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Fatty Liver
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Fatty Liver

A medium high power view of a liver
Note the normal looking hepatocytes to the right in this image - polygonal cells with a central vesicular nucleus and abundant pink cytoplasm.
Towards the left are many cells that contain a large empty looking space.
This is the fat that has been extracted during the histological processing.
(Description By:T.V.Rajan, M.D. )
(Image Contrib. by:T.V.Rajan, M.D. UCHC )
Fatty Metamorphosis
Etiology

Alcohol is the most common cause. Toxic, metabolic and hypoxic conditions of all types.
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 resulting in defective oxidation of fatty acids and aberrant 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, especially 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 change : microvesicular and macrovesicular.
Microvesicular: Numerous tiny fat vesicles, requires fat stain to be appreciated. Often, one would be surprised as how enormous 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 cells rupture.
Clinical Correlation

Macrovesicular: Hepatomegaly is the only sign; liver function tests are minimally abnormal, if at all.
Examples include: Alcohol - with a combination of macro and microvesicular fatty change, Malnutrition - in particular protein deficiency, starvation, diabetes, obesity , severe infection or burn, Medication and Toxins, Hypoximia.
Microvesicular: a different disease; this is a toxic, metabolically abnormal and serious condition; although the patient has mild hepatomegaly, severe liver function test abnormalities to the point of liver failure is common.
Pure examples would include: Reye's Synd., fatty liver of pregnancy and tetracyclinet toxicity.
The most common cause is alcohol.
References
Cotran, Kumar and Robbins: Pathologic Basis of Disease,
Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 857
Fatty Metamorphosis
Synopsis by: T.V.Rajan, M.D., Ph.D. (T56000M50080)[144]
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