From the Guidelines
A HIDA scan is a valuable diagnostic tool for acute cholecystitis, particularly when ultrasound results are inconclusive, with a sensitivity of approximately 84.2% as reported in a study comparing the diagnostic sensitivities of US, CT, and HIDA scan 1.
Diagnostic Approach
When diagnosing acute cholecystitis, the initial imaging modality is typically abdominal ultrasound (US) or computed tomography (CT) as suggested by the 2024 clinical practice guideline update by the Infectious Diseases Society of America 1. However, if the initial imaging is inconclusive, a HIDA scan can be considered as a subsequent imaging modality, especially if clinical suspicion for acute cholecystitis is high.
HIDA Scan Procedure and Benefits
The HIDA scan involves injecting a radioactive tracer intravenously, which is taken up by liver cells and excreted into the bile. The scan tracks this tracer as it moves through the liver, bile ducts, gallbladder, and small intestine. In acute cholecystitis, the inflamed gallbladder typically doesn't fill with the tracer, indicating blockage. The test takes about 1-2 hours and may include administration of cholecystokinin (CCK) to stimulate gallbladder contraction.
Considerations and Limitations
While HIDA scans are valuable, their utilization is limited due to the required resources and time, as noted in the 2020 World Society of Emergency Surgery updated guidelines for the diagnosis and treatment of acute calculus cholecystitis 1. Additionally, patients must fast for several hours before undergoing a HIDA scan, which may be a consideration in certain clinical scenarios.
Comparison with Other Imaging Modalities
A study comparing the sensitivity of CT and US showed different results, but a study considering only patients with a definitive diagnosis of acute cholecystitis found that HIDA scans had a higher sensitivity compared to US and CT, with respective values of 84.2%, 67.3%, and 59.8% (p = 0.017) 1. MRI/MRCP is also a reasonable option as subsequent imaging, providing a clearer picture of surrounding structures and faster time to result, but HIDA is considered the gold standard for diagnosing acute cholecystitis and is less costly.
Clinical Practice Guidelines
The 2024 clinical practice guideline update by the Infectious Diseases Society of America suggests that if additional imaging beyond US is required, the risk-to-benefit ratio of radiation exposure for CT should be considered, particularly for children 1. If CT is also equivocal and acute cholecystitis is suspected, MRI/MRCP and HIDA are both reasonable options as subsequent imaging studies beyond CT.
From the Research
Diagnostic Accuracy of HIDA Scan
- The sensitivity of HIDA scan in diagnosing acute cholecystitis was found to be 86% in a study published in the Journal of the American College of Surgeons 2.
- Another study published in The British journal of surgery found that HIDA scan was diagnostic in 19 out of 23 patients with proven acute cholecystitis, with a specificity of 100% in the absence of jaundice 3.
- A study published in Southern medical journal stated that HIDA scanning is a simple, safe, and accurate method for diagnosing acute cholecystitis, and is considered the diagnostic method of choice 4.
Comparison with Other Diagnostic Modalities
- A study published in the Journal of the American College of Surgeons found that HIDA scan is a more sensitive test than ultrasonography (US) in diagnosing acute cholecystitis, with a sensitivity of 86% compared to 48% for US 2.
- A study published in The American surgeon found that fluorodeoxyglucose positron emission tomography-computed tomography (18FDG PET-CT) has a high sensitivity and specificity for diagnosing cholecystitis, and may be a promising alternative to HIDA scan in cases where the diagnosis remains equivocal after ultrasound 5.
Clinical Guidelines and Overutilization
- A study published in Cureus found that HIDA scans are significantly overutilized in patients meeting clinical criteria for cholecystitis based on the Tokyo guidelines, and that proper utilization and reduction of unnecessary HIDA scans could improve patient care efficiency and reduce healthcare expenditures 6.
- The study recommended that HIDA scans should be reserved for cases with inconclusive US results but high clinical suspicion for cholecystitis 6.