Fig. 2

The difference in the laryngeal and the oesophageal retention rates between groups. The difference in the laryngeal and the oesophageal retention rates between groups according to the degree of differentiation is statistically significant (log-rank: P = 0.0002 and P = 0003, respectively). The difference in postoperative complication rates between groups A and B as examined using the log-rank test is not statistically significant (P = 0.9345)