Radiopharmaceutical: Tc-99m mebrofenin (Choletec) or Tc-99m disofenin, 5–8 mCi. Patient NPO 2–4h — but not >24h (prolonged fasting or TPN causes concentrated static bile → GB does not fill → false positive). Pretreat with sincalide 0.02 µg/kg IV × 30 min if NPO >24h or on TPN.
Morphine augmentation: 0.04 mg/kg IV at 60 min if GB not visualized — contracts sphincter of Oddi, redirecting bile into GB. If GB still not seen at 4h post-morphine → acute cholecystitis.
Findings and Interpretation
| Finding | Interpretation | Sensitivity / Specificity |
|---|---|---|
| GB non-visualization at 4h (after morphine augmentation at 60 min) | Acute cholecystitis — cystic duct obstruction | Sens ~96%, Spec ~90% |
| Rim sign — pericholecystic band of increased hepatic activity adjacent to GB fossa | Severe / gangrenous cholecystitis — surgical emergency; indicates transmural inflammation or perforation | Spec ~99%, Sens ~35% |
| GB visualization delayed (1–4h) but eventually fills | Chronic cholecystitis — partial/intermittent cystic duct obstruction | — |
| GB ejection fraction <35–40% after CCK (sincalide 0.02 µg/kg over 30–60 min) | Biliary dyskinesia — functional cystic duct dysfunction; surgical referral (cholecystectomy) | Sens ~78%, Spec ~87% |
| Focal accumulation outside hepatobiliary system, increasing over time | Bile leak — post-cholecystectomy, liver transplant anastomotic leak, or trauma; activity pools dependently | Sens ~94% |
| No CBD/bowel activity; intrahepatic duct dilation; activity retained in liver | Complete CBD obstruction — choledocholithiasis, stricture, or malignancy | — |
Rim sign = surgical emergency. Pericholecystic hepatic activity indicates transmural inflammation or early perforation. Sensitivity is low (~35%) but specificity is ~99% — when present, it predicts gangrenous cholecystitis and mandates urgent surgical consultation.
HIDA Pitfalls
| Pitfall | Explanation |
|---|---|
| Prolonged fasting / TPN (>24h NPO) | Concentrated bile fills GB → GB does not fill with new radiotracer → false positive for cholecystitis; pretreat with sincalide |
| Hepatic dysfunction (bili >5–7 mg/dL) | Delayed or absent biliary excretion; decreases sensitivity; consider US as primary modality |
| Duodenal bulb mistaken for GB | Duodenum adjacent to GB fossa; follow activity dynamically — bowel moves, GB stays; use LAO view |
| Accessory bile duct / choledochal cyst | Can mimic bile leak or abnormal focal uptake; MRCP for anatomic clarification |
| Acalculous cholecystitis | Same scintigraphic appearance as calculous cholecystitis; occurs in critically ill/ICU patients; sensitivity slightly lower (~80%) |