Fig. 1. Study flowchart. Flowchart of 123 consecutive patients with malignant extrahepatic biliary obstruction who underwent hepatobiliary scintigraphy (HBS) within one month of undergoing hepaticogastrostomy (HGS) at Aichi Cancer Center Hospital between April 2015 and July 2022. Nine patients with separated left and right hepatic ducts due to malignant tumors, three patients who underwent HGS using plastic stents, and 33 patients who underwent HGS combined with antegrade stenting were excluded. Finally, a total of 78 consecutive patients with malignant extrahepatic biliary obstruction who underwent HBS after HGS were examined during the study period.

Fig. 2. Hepatobiliary scintigraphy. (A) The region of interest (ROI) set at the hilar bile duct. (B) Time-activity curve (TAC). The peak time and decay rate were calculated from the TAC and used as a scale to evaluate bile excretion. An example of a hepatobiliary scintigraphy is shown. The peak time and decay rate, in this case, are 10 minutes and 68.9%, respectively. (C) Key images at 5, 10, 20, and 60 minutes. At 5 minutes, the bile is excreted into the stomach via the hepaticogastrostomy (HGS) route. At 10 minutes, the accumulation in the hilar bile duct is maximal. At 20 minutes, the accumulation in the hilar bile duct is reduced, and at 60 minutes, the accumulation in the hilar bile ducts is further reduced, with most of the isotope-labeled bile excreted into the stomach. Supplemental Video 1 shows this case.

Fig. 3. Scatter plots and scoring system created based on peak time and decay rate for each case obtained from hepatobiliary scintigraphy. Scatter plots and scoring systems. From this scatter plot, the peak time and decay rate were scored as 0, 1, and 2 points based on 20 and 35 min, and 10% and 50%, respectively, and bile excretion was evaluated based on the sum of these scores. A total score of 4 or 3 was defined as good bile excretion, while scores of 2, 1, or 0 indicated poor bile excretion.

Fig. 4. Examples of biliary scintigraphy in hepaticogastrostomy (HGS) cases classified according to the scoring system. In cases with a total score of 0, isotope-labeled bile stagnates in the bile ducts and excretion from the HGS route is poor. In cases with a total score of 4, the isotope-labeled bile was not stagnant and was excreted through the HGS route early on. In cases with a total score of 2, bile excretion was intermediate, ranging from 0 to 4. Supplemental Videos 2 and 3 show the cases with total scores of 4 and 0, respectively.

Fig. 5. Comparison between the good and poor bile excretion groups concerning the time to recurrent biliary obstruction (TRBO). The TRBO of the good bile excretion group was significantly longer than that of the poor bile excretion group; the good excretion groups did not reach the median TRBO value, while the median TRBO of the poor bile excretion group was 124 days (not reached vs. 124 days, p=0.026; log-rank test).

Graphical abstract