Use of Elastography in Liver Fibrosis Assessment

Liver fibrosis is a common consequence of chronic liver diseases like hepatitis, fatty liver, and alcohol-related liver injury. Early and accurate assessment of fibrosis is crucial in preventing progression to cirrhosis and liver failure. Elastography is a modern, non-invasive imaging technique that measures liver stiffness to evaluate the degree of fibrosis without needing a biopsy. This blog explores the types of elastography, their clinical applications, how the test is performed, and how it aids in liver disease management.

What is Elastography?

Elastography is an imaging modality that assesses tissue stiffness by measuring the speed of mechanical waves through the liver. Fibrotic liver tissue is stiffer than healthy tissue, and elastography provides a numerical measure (in kilopascals, or kPa) of that stiffness. This value correlates with the degree of fibrosis.

There are two main types of elastography used in liver evaluation:

• Transient Elastography (TE): Most commonly performed using FibroScan®, a specialized device for liver stiffness measurement.
• Shear Wave Elastography (SWE): Integrated into conventional ultrasound or MRI systems to provide localized tissue stiffness maps.

Why Assess Liver Fibrosis?

Fibrosis is the result of ongoing liver inflammation and damage. It is a key indicator of liver disease progression. Left untreated, fibrosis can advance to cirrhosis, liver failure, or hepatocellular carcinoma.

Timely fibrosis assessment helps in:

• Diagnosing the stage of liver disease
• Guiding treatment decisions
• Monitoring treatment response
• Predicting risk of liver-related complications

Previously, liver biopsy was the only reliable method of fibrosis staging. However, it is invasive, expensive, and carries risks of bleeding and sampling errors. Elastography has become a popular alternative due to its safety and ease of use.

Indications for Liver Elastography

Elastography is typically recommended in patients with:

• Chronic hepatitis B or C
• Non-alcoholic fatty liver disease (NAFLD)
• Alcohol-related liver disease
• Autoimmune hepatitis
• Primary biliary cholangitis (PBC)
• Hemochromatosis or Wilson’s disease
• HIV co-infection with liver involvement
• History of elevated liver enzymes with unknown cause

It is also used in preoperative assessment and to determine prognosis in established liver disease.

Types of Elastography Techniques

1. Transient Elastography (FibroScan)
This is the most widely used technique. A probe placed over the liver sends a low-frequency vibration into the tissue. The speed of wave propagation is measured to calculate stiffness.

• Quick (takes ~5–10 minutes)
• Painless and non-invasive
• Provides additional data such as Controlled Attenuation Parameter (CAP) to assess liver fat content

2. Shear Wave Elastography (SWE)
Uses acoustic radiation force impulses to generate shear waves in liver tissue and measures their velocity. It provides real-time imaging and more targeted assessment of specific liver areas.

• Available on many high-end ultrasound machines
• Offers both qualitative (color map) and quantitative data
• Can be combined with standard liver ultrasound in one exam

3. Magnetic Resonance Elastography (MRE)
This advanced method combines MRI with elastography sequences to produce a detailed map of liver stiffness.

• Highly accurate and reproducible
• Useful in obese patients or those with ascites
• Expensive and less available than ultrasound-based methods

How Elastography is Performed

Preparation

• Fasting for 3–6 hours before the test is often required
• Avoid alcohol and strenuous exercise prior to the test
• Inform the technician of any recent liver treatments or conditions

During the Exam

• You lie on your back with your right arm raised
• The probe is placed between your ribs over the liver
• Mild pulses are delivered, and wave data is captured
• The scan is painless and usually completed in a few minutes

After the Exam

• You can return to normal activities immediately
• The result is typically available on the same day or within a short time

Interpreting Elastography Results

Liver stiffness is reported in kilopascals (kPa). The values correspond to fibrosis stages (F0–F4) as defined by liver biopsy histology:

• F0–F1 (No or mild fibrosis): <7 kPa
• F2 (Moderate fibrosis): 7–9.5 kPa
• F3 (Severe fibrosis): 9.5–12.5 kPa
• F4 (Cirrhosis): >12.5 kPa

Thresholds can vary slightly based on the underlying liver disease and type of elastography used.

Advantages of Elastography

• Non-invasive: No needles or tissue removal required
• Quick and painless: Performed in an outpatient setting
• Reproducible: Allows regular monitoring of disease over time
• Lower cost than biopsy or MRI
• Applicable to a wide range of liver conditions
• Reduced complication risk compared to biopsy

Limitations and Challenges

• Technical limitations in obesity or ascites: Especially with transient elastography
• Operator dependency: Especially in ultrasound-based SWE
• Inflammation or congestion: Acute hepatitis or heart failure may falsely elevate stiffness values
• Less accurate in very early or very advanced disease
• Does not assess inflammation directly, only fibrosis

Despite these limitations, elastography remains a highly reliable method when used appropriately and interpreted alongside clinical and laboratory findings.

Elastography vs Liver Biopsy

While liver biopsy remains the definitive method for diagnosing liver histology, elastography is increasingly used as the first-line test in many clinical protocols, especially for screening and follow-up.

When is Elastography Recommended Over Biopsy?

Elastography is often preferred when:

• The goal is to screen for fibrosis in a large population
• There are contraindications to biopsy, such as coagulopathy
• Repeat monitoring is needed over time
• The patient refuses invasive procedures
• Non-invasive assessment is adequate for clinical decision-making

However, biopsy may still be required in cases of:

• Unexplained liver disease
• Suspected overlapping conditions
• Inconclusive elastography results
• Staging advanced or complex disease

Role of Elastography in Different Liver Diseases

• Hepatitis B/C: Helps guide antiviral therapy decisions and screen for cirrhosis
• NAFLD/NASH: Assists in assessing fibrosis in metabolic liver disease
• Alcohol-related liver disease: Monitors damage and recovery with abstinence
• Autoimmune hepatitis: Complements biochemical and histological findings
• Pediatric liver disease: Non-invasive alternative to biopsy in children

Conclusion

Elastography has become an essential tool in modern hepatology for assessing liver fibrosis. With its non-invasive nature, speed, and accuracy, it is well-suited for both diagnosis and longitudinal monitoring of chronic liver conditions. While not a complete substitute for biopsy in every case, it plays a central role in reducing the need for invasive procedures and improving patient care. If you are undergoing evaluation for liver disease, ask your healthcare provider if elastography is appropriate for you. It can provide valuable information about your liver health with minimal discomfort and risk.

Frequently Asked Questions (FAQs)

Is elastography painful?

No, the procedure is painless and does not require any incisions or needles.

How long does the test take?

Most elastography exams are completed in 10–15 minutes.

Do I need to prepare for elastography?

You may be asked to fast for 3–6 hours before the test to reduce interference from intestinal contents.

Is elastography safe during pregnancy?

Yes, ultrasound-based elastography is safe as it does not involve radiation or contrast agents.

Can I have the test if I am overweight?

Yes, though image quality may be affected in very obese individuals, especially with transient elastography.

How often should the test be repeated?

Frequency depends on your liver condition and treatment status—often yearly or as recommended by your doctor.

Does liver inflammation affect elastography results?

Yes, acute inflammation or liver congestion can temporarily raise stiffness values. Your doctor will consider this during interpretation.

Can elastography detect fatty liver?

Some machines (e.g., FibroScan) include CAP, which estimates liver fat content alongside stiffness.