A liver ultrasound is a non-invasive imaging procedure that uses high-frequency sound waves to create real-time pictures of the liver and surrounding structures within the upper abdomen. A small handheld device, called a transducer, transmits sound waves into the body, which bounce back as echoes. These echoes are processed by a computer to form a visual representation of the organ’s size, shape, and internal texture. This diagnostic tool serves as a primary method for screening and initial diagnosis without using ionizing radiation.
Common Reasons for Ordering the Scan
A physician often orders a liver ultrasound when clinical or laboratory findings suggest a potential issue with the liver or biliary system. One of the most frequent indications is the presence of unexplained elevated liver enzyme levels detected through routine blood work, as this can signal inflammation or damage to the liver cells. The scan helps determine if these abnormal lab results are due to structural changes within the organ.
Symptoms such as unexplained abdominal discomfort, swelling, or a yellowish tint to the skin and eyes, known as jaundice, also prompt an ultrasound examination. Jaundice suggests a problem with bile flow that the ultrasound can quickly investigate. The scan is also routinely used to monitor patients who have known chronic liver disease or risk factors, such as heavy alcohol consumption or viral hepatitis. This surveillance tracks disease progression and screens for complications.
Detecting Diffuse Liver Conditions
The ultrasound is highly effective at identifying diffuse liver conditions, which are widespread changes affecting the entire liver tissue. One common finding is hepatic steatosis, or fatty liver disease, caused by the abnormal accumulation of lipids within the liver cells. On an ultrasound image, a fatty liver appears brighter than normal, described as increased echogenicity or being hyperechoic.
This increased brightness, when compared to the adjacent right kidney, is a sign of fat infiltration. As the condition becomes more severe, sound waves are increasingly blocked, leading to poor visualization of the deep portions of the liver and the diaphragm boundary. Beyond steatosis, the scan can detect signs of advanced scarring, or fibrosis, which precedes cirrhosis.
Cirrhosis, the late stage of liver disease, is characterized by changes to the liver’s physical architecture. The ultrasound reveals a liver with an irregular, nodular surface and a coarse internal texture due to regenerating nodules and fibrous tissue. The overall size of the liver may also be reduced, especially in advanced cases. Specialized techniques, such as elastography, can measure the stiffness of the liver tissue, providing a non-invasive way to assess fibrosis severity.
Identifying Focal Masses and Lesions
In contrast to diffuse conditions, a liver ultrasound detects and characterizes focal masses, which are discrete, localized areas of abnormal tissue. The initial step is determining consistency, distinguishing between a solid mass and a fluid-filled area. Simple liver cysts, which are common benign findings, appear as smooth, well-defined, dark areas because the internal fluid does not reflect sound waves.
Solid masses, including benign tumors like hemangiomas and malignant growths such as hepatocellular carcinoma or metastatic tumors, appear with various levels of brightness and internal patterns. The ultrasound characterizes these lesions by examining their size, shape, borders, and internal structure, noting if they are homogeneous or heterogeneous. Hemangiomas, a type of benign blood vessel tumor, often present with a distinct, highly reflective, and bright appearance.
For malignant masses, the ultrasound provides information on features like irregular borders or cystic areas within a predominantly solid mass. Doppler ultrasound assesses blood flow patterns within the lesion, which helps differentiate between benign and malignant tumors. However, complex cases may require further imaging, such as contrast-enhanced ultrasound, for definitive characterization.
Assessing Associated Vascular and Biliary Structures
The evaluation of a liver ultrasound extends beyond the liver itself to include the surrounding vascular and biliary structures. The biliary system, consisting of the gallbladder and the bile ducts, is examined for obstruction. Gallstones within the gallbladder or bile ducts, which appear as bright, shadowing structures, are a common finding that can cause blockages.
If a blockage is present, the bile ducts may appear abnormally widened or dilated on the scan. This dilation indicates that bile is backing up, which is a potential cause of jaundice. The vascular system, particularly the portal vein and the hepatic veins, is also a focus of examination.
Doppler ultrasound checks the direction and speed of blood flow in these vessels. This is important for detecting signs of portal hypertension, a condition caused by resistance to blood flow within a diseased liver. Signs include an enlarged portal vein diameter, often exceeding 13 millimeters, and the development of new collateral vessels that reroute blood flow to bypass the liver.