What does a HIDA (Hepatobiliary Iminodiacetic Acid) scan result of 7% ejection fraction indicate and how is it managed?

HIDA Scan Ejection Fraction of 7%: Diagnosis and Management

A HIDA scan ejection fraction of 7% strongly indicates gallbladder dysfunction (biliary dyskinesia) and warrants cholecystectomy as the definitive treatment for symptom resolution and prevention of complications. 1

Diagnostic Significance of 7% Ejection Fraction

A 7% ejection fraction on a HIDA scan is significantly below the normal threshold and indicates severe gallbladder dysfunction:

• Normal gallbladder ejection fraction is ≥38% according to standardized protocols 1
• An ejection fraction of 7% represents severe hypomotility of the gallbladder
• This finding is consistent with biliary dyskinesia or acute calculous cholecystitis

Correlation with Clinical Presentation

The extremely low ejection fraction should be interpreted in the context of clinical symptoms:

• Typical symptoms include right upper quadrant pain, especially postprandial
• Nausea and vomiting often accompany the pain
• Symptoms may be episodic and food-related
• Pain reproduction during CCK administration during the HIDA scan strongly supports gallbladder pathology 2

Diagnostic Algorithm

1. Initial imaging: Ultrasound is the first-line imaging modality for suspected biliary disease 1

   • Evaluates for stones, sludge, wall thickening
   • If normal but symptoms persist, HIDA scan is indicated

2. HIDA scan interpretation:

   • EF <35% is considered abnormal
   • EF of 7% represents severe dysfunction
   • Reproduction of symptoms during CCK administration increases diagnostic confidence 2

3. Additional testing may be considered if diagnosis remains uncertain:

   • CT scan to rule out other pathologies
   • MRI/MRCP to evaluate biliary tract

Management Approach

Primary Management

Laparoscopic cholecystectomy is the definitive treatment for patients with:

• EF <35% (especially as low as 7%)
• Typical biliary symptoms
• No other identified cause of symptoms

The success rate of cholecystectomy for patients with low EF is excellent:

• 94.5% improvement or resolution of symptoms in patients with EF <50% 3
• Higher success rates correlate with lower EF values and symptom reproduction during testing 2

Post-Surgical Considerations

• Pathology examination often reveals chronic cholecystitis even in the absence of stones 2, 3
• Follow-up at 2 weeks and then at 3-6 months to assess symptom resolution
• Long-term symptom recurrence is rare (approximately 2.4%) 2

Special Considerations

Age-Related Factors

• Gallbladder ejection fraction naturally declines with age 4
• However, an EF of 7% is abnormal regardless of age

Hyperkinetic Gallbladder

While this case involves hypokinetic function (low EF), it's worth noting that:

• Some patients with hyperkinetic gallbladder (EF >80%) may also benefit from cholecystectomy 5
• This is a separate clinical entity from the current case

Pitfalls and Caveats

1. Technical considerations:

   • Ensure standardized CCK infusion protocol was used (0.02 μg/kg over 60 minutes) 1
   • Improper CCK administration can affect results

2. Differential diagnosis:

   • Common bile duct stones must be ruled out (5-15% of cases) 1
   • Other causes of right upper quadrant pain should be considered

3. Patient selection:

   • Best outcomes occur in patients with typical biliary symptoms
   • Atypical symptoms may indicate other pathologies

In conclusion, a HIDA scan ejection fraction of 7% represents significant gallbladder dysfunction and, in the appropriate clinical context, is a strong indication for laparoscopic cholecystectomy, which offers excellent outcomes for symptom resolution.