The gallbladder, a small organ located beneath the liver, stores and concentrates bile produced by the liver. Bile is released into the small intestine after meals to aid in the digestion and absorption of fats. Measuring the efficiency of this release mechanism is key to understanding the organ’s function. The Gallbladder Ejection Fraction (GB-EF) provides a quantifiable metric for this measurement.
Defining Gallbladder Ejection Fraction
The Gallbladder Ejection Fraction (GB-EF) is a measurement that expresses the percentage of bile the gallbladder expels upon stimulation. It is an indicator of the gallbladder’s motor function, or contractility. The measurement is calculated by comparing the volume of bile present in the gallbladder before and after it is prompted to contract.
This metric is expressed as a percentage. A higher percentage indicates stronger, more efficient contraction and emptying. Conversely, a low percentage suggests poor contractility, meaning the gallbladder is not squeezing forcefully enough to release an adequate amount of bile. This measurement is a clinical tool used to determine if gallbladder dysfunction is the cause of a patient’s symptoms, particularly when no gallstones are present.
The HIDA Scan Procedure for Measurement
The Gallbladder Ejection Fraction is calculated through a specialized imaging procedure known as a Hepatobiliary Iminodiacetic Acid (HIDA) scan, sometimes called cholescintigraphy. The procedure begins with the intravenous injection of a radioactive tracer that is absorbed by the liver’s bile-producing cells. This tracer follows the path of bile, traveling from the liver into the bile ducts, and eventually accumulating in the gallbladder.
A gamma camera tracks the tracer’s movement and captures images of the biliary system. Once the tracer has filled the gallbladder, a synthetic version of the hormone cholecystokinin (CCK), often administered as sincalide, is injected. The CCK mimics the natural hormonal response to a fatty meal, stimulating the gallbladder to contract and release its bile content.
The calculation of the GB-EF compares the amount of tracer activity in the gallbladder immediately before the CCK injection to the amount remaining after contraction. This difference, expressed as a percentage, provides the ejection fraction. Standard protocols often involve infusing the CCK over a period of 60 minutes to ensure a standardized and reliable measurement.
Interpreting Ejection Fraction Results
A normal GB-EF is generally defined as a value equal to or greater than 38% when measured using the standardized 60-minute CCK infusion protocol. This range indicates that the gallbladder is contracting with sufficient force to empty a healthy amount of bile.
A result below this threshold is considered abnormal and suggests impaired motor function. This low ejection fraction is frequently associated with functional gallbladder disorder or biliary dyskinesia. In this scenario, the organ’s muscle wall is not contracting properly, leading to symptoms like upper right quadrant abdominal pain, nausea, and bloating, particularly after eating fatty foods.
While a low ejection fraction is the most common finding, some patients may exhibit a high GB-EF, sometimes above 80%, which is referred to as a hyperkinetic gallbladder. Though less frequent, this finding can also be associated with similar symptoms of biliary pain. The ejection fraction result is always considered alongside a patient’s reported symptoms and the absence of gallstones on an ultrasound to establish a diagnosis.
Clinical Implications of Abnormal Function
A diagnosis of abnormal gallbladder function, typically indicated by a low Gallbladder Ejection Fraction, has specific clinical implications for management. The condition often presents as episodic, severe pain in the upper right abdomen that can last for hours, similar to pain caused by gallstones, but without any stones visible on imaging. This symptom complex, paired with a low GB-EF, is a common indicator of biliary dyskinesia.
For patients diagnosed with biliary dyskinesia, the initial management often includes dietary modifications, such as following a low-fat diet to reduce the stimulation for gallbladder contraction. However, the definitive and most effective treatment option is typically the surgical removal of the gallbladder, a procedure called a cholecystectomy. The success rate for symptom relief following this surgery is high, ranging from 80% to 90% in patients who have classic biliary pain and a low ejection fraction.
The procedure is usually performed laparoscopically, allowing for a minimally invasive approach and a quick recovery. After removal, the liver sends bile directly to the small intestine, bypassing the need for storage in the dysfunctional gallbladder.