Reference Values for Gallbladder Ejection Fraction in a Healthy Indian Cohort Using Fatty Meal Hepatobiliary Scintigraphy.

Purpose: The primary objective was to establish the reference value of gallbladder ejection fraction (GBEF) using a fatty meal-based hepatobiliary scintigraphy protocol tailored to the Indian population. In addition, the study assessed variations in GBEF across different time points and examined potential differences based on gender and age.

Materials and methods: This prospective study was conducted from January 2023 to January 2024. Hepatobiliary scintigraphy was performed on healthy individuals aged ≥18 years following a 4-h fasting period. Static images were acquired before and after ingesting a standard fatty meal. The premeal image displaying the highest gallbladder activity concentration and minimal liver activity was selected as the reference premeal image. GBEF was calculated using decay and background-corrected counts from the reference premeal and postmeal images. Statistical analyses included independent sample t-tests to evaluate gender differences, Pearson's correlation to assess relationships between age and GBEF, and repeated measures ANOVA with Bonferroni correction to compare GBEF across different time points. The reference value of GBEF was determined based on the 5^th percentile value at 60 min postmeal ingestion.

Results: Twenty-three consecutive healthy individuals (13 females and 10 males) with a mean age of 42 ± 12 years (median: 39 years; range: 23-62 years) participated in the study. The mean GBEF increased progressively over time, with values of 36% ± 20% at 30 min, 50% ± 23% at 45 min, and 55% ± 23% at 60 min, demonstrating statistically significant differences across time points (P < 0.0001). No significant differences in GBEF were observed between males and females at any time point (P ≥ 0.770). In addition, age was not significantly correlated with GBEF at any measured time point (P ≥ 0.820). The reference value of GBEF, determined based on the 5^th percentile at 60 min postmeal ingestion, was established as ≥20%, providing a clinically relevant threshold for assessing gallbladder function.

Conclusion: The study established the reference value of GBEF using a standard fatty meal protocol. In addition, using a culturally appropriate, low-cost fatty meal offers a practical alternative to sincalide-based cholescintigraphy, especially where sincalide is scarce or quality control is challenging. This patient-friendly method also shortens imaging sessions, reducing discomfort. These values support diagnostic thresholds in clinical practice.