% 34 89.5% cT1b 30 13.9% 26 14.6% 4 10.5% 0.509 RENAL Nephrometry score Low (4 to 6) 94 43.5% 76 42.7% 18 47.4% Intermediate (7 to 9) 112 51.9% 94 52.8% 18 47.4% High (≥ 10) 19 4.6% 8 4.5% 2 5.3% 0.829 TE tumor enucleation, SPN standard margin partial nephrectomy, IQR interquartile range.