Interobserver reliability of the RENAL nephrometry scoring system

Abstract

Objective: To determine the reliability of the RENAL nephrometry scoring system by studying its reproducibility among different observers.

Methods: We reviewed computed tomography or magnetic resonance imaging scans from 51 patients who underwent partial nephrectomy at our cancer center. Digitized axial and coronal images were available for all patients. Three surgeons independently scored the renal tumors using the RENAL nephrometry system. The scoring system had 5 components: R (tumor diameter), E (exophytic/endophytic), N (nearness to collecting system), A (anterior/posterior), and L (location in relation to polar lines). Interobserver variability was calculated for each of the 5 components using a frequency procedure and Kappa statistics.

Results: The reliability assessed by frequency procedure showed concordance among 3 observers in 94%, 76%, 66%, 80%, and 54% for the R, E, N, A, and L components, respectively. The corresponding kappa values for each of these 5 components were 0.95, 0.86, 0.76, 0.84, and 0.73, respectively.

Conclusion: The RENAL nephrometry scoring system has good interobserver reliability. Quantifying the tumor location (L) was more challenging and the least reliable of the 5 components. This variation might affect the total nephrometry score and should be considered when using the system to compare different series of patients undergoing partial nephrectomy.