Drain fluid collected after surgery in the two drains. White square: DS; black square: DM Values are expressed s mean ± standard deviation. Unpaired t test with Welch correction was used. There are no significant differences among the two group for each assessment. The amount of drain fluid decreased significantly from POD-1 to POD-4 in both groups (p <0.01 in DS; p <0.05 in DM).