The liver, a large organ located in the upper right abdomen, performs hundreds of functions essential for overall health, including detoxification, nutrient metabolism, and the production of bile for digestion. Maintaining liver health is important, and diagnostic imaging helps assess its condition.
How Ultrasound Examines the Liver
Ultrasound imaging, also known as sonography, uses high-frequency sound waves to create real-time pictures of internal organs.
A transducer (probe) contains piezoelectric crystals that convert electrical energy into sound waves. These sound waves are emitted into the body and travel through soft tissues and fluids. When the sound waves encounter boundaries between different tissue densities, such as between fluid and soft tissue or tissue and bone, some reflect back to the transducer as echoes.
The transducer converts these echoes back into electrical signals. A connected computer processes these signals, using the time it took for the echoes to return and their intensity, to construct a two-dimensional image. During a liver ultrasound, a clear gel is applied to the skin to ensure proper transmission. This non-invasive procedure typically takes about 30 minutes and does not involve radiation.
Liver Conditions Visible on Ultrasound
A liver ultrasound is often a first step in evaluating liver health. It visualizes the organ’s size, shape, texture, and abnormalities, detecting various liver conditions.
Fatty liver disease, or steatosis, often appears on ultrasound as an increased brightness or echogenicity of the liver tissue. This indicates fat buildup. Cirrhosis, a more advanced stage of liver disease characterized by scar tissue, can manifest as an irregular or nodular liver surface, a coarse texture, and changes in liver size. Ultrasound can also detect complications of cirrhosis like fluid accumulation in the abdomen (ascites) or an enlarged spleen.
Beyond diffuse changes, ultrasound can identify distinct lesions within the liver. Cysts, which are fluid-filled sacs, typically appear as well-defined, echo-free (dark) structures. Tumors, whether benign or malignant, may show up as abnormal spots or masses with varying brightness and characteristics. Ultrasound can also reveal signs of inflammation, such as hepatitis, or fibrosis by assessing the tissue’s stiffness, especially with specialized techniques like elastography.
When Ultrasound Isn’t Enough
While ultrasound is a useful screening tool for liver damage, it has limitations. It may not always detect very early stages of liver damage or precisely quantify the degree of fibrosis accurately. Differentiating between benign and malignant lesions can be challenging, often requiring further investigation. Accuracy can be influenced by equipment, image quality, sonographer experience, and patient factors such as obesity or bowel gas, which can obscure views.
Due to these limitations, ultrasound often serves as a preliminary step in the diagnostic process. If ultrasound findings suggest liver damage or abnormalities, other diagnostic tools provide a more comprehensive assessment. Blood tests, such as liver function tests, measure enzymes and proteins indicating liver injury. Advanced imaging techniques like Computed Tomography (CT) scans or Magnetic Resonance Imaging (MRI) provide more detailed views of the liver and surrounding areas, helping characterize lesions or disease extent. In some cases, a liver biopsy, taking a tissue sample for examination, remains the definitive method for diagnosing the type and severity of liver disease.