To investigate the relationship between the optimal dose of indocyanine green (ICG) and the fluorescence intensity and development rate in endoscopic retrograde cholangiopancreatography (ERCP).

Thirty-six patients with common bile duct stones undergoing ERCP and indwelling nasobiliary drainage in the Second Affiliated Hospital of Guangdong Medical University from December 2023 to October 2024 were enrolled in this prospective study. Among them, 21 patients were male and 15 female, aged from 22 to 89 years, with a median age of 68 years.The informed consents of all patients were obtained and the local ethical committee approval was received. All patients were randomly divided into three groups. ICG was intravenously injected slowly at a dose of 0.30, 0.35 and 0.40 mg/kg at 30 min before postoperative removal of nasobiliary drainage, respectively. Bile images were collected by endoscopic fluorescence camera system. The fluorescence intensity of the collected images was measured by Image J software, and the fluorescence intensity and development rate at corresponding dose of the patient were calculated. The fluorescence effect was evaluated objectively by visual analogue scale (VAS). Correlation analysis was performed by Pearson linear correlation. The diagnostic value of fluorescence intensity and VAS score was assessed by receiver operating characteristic (ROC) curve.

In the 0.30 mg/kg, 0.35 mg/kg and 0.40 mg/kg dose groups, 8, 12 and 11 cases experienced 30-min development of bile ducts, and the differences were statistically significant(χ²=6.039, P=0.040), and the fluorescence intensities were 70±9, 99±13 and 97±16, and the differences were also statistically significant (F=18.93, P<0.01). The 30-min visualization rate in the 0.35 mg/kg group was 100%. The ICG fluorescence intensity and dose were positively correlated (r=0.619, P<0.01). The VAS evaluation showed that at intravenous ICG doses of 0.35 mg/kg and 0.40 mg/kg, 100% of patients achieved visualization above the intuitive level; at 0.30 mg/kg, 60% achieved visualization above that level. ROC curve analysis showed that the area under the ROC curve (AUC) of ICG fluorescence intensity in bile was 0.942 (95%CI: 0.850-1.000, P<0.01), the sensitivity was 0.774 and the specificity was 1.000, respectively. The AUC of VAS score of fluorescence effect was 0.735 (95%CI: 0.483-0.988, P>0.05), the sensitivity was 0.968 and the specificity was 0.400, respectively.

The optimal intravenous dose of ICG in ERCP is ranged from 0.35 to 0.40 mg/kg, which can achieve the optimal development rate and fluorescence effect in bile. The fluorescence intensity yields good diagnostic value.