Liver elastography

Liver elastography brings together various non-invasive techniques that assess the stiffness of liver tissue using waves or vibrations. Its main purpose is to help estimate the risk of liver fibrosis, that is, the build-up of scar tissue. The result alone does not constitute a diagnosis and must be interpreted in conjunction with blood tests, medical history and other investigations.

What is liver elastography and what information does it provide?

Elastography generates small waves or vibrations and analyses how they travel through the liver tissue. Generally, these waves propagate differently when the liver is stiffer. As fibrosis tends to increase this stiffness, the measurement can help estimate the likelihood of significant scarring or advanced liver disease.

However, liver stiffness and fibrosis are not exactly the same thing. Stiffness can also be increased by severe inflammation, biliary obstruction, congestion associated with certain heart conditions, recent food intake or other factors.

For this reason, a high reading does not automatically mean cirrhosis, nor does a low reading prove that the liver is completely healthy.

In which situations might a liver elastography scan be recommended?

Elastography may be requested when knowing the risk of fibrosis can help determine the appropriate follow-up or the need for further tests. It may form part of the assessment in the following situations:

• Persistent abnormalities in liver function tests.

• Steatosis (fatty liver) detected on an imaging scan.

• Metabolic and dietary-related steatohepatitis (MASLD), a form of fatty liver associated with metabolic disorders such as being overweight or obese, type 2 diabetes, high blood pressure, or changes in cholesterol and triglyceride levels.

• Chronic hepatitis B or C.

• Alcohol-related liver disease.

• Autoimmune, cholestatic, metabolic or hereditary liver diseases.

• Monitoring of a known chronic liver disease.

• Test results that do not allow for a clear classification of the risk of fibrosis.

In people with MASLD, elastography is usually incorporated into a stepwise assessment alongside clinical data and specific blood markers.

It is not a universal test for every minor abnormality in blood test results or for every person who is overweight. Its use depends on the likelihood of disease and the information it can provide to the diagnostic process.

Types of liver elastography

The term ‘liver elastography’ encompasses several techniques. Their results are not directly comparable.

Transient elastography

This is performed using a probe placed on the skin which produces a gentle vibration and measures how the wave propagates through the liver. FibroScan® is a commercial device based on this modality. The brand name should not be used as a synonym for all forms of liver elastography.

Shear-wave elastography

This is integrated into certain ultrasound machines. It allows ultrasound images of the liver to be obtained and stiffness to be measured in selected areas during the same scan. The quality of the measurement depends on the area chosen, the patient’s cooperation and the correct technical execution.

Magnetic resonance elastography

This combines gentle vibrations with images obtained via magnetic resonance imaging. It allows a large area of the liver to be examined and may be useful when ultrasound modalities do not provide an adequate measurement or when a more extensive assessment is required.

No single modality is automatically superior in all situations. The choice depends on the clinical question, the patient’s characteristics and the available resources.

Liver elastography and measurement of liver fat

Liver stiffness and liver fat are different parameters. Some devices incorporate additional measurements, such as CAP (Controlled Attenuation Parameter), which allows the presence of steatosis to be estimated.

Elastography primarily assesses stiffness in relation to the likelihood of fibrosis, whilst CAP provides information on fat accumulation. CAP does not directly measure all the fat present in the liver, nor does it, on its own, allow for the diagnosis of inflammation or steatohepatitis.

A person may have steatosis without advanced fibrosis, fibrosis with little fat, or different patterns across both parameters.

How to prepare for a liver elastography scan

Preparation depends on the specific technique and the centre’s protocol. For ultrasound techniques, a period of fasting is usually required before the test. The aim is to minimise the temporary effect that food intake can have on blood flow and liver stiffness.

You should always follow the timetable stated on your appointment letter and not extend the fasting period on your own initiative. Elastography does not usually require you to stop taking your usual medication. It is advisable to inform the team of any treatments you are currently taking and to follow their instructions.

It may also be helpful to wear clothing that allows the upper right side of the abdomen to be easily exposed and to bring any previous blood test results, ultrasound scans or elastography results with you, where available.

When undergoing magnetic resonance elastography, you must inform the staff of any implanted devices, prostheses or metal objects, as well as any claustrophobia, pregnancy or possibility of pregnancy.

How a liver elastography scan is carried out

In ultrasound procedures, the patient usually lies on their back and keeps their right arm raised to allow access to the area between the ribs. The healthcare professional applies gel to the skin and places the probe on a suitable area of the liver.

During transient elastography, you may feel small pulses or vibrations. In ultrasound-integrated modalities, you may be asked to hold your breath briefly to minimise movement. Several measurements are taken. A single reading is not sufficient: the practitioner checks that the scan meets the quality criteria for the technique being used.

In resonance elastography, a device is placed on the abdomen which transmits gentle vibrations whilst the images are being acquired. External modalities do not usually require anaesthesia or sedation and typically allow patients to resume their normal activities after the examination.

What you might feel during a liver elastography scan

During ultrasound examinations, you may feel pressure from the probe between your ribs, a brief vibration, or some discomfort from keeping your arm raised. These sensations are usually mild, although the experience may vary from person to person.

During an MRI elastography scan, you may find the noise, the enclosed space or the need to remain still whilst the images are being acquired uncomfortable. If a technically valid measurement cannot be obtained, it may be necessary to adjust your position, repeat some scans, change the probe or consider another technique.

Ultrasound elastography is usually completed in a short time and generally requires no aftercare.

What information do the results of a liver elastography provide?

The result may be expressed in kilopascals or, in some ultrasound modalities, as the wave propagation velocity. There is no single figure that applies universally to all elastography scans. Interpretation depends on:

• The technique and equipment used.

• The liver condition being investigated.

• The purpose of the assessment.

• The quality of the measurement.

• The presence of inflammation, cholestasis or congestion.

• The validated criteria for each population.

For this reason, it is not advisable to interpret an individual result using general reference tables or to directly compare results obtained using different techniques.

Low liver stiffness

A low and technically reliable measurement usually makes the presence of advanced fibrosis less likely. It does not mean that the liver is completely healthy. There may be steatosis, mild inflammation, an early stage of disease or other abnormalities that elastography is not designed to detect.

Intermediate result

An intermediate reading may not allow the risk of fibrosis to be classified with sufficient certainty. The team may review the technical quality, correlate it with laboratory results, repeat the scan or use other tests.

Elevated liver stiffness

A high reading raises suspicion of significant or advanced fibrosis, but does not automatically indicate cirrhosis. Before drawing any conclusions, the underlying condition, laboratory results, platelet count, other imaging studies and factors that may temporarily increase stiffness must be assessed.

Liver elastography and monitoring of fibrosis

The test can be repeated to assess how liver risk evolves over time. Comparison is most useful when the same technique is used and measurements are taken under similar conditions.

A reduction in stiffness does not, in itself, prove that fibrosis has disappeared or regressed to the same extent. It may also reflect a reduction in inflammation or congestion. Similarly, an isolated increase may be due to clinical or technical factors.

Changes should be interpreted in conjunction with the progression of laboratory test results, the underlying disease and the treatment received.

Limitations of liver elastography

Elastography measures stiffness, but does not directly examine the cells or the microscopic architecture of the liver. Severe inflammation, cholestasis, cardiac congestion and recent food intake may increase the measured value without accurately reflecting the same degree of fibrosis.

Obesity, ascites in certain forms, patient movement or an unsuitable acquisition area may make it difficult to obtain a valid result. There are also indeterminate results which do not allow the risk to be clearly classified.

Nor does the test, on its own, identify the cause of liver disease or, in isolation, diagnose steatohepatitis, portal hypertension, oesophageal varices or liver cancer.

Risks and potential discomfort associated with liver elastography

External ultrasound techniques do not use ionising radiation, do not require needle punctures and usually do not require intravenous contrast. Any discomfort is generally related to the pressure of the probe, vibrations or the position maintained during the test.

Resonance elastography also does not use ionising radiation, but it shares the safety checks typical of magnetic resonance imaging. With this technique, one of the main precautions is not related to direct physical harm, but rather to avoiding the interpretation of a stiffness value out of its clinical context or without verifying the quality of the measurement.

Liver elastography and liver biopsy

Elastography and liver biopsy provide different types of information. In many cases, the combination of elastography, blood tests and other investigations allows the risk of fibrosis to be assessed without the need to obtain a tissue sample.

A biopsy directly examines the microscopic architecture and cells of the liver and can provide information on inflammation, cell damage and specific diseases.

It may be considered when non-invasive tests yield conflicting or indeterminate results, there are doubts about the cause of the disease, or microscopic information is required that cannot be obtained through imaging or laboratory tests.

Elastography can reduce the need for a biopsy in certain scenarios, but it does not universally replace it.

Elastography, FIB-4, ultrasound and other liver tests

Liver assessment may involve a combination of different tests, as each provides different information.

Blood tests can also be used to calculate indices such as FIB-4, an estimate of the risk of liver fibrosis that combines blood test data — such as transaminases and platelet counts — with age. It does not diagnose fibrosis on its own, but it can help identify which people are at low risk and which may require further assessment.

• An abdominal ultrasound provides information on the anatomy of the liver and can reveal steatosis or other structural abnormalities.

• Elastography adds a measurement of liver stiffness, which helps to estimate the likelihood of fibrosis.

• Magnetic resonance imaging (MRI) can provide more detailed information on liver tissue and other structures when indicated.

• A liver biopsy allows the tissue to be examined directly under a microscope and is reserved for situations where this information may be necessary to resolve the clinical question.

These tests may form part of a stepwise diagnostic process. They are not interchangeable nor do they compete with one another: each addresses a different clinical question and can complement the others.

Liver elastography in special circumstances

In people with obesity, it may be more difficult to obtain a measurement using certain ultrasound techniques. Some devices have specially adapted probes and, if the scan is inconclusive, another imaging modality may be considered.

Ascites may interfere with some forms of transient elastography. Congestion associated with certain heart conditions may increase liver stiffness and must be taken into account when interpreting the result.

Severe liver inflammation or biliary obstruction may also cause transient elevations in the measurement. During pregnancy, the indication and imaging modality must be tailored to the individual, and pregnancy or the possibility thereof must always be disclosed prior to the test.

Specialists in liver elastography at the Publio Cordón Memorial Hospital

At Publio Cordón Memorial Hospital, the assessment of liver diseases is carried out within the Metabolic Centre and can be managed by either the Gastroenterology Department or the Endocrinology and Nutrition Department, depending on the clinical context.

The Gastroenterology department is headed by Dr Malena García Arredondo and features a Hepatic-Metabolic Unit dedicated to the diagnosis, monitoring and management of liver diseases, particularly those related to metabolic disorders. ()

In the Endocrinology and Nutrition department, the team comprises Dr Susana Monereo Megías and Dr José Atencia Goñi. Dr Monereo specifically includes liver elastography amongst the techniques used in her clinical practice, particularly in the context of metabolic liver disease and cardiometabolic assessment.

Medical information for general guidance

This factsheet aims to help you understand what liver elastography measures, how it can help assess the risk of fibrosis, how it is carried out and why its results should be interpreted as part of a broader liver assessment.

The Publio Cordón Memorial Hospital is committed to providing accurate, understandable and useful medical information, linked to specialist care, research, scientific dissemination and medical progress.

The indication for elastography, patient preparation, the chosen method and the interpretation of liver stiffness must be tailored to the individual’s condition, the quality of the measurement and their clinical situation. A single figure should not be used to confirm or rule out cirrhosis, nor to alter treatment without professional assessment.