From the Guidelines
A normal ejection fraction on a HIDA scan is considered to be ≥38%, as defined by a standardized protocol involving infusion of 0.02 g/kg of sincalide over 60 minutes 1. This threshold is recommended by an interdisciplinary panel for assessing gallbladder contraction and calculating the gallbladder ejection fraction (GBEF) in adults. The ejection fraction is calculated by measuring the radiotracer activity in the gallbladder before and after stimulation, representing how effectively the gallbladder contracts.
Some key points to consider when interpreting HIDA scan results include:
- The normal range for ejection fraction may vary slightly between facilities, but ≥38% is a widely accepted threshold 1
- Values below this threshold suggest gallbladder dysfunction, which may be associated with symptoms such as biliary pain 1
- The test is particularly useful for evaluating patients with right upper quadrant pain when ultrasound shows no gallstones, and patients with low ejection fractions who also have typical biliary pain may benefit from cholecystectomy, even in the absence of gallstones
It's essential to interpret the results in the context of the patient's clinical symptoms, as the test provides a physiologic, noninvasive, and quantitative method for assessing gallbladder contraction 1.
From the Research
Normal Ejection Fraction on HIDA Scan
- A normal ejection fraction on a HIDA scan is generally considered to be greater than 35% 2, 3.
- Some studies suggest that an ejection fraction greater than 80% may be associated with biliary hyperkinesia, a condition that can cause symptoms similar to biliary dyskinesia 4.
- However, the definition of a normal ejection fraction can vary depending on the specific criteria used and the population being studied.
- For example, one study found that patients with an ejection fraction greater than 35% and reproducible symptoms on infusion of CCK may have a novel diagnosis called normokinetic biliary dyskinesia 3.
Diagnostic Criteria
- Biliary dyskinesia is typically diagnosed with an ejection fraction less than 35% on a HIDA scan 2, 5.
- However, some studies suggest that patients with normal or elevated ejection fractions may still have biliary dyskinesia or other conditions that can cause symptoms 4, 3.
- The use of HIDA scans with ejection fraction to diagnose biliary dyskinesia is not universally accepted, and some studies have questioned its utility in certain patient populations 5, 6.
Clinical Implications
- The results of a HIDA scan with ejection fraction should be interpreted in the context of the patient's symptoms and other diagnostic findings 2, 6.
- Patients with symptoms suggestive of biliary dyskinesia and a normal or elevated ejection fraction on a HIDA scan may still benefit from further evaluation and treatment, including laparoscopic cholecystectomy 4, 3.
- However, the decision to proceed with surgery should be made on a case-by-case basis, taking into account the patient's overall clinical picture and the potential risks and benefits of the procedure 6.