Preoperative Prediction and Postoperative Surgeon Assessment of Volume Preservation Associated with Partial Nephrectomy: Comparison with Measured Volume Preservation

Objective To evaluate whether surgeons can predict the percent parenchymal mass that will be preserved by partial nephrectomy (PN) based on preoperative imaging, which could have potential utility for preoperative surgical planning and patient counseling. The proportion of preserved viable parenchyma following PN is the primary determinant of functional recovery. However, direct measurement of parenchymal volume preservation (VP) can be complex and time consuming. Materials and Methods For patients managed with PN at our institution (2007-2014), we randomly selected 45 with a third in each of low, intermediate, or high R.E.N.A.L. complexity groups. All patients had recorded postoperative surgeon assessment of volume preservation (SAVP) and measured VP based on preoperative or postoperative computed tomography. Nine clinical providers predicted VP based solely on review of preoperative imaging while blinded to SAVP and measured VP. Clinical experience of the providers ranged from medical students to experienced urologic surgeons. Results Median age was 66 years, median tumor size was 4.0 cm, and median R.E.N.A.L. was 8. Median measured VP was 81% (interquartile range of 74-89%). Preoperative prediction of VP correlated poorly with measured VP among the different surgeons (mean correlation coefficient, R = 0.34, range = 0.24-0.40). Surgeon experience provided minimal incremental improvement. Correlation between R.E.N.A.L. and measured VP was also marginal (R = 0.43). In contrast, correlation between postoperative SAVP and measured VP was much more robust (R = 0.75, P <.001). Conclusion Preoperative prediction of VP and R.E.N.A.L. score correlated poorly with measured VP for patients managed with PN. In contrast, postoperative SAVP provided a relatively reliable estimate of VP, and should be considered an acceptable substitute in most clinical circumstances.