Functional Implications of Renal Tumor Enucleation Relative to Standard Partial Nephrectomy

To compare the surgical precision for optimizing nephron-mass preservation of tumor enucleation (TE) vs standard partial nephrectomy (SPN), with primary focus on functional outcomes. TE is presumed to optimize preservation of parenchymal mass and function but this has not yet been rigorously studied and quantified.

Robotic partial nephrectomy patients who had appropriate pre- and postoperative studies for analysis of parenchymal mass preservation specific to the operated kidney were included. Computed tomography or magnetic resonance imaging and estimated glomerular filtration rate were required to be <2 months prior and 4-12 months after surgery. Parenchymal mass preservation and surgical precision were estimated for each technique, with precision defined as actual postoperative parenchymal volume or predicted postoperative parenchymal volume, presuming loss of a 5 mm rim of parenchyma associated with tumor excision and reconstruction.

Analysis included 57 TE and 53 SPN. Median age, body mass index, and tumor size were comparable. Percent parenchymal mass preserved in the operated kidney with TE was 96% (interquartile range [IQR] = 90-100) vs 89% (IQR = 83-96) for SPN (P = .003). Precision of excision or reconstruction was 101% (IQR = 96-105) for TE vs 94% (IQR = 88-100) for SPN (P < .001). On multivariable analysis, only TE correlated with improved surgical precision (coefficient = 6.7, 95% confidence interval = 1.6-11.8, P = .01). Although preservation of global renal function also favored TE, the differences were marginal (96% vs 93%), and statistical significance was not observed (P = .2).

Our analysis, which specifically focuses on the functional implications of TE, demonstrates that TE maximally spares normal parenchyma compared to SPN. Thus far, functional differences remain marginal and not statistically significant. Clinical significance of these findings in various clinical settings will require further investigation.