A retrospective study of using a three-dimensional printed kidney model to evaluate R.E.N.A.L. nephrometry score: an educational tool to improve the diagnostic accuracy of urology residents

Abstract Background The R.E.N.A.L. nephrometry scoring system is used to evaluate the complexity of renal tumors; however, inconsistency among evaluators, especially junior physicians, is an issue. The objective of the study was to evaluate whether it is useful for junior physicians to use a three-dimensional (3D) kidney model when evaluating the R.E.N.A.L. nephrometry score. Methods An expert and four urology residents retrospectively evaluated the R.E.N.A.L. nephrometry scores of 64 renal tumors (62 patients) which underwent robot-assisted partial nephrectomy at our hospital. The expert evaluated 64 R.E.N.A.L. nephrometry scores with computed tomography (CT) scan imaging, while four residents evaluated 32 cases using only CT and the other 32 cases using CT and 3D kidney model. Consistency between the expert and residents was assessed by Cohen’s kappa score. Patient-specific 3D kidney models were created in a gird style using a 3D printer based on the CT or magnetic resonance imaging of the patient. Results For all four residents, the accuracy of the overall R.E.N.A.L. nephrometry score was significantly higher by 3D model and CT than CT only (p < 0.001). Regarding individual components of the R.E.N.A.L. nephrometry score, the accuracy of “E,” “N,” “A,” and “L” scores was higher by 3D model and CT than by CT only (p = 0.020–0.089). Conclusion Patient-specific 3-D printed kidney model would improve the resident’s understanding of renal tumor complexity and could be an important educational tool for residents.