What does a gallbladder ejection fraction of 2% on a Hepatobiliary Iminodiacetic Acid (HIDA) scan indicate?

Gallbladder Ejection Fraction of 2% on HIDA Scan: Diagnosis and Implications

A gallbladder ejection fraction (GBEF) of 2% on a HIDA scan is significantly abnormal and strongly indicates functional gallbladder disorder, which is a valid indication for cholecystectomy in patients with typical biliary symptoms.

Understanding GBEF Measurement and Normal Values

• A normal GBEF is defined as ≥38% when measured using the standardized cholecystokinin-cholescintigraphy (CCK-CS) protocol with infusion of 0.02 μg/kg sincalide over 60 minutes 1, 2
• The upper limit of normal GBEF approaches 100%, with no clinical significance attributed to high normal values 1, 2
• A GBEF of 2% is substantially below the normal threshold and indicates severely impaired gallbladder contractility 1

Clinical Significance of Low GBEF

• A GBEF <38% is considered abnormal and, in the appropriate clinical setting, is consistent with functional gallbladder disorder 1
• Low GBEF values (such as 2%) are associated with:
  • Chronic acalculous cholecystitis 3
  • Functional gallbladder disorder (also called gallbladder dyskinesia) 1
  • Potential biliary pain symptoms including postprandial right upper quadrant pain, nausea, and vomiting 4

Diagnostic Algorithm for Patients with Low GBEF

1. Confirm proper test methodology:

   • Verify that the HIDA scan was performed using standardized protocol (0.02 μg/kg sincalide over 60 minutes) 1
   • Ensure proper patient preparation (fasting, avoidance of medications affecting gallbladder contraction) 1

2. Correlate with clinical symptoms:

   • Typical biliary symptoms (postprandial right upper quadrant pain, nausea) strongly support the diagnosis of functional gallbladder disorder when combined with low GBEF 4, 3
   • Symptom reproduction during CCK infusion may provide additional diagnostic support, though this is more reliable with standardized 60-minute infusion protocols 3

3. Rule out other biliary pathologies:

   • Confirm absence of gallstones, sludge, or gallbladder wall thickening on ultrasound 1, 5
   • Consider evaluation for common bile duct stones if liver function tests are abnormal, particularly elevated GGT 1

Management Recommendations

• For GBEF of 2% with typical biliary symptoms:

  • Laparoscopic cholecystectomy is the recommended treatment 4, 3
  • Studies show 66-82% symptom resolution rate in patients with low GBEF who undergo cholecystectomy 4, 6

• Before proceeding with surgery:

  • Rule out other causes of upper abdominal pain 2
  • Consider the patient's overall clinical picture, as the final interpretation should be made by the ordering clinician who is most familiar with the patient 1

Important Caveats and Considerations

• Avoid rapid CCK infusion (<30 minutes) as this can cause non-specific abdominal symptoms that confound interpretation 1, 2
• HIDA scan has higher sensitivity and specificity for gallbladder pathology compared to ultrasound, but ultrasound remains the initial test of choice for right upper quadrant pain due to its ability to evaluate multiple structures 1
• Pathological examination of gallbladders removed for low GBEF frequently shows chronic cholecystitis, supporting the validity of this indication for surgery 3

Alternative Diagnoses to Consider

• If symptoms persist after cholecystectomy, consider:
  • Sphincter of Oddi dysfunction 2, 7
  • Functional gastrointestinal disorders 2, 7
  • Gastroesophageal reflux disease 2, 7
  • Peptic ulcer disease 2, 7

Remember that while a GBEF of 2% is significantly abnormal, the decision for cholecystectomy should be based on the correlation between this finding and the patient's clinical presentation.