Comparison of patients from the first to fourth nephrectomy groups with tumors on the left or right side with respect to tumor size, operating time, and blood loss. A: Operating time. B: Blood loss. C: Tumor size. D: Operating time in each nephrectomy group. E: Blood loss in each nephrectomy group. Median values are shown in the box plots. Bold circled P values were obtained by using the Kruskal-Wallis test to compare the four groups.