Fig. 3

Subgroup analysis of assessing PBD for postoperative HAIs. A HAIs incidence and adjusted analyses assessing PBD for postoperative HAIs in subgroups. B HAIs incidence and adjusted analyses assessing type of PBD for postoperative HAIs in subgroups. C HAIs incidence and adjusted analyses assessing PBD-surgery interval for postoperative HAIs in subgroups. Groups whose sample size was too small to be included in the logistic regression analysis were excluded. In Fig. (3 B), we combined those with a BMI of 24–27 and ≥ 27 into BMI ≥24 because of the sample size. In Fig. (3 C), we divided the intervals under the robotic surgery subgroup into: ≤2 week ,2–4 week, and ≥ 4 week. PBD, preoperative biliary drainage; PTBD, percutaneous transhepatic biliary drainage; EBS, endoscopic biliary stenting; ENBD, endoscopic nasobiliary drainage; HAIs, healthcare-associated infections; BMI, Body Mass Index; RR, risk ratios