Ultrasound
Real-time imaging without radiation
Health Insurance Regulations
Important information:
- Health insurance prohibits multiple ultrasounds per day
- Only one ultrasound is reimbursed per day
- Exception: multiple musculoskeletal regions together are allowed
If in doubt, you can call us at 09 233 08 93.
Types of Ultrasound
Doppler legs
Please specify venous OR arterial, given the fundamentally different etiology. Of course both if needed.
Upper abdomen ultrasound
Fasting
Lower abdomen ultrasound
Transabdominal: moderately full bladder (drink 1/2 liter one hour before examination)
Liver Steatosis (NAFLD)/Fibrosis (NASH): Objectification
15-20% of the adult population has a form of steatosis (NAFLD: Non-Alcoholic Fatty Liver Disease, 'foie gras', fatty liver). In obesity (BMI > 30), 80% appear to have NAFLD. In steatosis, there is an accumulation of triglyceride macrovesicles, the grade (S0 > S3) of which depends on the % fatty vs. normal liver tissue. In the US, NAFLD is expected in half the population by 2030.
A steatosis that is in principle reversible, however, evolves in 20% to an irreversible steatohepatitis: NASH (Non-Alcoholic Steato-Hepatitis). NASH is an active inflammation, where hepatocytes are irreparably replaced by fibrotic scar tissue. Fibrosis is graded F0 > F4 (METAVIR). NASH evolves in 10% to cirrhosis (F4), half of which evolves to hepatocellular carcinoma. At this time, this group already appears to be the main indication for liver transplantation.
Since the steatosis group is already large and growing, there appears to be a need for a simple, reproducible and affordable screening method for objectifying steatosis/steatohepatitis. Note that in 50% of steatosis patients, transaminases appear normal. Liver fibrosis is not always preceded by steatosis. So both the degree of steatosis and the degree of fibrosis should be evaluated when chronic liver pathology is suspected.
Liver Steatosis (NAFLD)
Objectification of Steatosis
Steatosis can be objectively assessed by various methods, each with specific advantages and disadvantages:
| Method | Advantages | Disadvantages |
|---|---|---|
| Biopsy | Direct tissue analysis | Invasive (mortality 0.3 ‰), small sample, expensive, intramural, 25% false negative |
| MR | H1-MR-Spectroscopy. Reliable | Expensive and not readily available |
| CT | Reasonably reliable, good visualization | Radiation risk, fairly expensive, moderately readily available |
| Ultrasound | Hepato-Renal Index: Reliable, reasonable cost, no radiation | (Still) moderately readily available |
Hepato-Renal Index (HRI)
The Hepato-Renal Index (HRI) is an ultrasound method to objectively assess the fat content in the liver. This technique compares the echogenicity (degree of reflection of sound waves) of the liver parenchyma with that of the right kidney.
In steatosis, the liver becomes more echogenic (whiter) due to fat infiltration, while the kidney serves as a reference organ. The ratio between these two measurements forms the HRI value.
Steatosis Grading (HRI)
| Grade | HRI Value | Fat Content | Assessment |
|---|---|---|---|
| S0 | < 1.5 | < 5% | Normal |
| S1 | 1.5 - 1.9 | 5-33% | Mild steatosis |
| S2 | 1.9 - 2.2 | 33-66% | Moderate steatosis |
| S3 | > 2.3 | > 66% | Severe steatosis |
Example of HRI measurement:
HRI = 53.29 / 26.48 = 2.01 which corresponds to moderate 'S2' steatosis (33-66% fat content)
The white arrows show the measurement areas: left the liver parenchyma, right the right kidney. The difference in echogenicity (brightness) between these areas determines the HRI value.
Clinical Relevance
- Steatosis (NAFLD) is a reversible condition with adequate lifestyle changes
- Early detection and intervention can prevent progression to NASH
- In 50% of steatosis patients, transaminases are normal, making imaging crucial
Liver Fibrosis (NASH)
Objectification of Fibrosis
The degree of fibrosis can be objectively assessed by various methods, each with specific advantages and disadvantages:
| Method | Advantages | Disadvantages |
|---|---|---|
| Biopsy | Direct tissue analysis | Small sample, invasive (mortality 0.3 ‰), expensive, intramural, 25% false negative sample |
| MR-Elastography | Reliable | Difficult to access, expensive |
| Fibroscan | Moderately reliable, reasonable cost, good reproducibility | Moderately readily available (intramural), no visualization of location, quite a lot of false- and false+ |
| Ultrasound (Shear-wave Elastography) | More reliable than Fibroscan, readily available, reasonable cost, no radiation risk, suitable for follow-up | Requires a radiologist |
Shear Wave Elastography
Shear Wave Elastography is a non-invasive ultrasound technique that measures the stiffness of liver tissue. In liver fibrosis, the stiffness of the liver tissue increases, causing a measurable change in the propagation velocity of the sound waves.
The measurements are expressed in meters per second (m/s) or kilopascal (kPa) and interpreted according to the METAVIR score, an internationally recognized classification system for fibrosis.
This technique is available on high-end ultrasound machines and makes it possible to take about 10 different samples in places where there are no vessels or liver lesions, which increases reliability. In liver steatosis without fibrosis, this can avoid a liver biopsy.
Shear-wave elastography measurement with METAVIR score. The median velocity (1.27 m/s) is the most reliable parameter.
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Shear-wave elastography with color coding for stiffness values. Two measurement areas are shown with elasticity values.
Fibrosis Grading (METAVIR)
| Grade | Velocity (m/s) | Assessment |
|---|---|---|
| F0 | 0.81 - 1.22 | Normal |
| F1-F2 | 1.22 - 1.37 | Normal to mild fibrosis |
| F2-F3 | 1.37 - 2.00 | Mild to moderate fibrosis |
| F3-F4 | > 2.00 | Moderate to severe fibrosis (cirrhosis) |
Clinically relevant differentiation: The distinction between
Clinical Implications of Fibrosis
- Early detection of fibrosis is crucial for determining prognosis
- Patients with advanced fibrosis (F3-F4) have a higher risk of complications
- Regular follow-up via elastography can monitor the evolution of fibrosis
- Liver fibrosis (NASH) is not yet reversible, unlike steatosis
Elastography versus Liver Biopsy
Elastography offers a non-invasive alternative to liver biopsy, with several advantages:
- Non-invasive and thus no risk of complications (versus mortality of 0.3‰ with biopsy)
- 50% of liver biopsies can be avoided with elastography
- Elastography provides an image of a larger liver volume, while biopsy only evaluates a small sample (with 25% chance of false-negative result)
- Enables annual follow-up to monitor evolution
Recommendations for Referral
When steatosis/fibrosis is suspected, determining the HRI and Elastography through liver ultrasound is a reliable method for objectifying the degree of fatty infiltration (S0 > S3) and fibrosis (METAVIR F0 > F4).
Patients with the following risk factors may benefit from an ultrasound evaluation:
Make an Appointment
A referral from your doctor is required for an ultrasound. Contact us for more information or to make an appointment.