When should a HIDA (Hepatobiliary Iminodiacetic Acid) scan be ordered?

From the Guidelines

A HIDA scan should be ordered when clinical suspicion for acute cholecystitis is high and initial ultrasound (US) is equivocal, as it can provide valuable diagnostic information in such cases. This approach is supported by the 2024 clinical practice guideline update by the Infectious Diseases Society of America, which suggests that for suspected acute cholecystitis in non-pregnant adults, if clinical suspicion is high and initial US is equivocal, it may be appropriate to proceed directly from US to HIDA scan 1.

Key Considerations for Ordering a HIDA Scan

• The HIDA scan is particularly useful when ultrasound results are inconclusive or normal despite persistent symptoms, especially in patients with right upper quadrant pain, particularly after meals.
• It is indicated for patients with suspected gallbladder disorders, such as acute cholecystitis, chronic cholecystitis, or biliary dyskinesia.
• The scan can also assess bile leaks after hepatobiliary surgery or trauma and evaluate biliary atresia in infants.
• Patients should fast for 4-6 hours before the scan, and certain medications like opioids and anticholinergics should be discontinued temporarily to avoid affecting gallbladder contractility and leading to false-positive results.

Diagnostic Criteria and Imaging Modalities

• In acute cholecystitis, the gallbladder fails to fill with the tracer on a HIDA scan, while in biliary dyskinesia, the gallbladder ejection fraction is abnormally low (typically less than 35-40%) after administration of cholecystokinin (CCK) 1.
• The choice between a HIDA scan and other imaging modalities like CT or MRI/MRCP depends on the clinical context and the availability of these modalities, with HIDA scans having high sensitivity and specificity for diagnosing acute cholecystitis 1.
• If complications of acute cholecystitis or acute cholangitis are suspected, CT with IV contrast is preferable as subsequent imaging before a HIDA scan 1.

Clinical Decision-Making

• The decision to order a HIDA scan should be based on a thorough clinical evaluation, including the patient's symptoms, laboratory findings, and the results of initial imaging studies like ultrasound.
• In cases where both US and CT are equivocal or nondiagnostic and clinical suspicion persists, obtaining either an abdominal MRI/MRCP or a HIDA scan as subsequent imaging may be considered to diagnose acute cholecystitis 1.

From the Research

Indications for a HIDA Scan

A HIDA (Hepatobiliary Iminodiacetic Acid) scan is a diagnostic tool used to evaluate the function and structure of the gallbladder and biliary system. The following are indications for ordering a HIDA scan:

• Patients with typical biliary pain but a normal trans-abdominal ultrasound scan (US) 2
• Patients with atypical symptoms of biliary colic, as the HIDA scan can predict symptom improvement in this group 3
• Suspected acute cholecystitis, especially in the absence of jaundice, as the HIDA scan is more specific for confirming acute cholecystitis 4
• Biliary dyskinesia, defined as symptoms of biliary colic in the absence of gallstones, as the CCK-HIDA scan can diagnose and predict improvement after cholecystectomy 5

Specific Scenarios

• In patients with suspected acute cholecystitis, the HIDA scan is recommended as the first diagnostic modality, with ultrasound used to confirm the presence of gallbladder stones rather than to diagnose acute cholecystitis 6
• In patients with biliary dyskinesia, a CCK-HIDA scan with an ejection fraction (EF) <50% is indicative of biliary dyskinesia, and cholecystectomy can be considered 5
• In patients with typical symptoms of biliary colic and a negative ultrasound, a HIDA scan with EF may not be useful in making a decision for cholecystectomy 3

Key Points

• The HIDA scan is a useful diagnostic tool in evaluating the gallbladder and biliary system
• The scan can be used to diagnose acute cholecystitis, biliary dyskinesia, and other biliary disorders
• The CCK-HIDA scan is particularly useful in diagnosing biliary dyskinesia and predicting improvement after cholecystectomy 2, 5