Hepatobiliary Sequence Scintigraphy

Hepatobiliary sequence scintigraphy (HBSS) is a nuclear medicine procedure used to visualize the functionality of the liver and biliary system. The liver is the central metabolic organ of the human organism. It is supplied by two different circulations. The blood supply is provided by the liver‘s own arteries (A. hepatica propria) and by the portal circulation (V. portae hepatis). In the digestive tract, macro- and micronutrients (nutrients and vital substances) are absorbed (taken up) and delivered via the portal vein to the liver, where they are fed into various metabolic pathways. The liver thus has an important synthesis and metabolization function in carbohydrate, protein and lipid metabolism (sugar, protein and fat metabolism). This also results in its crucial role in detoxification (detoxification) of endogenous (endogenous) or xenogenous (exogenous) substances. The products synthesized in the liver can, on the one hand, be released into the bloodstream and, on the other hand, be secreted (excreted) with the bile into the small intestine. In nuclear medicine diagnostics, liver function is visualized by radioactively labeled pharmaceuticals (tracers). In contrast to static liver scintigraphy, in which the tracers are absorbed into the hepatocytes (liver cells) and remain there, radiopharmaceuticals are used in liver sequence scintigraphy that are relatively quickly excreted into the bile duct system of the liver. Detection of tracer accumulation mismatches offers clues to local liver dysfunction or pathology of the biliary system.

Indications (areas of application)

Hepatobiliary sequence scintigraphy is used to visualize hepatobiliary function (HBF). Conclusions can be made regarding the excretory function of the liver as well as the drainage conditions of the biliary system. Sequence scintigraphy may be indicated (indicated) for:

  • Functional assessment of the biliary tract: In addition to morphologic imaging of the biliary tract (sonography, CT, MRI/MRCP, ERCP), functional scintigraphy can be performed (e.g., in children). Functional limitations can be detected at a very early stage, even often before changes in laboratory parameters. Detectable parameters include:
    • Bile duct obstructions: No activity measurable in the small intestine, because the tracer does not arrive there or delayed tracer accumulation in incomplete occlusions.
    • Occlusion of the ductus cysticus (gallbladder duct): no tracer accumulation in the gallbladder.
    • Acute or chronic cholecystitis (gallbladder inflammation): no or delayed tracer accumulation in the gallbladder.
    • Bile duct ectasias (dilated bile ducts): increased tracer accumulation in the bile ducts, e.g., in Karoli syndrome (cystic dilatation of the intrahepatic bile ducts).
    • Bile leakage (leaky bile ducts): pathological tracer leakage, e.g., after surgery, puncture, or trauma.
    • Gallbladder-colon fistula (connection of gallbladder and colon): tracer detectable in the colon.
  • Liver parenchymal damage: lesions of liver tissue are detectable by delayed elimination of radioactivity. An indication for functional scintigraphy exists especially for progress controls in hepatotoxic (“damaging the liver”) drug therapy (eg cytostatics), liver-specific conservative therapy (eg with UDCA = ursodeoxycholic acid) or acute liver failure.
  • Control of liver transplants: Rejection, bile duct obstruction (bile duct obstruction) or bile leakage can be detected.

It should be noted that due to technological advances in sonography, CT and MRI, hepatobiliary sequential scintigraphy is increasingly taking a back seat.

Contraindications

Relative contraindications

  • Lactation phase (breastfeeding phase) – breastfeeding must be interrupted for 48 hours to prevent risk to the child.
  • Repeat examination – no repeat scintigraphy should be performed within three months due to radiation exposure.

Absolute contraindications

  • Gravidity (pregnancy)
  • Stimulation with ceruletide should be omitted in v. a. cholelithiasis (gallstone disease), as contraction could induce colic.

Before the examination

  • For proper gallbladder imaging, patients should remain fasting before the examination.

The procedure

  • Radiopharmaceuticals are radioactive derivatives (chemical derivatives) of lidocaine (local anesthetic/drug for local anesthesia) that are taken up by hepatocytes and excreted through the biliary (affecting the bile) system: e.g., 99mTc-HIDA = N-[2,6-diethylacetanilido iminodiacetate].
  • The tracer is applied (administered) intravenously and scintigraphic registration of activity is started without delay.
  • High-resolution multiscope systems are used in liver diagnostics (SPECT = single-photon emission computed tomography), which allow detection of small (up to 0.5 cm) lesions. In this process, single images are taken every 5-10 min within approximately one hour.
  • After 30-40 min, filling of the gallbladder with the radiopharmaceutical is usually achieved. Then a contraction stimulus is caused by medication (with ceruletide), so that the gallbladder contracts and releases increased bile into the bile ducts and intestine. Scintigraphically, an increase in activity over these areas becomes measurable approximately 2-3 min after stimulation.
  • Semiquantitative evaluation is possible using memory curves over the liver, gallbladder, bile ducts, and small intestine.

Possible complications

  • Intravenous application of radiopharmaceutical may result in local vascular and nerve lesions (injuries).
  • Radiation exposure from the radionuclide used is rather low. Nevertheless, the theoretical risk of radiation-induced late malignancy is increased, so that a risk-benefit assessment should be performed.
  • Irritation with ceruletide may cause biliary colic, particularly in cholelithiasis (gallstone disease).