Fatty Liver And Pitfall

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Fatty Liver And Pitfall

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  • 1. Fatty Liver: Imaging Patterns and Pitfalls Presented by EKKASIT SRITHAMMASIT, MD. Okka W. Hamer, MD et al RadioGraphics 2006; 26:16371653
  • 2. Introduction The image-based diagnosis of fatty liver usually is straightforward, but fat accumulation may be manifested with unusual structural patterns that mimic neoplastic, inflammatory, or vascular conditions. Leading to : Unnecessary diagnosis test and Invasive procedure
  • 3. Table of content
    • Risk Factors and Pathophysiologic Features
    • Imaging-based Diagnosis of Fatty Liver
    • Patterns of Fat Deposition
    • Differential Diagnosis
    • Pitfalls
  • 4. Risk Factors and Pathophysiologic Features Histologically Fatty liver: Triglyceride accumulation within the cytoplasm of hepatocytes. Term fatty infiltration of the liver is misleading because fat deposition is characterized by accumulation of discrete triglyceride doplets in hepatocytes and rarely, in other cell types. The term fatty liver is more accurate.
  • 5. Conditions Associated with Fatty Liver
  • 6. Pathophysiologic Features
    • Triglyceride accumulation (steatosis) within hepatocytes by altering
    • the hepatocellular lipid metabolism ,
    • in particular, by causing
    • defects in free fatty acid metabolic pathways .
  • 7. Pathophysiologic Features
    • Hepatocytes in the center of the lobule (near the central vein) are tend to accumulate lipid earlier than periphery.
    • In advanced cases, there is diffuse, relatively homogeneous involvement of the entire lobule.
    • Steatosis may progress to steatohepatitis ( with inflammation, cell injury, or fibrosis accompanying steatosis) and cirrhosis .
  • 8. Pathophysiologic Features
    • To grade steatosis, pathologist visually estimate the fraction of hepatocytes that contain fat droplets.
    • 0%, 1-5%, 6-33%, 34-66%, 67%.
    • Size of fat droplets is not considered.
  • 9. Prevalence of Fatty Liver
    • General population about 15%.
    • Higher in
      • 40% of consume large quanities of alcohol (>60g /day)
      • 50% of Hyperlipidemia
      • 75% of Obesity (BMI> 30 kg/m 2 )
      • 95% of Both obesity and high alcohol consumption
  • 10. Imaging-based Diagnosis of Fatty Liver
    • Diagnosis at US
    • Diagnosis at CT
    • Diagnosis at MR Imaging
  • 11. Diagnosis at US
    • Normal Liver
    • Echogenicity of the normal liver equals or minimally exceeds that of the renal cortex or spleen.
    • Intrahepatic vessels are sharply demarcated
    • Posterior aspects of the liver are well depicted
    • Fatty liver
    • Liver echogenicity exceeds that of renal cortex and spleen
    • Poor delineation of the intrahepatic architecture
    • Loss of definition of diaphragm
  • 12. Normal Liver Fatty Liver To avoid false-positive interpretations, fatty liver should not be considered present if only one or two of these criteria are fulfilled
  • 13. Diagnosis at CT
    • Normal Liver
    • The normal liver has slightly greater attenuation than the spleen and blood.
    • Intrahepatic vessels are visible as hypoattenuated structures
    • Fatty liver
    • Unenhanced CT
    • Attenuation of the liver is at least 10 HU less than that of the spleen or attenuation of fatty liver is less than 40 HU
    • In severe cases, intrahepatic vessels may appear hyperattenuated relative to fat-containing liver tissue.
  • 14. Normal Liver
  • 15. Fatty Liver
  • 16. Normal Liver Fatty Liver
    • At enhanced CT, the comparison of liver and spleen attenuation value is not reliable.
    • Fatty liver can be diagnosed at contrast-enhanced CT if absolute attenuation is less than 40 HU, but this threshold has limited sensitivity .
  • 17. Diagnosis at MR Imaging
    • Normal Liver
    • The signal intensity of the normal liver parenchyma is similar on in-phase and opposed-phase images
    Fatty liver The signal intensity loss on opposed-phase images in comparison with in-phase images. Chemical shift gradient-echo(GRE) imaging with in-phase and opposed-phase acquisitions is the most widely used MR imaging technique for the assessment of fatty liver.
  • 18.
    • Normal Liver
    • The signal intensity of the normal liver parenchyma is similar on in-phase and opposed-phase images
    Chemical shift gradient-echo(GRE) imaging with in-phase and opposed-phase
  • 19.
    • Fatty liver
    • The signal intensity loss on opposed-phase images in comparison with in-phase images.
    Chemical shift gradient-echo(GRE) imaging with in-phase and opposed-phase
  • 20. Chemical shift gradient-echo(GRE) imaging opposed-phase in-phase
  • 21. Accuracy for Detection and Grading of Fat Deposition
    • Sensitivity Specificity
    • US 60-100% 77-95%
    • NECT 43-95% 90%
    • Chemical shift
    • GRE MRI 81% 100%
  • 22. Patterns of Fat Deposition
    • Diffuse Deposition.
    • Focal Deposition and Focal Sparing.
    • Multifocal Deposition.
    • Perivascular Deposition.
    • Subcapsular Deposition.
  • 23. Diffuse Deposition
    • Diffuse fat deposition in the liver is the most frequently encountered pattern .
    • Liver involvement usually is homogeneous .
    • The image interpretation is straightforward if the rules specified earlier are applied
  • 24. Diffuse Deposition
  • 25. Diffuse Deposition
  • 26. Diffuse Deposition
  • 27. Focal Deposition and Focal Sparing
    • Slightly less common
    • More difficult to diagnosis because may resemble mass lesions .
  • 28. Focal Deposition and Focal Sparing
    • Fat content
    • Location in areas characteristic of fat deposition or sparing
    • Absence of a mass effect on vessels and other liver structures
    • A geographic configuration rather than a round or oval shape
    • Poorly delineated margins
    • Contrast enhancement that is similar to or less than that of the normal liver
    Imaging findings suggestive of fatty pseudolesions rather than true masses include the following:
  • 29. Focal Deposition and Focal Sparing
    • Adjacent to the falciform ligament
    • In the porta hepatis
    • In the gallbladder fossa
    focal fat deposition or focal fat sparing characteristically occurs in specific areas: Focal fat deposition adjacent to insulinoma metastases , probably due to local insulin effects on hepatocyte triglyceride synthesis and accumulation.
  • 30. Focal Deposition and Focal Sparing
    • Focal fat accumulation in the liver at US. Transverse image.
  • 31. Focal Deposition and Focal Sparing
    • Focal fat accumulation in the liver at CT. Axial contrast-enhanced image obtained during the portal venous phase.
  • 32. Foca