HIDA Scan: Definition and Clinical Applications
A HIDA (hepatobiliary iminodiacetic acid) scan is a nuclear medicine imaging study that uses Tc-99m-labeled radiopharmaceuticals to evaluate hepatocyte function, biliary excretion, and gallbladder contractility by tracking radiotracer uptake by the liver and its excretion through the biliary system. 1, 2
What the HIDA Scan Evaluates
The scan provides functional assessment of three key components:
- Hepatocyte clearance: Measures liver uptake function of the radiotracer from blood 3
- Parenchymal transit: Evaluates movement through liver tissue and bile ducts 4
- Biliary excretion: Visualizes bile flow into the gallbladder and duodenum 2
Primary Clinical Indications
Functional Gallbladder Disorder (Most Common)
The primary indication for HIDA scan with cholecystokinin (CCK) stimulation is evaluation of suspected functional gallbladder disorder in well-selected patients with biliary-type pain and a normal-appearing gallbladder on ultrasound. 1
The standardized protocol requires:
- 0.02 μg/kg sincalide infused over 60 minutes
- Abnormal gallbladder ejection fraction (GBEF) defined as <38% 1
- Patient must fast 4-6 hours minimum (preferably overnight) 1
- Withhold opiates and anticholinergics for 48 hours prior 1
Acute Cholecystitis
- Non-visualization of the gallbladder after 60 minutes in a properly prepared patient suggests acute or chronic cholecystitis 1
- Ultrasound remains first-line imaging; HIDA is reserved for equivocal cases 5
Critical caveat: HIDA scans delay time to surgery by approximately 24-28 hours compared to ultrasound alone (68.4 vs 54.1 hours, p=0.039), and should only be ordered when ultrasound findings are truly equivocal 5. The test has relatively weak discriminatory power, with sensitivity of 80.4% and specificity of only 33.3% for pathological findings 6.
Other Applications
- Post-liver transplant monitoring: Non-invasive assessment of graft function, rejection, vascular complications, and biliary problems 7
- Intrahepatic cholestasis: Distinguishes from extrahepatic obstruction by showing disproportionately increased parenchymal transit time 4
- Biliary atresia in infants: High sensitivity but moderate specificity; high negative predictive value makes it useful for ruling out biliary atresia 8
Important pitfall: Biliary excretion seen on HIDA scan does NOT exclude biliary atresia—false negatives occur and can lead to dangerous delays in diagnosis 9. Histopathological confirmation remains essential.
Technical Considerations
The scan involves:
- IV injection of Tc-99m HIDA radiotracer
- Imaging up to 1 hour to visualize gallbladder filling
- For functional assessment: sincalide infusion with dynamic imaging over 60 minutes 1
- Calculation of GBEF from region of interest analysis 1
Contraindications: Known sincalide allergy, intestinal obstruction, pregnancy (sincalide may stimulate preterm labor) 1