Hepatobiliary Scintigraphy

Excerpt

Hepatobiliary scintigraphy is a diagnostic nuclear medicine procedure which uses radiotracers to evaluate the biliary system and also, indirectly, the liver. The radiotracer first used was iminodiacetic acid (IDA), a lidocaine derivative initially investigated for cardiac scintigraphy. When its potential as a hepatobiliary imaging agent was realized, the term HIDA scan was coined. Since then, the original radiotracer has undergone several modifications, and the initial HIDA agent is no longer commercially available. HIDA and its current modern variants are administered intravenously, bound to albumin, transported to the liver, and excreted into the biliary system. The utility of hepatobiliary scintigraphy (HBS) is that the radiotracer follows the bilirubin metabolic pathway and excretion into the bile ducts. As such, it has proven extremely useful in the diagnosis of acute cholecystitis, chronic gallbladder disease, biliary leaks, biliary obstruction, and biliary atresia.

Ultrasound (US) remains the primary modality for initially assessing suspected biliary pathology. Ultrasound is readily available, fast, requires minimal patient preparation, avoids ionizing radiation, and may offer alternative diagnoses. Despite these benefits, US can suffer from both suboptimal sensitivity and specificity in the assessment of biliary disorders, and thus HBS remains critical to the evaluation of patients with right upper quadrant pain and other symptoms of hepatobiliary disease.