Comparison of the first to fourth nephrectomy groups (n = 20 each) with regard to tumor size, operating time, blood loss, and incision length. A: Tumor size. B: Spearman's rank correlation coefficients for the relation between operating time and blood loss. C: Incision length. D: Operating time. E: Blood loss. Median values are shown in the box plots (A, C, D, and E). Bold circled P values were obtained by comparing the four groups with the Kruskal-Wallis test.