Initially the gallbladder is assessed in the fasting state. Afterwards, the gallbladder is induced to contract. Methods to achieve gallbladder contraction:
(1) fatty meal
(2) infusion of cholecystokinin
After the contraction is initiated, measurements may be taken at set times. Some protocols use measurements at 30, 60 and 90 minutes after the stimulus. Others can be completed within 30 minutes.
Scintigraphic Method
Commonly used radionuclide for cholescintigraphy: Technetium-99m HIDA
reading =
= (counts with source material) – (background counts)
ejection fraction in percent =
= 100% * ((gallbladder reading before evacuation) – (gallbladder reading after evacuation)) / (gallbladder reading before evacuation)
Ultrasonography
volume of the gallbladder in cubic cm =
=
π/6 * (length in cm) * (lateral diameter in cm) * (anterior-posterior diameter in cm)
ejection fraction in percent =
= 100% * ((gallbladder fasting volume) – (gallbladder residual volume)) / (gallbladder fasting volume)
ejection volume in cubic cm =
= (fasting volume in cc) – (residual volume in cc)
This method may experience problems when the gallbladder deviates from the idealized shape due to scarring or other causes.
Interpretation
Impaired biliary emptying may be associated with increased fasting volumes and low ejection fraction.
Criteria for poor contraction:
(1) ejection fraction of 20-40%
(2) ejection volume < 50% of prefasting volume
