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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, NASH), drug-induced liver injury
Gross yellow colour, greasy/slippery feelling, enlarged
Site liver - see medical liver disease

Associated Dx obesity, alcoholism
Prevalence very common
Prognosis dependent on underlying cause
Clin. DDx ASH, NASH, 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.


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.[10]


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

  • Mild <33%, moderate >33% & <66%, marked >66%.[11]


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. STC. 6 December 2010.
  11. Guindi, M. September 17, 2009.