This CPD piece aims to highlight the useful features that can be utilised, reaffirming knowledge and perhaps introducing new techniques to improve both the sensitivity and specificity when assessing for liver disease.
Six key points
Looking for steatosis/fatty change/fatty infiltration –
- Compare the liver parenchyma to the cortex of the right kidney and/or spleen.
- Look for the echogenic portal vessel walls and check if you can visualise the intrahepatic vessels themselves. This can be difficult in cases of steatosis.
- Can you visualise the deeper/posterior aspect of the liver? Poor visualisation of the diaphragm is a sign of increased attenuation in keeping with steatosis.
Echotexture – This can be difficult and subjective. You could try comparing the echotexture with the spleen in the determination of a heterogeneous echotexture.
Capsule – Use a high frequency probe to assess the capsule for any undulations (sometimes subtle). Lobulation of the capsule can be a strong predictor of fibrosis in a patient with liver disease and could impact the follow up and/or surveillance of a patient.
Size – Look for atrophy which is common in cases of severe fibrosis and cirrhosis and hepatomegaly which can be a sign of an underlying liver pathology ie hepatitis.
- Quantitative methods can be difficult to perform consistently.
- Look to see if the inferior aspect of the liver extends beyond the lower pole of the right kidney (hepatomegaly, if Reidel’s lobe excluded).
- Blunting of the inferior margins of the right and left lobe of liver.
- Caudate lobe hypertrophy (enlargement) is a good predictor for underlying liver disease.
Portal vein flow – It is important to also utilise spectral Doppler techniques, in addition to stating antegrade portal vein flow in the assessment of liver disease.
- Normal portal vein velocity range is between 20-40cm/s.
- Low velocities (<12cm/s) may be suggestive of portal hypertension.
- Spectral Doppler may also help in cases where no flow is visualised using Doppler/power Doppler to demonstrate stagnant flow with low velocity waveforms both above and below the baseline, potentially avoiding the need for unnecessary anticoagulation treatment.
Liver function tests (LFTs) – These are important for sonographers to understand, as they can be abnormal in someone with a normally functioning liver.
- Alanine transaminase (ALT) and aspartate aminotransferase (AST) are enzymes found in the bloodstream when the liver cells (hepatocytes) are damaged. Levels are usually high is cases of hepatitis and can be used to assess the degree of fibrosis.
- Alkaline phosphatase (ALP) and Gamma-glutamyl transferase (GGT) are enzymes related to the biliary system. When elevated can indicate cholestatic liver disease i.e. biliary obstruction. GGT may also indicate how much alcohol is being consumed but can also be high in cases of non-alcoholic fatty liver disease (NAFLD).
- How well could you describe the different LFTs and the potential implications for ultrasound, if you were to teach this to someone else? Is further reading required to become familiar with the various LFT results and their indications?
- Before performing an examination, do you always check the LFT results? This can often help when interpreting the ultrasound features.
- Do you always look at the features discussed in this CPD article when scanning the liver?
- Are there any additional skills or knowledge in relation to the various ultrasound features of liver disease you need to develop: heterogeneity, size, capsule, portal vein flow (with spectral Doppler)?
- Have you used the three features/tools for fatty infiltration assessment: kidney comparison, vessel wall/vessel visualisation, attenuation (can you visualise the posterior liver/diaphragm)?
- Do you routinely use a high frequency probe to assess the liver capsule in cases of suspected liver disease and in cases where unexpected features are visualised? If not, is this something to introduce to future practice?
Jamie Wild is Consultant Accredited Specialist Sonographer at Sheffield Teaching Hospitals NHS Foundation Trust.
British Liver Trust - Pioneering Liver Health
Iranpour, P., Lall, C., Houshyar, R., Helmy, M., Yang, A., Choi, J.I., Ward, G. and Goodwin, S.C., 2016. Altered Doppler flow patterns in cirrhosis patients: an overview. Ultrasonography, 35(1), p.3.
You can read the full version of this article in Insight magazine Edition 8 / Summer 2023.