What is Gallbladder Ejection Fraction (EF)?
Gallbladder ejection fraction (GBEF) is a quantitative measure of how much bile the gallbladder empties in response to hormonal stimulation, expressed as a percentage of the total gallbladder volume. 1
Physiologic Basis
- The gallbladder stores and concentrates bile during fasting, then empties postprandially through coordinated contraction of the gallbladder and simultaneous relaxation of the sphincter of Oddi 1
- Cholecystokinin (CCK) is the principal hormone controlling gallbladder emptying after meal ingestion, binding to receptors in the gallbladder causing contraction 1
- GBEF quantifies this contractile function by measuring the percentage of bile expelled from the gallbladder 1
Measurement Methodology
- GBEF is measured using cholecystokinin-cholescintigraphy (CCK-CS), which involves injecting a radiotracer (Tc-99m hepatobiliary iminodiacetic acid) followed by infusion of sincalide (synthetic CCK analogue) 1, 2
- The standardized protocol requires infusion of 0.02 μg/kg sincalide over 60 minutes with dynamic imaging and GBEF calculation at 60 minutes 2, 3
- Rapid infusion (<30 minutes) should be avoided as it causes non-specific abdominal cramping that confounds interpretation 3, 4
- Alternative methods using fatty meals (half-and-half milk) exist but show wider variability and lower mean GBEF values compared to CCK infusion 5
Normal and Abnormal Values
- Normal GBEF is defined as ≥38% using the standardized 60-minute sincalide infusion protocol 2, 3, 4
- The upper limit of normal approaches 100%, with no established clinical significance for high normal values historically 2, 3
- A GBEF <38% is considered abnormal and indicates impaired gallbladder contractility (hypokinesia) 2
- Severely reduced values (such as 2%) indicate markedly impaired gallbladder function 2
- GBEF values decline with age in patients with acalculous biliary symptoms 6
Clinical Applications
- CCK-CS with GBEF calculation is used to diagnose functional gallbladder disorder (also called biliary dyskinesia or chronic acalculous cholecystitis) in patients with biliary-type pain but no gallstones on ultrasound 1, 2
- The test helps identify patients who may benefit from cholecystectomy when structural causes of pain have been excluded 1
- GBEF measurement aids in diagnosing partial biliary obstruction, sphincter of Oddi dysfunction, and chronic gallbladder disease 1
- Nuclear medicine hepatobiliary imaging with GBEF is accepted under Society of Gastrointestinal and Laparoendoscopic Surgeons guidelines for evaluating pain of biliary origin 1
Important Caveats
- Patient selection critically impacts test utility—patients should meet Rome III criteria for functional gallbladder disorder (episodes of right upper quadrant/epigastric pain lasting ≥30 minutes, recurring at different intervals, building to steady level, severe enough to interrupt activities) 1
- Symptom provocation during CCK infusion is not a reliable diagnostic indicator and should not guide management 4
- The test has limited accuracy in predicting gallbladder pathology, with studies showing poor negative predictive value (23.5%) even with optimal cut-offs 6
- GBEF is most useful in patients with typical biliary symptoms; its utility is questionable in those with atypical presentations 1, 7