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Diagnosis in short

Steatosis. Elastic Masson's trichrome stain.

Synonyms fatty liver

LM fatty change (macrovesicular or microvesicular and periportal or centrilobular), negative for ballooning degeneration, negative for significant inflammation - esp. neutrophils
Subtypes macrovesicular steatosis (periportal, centrilobular), microvesicular steatosis
LM DDx steatohepatitis (ASH, MASH), drug-induced liver injury
Gross yellow colour, greasy/slippery feeling, enlarged
Site liver - see medical liver disease

Associated Dx obesity, alcoholism
Prevalence very common
Radiology may be estimated by proton density fat fraction (PDFF)
Prognosis dependent on underlying cause
Clin. DDx ASH, MASH, drug-induced liver injury
Treatment dependent on underlying cause

Steatosis, also fatty liver, is a fatty change in the liver associated with a number of underlying (medical) causes.



Can be divided into:

  1. Macrovesicular steatosis.
    • Common.
  2. Microvesicular steatosis.
    • Rare.
    • Potentially life threatening.[1]


  • It is considered technically incorrect to say the liver, in steatosis/steatohepatitis, contains adipocytes; they are lipid-laden hepatocytes,[2] despite that:
    • Histologically, these cells look like adipocytes.
    • Lipid-laden hepatocytes have gene activations suggestive of adipogenic-like transformation.[3]


Microvesicular steatosis

Microvesicular steatosis DDx:[4]

  • Acute fatty liver of pregnancy,
  • Reye's syndrome.
  • Drug toxicity:
    • Sodium valproate toxicity.
    • High-dose tetracycline toxicity.
  • Jamaican vomiting sickness.
  • Congenital defects of urea cycle enzymes.

Less common causes:

  • Alcoholism.
  • Hepatitis D.
  • Weird stuff:
    • Congenital defects of fatty acid beta oxidation.
    • Cholesterol ester storage disease.
    • Wolman disease and Alpers syndrome.

The classic causes of microvesicular steatosis are:[5]

  • Fatty liver of pregnancy.
  • Aspirin (Reye's syndrome).
  • Tetracycline.

It was once thought that all other causes of fatty liver produce macrovesicular steatosis.

Macrovesicular steatosis

Can sometimes be divided into centrilobular predominant and periportal predominant.[6]

Centrilobular predominant (zone III) - DOA:[6]

Periportal predominant (zone I) - TAPES:[6]

  • Total parenteral nutrition (TPN).
  • AIDS.
  • Phosphorus poisoning.
  • Exogenous steroids.
  • Starvation.[7]


  • HCV genotype 3 is reported to cause periportal steatosis.[8]
  • Donor livers with more macrovescicular steatosis = worse outcome.


  • Yellow colour.
  • Greasy/slippery feeling.
  • Enlarged.


  • May be estimated on MRI by proton density fat fraction (PDFF).[10]


Features - macrovesicular steatosis.

  • One large vacuoles - similar to mature adipose tissue.
  • Nucleus is eccentric.

Features - microvesicular steatosis.

  • Multiple small (clear) cytoplasmic vacuoles - similar to brown fat, as seen in a hibernoma.
  • Nucleus is central.[11]


Quantity of fat is usually given as a percentage and graded mild, moderate, or marked.

  • Mild <33%, moderate >33% & <66%, marked >66%.[12]


See also


  1. Jolly, RA.; Ciurlionis, R.; Morfitt, D.; Helgren, M.; Patterson, R.; Ulrich, RG.; Waring, JF.. "Microvesicular steatosis induced by a short chain fatty acid: effects on mitochondrial function and correlation with gene expression.". Toxicol Pathol 32 Suppl 2: 19-25. PMID 15503661.
  2. Guindi, M. September 2009.
  3. URL: Accessed on: 23 September 2009.
  4. Hautekeete ML, Degott C, Benhamou JP (1990). "Microvesicular steatosis of the liver". Acta Clin Belg 45 (5): 311–26. PMID 2177300.
  6. 6.0 6.1 6.2 Steatosis. URL: Accessed on: 2 Sep 2009.
  7. Nagy, I.; Németh, J.; Lászik, Z. (Jan 2000). "Effect of L-aminocarnitine, an inhibitor of mitochondrial fatty acid oxidation, on the exocrine pancreas and liver in fasted rats.". Pharmacol Res 41 (1): 9-17. doi:10.1006/phrs.1999.0565. PMID 10600264.
  8. Yoon EJ, Hu KQ. Hepatitis C virus (HCV) infection and hepatic steatosis. Int J Med Sci. 2006;3(2):53-6. Epub 2006 Apr 1. PMID 16614743. Avialable at: Accessed on: September 9, 2009.
  9. STC. 6 December 2010.
  10. Tang, A.; Tan, J.; Sun, M.; Hamilton, G.; Bydder, M.; Wolfson, T.; Gamst, AC.; Middleton, M. et al. (May 2013). "Nonalcoholic fatty liver disease: MR imaging of liver proton density fat fraction to assess hepatic steatosis.". Radiology 267 (2): 422-31. doi:10.1148/radiol.12120896. PMID 23382291.
  11. STC. 6 December 2010.
  12. Guindi, M. September 17, 2009.