What is the recommended pharmaceutical and protocol for a HIDA (Hepatobiliary Iminodiacetic Acid) scan?

HIDA Scan Protocol and Pharmaceutical Recommendations

For HIDA (Hepatobiliary Iminodiacetic Acid) scans, Technetium-99m mebrofenin is the recommended radiopharmaceutical, administered with a standardized 60-minute sincalide infusion protocol at a dose of 0.02 μg/kg for optimal gallbladder ejection fraction assessment. 1, 2

Recommended Radiopharmaceutical

• Technetium-99m mebrofenin is the preferred radiotracer for HIDA scans 2
• Following IV administration, it is rapidly cleared from circulation with only 17% remaining in blood at 10 minutes
• The liver is visualized by 5 minutes with maximum uptake at 11 minutes
• Hepatic ducts and gallbladder visualization occurs by 10-15 minutes
• Intestinal activity is typically visualized by 30-60 minutes in patients with normal hepatobiliary function

Patient Preparation

• Patient should fast overnight or at least 4-6 hours prior to the study 1
• HIDA scans for functional gallbladder disorder evaluation should be performed on an outpatient basis, not during hospitalization or acute illness
• Medications to withhold:
  • Opiates and anticholinergic drugs: at least 48 hours before testing
  • Other medications to withhold 24 hours prior: nifedipine, indomethacin, octreotide, theophylline, benzodiazepines, phentolamine, isoproterenol, and progesterone
  • Nicotine and alcohol should also be avoided prior to testing

Contraindications

• Known allergic reaction to sincalide
• Intestinal obstruction
• Pregnancy (sincalide is contraindicated as it may stimulate preterm labor) 1

Standard HIDA Scan Protocol

1. Equipment Setup: Use a large field of view gamma camera with low-energy collimator; images acquired with 140 keV photopeak and 20% window 1

2. Pre-Sincalide Procedure:

   • Start an intravenous line and inject the Tc-99m HIDA radiotracer with patient supine
   • Obtain images up to 1 hour to ensure gallbladder visualization
   • If gallbladder has not filled by 60 minutes in a properly prepared patient, report as abnormal (potentially consistent with acute or chronic cholecystitis)
   • If gallbladder has filled, position camera in left anterior oblique projection (35-40 degrees) to minimize overlap of gallbladder with duodenum and small bowel

3. Sincalide Infusion Procedure (for functional gallbladder assessment):

   • Prepare 0.02 μg/kg dose of sincalide diluted with normal saline in a 30-50 mL syringe
   • Place syringe in infusion pump and fill tubing with sincalide infusate before starting
   • Set infusion pump to deliver continuously over exactly 60 minutes
   • Start dynamic imaging (1 image per minute) simultaneously with sincalide infusion
   • Continue imaging for the full 60-minute infusion period

4. Computer Processing and Quantification:

   • Draw region of interest (ROI) around the gallbladder
   • Draw background liver ROI about 1-2 cm superior lateral to the gallbladder
   • Calculate gallbladder ejection fraction (GBEF)
   • An abnormal GBEF is defined as <38% 1

Clinical Significance

• The 60-minute sincalide infusion protocol shows significantly less variation in GBEF values compared to 15-minute or 30-minute protocols 1
• This standardized protocol provides more reliable results for diagnosing functional gallbladder disorders
• HIDA scans have high sensitivity (84-89%) and specificity (67-79%) for acute cholecystitis 3

Common Pitfalls and Caveats

• Elevated serum bilirubin levels increase renal excretion of Tc-99m HIDA agents 2
• In jaundiced patients, blood clearance may be delayed and hepatobiliary transit times increased
• Image quality may diminish in patients with jaundice
• False positive results may occur in patients who are acutely ill or hospitalized 1
• Ensure proper patient preparation to avoid false positive results
• For suspected acute cholecystitis, HIDA scan should be considered as a third-line imaging modality after ultrasound and CT 3

This standardized protocol based on the Society of Nuclear Medicine guidelines provides optimal assessment of hepatobiliary function and gallbladder contractility, with clear diagnostic criteria for interpretation.