Nephrometry Scores: a validation of three systems for peri-operative outcomes in retroperitoneal robotic partial nephrectomy.

OBJECTIVE To externally validate the R.E.N.A.L., PADUA and SPARE nephrometry scoring systems for use in retroperitoneal RAPN. MATERIALS AND METHODS Nephrometry scores were calculated for 322 consecutive patients receiving retroperitoneal RAPN at a tertiary referral centre from 2017. Patients with multiple tumours were excluded. Scores were correlated with peri-operative outcomes including the Trifecta both as continuous and categorical variables. Comparisons were performed using Spearman Correlation and ability to predict the Trifecta assessed using binomial logistical regression. RESULTS All three scoring systems correlated significantly with the main variables (operative time, warm ischaemia time and estimated blood loss) both as continuous and categorical variables. Only PADUA and SPARE were able to predict achievement of the Trifecta (PADUA AUC: 0.623, 95%CI 0.559-0.668; SPARE AUC: 0.612, 95%CI 0.548-0.677). CONCLUSION This study validates the RENAL, PADUA and SPARE scoring systems to predict key intra-operative outcomes in retroperitoneal RAPN. Only PADUA & SPARE were able to predict achievement of the Trifecta. As a simplified version of the PADUA scoring system and with comparable outcomes, we recommend using the SPARE system.