Functional outcomes of robot-assisted partial nephrectomy in patients with a solitary kidney

Objectives To evaluate the long-term functional outcomes of robot-assisted partial nephrectomy (RAPN) in patients with and without a solitary kidney. Materials and Methods A retrospective review was performed using the prospectively maintained, institutional review board-approved database to identify all consecutive patients who underwent RAPN between 2006 and 2023. A propensity-score-matched analysis was subsequently undertaken to compare patients with and without a solitary kidney. The analysis controlled for various baseline clinicodemographic variables, including age, comorbidities, and baseline tumour characteristics. Results Of the 1698 RAPN patients included in our series, 86 were identified to have a pre-existing solitary kidney. Following a 1:1 propensity-score-matched comparison analysis, the solitary kidney cohort was noted to have similarly favourable long-term functional outcomes to the cohort with bilaterally functioning kidneys. This was also indicated by our Kaplan-Meier analysis, which highlighted identical survival from kidney disease progression at a median follow-up duration of 45 months (P = 0.101). Improvements in functional outcomes could be observed as early as 3 months after the respective surgery (median glomerular filtration rate preservation in the solitary vs non-solitary kidney group: 63.7% vs 64.7%; P = 0.815). Of note, the solitary kidney group was more at risk of postoperative acute kidney injury (AKI; solitary vs non-solitary kidney group: 79.7% vs 57.7%; P < 0.001). Lower preoperative renal function (odds ratio [OR] 0.963, 95% confidence interval [CI] 0.922-0.991; P = 0.028), main artery clamping (OR 5.015, 95% CI 1.044-27.462; P = 0.027), and ischaemia time beyond 25 min (OR 4.335, 95% CI 1.381-13.846; P = 0.014) were identified as independent predictors of AKI. Conclusion Leveraging a large series of RAPN cases in patients with a solitary kidney, we identified similarly favourable long-term functional outcomes between patients with a solitary kidney and those with bilaterally functioning kidneys. Notably, patients with solitary kidneys remained at increased risk of postoperative AKI. Additional vulnerability to AKI can be conferred by other variables, such as pre-existing kidney disease and warm ischaemia time exceeding 25 min.