Introduction: Near-infrared (NIR) fluorescent cholangiography (FC) using indocyanine green (ICG) in laparoscopic cholecystectomy (LC) has been used as a technique for real-time visualiza- tion of bile ducts for approximately ten years; however, no standard protocol has been deter- mined. This study aimed to determine the optimal time of administration of ICG.

Material and methods: In this prospective study, patients (n1⁄430) indicated for LC were div- ided into two groups. The first group received ICG 1 h before anesthesia at a dose of 0.1 mg/kg (1h group), whereas the other group received ICG immediately after anesthesia with the same dose (0 h group).

Results: The rates of identification of the cystic duct (CD) and common bile duct (CBD) using NIR FC before and after dissection of Calot’s triangle were comparable between the two groups. The fluorescence intensity ratios of CD/Liver and CBD/Liver were significantly higher in the 1h group (2.2 vs. 0.49 and 2.1 vs. 0.38, respectively, p < .001) with minimal background liver fluores- cence interference in the 1 h group.

Conclusions: The study illustrates that administration of ICG 1 h before surgery with a dose of 0.1 mg/kg allows superior visualization of the extrahepatic bile ducts with minimal fluorescence interference from the background liver.

Abbreviations: BDI: bile duct injury; BMI: body mass index; CBD: common bile duct; CD: cystic duct; CHD: common hepatic duct; CVS: critical view of safety; FC: fluorescent cholangiography; FI: fluorescence intensity; GB: gallbladder; ICG: indocyanine green; IOC: intraoperative cholangi- ography; LC: laparoscopic cholecystectomy; NIR: Near-infrared; WL: white light