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FATTY METAMORPHOSIS OF LIVER

Etiology: • Alcohol is the most common cause. Toxic, metabolic and hypoxic conditions of all type as mentioned above.

Pathogenesis: • Liver is the principle organ of fat metabolism and synthesis. • Interference with mobilizing triglycerides out of the liver is the usual mechanism. • This happens when toxins or agents affect the mitochondrial and microsomal functions - defective oxidation of fatty acids and mitochondrial function. • Factors casuing fatty change do not all act in the same way.

Epidemiology: • This is a common condition, but it is usually secondary to other diseases; again, alcohol is the most common cause, in the industrial world; however, among children and in the developing countries, malnutrition, specially protein and iron deficiencies, are the most common.

General Gross Description: • In severe and diffuse cases, the liver is enlarged, yellow, smooth, firmer than normal and greasy. • In partial involvement, a pale or yellow blotchy appearance is often noted.

General Microscopic Description: • There are two forms of fatty chnage : Microvesicular and macrovesicular. • Microvesicular: Numerous tiny fat vesicles, requires fat stainto be appreciated. Often, one would be surprised as howenormous fat accumulation is without being seen in H&E sections. This is a toxic condition causing hepatocellular failure. • Macrovesicular: A few large clear vacuoles in the cytoplasm of hepatocytes, pushing the nucleus aside. Usually, has no effect on the function of the hepatocyte. • There is usually no inflammatory reaction to this unless, the fatty cell rupture.

Clinical Correlations: • Macrovesicular: Hepatomegaly is the only sign; liver function tests are minmally abnormal, if at all. • Examples include: Alcohol - with a combination of macro and micro vesicular fatty change, Mal-nutrition - inparticular protein deficiency, starvation, Diabetes, Obesity , Severe Infection or Burn, Medication and Toxins, Hypoximia. • Microvesicular: Is a different disease; this is a toxic, metabolically abnormal and serious condition; patient has mild hepatomegaly, however, severe liver function test abnormality to the point of liver failure is common. • Pure examples would include: Reye's Synd., Fatty Liver of Pregnancy and Tetracycline Toxicity. • The most common cause is alcohol.

References: Robbins