What is Injected During a HIDA Scan
A technetium-99m (Tc-99m) labeled hepatobiliary iminodiacetic acid (HIDA) radiopharmaceutical is injected intravenously during a HIDA scan. 1, 2
Specific Radiopharmaceuticals Used
The most commonly used Tc-99m labeled HIDA agents include:
- Tc-99m mebrofenin - the preferred agent, typically administered at 5 mCi intravenously 1, 2
- Tc-99m disofenin - an alternative HIDA derivative 1, 2
Both agents are iminodiacetic acid derivatives with no known pharmacologic action at recommended doses 2.
Mechanism and Pharmacokinetics
These radiopharmaceuticals are rapidly extracted by hepatocytes in the liver and excreted into the biliary system, similar to bilirubin. 2, 3
Key pharmacokinetic properties include:
- Rapid blood clearance - only 17% of injected dose remains in blood at 10 minutes in normal subjects 2
- Liver visualization occurs by 5 minutes with maximum uptake at 11 minutes post-injection 2
- Gallbladder and hepatic duct visualization typically occurs by 10-15 minutes 2
- Intestinal activity is visualized by 30-60 minutes in patients with normal hepatobiliary function 2, 4
- Minimal renal excretion - only 1% excreted in urine during first 3 hours in normal subjects 2
Additional Agent for Functional Studies
For functional gallbladder disorder evaluation (CCK-cholescintigraphy), sincalide (synthetic cholecystokinin) is administered after gallbladder filling. 1
The standardized protocol requires:
- Dose: 0.02 μg/kg (or 1.4 μg/kg based on patient weight) 1, 5
- Administration: infused intravenously over 60 minutes 1
- Purpose: to stimulate gallbladder contraction and calculate gallbladder ejection fraction (GBEF) 1
- Normal GBEF: ≥38% 1, 5
Important Clinical Considerations
CCK/sincalide is NOT used for acute cholecystitis evaluation - it is specifically indicated for functional gallbladder disorder and chronic acalculous cholecystitis where gallbladder contractility assessment is needed. 5 For acute cholecystitis diagnosis, only the Tc-99m HIDA agent is injected to assess cystic duct patency. 1
In jaundiced patients, elevated serum bilirubin increases renal excretion of Tc-99m HIDA agents and may delay hepatobiliary transit, potentially diminishing image quality. 2 Patients with mean bilirubin of 9.8 mg/dL showed 3% urinary excretion at 3 hours (versus 1% in normals) and 14.9% excretion at 24 hours. 2