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Liver: Perfusion Changes Imaging Pearls - Educational Tools | CT Scanning | CT Imaging | CT Scan Protocols - CTisus
Imaging Pearls ❯ Liver ❯ Perfusion Changes

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  • “ The advances in CT data acquisition and post-processing provide new opportunities for tumor characterization, by elucidating the tissue characteristics, enhancement patterns, and vascularity of the lesion. It is important to recognize that use of 3D post-processing tools provides incremental diagnostic information without additional radiation exposure to the patient.”
    Defining vascular signatures of malignant hepatic masses: role of MDCT with 3D rendering
    Ahmed S, Johnson PT, Fishman EK
    Abdom Imaging (2013) 38:763-773
  • “ Rendering of vascular maps with 3D CT aids in defining malignant neovascularity with the potential for improved diagnosis.”
    Defining vascular signatures of malignant hepatic masses: role of MDCT with 3D rendering
    Ahmed S, Johnson PT, Fishman EK
    Abdom Imaging (2013) 38:763-773
  • Passive Hepatic Congestion
    Stasis of blood in the liver
    - Secondary to impaired hepatic venous drainage (from cardiac disease)
    - Most commonly right sided heart disease
    - CHF, constrictive pericarditis, cardiomyopathy, tricuspid or pulmonary valvular disease
    - Can present with elevated LFT’s
    - Can progress to frank cirrhosis
  • Passive Hepatic Congestion
    1. Reflux of contrast into dilated IVC and hepatic veins
    - Can be seen in forceful injections in normals
    2. Heterogeneously enhancing liver
    - “Mottled”
    3. Poor enhancement of peripheral liver due to stasis of blood flow
    4. Hepatomegaly and ascites
  • Hepatic Infarction   
    1. Uncommon due to dual blood supply of the liver
    2. Usually hepatic arterial occlusion + portal vein abnormality
    3. Causes:
    - Liver Transplant, Iatrogenic, Hypercoagulability, infection, vasculitis
  • Hepatic Infarction
    CT Findings:
    1. Usually wedge shaped, peripheral, and low attenuation
    - Can be rounded or irregularly shaped
    2. Can evolve into bile lakes
    3. Gas can be seen in both sterile and infected infarcts
  • Hereditary Hemorrhagic Telangiectasia
    1. Osler-Weber-Rendu Syndrome
    2. Autosomal Dominant
    3. Multiple telangiectasias & AVM’s
    4. Arteriovenous and portovenous shunting
    - Can result in cirrhosis
    5. 75% have hepatic involvement
  • Hereditary Hemorrhagic Telangiectasia
    CT Findings:
    - Dilated hepatic veins, hepatic arteries, and portal veins
    - Early filling of PV’s and HV’s
    - Heterogeneous liver enhancement
    - Large vascular malformations and telangiectasias
  • Portal Vein Thrombosis
    Causes:
    1. Cirrhosis and Portal Hypertension   
    - Slow flow and stasis in portal vein combined with hypercoagulability
    - 1% of patients with cirrhosis develop portal vein thrombosis
    2. Malignancy
    3. Hypercoagulable States
    4. Iatrogenic
    5. Unknown in 1/3 of cases
  • Portal Vein Thrombosis
    CT Findings:
    1. Filling defect in the vein
    2. Thrombus should show no enhancement
    3. Thread-and-streak sign: Tumor thrombus
    - Arterial hyperenhancement in the thrombus
    4. Chronically, mural thickening along the periphery of the vein with calcification
    5. Cavernous transformation
  • Malignant Versus Benign Portal Vein Thrombosis
    1. Malignant portal vein thrombus
    - 35% of patients with HCC
    - Poor prognosis and high rates of recurrence
    - Liver transplant is contraindicated
    - Systemic chemotherapy only real option
    2. Liver transplant still potentially an option with bland thrombus 
  • SMV Thrombosis
    Causes:
    1. Hypercoagulability
    2. Inflammatory conditions in the abdomen (i.e. appendicitis, diverticulitis)
    - Septic thrombophlebitis
    4. Iatrogenic
    5. No cause identified in 1/3 of patients
  • "In conclusion, transient hepatic attenuation differences must be considered neither pitfalls nor nodular lesions. Instead they are imortant signs of an underlying liver disorder and for this reason they are useful to detect and characterize a large variety of liver diseases"
  •  

    Transient Hepatic Attenuation Differences
    Colagrande S et al.
    AJR 2004;183:459-464

  • Transient Hepatic Attenuation Differences: Causes
    - Increase in Hepatic arterial blood flow due to decreased portal venous flow
    - Portal vein thrombosis
    - Hepatic vein thrombosis
    - Compression by adjacent masses
    - Abscesses
    - Long standing biliary obstruction
    - Trauma
    - Arterioportal shunt
  • Transient Hepatic Attenuation Differences: Causes
    - Primary increase in arterial blood flow
    - Focal hypervascular lesions Inflammation of adjacent organs (gallbladder or pancreas)
    - Aberrant hepatic arterial supply
  • Transient Hepatic Attenuation Differences: Facts
    - Defined as areas of increased CT attenuation typically seen on arterial phase imaging
    - They can have both a range of causes and a range of CT appearances
    - They can be a result of an underlying tumor (benign or malignant tumor) or can simulate a tumor (pitfall)
  • Hot Spot in the liver can also occur due to
    - Budd Chiari syndrome
    - Liver abscess
    - Hemangioma
    - Focal nodular hyperplasia
    - Hepatoma
    - These occur to areas beyond segment IV
  • Focal Hepatic Hot Spot Sign
    - Focal area of increased CT attenuation on early phase imaging in segment IV of the liver
    - Occurs typically in patients with SVC obstruction
    - Due to portosystemic shunting of blood between the SVC and the portal vein
    - The flow is via the internal mammary and left umbilical veins to the left hepatic lobe
  • Passive Hepatic Congestion: CT Findings
    - Retrograde flow into IVC and hepatic veins
    - Mottled enhancement of the liver due to hepatic congestion
    - Hepatomegaly
    - Ascites
    - Periportal edema
  • "Because of the low positive predictive value of non-wedge-shaped, centrally located, early enhancing lesions in the diagnosis of HCC, the serial follow-up for examining lesion growth is essential to the correct diagnosis of small hypervascular lesions in cirrhotic livers."

    Small Hypervascular Enhancing Lesions on Arterial Phase Images of Multiphase Dynamic Computed Tomography in Cirrhotic Liver: Fate and Implications
    Hwang SH et al.
    J Comput Assist Tomogr 2008;32:39-45
  • "When small hepatic arterial phase enhancing lesions on dynamic CT are observed, a serial, close follow-up of the lesions is still essential for correct diagnosis( 4 months)."

    Small Hypervascular Enhancing Lesions on Arterial Phase Images of Multiphase Dynamic Computed Tomography in Cirrhotic Liver: Fate and Implications
    Hwang SH et al.
    J Comput Assist Tomogr 2008;32:39-45
  • "MDCT with advanced image processing is useful in delineating uncommon hypervascular liver lesions that simulate tumors. Familiarity with the appearance of these lesions may help reduce the need for additional imaging, follow-up, and histologic confirmation."

    Incidental Nonneoplastic Hypervascular Lesions in the Noncirrhotic Liver: Diagnosis with 16-MDCT and 3D CT Angiography Kaml IR, Liapi E, Fishman EK
    AJR 2006; 187:682-687.
  • " Micrometastases in an apparently normal liver caused a 34% decrease in portal blood flow and a 25% increase in the mean transit time for the blood to pass through the liver. Similar but greater changes were found in macrometastases."
  • CT Imaging of the Liver: Perfusion

    conclusion:

    "Occult liver micrometastases in rats generate changes in liver perfusion that can be detected with CT."

    Early Changes in Liver Perfusion Caused by Occult Metastases in Rats:Detection with Quantitative CT Cuenod CA et al. Radiology 2001; 218:556-561

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