From the Guidelines
A Hepatobiliary Iminodiacetic Acid (HIDA) scan should be ordered when evaluating patients for suspected acute cholecystitis, particularly when ultrasound findings are equivocal or normal despite clinical suspicion. This recommendation is based on the most recent and highest quality study available, which suggests that HIDA scan has the highest sensitivity and specificity for diagnosing acute cholecystitis compared to other imaging modalities 1.
Indications for HIDA Scan
The following are indications for a HIDA scan:
- Evaluating patients for suspected acute cholecystitis, particularly when ultrasound findings are equivocal or normal despite clinical suspicion
- Assessing biliary tract patency
- Identifying bile leaks after hepatobiliary surgery or trauma
- Evaluating biliary atresia in infants
- Determining gallbladder function in patients with chronic right upper quadrant pain suggestive of biliary dyskinesia
Procedure and Preparation
The test involves intravenous administration of a radiotracer (typically technetium-99m-labeled iminodiacetic acid derivatives) that is taken up by hepatocytes and excreted into the biliary system. Patients should fast for 4-6 hours before the scan, and those receiving total parenteral nutrition should have it discontinued 4 hours prior. Certain medications like morphine may be administered during the procedure to enhance gallbladder filling or to differentiate between gallbladder pathology and normal variants. The scan typically takes 1-4 hours to complete, depending on the clinical question being addressed.
Diagnostic Accuracy
In acute cholecystitis, the gallbladder typically fails to visualize within 60 minutes due to cystic duct obstruction, yielding a sensitivity of 95% and specificity of 90% for this condition 1.
Clinical Considerations
It is essential to consider the clinical context and patient factors when ordering a HIDA scan. For example, in pregnant patients, ultrasound or MRI may be preferred as the initial diagnostic imaging modality 1. In elderly patients, the evaluation of the risk for acute cholecystitis should include mortality rate, rate of gallstone-related disease relapse, age-related life expectancy, and patient frailty evaluation 1.
Imaging Modalities
Other imaging modalities, such as CT and MRI, may be used in conjunction with or instead of HIDA scan, depending on the clinical question and patient factors. However, HIDA scan remains the gold standard for diagnosing acute cholecystitis due to its high sensitivity and specificity 1.
From the Research
Indications for HiDA Scan
The following are indications for ordering a HiDA scan:
- Typical biliary pain with normal trans-abdominal ultrasound (TUS) scan 2
- Biliary dyskinesia, defined as symptoms of biliary colic in the absence of gallstones 3
- Persistent jaundice in infants to evaluate for biliary atresia (BA) 4
- Acute abdomen with suspected acute gall-bladder disease 5
- Chronic gall-bladder disease to assess gall-bladder function 5
Clinical Scenarios
In the following clinical scenarios, a HiDA scan may be useful:
- Patients with typical biliary symptoms and a normal TUS scan to assess for biliary dyskinesia or other hepatobiliary disorders 2, 3
- Infants with persistent jaundice to evaluate for biliary atresia (BA) and other treatable hepatic conditions 4
- Patients with acute abdomen and suspected acute gall-bladder disease to confirm or exclude the diagnosis 5
- Patients with chronic gall-bladder disease to assess gall-bladder function and guide treatment decisions 5
Diagnostic Criteria
A HiDA scan is considered abnormal if: