Interobserver Reliability of the RENAL Nephrometry Scoring System: Experience From a Developing Nation

Introduction The RENAL (radius, exophytic/endophytic properties, nearness of tumor to the collecting system or sinus in millimeters, anterior/posterior, location relative to polar lines) nephrometry score (RENAL-NS) has been described as a structured and quantifiable method to describe a renal tumor’s relevant anatomic features as they relate to the complexity of the lesion. We aim to evaluate a tumor’s RENAL-NS and to assess the reproducibility of the score among different observers. Methods This retrospective study included 49 patients diagnosed with renal cell carcinoma (RCC) who had complete computed tomography (CT) data, RENAL-NS, and histopathology results. All patients underwent renal surgery/intervention at our center between January 2008 and December 2018. The radius of the lesion, exophytic/endophytic properties, nearness to the collecting system, anterior or posterior description, and location relative to the polar lines was used to calculate the score. Tumor complexity was graded as low, intermediate, or high. Two body imaging radiologists evaluated the data independently. Results Interobserver agreement for each of the RENAL-NS parameters, respectively, and overall complexity was calculated. The total agreement was 82%, 51%, 84%, 69%, 73%, and 90%, corresponding to Kappa values of 0.72, 0.33, 0.44, 0.49, 0.58, and 0.83, respectively. The radius, nearness to the collecting system, and total complexity showed the best agreement. Exophytic properties of the lesion showed the least agreement. For cases that were discordant in terms of the final score, no major implications in surgical planning were observed. Conclusion The results of this study show that the RENAL-NS is a useful tool to assess the anatomical features of renal tumors and it is easily reproducible, even for less experienced radiologists in a developing nation.