Performance Prediction for Surgical Outcomes in Partial Nephrectomy Using Nephrometry Scores: A Comparison of Arterial Based Complexity (ABC), RENAL, and PADUA Systems.

BACKGROUND

Several standardized scoring systems are used to quantify renal tumor complexity on the basis of anatomic features to predict perioperative and postoperative outcomes of partial nephrectomy (PN).

OBJECTIVE

To compare the predictive accuracy and utility of the Arterial Based Complexity (ABC), RENAL, and PADUA scores.

DESIGN, SETTING, AND PARTICIPANTS: Between January 2013 and March 2016, 304 patients at our institution underwent PN plus complete triphasic contrast computed tomography (CT) scans. Two urologists independently scored CT images to retrospectively evaluate each patient using the ABC, RENAL, and PADUA nephrometry scoring systems.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Interobserver variability was reported for each of the three nephrometry scores; κ=1 represented perfect agreement between the two urologists and κ=0 represented as much agreement as expected by chance. Univariate and multivariable linear regression models were used to investigate associations of the nephrometry scores with estimated blood loss (EBL), ischemia time, and estimated glomerular filtration rate (eGFR) at 18 mo. Coefficients of determination (R) were compared to determine which nephrometry score accounted for the most variation in outcome.

RESULTS AND LIMITATIONS

The κ value was 0.52 for ABC, 0.53 for RENAL, and 0.63 for PADUA (all p≤0.001). On univariate analysis, there were no significant associations between nephrometry scores and postoperative eGFR; all three scores were highly associated with ischemia time (p<0.0001) and EBL (p≤0.001). R was not significantly different among the three scoring systems. On multivariable analysis, all three nephrometry scores were significantly associated with ischemia time (p<0.0001) and EBL (p≤0.01); only the RENAL score was associated with postoperative eGFR (p=0.044), so its performance on this metric could not be compared to that of ABC or PADUA.

CONCLUSIONS

The ABC, RENAL, and PADUA systems have similar performance for predicting EBL and ischemia time outcomes in PN, and are thus equally useful for assessing PN complexity. Further education and training are needed to reduce interobserver variability.

PATIENT SUMMARY

A new score system called Arterial Based Complexity (ABC) can be used to evaluate the complexity of a renal tumor and predict how difficult the tumor resection (partial nephrectomy) may be. This system performs well compared to other established systems and seems easy to learn and use.