Number of Renal Columns Invaded by Tumor: A Novel Parameter for Predicting Complexity and Outcomes of Off-Clamp Open Partial Nephrectomy

The number of renal columns invaded by tumor (NRC) can determine the tumor complexity and perioperative outcomes of off-clamp open partial nephrectomy (OPN). We aimed to propose a novel and simple scoring system and examine the relationship between NRC and perioperative outcomes after off-clamp OPN.

We retrospectively evaluated 202 patients with contrast-enhanced CT imaging who underwent off-clamp OPN between January 2008 and November 2014. The number of renal columns invaded by tumor was correlated to baseline demographics and perioperative outcomes as a categorical variable using multivariable logistic regression analysis.

The mean tumor size was 2.5 cm (±1.3 cm). The number of renal columns invaded by tumor had the highest correlation coefficients with estimated blood loss (coefficient = 0.485; p < 0.001), operative time (coefficient = 0.310; p < 0.001), postoperative drainage (coefficient = 0.307; p < 0.001), and hospital length of stay (coefficient = 0.144; p = 0.041). Multivariable logistic regression demonstrated NRC to be an independent predictor of estimated blood loss ≥500 mL, postoperative renal function, operative time, and surgical complications. This predictive ability of NRC was superior to the R.E.N.A.L. (radius exophyic/endophytic nearness anterior/posterior location) score and PADUA (preoperative aspects and dimensions used for an anatomical) score. Spearman correlation coefficient of NRC calculations between the 2 observers was 0.941 (p < 0.001).

The number of renal columns invaded by tumor is a novel, intuitive, and practical parameter that could be used to quantify renal tumor complexity and predict the risk of perioperative outcomes after off-clamp OPN. Specifically, NRC correlates with estimated blood loss, operative time, surgical complications, renal function, and conversion to on-clamp. In the future, NRC can be integrated with other parameters, such as tumor location, to assemble a new scoring system.