Normal Gallbladder Ejection Fraction on HIDA Scan
A normal gallbladder ejection fraction (GBEF) is ≥38% when using the standardized protocol of 0.02 μg/kg sincalide infused over 60 minutes. 1
Standardized Definition
The interdisciplinary consensus panel from the Society of Nuclear Medicine and the AGA Institute established this threshold based on a comprehensive review of methodology and clinical outcomes. This represents the most authoritative guideline for interpreting HIDA scan results in adults, including 19-year-old males 1.
Key Protocol Requirements
The normal value of ≥38% is only valid when the following standardized protocol is used:
- Sincalide dose: 0.02 μg/kg
- Infusion duration: 60 minutes (not rapid bolus)
- Calculation method: Standardized region of interest technique
This standardization is critical because different infusion rates and doses produce markedly different results, making comparison across centers impossible without protocol uniformity 1.
Important Clinical Caveats
Protocol Variation Affects Normal Values
If your imaging center uses a different protocol, the ≥38% threshold may not apply. Common variations include:
- Fatty meal stimulation: Studies using fatty meals report different normal ranges (e.g., 27.46% at 30 min, 61.44% at 60 min in one study 2; ≥20% at 60 min in another 3)
- Rapid sincalide infusion: Shorter infusion times (3-5 minutes) may yield different normal values
- Different sincalide doses: Non-standardized dosing produces unreliable results
Age and Gender Considerations
For a 19-year-old male specifically:
- No age-specific adjustment is needed - the ≥38% threshold applies to all adults 1
- Gender does not significantly affect GBEF in most studies 2, 3
- The standardized protocol was developed for adults and applies to this age group
Clinical Interpretation Algorithm
For a 19-year-old male with HIDA scan results:
- Verify the protocol used - Confirm 60-minute sincalide infusion at 0.02 μg/kg
- If GBEF ≥38%: Normal gallbladder function
- If GBEF <38%: Abnormal, suggestive of functional gallbladder disorder (if symptomatic with biliary-type pain and normal gallbladder anatomy)
- If protocol differs: Cannot reliably use the 38% threshold; consult your institution's locally validated normal values
Upper Limit Considerations
While the consensus focuses on the lower limit (≥38%), emerging evidence suggests biliary hyperkinesia (excessively high GBEF) may also be clinically relevant. One study found that GBEF ≥81% in symptomatic patients was associated with symptom resolution after cholecystectomy 4. However, this remains controversial and is not part of the standardized consensus recommendations.
Common Pitfalls to Avoid
- Do not apply the 38% threshold to fatty meal studies - these use entirely different stimulation mechanisms
- Do not interpret results without knowing the infusion protocol - rapid bolus vs. 60-minute infusion produces different values
- Do not diagnose functional gallbladder disorder based solely on low GBEF - requires appropriate clinical symptoms (biliary-type pain) and exclusion of structural abnormalities 1