“…Six studies were RCTs, 22,25,28,29,32,35 16 were case-control studies 2, 18, 21, 23, 24, 27, 31, 33, 36-42 and five prospective studies. 19,20,26,30,34 Eleven studies included both open and laparoscopic surgery in the study, 19-21, 23, 24, 27, 33, 35, 37, 39, 40 ten studies included only open liver surgery patients, 2, 18, 25, 26, 30-32, 34, 41, 42 five studies included only laparoscopic surgery patients, 22,28,29,36,38 whilst one study performed a separate analysis for laparoscopic surgery and open surgery. 21 A detailed characteristic of included studies is shown in Table 1.…”