Posted on Nov 06, 2019
A painless procedure that uses sound waves instead of radiation, a liver ultrasound is relatively quick and inexpensive to perform compared to other imaging studies. And because early-stage liver cancers are typically asymptomatic, a liver ultrasound can be extremely helpful in finding tumors that would have otherwise gone undetected. In fact, many liver lesions are discovered incidentally, during an exam for an unrelated issue.
Whether you are dealing with a new liver lesion diagnosis or are monitoring changes in a previously detected mass, understanding your liver ultrasound is key for determining the next best steps. From what it means to have an echogenic liver to when you should get further imaging - we spoke with Dr. Barbara McComb, a former Mayo Clinic diagnostic radiologist and ultrasound expert with over 38 years of experience, to find out what you should know about your liver ultrasound.
[DocPanel] What symptoms indicate a liver ultrasound is needed?
[Dr. McComb] Actually, a wide variety of signs, symptoms, and laboratory findings can be associated with liver disease and may prompt the ordering of an ultrasound study. Some examples include unexplained weight loss, abdominal discomfort or swelling, early satiety, nausea or vomiting, weakness, jaundice, palpable mass, coagulation problem, and liver or spleen enlargement on a physical examination.
[DocPanel] What does a liver ultrasound scan show?
[Dr. McComb] Ultrasound is excellent both at showing normal anatomy and the presence of abnormalities in the liver. It is particularly excellent for differentiating cysts from solid masses. Simple cysts have a thin wall and contain fluid, which shows up as a darker center than solid masses have on ultrasound. Complex cysts may have associated lumps (nodules), calcifications, or multiple tissue bands. Solid masses can even be evaluated for blood flow by a technique called Doppler ultrasound, and cystic areas within masses can be distinguished from the solid parts.
Ultrasound can also evaluate diffuse liver disease, such as fatty liver, hepatitis, and cirrhosis. For example, a fatty liver (steatosis) is typically brighter (more “echogenic” or “hyperechoic”) on a liver ultrasound than normal liver, while hepatitis may be less bright (“hypoechoic”). A cirrhotic liver often looks shrunken and lumpy. A special technique called elastography can be added to an ultrasound study to help measure the elasticity of the liver and assess the severity of fibrosis.
Dilated bile ducts and any fluid near the liver (ascites, fluid collections) will also typically show up on a liver ultrasound. Other organs, including the gallbladder, right kidney, and at least a portion of the pancreas are often seen as well.
[DocPanel] Can a liver ultrasound detect liver cancer?
[Dr. McComb] Ultrasound can detect many cancerous (malignant) and non-cancerous (benign) liver masses. A mass is generally more easily seen by ultrasound the more it differs in appearance, and therefore stands out, from background tissue. Although not a hard-fast rule, in many cases a larger mass is more easily detected than a smaller mass.
But the detection of any mass is only possible if there is a good ultrasound “window.” Unfortunately, bone, calcification, and gas act as barriers to a liver ultrasound beam. Fatty tissue in front of or within the liver also reduces the penetration of the beam and the visibility of masses.
Another thing to recognize is that there is some overlap in the appearances of cancerous and non-cancerous masses. Fortunately, contrast-enhanced ultrasound (CEUS) has fairly recently been emerging in the United States as a useful technique to further evaluate liver lesions not well characterized by conventional ultrasound. It has been used in Europe and Asia for several years.
With CEUS, a microbubble contrast agent is injected into a vein during the liver ultrasound study to help better visualize blood flow. Analysis of flow patterns has been shown to be useful in differentiating certain lesions from one another, as well as in following certain lesions.
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[DocPanel] The liver is the largest solid organ in the body - does this make it a more difficult area to image?
[Dr. McComb] The size of the liver compared to other organs is not an impediment to liver ultrasound imaging. In fact, liver tissue is very well suited to ultrasound evaluation as long as there is a good “window” for the ultrasound beam and it can penetrate sufficiently. Technologists performing liver ultrasound are experts at working with patients to get the best possible images.
For example, since ultrasound cannot pass through ribs, a technologist may ask a patient to take a deep breath and/or to roll in order to bring more of the liver down below the ribs so that it can be better seen.
[DocPanel] What terms on a liver ultrasound report should a patient be aware of?
[Dr. McComb] Many different terms are used in liver ultrasound reports to describe both normal liver and liver abnormalities. Radiologists frequently describe the “echogenicity” and “echotexture” of background liver tissue and report any lesions (such as cysts, solid masses, etc) visible on the examination.
They may describe whether a particular lesion is darker than (hypoechoic), similar to (isoechoic), or brighter than (echogenic) background liver tissue. Margins of the lesion are often described (smooth, irregular, etc) as well as any visible blood flow within the lesion on Doppler ultrasound, if performed. The presence of any abnormal enlargement (dilatation) of bile ducts in or outside the liver will be reported, along with any abnormal fluid (ascites or fluid collection) next to the liver. Other organs or portions of them can also be seen while scanning the liver, and a patient may see gallbladder or kidney stones (calculi) reported.
[DocPanel] What does it mean to have an ‘echogenic liver’? What are the possible causes?
[Dr. McComb] A liver is described as “echogenic” by a radiologist when the echoes reflected from the ultrasound beam appear brighter (whiter) than those from a normal liver.
This appearance most commonly indicates the presence of fatty liver (steatosis). It can also sometimes be associated with cirrhosis and chronic hepatitis. In these cases, the liver echotexture may also be described as abnormally coarse. Certain other diseases that infiltrate or deposit in the liver may also increase the echogenicity, including certain storage and infectious diseases.
[DocPanel] Under what circumstances should a patient get further imaging tests, like a CT scan or MRI?
[Dr. McComb] The decision to perform a different study, such as CT or MRI, may be based on various factors, including patient history and symptoms as well as research that has shown that certain abnormalities are better evaluated with certain imaging studies.
For example, although the presence of fat in the liver can be visible on ultrasound and CT, MRI is extremely sensitive for liver fat and can even be used to calculate the percentage of fat when necessary. Certain liver masses can be definitively diagnosed by their imaging characteristics on certain studies performed in certain ways, potentially allowing biopsy to be avoided.
Sometimes the liver is also simply not completely or sufficiently seen by ultrasound, necessitating CT or MRI.