Focal hepatic steatosis

Dr Dan J Bell and A.Prof Frank Gaillard et al.

Focal hepatic steatosis is common and seen in a number of clinical settings, essentially the same as those that contribute to diffuse hepatic steatosis:

  • diabetes mellitus
  • obesity
  • alcohol abuse
  • exogenous steroids
  • drugs (amiodarone, methotrexate, chemotherapy)
  • IV hyperalimentation

In general treatment of the underlying condition will reverse the findings.

A characteristic location for focal fatty change is the medial segment of the left lobe of the liver (segment IV) either anterior to the porta hepatis or adjacent to the falciform ligament. This distribution is the same as that seen in focal fatty sparing and is thought to relate to variations in vascular supply. This also would account for focal fatty change/sparing sometimes seen related to vascular lesions.

Ultrasound features only become apparent when the amount of fat reaches 15-20%. Features include:

  • increased hepatic echogenicity
  • hyperattenuation of the beam
  • mild or absent positive mass effect
  • geographic borders
  • no distortion of vessels
  • inability to visualise the portal vein walls (as the parenchyma is as bright as the wall)
  • decreased attenuation (non-contrast CT)
    • normal liver 50-57 HU
    • decreases by 1.6 HU per mg of fat in each gram of liver
  • decreased attenuation (post contrast CT)
    • liver and spleen should normally be similar on delayed (70 second) scans
    • earlier scans are unreliable as the spleen enhances earlier than the liver (systemic supply rather than portal)

MRI is the imaging modality of choice in any case where the diagnosis is felt to be less than certain

  • increased T1 signal
  • signal drop-out on opposed-phase imaging
  • ability to quantify fat fraction

When located in characteristic locations then there is usually little difficulty in making the correct diagnosis. If unusual in location or appearance then differentials to be considered include:

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Article information

rID: 1344
Tag: liver
Synonyms or Alternate Spellings:
  • Focal fatty change
  • Focal fatty infiltration
  • Focal fatty infiltration of the liver
  • Focal hepatic fatty infiltration
  • Focal fat infiltration
  • Focal fat infiltration of the liver

Cases and figures

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    Case 1: ultrasound
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    Case 1 : CT
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    Case 1: MRI in phase
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    Case 1: MRI out of phase
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    Case 1: T2
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    Case 1: T2 FS
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    Case 1: T1 Gad FS
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    Case 2: out of phase
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    Focal fat infiltr...
    Case 3
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    Case 4
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