Why Narcotics Are Avoided Before and During HIDA Scans
Opioid narcotics must be withheld for at least 48 hours before HIDA scanning because they cause spasm of the sphincter of Oddi and impair gallbladder contraction, leading to false-positive results that can mimic bile duct obstruction or falsely decrease gallbladder ejection fraction. 1, 2
Mechanism of Interference
Opioids directly cause biliary sphincter spasm, which has two critical effects on HIDA scan interpretation:
- They markedly delay clearance of the radiotracer (Tc-99m HIDA) from the common bile duct, simulating common bile duct obstruction in otherwise healthy individuals 3
- They spuriously decrease gallbladder ejection fraction (GBEF) by acting on the sphincter of Oddi and reducing gallbladder contractility, even though the gallbladder itself may be functioning normally 4
- Opioid metabolites circulate in the blood for many hours and continue to affect biliary sphincter function long after administration 4
Clinical Consequences of Opioid Use
The interference from narcotics can lead to serious diagnostic errors:
- False-positive diagnosis of bile duct obstruction when delayed radiotracer clearance is misinterpreted as anatomical obstruction, potentially leading to unnecessary common bile duct exploration 3
- False-positive diagnosis of chronic cholecystitis or biliary dyskinesia when a low ejection fraction (<38%) is actually caused by opioid-induced sphincter dysfunction rather than true gallbladder disease 1, 4
- Nonvisualization of the gallbladder may occur due to functional obstruction at the sphincter of Oddi rather than true cystic duct obstruction 4
Specific Medication Restrictions
The following drugs must be avoided before HIDA scanning:
- Opiates: withhold for at least 48 hours (includes morphine, meperidine, hydromorphone, oxycodone, hydrocodone, fentanyl, and all other opioid analgesics) 1, 2, 3
- Anticholinergic drugs: withhold for at least 48 hours because they directly impair gallbladder contraction 1
- Other medications to avoid within 24 hours: nifedipine, indomethacin, octreotide, theophylline, benzodiazepines, phentolamine, isoproterenol, and progesterone 1
- Nicotine and alcohol should also be avoided prior to testing 1
Critical Pitfalls to Avoid
Taking a careful drug history is essential before interpreting any HIDA scan with abnormal findings, especially when evaluating for:
- Chronic acalculous cholecystitis or biliary dyskinesia (where GBEF is the primary diagnostic criterion) 4
- Suspected bile duct obstruction (where delayed clearance is the key finding) 3
If a patient has received opioids within 48 hours of the scan, the study should ideally be rescheduled rather than proceeding with interpretation that may be unreliable 1, 2. If clinical urgency prevents rescheduling, the interpreting physician must be informed of recent opioid use so results can be interpreted with appropriate caution 4.
Additional Patient Preparation Requirements
Beyond medication restrictions, proper HIDA scan preparation includes:
- Fasting for at least 4-6 hours (optimally overnight) to ensure adequate gallbladder filling and avoid false-positive results 1, 2
- Performing the study on an outpatient basis when possible, not during acute illness, to avoid confounding factors 1, 2
- Avoiding the study in patients taking chronic opioid therapy unless they can safely discontinue for 48 hours, as chronic use may cause persistent sphincter dysfunction 4