hypervascularity of adenomas can be demonstrated on Doppler US. Color Doppler US modalities are useful tools in the differential diagnosis of LCA and FNH ...
ISSN 1891-179x
MedViz Report 2008 - Number 3 Title:
Benign Liver Lesions: CEUS
Author: Odd Helge Gilja
Conference presentation: XXSIUMB National Congress Time/place:
Nov. 2008, Rome
Benign Liver Lesions: CEUS Odd Helge Gilja, National Centre for Ultrasound in Gastroenterology, Department of Medicine, Haukeland University Hospital, and Institute of Medicine, University of Bergen, Bergen, Norway The role of US in the characterisation of focal liver lesions has been transformed with the introduction of specific contrast media and the development of specialized imaging techniques. Ultrasound now can fully characterise the enhancement pattern of hepatic lesions, similar to that achieved with contrast enhanced multiphasic computed tomography (CT) and magnetic resonance imaging (MRI). US contrast agents are safe, well-tolerated and have very few contraindications. Furthermore, real-time evaluation of the vascularity of focal liver lesions has become possible with the use of the newer microbubble contrast agents and advanced post-processing tools for detailed perfusion analysis. Three contrast phases can be differentiated due to the specific blood supply of the liver: •
The arterial phase (hepatic artery) starts 10 to 20 seconds after intravenous injection and lasts for 10 to 15 seconds
•
The venous phase (portal vein) extends from 30 to 35 seconds and lasts up to 120 seconds
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The late phase starts at 120 seconds and lasts up to five minutes post-injection with the disappearance of bubbles
Patterns seen with common hepatic lesions include the following: Hemangiomas have a peripheral globular contrast pooling in the early phase (a cotton wool appearance), with the globules becoming larger and more numerous (centripetal fill-in). Nicolau (2004) showed the frequency and percentage of focal liver lesions correctly classified as hemangiomas in the vascular and late phases. By typical contrast-enhancement patterns, 19 of 22 hemangiomas could be correctly identified in the late phase (86.4%) and 18 in the vascular phase (81.8%). Ding (2005) showed sensitivity of 96.3% and specificity of 97.5% when centripetal fill-in enhancement was regarded as a positive finding of hemangioma. Focal nodular hyperplasia has a centrifugal stellate branching in early arterial phase followed by an intense homogenous uptake (spoke wheel pattern). Rapid washout occurs thereafter and an isoor hyperechoic lesion is seen in portal venous phase. When these characteristic features are regarded as positive findings of FNH, the sensitivity and specificity of contrast-enhanced low MI real-time US are 87.6% and 94.5%, respectively (Di Stasi 1996). Liver cell adenoma (LCA) is a rare primary benign neoplasm found mainly in young women with a history of oral contraceptive use, androgen steroid therapy or in patients with glycogen-storage disease
On grey scale US, LCA can be hypo, iso or hyperechoic or it can show a mixed-echoic pattern. The hypervascularity of adenomas can be demonstrated on Doppler US. Color Doppler US modalities are useful tools in the differential diagnosis of LCA and FNH because they can identify peripheral peritumoral vessels in LCA, whereas intratumoral vessels radiating from the center to the periphery of the lesion are usually depicted in FNH. By using a continuous low-MI imaging, CEUS with SonoVue allows the identification of the early and homogeneous hyperechoic enhancement in the periphery of the tumor, reflecting the presence of the subcapsular feeding arteries. The enhancement of LCA in the portal and late phases is nearly comparable with that of liver parenchyma, but LCA can remain slightly hypoechoic in relation to the adjacent liver. Hepatic cysts are the most common focal lesion of the liver, but are usually easily recognised on ultrasound due to the thin wall, anechoic content and posterior enhancement. However, in a patient with liver metastasis, small cysts can sometimes be difficult to distinguish from small metastasis. Then CEUS scanning both in arterial phase and in late phase (also using burst technique) may disclose the true nature of the lesion. Focal fatty lesions often appear as suspect hyperechoic lesions on B-mode images and focal fatty sparing may resemble metastasis. In these cases, the use of CEUS will help to differentiate benign from malignant lesions. Particularly, the normal enhancement pattern in the late phase (isoechoic to surrounding liver tissue) strongly indicates a benign lesion.
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EFSUMB study group. Guidelines and good clinical practice recommendations for CEUS – Update 2008. Ultraschall / EJU 29:28-44.
