HIDA Scan and Gallbladder Ejection Fraction

Introduction

Hepatobiliary scintigraphy — the HIDA scan — images the liver's production and flow of bile in real time, and its most important quantitative output, the gallbladder ejection fraction (GBEF), is only as trustworthy as the protocol that produces it. The study answers questions no anatomic image can: is the cystic duct open, is there acute cholecystitis, and does the gallbladder contract normally when stimulated.¹

The name "HIDA" is historical, from the original hepatic iminodiacetic-acid agents. Modern practice uses Tc-99m mebrofenin or Tc-99m disofenin, which are extracted by hepatocytes along the same pathway as bilirubin and excreted into bile. That physiology lets a gamma camera follow tracer through the liver, biliary tree, gallbladder, and small bowel over about an hour.¹³

What separates a decisive HIDA study from an ambiguous one is technique: correct patient preparation, the right pharmacologic intervention for the clinical question, and a counting method that yields a reproducible GBEF. A rushed sincalide bolus, an unrecognized recent meal, or sloppy region-of-interest drawing can turn a normal gallbladder into an apparent disease. This guide explains the physics and physiology of the study, how the GBEF is calculated, why the standardized sincalide method matters, and how DRPS supports nuclear medicine programs through PET/CT and nuclear medicine physics and medical physics consulting.

Topic Explanation

What the HIDA scan measures

Hepatobiliary scintigraphy is a functional study: it shows how bile moves, not just where the anatomy is. After intravenous injection, the Tc-99m iminodiacetic-acid tracer is cleared from blood by the liver, concentrated by hepatocytes, and secreted into the biliary canaliculi. Sequential gamma-camera images then depict, in order, hepatic uptake, then the intrahepatic and extrahepatic ducts, then the gallbladder (if the cystic duct is patent), and finally tracer entering the duodenum.¹

The clinical questions the study answers include:

• Acute cholecystitis — is the cystic duct obstructed? A gallbladder that never fills, despite good hepatic uptake and bowel activity, points to cystic-duct obstruction.¹⁴
• Functional gallbladder disorder (biliary dyskinesia) — does the gallbladder contract adequately? This is quantified by the GBEF after sincalide stimulation.¹²
• Bile leak, biliary atresia, post-surgical anatomy, and hepatocyte function — bile flow and clearance patterns address these as well.¹³

The adult tracer activity is typically 111–185 MBq (3–5 mCi) of Tc-99m mebrofenin, with dynamic imaging over about 60 minutes.¹ Mebrofenin has high hepatic extraction and remains usable even with moderately elevated serum bilirubin, which is one reason it is preferred over older iminodiacetic-acid agents.¹³

Why patient preparation drives the result

Two preparation errors account for many non-diagnostic studies:

• Recent food. Eating within about 4 hours triggers endogenous cholecystokinin release, contracting the gallbladder so it will not fill with tracer — a false nonvisualization that mimics cystic-duct obstruction.
• Prolonged fasting or total parenteral nutrition (TPN). Fasting beyond 24 hours (or TPN) lets the gallbladder fill with thick, concentrated bile that resists tracer entry. In this setting, pretreatment with sincalide to empty the gallbladder before the tracer is injected prevents false nonvisualization.¹

The guideline target is therefore a fast of at least 4 hours but generally not more than 24 hours before the study.¹

Key Technical Principles

Calculating the gallbladder ejection fraction

The GBEF is the fractional drop in gallbladder counts after the gallbladder is stimulated to contract. A region of interest is drawn around the gallbladder, a background region is chosen (often adjacent liver), and net counts are tracked over time. The ejection fraction is:

where $C_{\max }$ is the net (background-subtracted, decay-corrected) gallbladder counts at the start of stimulation and $C_{\min }$ is the net counts at the end.¹²

Because Tc-99m decays with a 6.0-hour half-life, counts fall over the measurement window from physical decay as well as from gallbladder emptying. Without correction, decay alone would inflate the apparent ejection fraction. Each count value is decay-corrected to the reference time using:

Over a 60-minute window with $T_{1/2}=6.0$ h, the correction factor is $e^{(\ln 2/6)\times 1}=e^{0.1155}\approx 1.12$, a 12% adjustment that is not optional for an accurate GBEF.¹

Worked GBEF example

Suppose the gallbladder region shows 12,000 net counts at the start of the sincalide infusion, and at 60 minutes the raw net counts are 4,800. Decay-correcting the later value:

A GBEF of 55% is comfortably normal. Had the decay-corrected minimum been about 7,500 counts, the GBEF would fall to roughly 38% — exactly at the lower limit of normal, where technique and reproducibility matter most.²

Comparison of interventions

The pharmacologic intervention is chosen to match the clinical question. The table summarizes the standard options.

Why the sincalide infusion must be slow

The single most important lesson in GBEF standardization is that how sincalide is given determines whether the number is reproducible. A rapid bolus can provoke gallbladder-neck spasm and abdominal cramping and produce a falsely low, highly variable ejection fraction. A multicenter trial of 60 healthy volunteers compared 15-, 30-, and 60-minute infusions of 0.02 µg/kg sincalide and found the coefficient of variation was smallest for the 60-minute infusion — about 19%, versus 35% for the 30-minute and 52% for the 15-minute infusion. From that data, the lower limit of normal GBEF for the 60-minute method was established at 38% (first percentile).²

That is why a GBEF is only interpretable against the normal range for the exact method used. A "low GBEF" from a 3-minute bolus is not comparable to the 38% threshold derived for the 60-minute infusion, and mixing methods is a common source of over-diagnosis of biliary dyskinesia.¹²

Clinical Impact

A well-performed HIDA scan changes management; a poorly standardized one can send a patient to unnecessary surgery. In suspected acute cholecystitis, morphine-augmented cholescintigraphy is highly accurate: in a series of 163 hospitalized patients, morphine cholescintigraphy achieved a sensitivity of 99%, specificity of 91%, and overall accuracy of 94% for acute cholecystitis, with a negative predictive value of 0.99 — meaning a gallbladder that fills after morphine reliably excludes the diagnosis.⁴ That performance lets clinicians avoid negative surgery in ambiguous, critically ill patients where clinical signs are unreliable.

For functional gallbladder disorder, the GBEF is more nuanced. A low GBEF supports the diagnosis in a patient with typical biliary-type pain, but the number alone does not guarantee a good surgical outcome. A large single-center study of acalculous biliary disease found that symptom reproduction during cholecystokinin administration was a better predictor of favorable response to cholecystectomy than the calculated ejection fraction itself, and that outcomes after surgery were similar across normokinetic and hypokinetic ejection-fraction groups.⁵ The clinical message is that the GBEF is one input into a decision, not a stand-alone verdict — which makes technical reproducibility all the more important, because the number must be trustworthy to be weighed correctly.

The radiation burden is modest. Hepatobiliary scintigraphy uses a small, short-lived technetium-99m activity; the effective dose is on the order of a few millisieverts for a typical administered activity, with the gallbladder wall and upper large intestine among the higher-dose organs.⁷ Reproducibility, not dose, is the dominant quality driver for this study.

Practical Optimization Tips

1. Standardize the sincalide infusion

Use 0.02 µg/kg infused over 60 minutes and read the GBEF against the 38% lower limit derived for that method. Do not compare a bolus-derived GBEF to the infusion-based normal range.¹²

2. Confirm preparation before injecting

Verify a fast of at least 4 hours and not more than 24 hours. For patients fasting longer than 24 hours or on TPN, pretreat with sincalide and wait at least 30 minutes before injecting the tracer to avoid false nonvisualization.¹

3. Draw regions of interest carefully

Place the gallbladder region tightly around the organ and choose a background region that avoids duodenal or bile-duct activity. Because the GBEF is a ratio of net counts, background choice and region drift directly change the result. Consistent, motion-aware region placement is essential for reproducibility.¹

4. Always decay-correct

Apply Tc-99m decay correction across the emptying window. Skipping it biases the GBEF upward by roughly the 12% decay over a 60-minute measurement and can mask a truly low ejection fraction.¹

5. Match the intervention to the question

Use morphine augmentation (0.04 mg/kg) to resolve gallbladder nonvisualization for suspected acute cholecystitis, and reserve sincalide-stimulated GBEF for the functional-disorder question. Document which intervention was used and why.¹⁴

Common pitfalls to avoid

• Bolus sincalide. Produces a falsely low, high-variability GBEF and over-diagnosis of biliary dyskinesia.²
• Ignoring recent food. A meal within 4 hours contracts the gallbladder and mimics obstruction.¹
• Skipping decay correction. Inflates the ejection fraction and hides disease.¹
• Comparing across methods. A GBEF is only interpretable against the normal range for its own infusion protocol.²
• Treating a low GBEF as an automatic surgical indication. Correlate with symptoms and clinical context.⁵

Regulatory Considerations

Hepatobiliary scintigraphy is a medical use of byproduct material and is governed by NRC or Agreement State materials rules, layered on top of professional practice guidelines. The technetium-99m tracer, sincalide, and morphine are administered under the facility's radioactive material license and radiation safety program.

• 10 CFR Part 35 — Medical Use of Byproduct Material. Tc-99m radiopharmaceuticals for imaging are administered under the authorized-user and written-directive framework of Part 35 (diagnostic imaging generally does not require a written directive, but authorization, measurement, and record requirements apply).⁸
• 10 CFR Part 20 — Standards for Protection Against Radiation. Occupational and public dose limits, ALARA, and survey and record requirements apply to the hot lab and imaging areas.⁹
• Professional standards. The SNM Practice Guideline for Hepatobiliary Scintigraphy 4.0 defines the acquisition, interventions, and interpretation, and the joint EANM/SNMMI/IHPBA procedure guideline standardizes quantitative mebrofenin studies for liver-function applications.¹³

Agreement State context matters for the license, not the physics. Of the states DRPS serves, Florida, Maryland, Virginia, California, Nevada, Pennsylvania, New York, and New Jersey are NRC Agreement States that administer their own medical-use programs, while Washington, DC and Delaware are regulated directly by the NRC for radioactive material. A facility must verify which authority issues its license and which reporting and record requirements apply. Dose-calibrator accuracy for the administered activity and radiochemical purity of the tracer are part of the same quality chain — see our guides to dose calibrator quality control and radiochemical purity and TLC quality control. DRPS supports these programs through radiation safety training and PET/CT and nuclear medicine physics.

Frequently Asked Questions (FAQs)

What is a HIDA scan?

A HIDA scan, or hepatobiliary scintigraphy, is a nuclear medicine study that images bile production and flow. A technetium-99m-labeled iminodiacetic-acid tracer such as Tc-99m mebrofenin is injected intravenously, extracted by hepatocytes, and excreted into bile, letting a gamma camera follow the tracer through the liver, bile ducts, gallbladder, and bowel.

What is gallbladder ejection fraction (GBEF)?

Gallbladder ejection fraction is the percentage of tracer-containing bile the gallbladder expels after it is stimulated to contract, usually with an infusion of the cholecystokinin analog sincalide. It is calculated from the fall in gallbladder counts and is the main quantitative result of a cholecystokinin cholescintigraphy study for suspected functional gallbladder disorder.

What is a normal gallbladder ejection fraction?

With the standardized method — 0.02 micrograms of sincalide per kilogram infused over 60 minutes and the ejection fraction measured at 60 minutes — the lower limit of normal is 38 percent. A GBEF below 38 percent with this method is considered abnormal and can support a diagnosis of functional gallbladder disorder in the right clinical setting.

Why is sincalide infused slowly instead of injected as a bolus?

A rapid sincalide bolus can cause the gallbladder neck to spasm and produce a falsely low ejection fraction with wide variability. A multicenter trial showed the 60-minute infusion had the lowest coefficient of variation, about 19 percent, compared with 35 percent for a 30-minute and 52 percent for a 15-minute infusion, which is why the slow infusion is the standard.

What is morphine used for in a HIDA scan?

When the gallbladder is not seen by 60 minutes, morphine sulfate is given to contract the sphincter of Oddi, raising bile-duct pressure and redirecting bile into a patent cystic duct. If the gallbladder still does not fill, cystic-duct obstruction and acute cholecystitis are likely. Morphine augmentation shortens the study and improves accuracy compared with delayed imaging alone.

Is a HIDA scan safe, and what is the radiation dose?

Hepatobiliary scintigraphy uses a small, short-lived amount of technetium-99m and delivers a modest radiation dose, on the order of a few millisieverts for a typical administered activity. The gallbladder wall and upper large intestine are among the higher-dose organs. The tracer and any sincalide or morphine are given under nuclear medicine and licensing controls.

How should a patient prepare for a HIDA scan?

Patients should fast for at least 4 hours but generally no more than 24 hours before the study. Eating within about 4 hours can release endogenous cholecystokinin and keep the gallbladder contracted, causing false nonvisualization, while fasting beyond 24 hours or being on total parenteral nutrition can fill the gallbladder with viscous bile — both situations may require sincalide pretreatment before the tracer is injected.

Key Takeaways

• HIDA is a functional study of bile flow. A Tc-99m iminodiacetic-acid tracer is extracted by hepatocytes and excreted into bile, imaged dynamically over about 60 minutes.
• GBEF is a net-count ratio and must be decay-corrected. The ejection fraction is the fractional drop in decay-corrected gallbladder counts after stimulation.
• The method defines the normal range. With 0.02 µg/kg sincalide over 60 minutes, the lower limit of normal is 38%; bolus methods are not comparable.
• Slow sincalide infusion minimizes variability. The 60-minute infusion has the lowest coefficient of variation (~19%).
• Morphine augmentation is highly accurate for acute cholecystitis. Reported sensitivity ~99% and negative predictive value ~0.99 when the gallbladder fills.
• The GBEF is one input, not a verdict. Correlate with symptoms; a low number alone does not guarantee surgical benefit.

Conclusion

The HIDA scan endures because it measures something anatomy cannot: whether bile actually flows and whether the gallbladder actually contracts. But its value rests entirely on disciplined technique. The gallbladder ejection fraction is a simple ratio, yet it is sensitive to how sincalide is infused, whether counts are decay-corrected, how regions of interest are drawn, and how the patient was prepared. Standardize those elements — the 60-minute sincalide infusion, the 38% threshold matched to that method, careful counting, and the right intervention for the clinical question — and the study delivers a reproducible number a clinician can act on.

For nuclear medicine programs, the physicist's contribution is to keep the quantitative chain intact: an accurate dose calibrator, a pure tracer, a correctly configured processing workstation, and a documented protocol that matches the published normal values. That is what turns a HIDA scan from a picture of the biliary tree into a decision-grade measurement.

How DRPS Can Help

Diagnostic Radiation Physics Services supports nuclear medicine facilities in keeping quantitative studies like hepatobiliary scintigraphy accurate and defensible. This includes PET/CT and nuclear medicine physics, gamma-camera and processing-workstation quality control, dose-calibrator and radiopharmaceutical quality assurance, protocol and normal-value review, radiation safety training, and medical physics consulting by board-certified medical physicists.

DRPS supports facilities across our service locations, including Florida, Maryland, Virginia, Washington DC, California, Nevada, New York, Pennsylvania, New Jersey, and Delaware.

A strong nuclear medicine quality program is not just about the camera. It is about making sure every number the study reports means what the clinician thinks it means.

Related Resources

• Gastric emptying scintigraphy
• Renal scintigraphy: split renal function and GFR
• Dose calibrator quality control
• Radiochemical purity and TLC quality control
• PET/CT and nuclear medicine physics
• Radiation safety training
• Medical physicist consulting

References

1. Tulchinsky M, Ciak BW, Delbeke D, et al. SNM practice guideline for hepatobiliary scintigraphy 4.0. Journal of Nuclear Medicine Technology. 2010;38(4):210-218. doi:10.2967/jnmt.110.082289. doi.org
2. Ziessman HA, Tulchinsky M, Lavely WC, et al. Sincalide-stimulated cholescintigraphy: a multicenter investigation to determine optimal infusion methodology and gallbladder ejection fraction normal values. Journal of Nuclear Medicine. 2010;51(2):277-281. doi:10.2967/jnumed.109.069393. doi.org
3. Arntz PJW, Deroose CM, Marcus C, et al. Joint EANM/SNMMI/IHPBA procedure guideline for [99mTc]Tc-mebrofenin hepatobiliary scintigraphy SPECT/CT in the quantitative assessment of the future liver remnant function. HPB (Oxford). 2023;25(10):1131-1144. doi:10.1016/j.hpb.2023.06.001. doi.org
4. Flancbaum L, Choban PS, Sinha R, Jonasson O. Morphine cholescintigraphy in the evaluation of hospitalized patients with suspected acute cholecystitis. Annals of Surgery. 1994;220(1):25-31. doi:10.1097/00000658-199407000-00005. doi.org
5. Pihl KD, Jones MW, Deppen JG, Ferguson TM, Hanses SM. Effects of laparoscopic cholecystectomy in normokinetic biliary dyskinesia. American Journal of Surgery. 2017;215(1):116-119. doi:10.1016/j.amjsurg.2017.04.012. doi.org
6. Tulchinsky M. The SNM practice guideline on hepatobiliary scintigraphy. Journal of Nuclear Medicine. 2010;51(12):1825. doi:10.2967/jnumed.110.084475. doi.org
7. International Commission on Radiological Protection. ICRP Publication 128: Radiation Dose to Patients from Radiopharmaceuticals — A Compendium of Current Information Related to Frequently Used Substances. Annals of the ICRP. 2015;44(2 Suppl). icrp.org
8. U.S. Food and Drug Administration. Kinevac (sincalide) for injection prescribing information. accessdata.fda.gov
9. U.S. Nuclear Regulatory Commission. 10 CFR Part 35: Medical Use of Byproduct Material. ecfr.gov
10. U.S. Nuclear Regulatory Commission. 10 CFR Part 20: Standards for Protection Against Radiation. ecfr.gov