Presentation Authors: Hajime Tanaka*, Yanbo Wang, Yunlin Ye, Chalairat Suk-Ouichai, Diego Aguilar Palacios, Elvis R. Caraballo, Erick M. Remer, Jianbo Li, Robert Abouassaly, Steven C. Campbell, Cleveland, OH
Introduction: Percent parenchymal mass preserved (PPMP) is the primary determinant of functional outcomes after partial nephrectomy (PN). Accurate methods for predicting PPMP based on preoperative imaging could facilitate patient counseling.
Methods: 428 PN patients with necessary studies to assess ipsilateral parenchymal mass/function preserved were evaluated. Preoperative/postoperative ipsilateral parenchymal mass were measured from contrast-enhanced CT < 2 months prior and 3-12 months after PN and actual PPMP was determined. Ipsilateral PPMP was estimated from preoperative imaging using subjective estimation (SE) based on surgeon's prior experience, quantitative estimation (QE), or estimation derived from contact surface area (CSA) or R.E.N.A.L. QE of PPMP was derived from free-hand scripting on preoperative CT, presuming that a 10 mm rim around tumor and radially located parenchyma would be excised/devascularized. Final global GFR was estimated: (preoperative ipsilateral GFR Ã— estimated ipsilateral PPMP) + preoperative contralateral GFR.
Results: Median tumor diameter was 3.5cm. Median CSA and R.E.N.A.L. were 24cm2 and 8, respectively. Median actual ipsilateral PPMP and percent global GFR preserved were 84% and 89%, respectively. Median estimated ipsilateral PPMP was 85%/87%/88%/83% based on SE/QE/CSA/R.E.N.A.L., respectively. Correlations between actual PPMP and estimated PPMP were relatively weak in all instances (all r â‰¤ 0.46). Prediction of final global GFR was strong for all 4 methods (all r = 0.91, Figure A-D); however, similarly strong correlation was also obtained when presuming that 89% of the preoperative global GFR will be saved in each case, which was the median value (r = 0.91, Figure E). On multivariable analyses, solitary kidney, preoperative GFR, and various estimates of PPMP significantly associated with final global GFR. However, preoperative GFR proved to be the strongest predictor; it was >10-fold more impactful than estimated PPMP or solitary kidney.
Conclusions: Currently available methods for estimating PPMP have important limitations. Final global GFR, the most important functional outcome, can be predicted fairly accurately by all of the tested methods but none are better than simply presuming that 89% of function will be saved, due to strong anchoring to preoperative GFR.