Objective To investigate the preoperative administration time and dose of indo⁃cyanine green (ICG) for extrahepatic biliary tract imaging in the laparoscopic cholecystectomy (LC).

Methods The retrospective study was conducted. The clinical data of 252 patients with gallbladder diseases who were admitted to The Affiliated Hospital of Anhui Medical University from December 2022 to December 2024 were collected. There were 137 males and 115 females, aged (45±4)years. All patients underwent LC after injection of 1.25 mg or 2.50 mg ICG, with ICG fluore-scence navigation during the operation. Observation indicators: (1) effective fluorescence imaging during surgery; (2) the ratio of fluorescence intensity between gallbladder duct and liver, and the ratio of fluorescence intensity between common bile duct and liver; (3) the imaging effect of extra-hepatic biliary tract. Comparison of measurement data with skewed distribution among groups was conducted using the Kruskal-Wallis H test, and the Bonferroni method was used for pairwise com-parison. The consistency evaluation was conducted using the Kendall test.

Results (1) Effective fluorescence imaging during surgery. The Kendall coefficient index was 0.83, indicating high consis-tency in evaluation of fluorescence imaging of extrahepatic biliary tract between doctors. The effective fluorescent imaging sites during surgery were located in the liver, cystic duct, common bile duct, cystic duct-common bile duct junction, hepatic duct, and gallbladder. The intraoperative effective fluorescence imaging of patients who received intravenous injection of 1.25 mg and 2.50 mg ICG before surgery showed that as the interval between ICG injection and surgery increased, the proportion of fluorescence imaging in the liver and gallbladder gradually decreased. The proportion of fluorescence imaging in the gallbladder duct, common bile duct, cystic duct-common bile duct junction, common hepatic duct showed a trend of first increasing and then decreasing. (2) The ratio of fluorescence intensity between gallbladder duct and liver, and the ratio of fluorescence intensity between common bile duct and liver. Results of Kruskal Wallis H test showed that there were significant differences in the fluorescence intensity ratios of gallbladder duct to liver and the fluorescence intensity ratio of common bile duct to liver among patients who received intravenous injection of 1.25 mg ICG at different time intervals to surgery (H=73.22, 77.17, P<0.05). Results of pairwise comparison showed that there were significant differences in the fluorescence intensity ratio of gallbladder duct to liver and the fluorescence intensity ratio of common bile duct to liver between patients who received intravenous ICG injection 4.0-<6.0 hours before surgery and those who received ICG injection <0.5 hours, 0.5-<2.0 hours, 2.0-<4.0 hours, 6.0-<8.0 hours, 8.0-<10.0 hours, and 10.0-<12.0 hours before surgery, respectively (P<0.002). There were significant differences in the fluorescence intensity ratio of gallbladder duct to liver and the fluorescence intensity ratio of common bile duct to liver among patients who received intravenous injection of 2.50 mg ICG at different time intervals to surgery (H=127.06, 126.39, P<0.05). Results of pairwise comparison showed there were significant differences in the fluorescence intensity ratio of gall-bladder duct to liver and the fluorescence intensity ratio of common bile duct to liver between patients who received ICG injection 8.0-<10.0 hours before surgery and those who received ICG injection <0.5 hours, 0.5-<2.0 hours, 2.0-<4.0 hours, 4.0-<6.0 hours, 6.0-<8.0 hours, 12.0-<14.0 hours, and 14.0-<16.0 hours before surgery (P<0.001). (3) The imaging effect of extrahepatic biliary tract. Among 102 patients who received preoperative intravenous injection of 1.25 mg ICG, the number of patients with grade A extrahepatic biliary system imaging increased and then decreased as the interval time extending, reaching a peak at 4.0-<6.0 hours. Among 150 patients who received preoperative intravenous injection of 2.50 mg ICG, the number of patients with grade A extrahepatic biliary tract imaging increased and then decreased as the interval time extending, reaching a peak at 8.0-<10.0 hours.

Conclusion Prolonging the time interval between ICG administration and surgery can effectively reduce the fluorescence intensity of the liver background, thereby increasing the fluorescence intensity ratio of gallbladder duct to liver and common bile duct to liver to obtain the best development effect. Intravenous injection of 1.25 mg ICG 4.0-<6.0 hours before surgery or 2.50 mg ICG 8.0-<10.0 hours before surgery provide better results for intraoperative extrahepatic biliary tract imaging.