HIDA (Hepatobiliary Iminodiacetic Acid) scans are an imaging procedure used to assess the function of the liver and biliary system. This tool provides insights into how the liver produces and flows bile through the ducts and gallbladder. Evaluating these processes helps identify various issues affecting these organs.
Understanding HIDA Scans
A HIDA scan is a nuclear medicine imaging test that involves injecting a radioactive tracer into a patient’s bloodstream. This radiotracer travels to the liver where it is absorbed by the bile-producing cells. From the liver, the tracer mixes with bile and moves through the biliary ducts to the gallbladder and then into the small intestine.
Special cameras, called gamma cameras, detect the gamma rays emitted by the tracer as it moves through the body. These cameras, along with computer processing, create detailed pictures that show the activity of the liver, bile ducts, and gallbladder. The scan assesses bile flow and the organs’ ability to process and transport it.
What HIDA Scans Reveal
HIDA scans are designed to diagnose problems related to the gallbladder and bile ducts. They are often used to identify acute cholecystitis, a sudden inflammation of the gallbladder, often caused by gallstones. The scan can also help diagnose chronic cholecystitis, repeated episodes of gallbladder inflammation.
Beyond inflammation, HIDA scans can detect bile duct obstructions, like gallstones or other blockages. They are also useful for identifying bile leaks after surgery or injury, and congenital abnormalities of the biliary system such as biliary atresia in newborns. Additionally, the scan can measure the gallbladder’s ejection fraction, indicating its efficiency in releasing bile, which can point to chronic inflammation.
HIDA Scans and Liver Cancer
HIDA scans are not a diagnostic tool for detecting liver cancer. The scan primarily evaluates bile production and flow, not solid masses or tumors within the liver. While a large tumor could impact bile flow by compressing a bile duct, leading to an abnormal HIDA scan, it would indicate a bile flow issue, not a cancerous mass.
If a HIDA scan shows slow tracer movement or an obstruction, it suggests a problem with bile flow or liver function. These findings are not specific to cancer and could be caused by gallstones, inflammation, or other liver diseases. A HIDA scan might indirectly suggest an issue, but it cannot differentiate between cancer and other causes of obstruction or impaired function. Other imaging methods are used for direct visualization of liver masses.
Diagnosing Liver Cancer
Diagnosing liver cancer involves a combination of specialized imaging techniques and laboratory tests designed to visualize and characterize masses within the liver. Ultrasound is an initial imaging test, as it can show abnormal growths or lesions in the liver. However, ultrasound alone cannot definitively diagnose cancer or distinguish between benign and malignant tumors, often requiring further investigation.
Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI) are more detailed imaging methods used to detect and characterize liver tumors. CT scans use X-rays to create cross-sectional images, revealing the size, shape, and location of tumors. MRI scans utilize radio waves and strong magnets to produce detailed images of soft tissues, which are helpful for evaluating liver tumors and assessing for spread. Contrast agents are used with both CT and MRI to enhance the visibility of tumors.
Blood tests also play a role in diagnosing liver cancer, though they cannot provide a definitive diagnosis on their own. Liver function tests can indicate how well the liver is working, and specific tumor markers, such as alpha-fetoprotein (AFP), may be elevated in some cases of liver cancer. For a definitive diagnosis, a liver biopsy is performed. This procedure involves removing a small sample of liver tissue, typically using a needle guided by imaging, which is then examined under a microscope for cancer cells. While imaging results can sometimes be conclusive, a biopsy provides direct confirmation of cancer.